Development and Validity of the Rating-of-Fatigue Scale

Examining the Independent and Interactive Carryover Effects of Cognitive and Physical Exertions on Physical Performance

ObjectiveThis study compared the effects of prior cognitive, physical, and concurrent exertion on physical performance.BackgroundFatiguing cognitive and physical exertions have been shown to negatively affect subsequent task performance. However, it is not clearly understood if concurrent physical and cognitive effort may exaggerate the negative carryover effects on physical task performance when compared to cognitive or physical exertion alone.MethodTwenty-five participants completed four isometric handgrip endurance trials on different days. The endurance trials were preceded by four, 15-minute experimental manipulations (cognitive, physical, concurrent, control). Electromyography (EMG) and force tracing performance were monitored, with handgrip strength measured pre and post. Subjective ratings of mental and physical fatigue, as well as affect, motivation, and task self-efficacy, were also assessed.ResultsHandgrip strength decreased following both physical (-14.4% MVC) and concurrent (-12.3% MVC) exertion manipulations, with no changes being observed for the cognitive and control conditions. No differences were observed across conditions for endurance time, EMG, nor tracing performance. When compared to the control conditions, perceptions of mental and physical fatigue were higher following the experimental manipulation. Endurance trial self-efficacy was lower for the mental, physical and concurrent conditions compared to control.ConclusionThe concurrent condition resulted in similar decreases in strength as the physical fatigue condition, but otherwise resulted in similar carryover effects on endurance performance across all conditions. Further study is required at higher exposure levels, or for longer exposure durations, to further probe the influence of concurrent physical and cognitive effort on task performance.ApplicationConcurrent cognitive and physical effort resulted in similar physical performance decrements to physical effort alone.

The Acute Effect of Moderate-Intensity Steady-State Exercise and High-Intensity Interval Exercise in a Mentally Fatigued State on Subjective Ratings of Mental Fatigue

We investigated the effect of 10 min moderate-intensity steady-state exercise (SS) vs. high-intensity interval exercise (HIIE) in a mentally fatigued state on ratings of mental fatigue (MF). Twelve physically active males (age 20.5   ±   0.5 years) completed a 30 min computerized Incongruent Stroop-Word-and-Colour-Test (C-ISWCT) followed by one of the following in a randomized order: A) 5 min light-intensity warm-up, then continuous cycling at 60% maximum heart rate (SS), B) 5 min light-intensity warm-up, then 3  ×  20s sprints interspersed with 3 min unloaded cycling (HIIE), C) 15 min rest (CON). Mental fatigue visual analogue scale (VAS) ratings increased statistically significantly pre- to post-MF protocol in all trials (F1,11 = 114.11, p < .001). Post-warm-up MF ratings were not statistically significantly different between trials but showed a moderately greater reduction in SS vs. CON (dunb = -0.66) and a large reduction in HIIE vs. CON (dunb = -0.84). Post-exercise MF ratings were statistically significantly lower in SS and HIIE vs. CON (p = .005, dunb = -1.52 and p = .006, dunb = -1.43, respectively). Ten minutes SS exercise and HIIE are similarly effective at attenuating perceptions of MF compared with CON. Short bouts of exercise may combat perceived MF.

Oleuropein Supplementation Increases Resting Skeletal Muscle Fractional Pyruvate Dehydrogenase Activity but Does Not Influence Whole-Body Metabolism: A Randomized, Double-Blind, and Placebo-Controlled Trial in Healthy, Older Males

BACKGROUND

The polyphenol oleuropein activates mitochondrial calcium import, which increases pyruvate dehydrogenase (PDH) activity. Preclinically, this increase in PDH activity following oleuropein supplementation resulted in improved mitochondrial bioenergetics and fatigue resistance.

OBJECTIVES

This study aimed to examine the effects of acute and chronic oleuropein supplementation on muscle energy metabolism, whole-body substrate metabolism, strength, and fatigue resistance in older males.

METHODS

In a randomized, double-blind, placebo-controlled trial, 40 healthy older males (60 ± 5y) received either placebo (PLA) or 100 mg oleuropein from 250 mg olive leaf extract (OLE) supplementation daily for 36 d. On day 1 and day 36, muscle and blood samples were collected, and indirect calorimetry was performed before and ≤120 min following supplement intake. Leg strength and fatigue were measured before and after 29 d of supplementation. Results were analyzed using analysis of covariance or robust analysis of covariance.

RESULTS

OLE ingestion on day 1 and day 36 increased plasma oleuropein metabolites (P < 0.001). On day 1, no differences were observed in muscle PDH activity, mitochondrial respiration, or whole-body substrate metabolism 120 min after acute OLE ingestion. Ribonucleic acid sequencing revealed upregulation of oxidative phosphorylation gene pathways (false discovery rate < 0.05), whereas PDH-Serine293-phosphorylation was higher after acute OLE compared with PLA ingestion (P = 0.015). Following chronic supplementation, fractional PDH activity was ∼25% greater in OLE compared with PLA (49 ± 14 compared with 38 ± 10%; P = 0.016) with no differences in absolute PDH activity and PDH-Serine293-phosphorylation between groups. Mitochondrial respiration and protein content, whole-body substrate metabolism, leg strength, and fatigue resistance were not different between OLE and PLA. Plasma low-density lipoprotein cholesterol was lower after chronic OLE compared with PLA (P = 0.043), with no differences in other blood metabolic markers.

CONCLUSIONS

Chronic OLE supplementation resulted in higher skeletal muscle fractional PDH activity in healthy, older males, which may impact resting energy metabolism. Acute or chronic oleuropein supplementation does not modulate skeletal muscle mitochondrial respiration, muscle strength, muscle fatigue, or whole-body substrate metabolism. This trial was registered at clinicaltrials.gov as NCT05217433.

Neuromuscular Responses to 5 K Time Trial Load Carried by Spanish Army Marines

One of the physical requirements for marines involves covering a specific distance while carrying individual combat gear, supplies, or other military equipment across challenging terrain. Training for this physically and mentally demanding task is a routine component of their preparation. However, further research is needed to better understand the neuromuscular impact of such demanding efforts, strenuous maneuvers, and the recovery process in the subsequent days. Twenty-nine marines completed a 5 km time trial while carrying 24 kg of combat gear, undergoing evaluations at four time points: pre exercise, immediately post exercise, 24 h post exercise, and 48 h post exercise. Repeated measures ANOVA, paired samples t-test, and effect size (ES) analysis were conducted, presenting the results as the mean ± standard deviation (SD). The significance level was set at p ≤ 0.05. Several variables and their corresponding p-values demonstrated changes over time, including the following: the isometric mid-thigh pull (IMTP) (p = 0.001); countermovement jump height (VJ CMJ) (p ≤ 0.001); rating of fatigue scale (ROF) (p ≤ 0.001); blood lactate (BL) levels (p ≤ 0.001); maximum pull-ups (PUmax) (p ≤ 0.001); body mass (BM) (p ≤ 0.001); dominant hand grip strength (DHGS) (p = 0.406); and non-dominant hand grip strength (NDHGS) (p = 0.805). Incident reports and perceived effort (IRPE) revealed a progressive and significant increase between the first and last kilometer of the test, specifically in perceived variables of fatigue, muscle pain, joint pain, shortness of breath, palpitations, excessive sweating, and muscle tremors (all p ≤ 0.001). These findings may contribute to optimizing training programs to better align with operational demands, thereby improving task performance and overall mission effectiveness. In conclusion, the military test had a significant neuromuscular impact on the body, initially resulting in the potentiation of absolute global isometric strength and lower-limb power. However, these values declined below the baseline levels at 24 and 48 h post test.

Recovery Patterns of Low-frequency Fatigue in Elite Youth Soccer Players after Official Matches

This study aimed to analyze the associations between recovery of low-frequency fatigue, jump height, and perceptual responses following official soccer matches. Forty-two male youth elite soccer players (age: 17.13±0.70 years; height: 179.17±5.94 cm; weight: 69.74±4.91 kg) participated in this study. Low-frequency fatigue, countermovement jump, perceived fatigue, muscle soreness, and perceived recovery were assessed at - 2 h, +30 min, +24 h and +48 h relative to the match. Linear mixed models analysis showed that low-frequency fatigue was reduced at the match-end (ES=- 0.679 [95% CI =- 1.01; - 0.34]; p<0.001) but returned to baseline after 24 h (ES=0.149 [95% CI = - 0.26; 0.56]; p=1.00). Perceptual responses were impaired for up to 48 hours following the match (ES=- 0.868-1.174; p<0.001). Countermovement jump did not differ between any time point (ES=- 0.204-0.216; p>0.05). Additionally, the within-subject correlation analysis showed that low-frequency fatigue pre- to post-match changes presented moderate to large associations with perceived fatigue (rm[57]=- 0.43; p<0.001), muscle soreness (rm[57]=- 0.52; p<0.001), and perceived recovery (rm[57]=0.38; p=0.003). The assessment of low-frequency fatigue could serve as an additional objective measurement for monitoring post-match fatigue, as findings suggest that young elite soccer players experience transient reductions following match-play, which are strongly correlated with subjective markers of recovery.

Perceived fatigue does not alter effort-based decision making but does undermine confidence in the ability to perform physical actions

Fatigue may affect the decision to deploy effort (cost) for a given rewarded outcome (benefit). However, it remains unclear whether these fatigue-associated changes can be attributed to simply feeling fatigued. To investigate this question, twenty-two healthy males made a series of choices between two rewarded options: a fixed, no effort option, where no physical effort was required to obtain a set, low reward vs. a variable, effortful option, in which both the physical effort requirements (i.e. different durations of a sustained contraction performed in the lower limbs) and rewards (i.e. greater monetary incentives) was varied. Effort-based choices were made under two conditions: (1) a rested (control) state, (2) a pre-induced state of perceived fatigue, evoked through physical exertion in the upper-limbs, thus controlling for the physical manifestation of fatigue (i.e. decline in muscular force production in the lower limbs) on the decision process. Though prior physical exertion increased the perception of fatigue, participants choices did not significantly differ between control and fatigue conditions. Across both conditions, participants demonstrated an anticipated aversion to effort, with greater effort requirements reducing the decision to engage in actions associated with higher rewards. However, in the fatigue state only, decision time was prolonged and self-reported confidence in individuals' ability to perform high effort actions was reduced. The findings suggest that a perceived state of fatigue does not necessarily alter cost/benefit comparisons within effort-based decisions, but may introduce greater uncertainty within choice and reduce self-confidence. These findings evidence altered evaluative processes during decision making under conditions of fatigue.

Hematological Adaptations to Altitude Training in Female Water Polo Players: A Case Report of a World Championships Medal-Winning Team

BACKGROUND

The effective monitoring of athletes' adaptation is crucial to optimize the outcomes of altitude camps and minimize the risk of maladaptation to the hypoxic stress and intensive training. This case report assessed the hematological adaptations in 22 world-class female water polo players during a 16-day 'live high-train high' (LHTH) altitude camp (2320 m) and evaluated the differences between selected (n = 13) and non-selected (n = 9) players and between playing positions.

METHODS

Hematological parameters, including total hemoglobin mass (tHBmass) and blood volume, were measured before and after the camp. Resting heart rate, peripheral oxygen saturation, body mass, fatigue, and sleep were monitored daily.

RESULTS

Relative tHbmass increased PRE to POST (5.4 ± 5.1%, range -3.9-20.2), but blood volume did not change (p = 0.797). Erythrocyte count, hemoglobin concentration, hematocrit, and red cell distribution width increased PRE-POST (p < 0.001, ES = 1.21-2.69), while mean corpuscular volume and hemoglobin decreased (p < 0.001, ES = 0.51 and 0.72, respectively). No substantial differences were observed in the hematological parameters between selected and non-selected players. There was a large difference in the change in relative blood volume between centers (n = 4, PRE 74.1 ± 5.4, POST 69.7 ± 5.9 mL/kg; mean ± SD) and field players (n = 15, PRE 80.8 ± 10.6, POST 82.8 ± 6.8 mL/kg; adj p = 0.046, ES = 1.15) and between centers and goalkeepers (n = 3, PRE 89.7 ± 9.6, POST 82.0 ± 7.1 mL/kg; adj p = 0.046, ES = 1.62).

CONCLUSIONS

A 16-day LHTH camp can induce favorable hematological adaptations in world-class women's water polo players, without substantial differences between selected and non-selected players, and larger increases in field players.

Effects of a 30 K Military Loaded Carriage on the Neuromuscular System in Spanish Army Marines

Infantry soldiers must cover long distances carrying heavy and bulky combat equipment. Since the beginning of their training, Spanish Marines have undergone this characteristic and demanding test. However, little is known about its effects on neuromuscular function and recovery in the days following the test. Twenty-six Spanish Marines completed the test, three of whom suffered injuries and had to withdraw from the study, resulting in a final sample of twenty-three Marines. These participants underwent evaluations before (pre), immediately after (post), and 24 and 48 h post-exercise, following a 30 km endurance march carrying their 34 kg combat equipment. A repeated-measures ANOVA, paired-samples t-test, and effect size (ES) analysis were conducted; the results are presented as mean ± SD. The significance level was set at p ≤ 0.05. The variables and p-values of changes over time are presented. Isometric mid-thigh pull (IMTP) (p = 0.004), countermovement jump (CMJ) (p ≤ 0.001), rating of fatigue scale (ROF) (p ≤ 0.001), maximum pull-ups in two minutes (PUmax) (p ≤ 0.001), body mass (BM) (p ≤ 0.001), hand grip strength (HGS): dominant (p = 0.180) and non-dominant (p = 0.616), and incident reports (IRPE) showed a significant increase over time and between the first 10 km and last 5 km in fatigue, muscle pain, joint pain, shortness of breath, excessive sweating (p ≤ 0.001), and muscle tremors (p = 0.028), except for palpitations (p = 0.189). In conclusion, the results indicate that the test had a significant impact on neuromuscular function, with no recovery observed in overall strength and lower limb power after 48 h, even though their perceived fatigue decreased substantially. The resilient spirit of operational military units and their philosophy of always being ready for combat could increase the injury rate.

Relationships between spatiotemporal and kinematic domains during treadmill gait change across adulthood

BACKGROUND

Spatiotemporal and kinematic variables during gait undergo characteristic changes with aging. However, the relationships between these domains, and how these change with aging, have not been extensively investigated.

RESEARCH QUESTION

How does age affect relationships between spatiotemporal and joint/segment range-of-motion variables during treadmill gait?

METHODS

In this cross-sectional study, a motion capture system tracked 60 participants (20-80 years old), walking at self-selected and slow speeds on a treadmill. Spatiotemporal (step length, width, time, velocity) and range-of-motion (ankle, knee, hip, pelvis, trunk) variables were extracted from 50 steps at each speed. Mixed-effects models were used to quantify relationships between spatiotemporal variables and age, range-of-motion, and interactions between age and range-of-motion.

RESULTS

Significant relationships with range-of-motion were found for some spatiotemporal variables; the direction of the relationship was most often positive, with several negative relationships. Significant interaction effects were observed for several pairings (ankle range-of-motion - step length, ankle range-of-motion - step velocity, hip range-of-motion - step velocity), with stronger relationships between spatiotemporal and range-of-motion variables as age increased.

SIGNIFICANCE

Stronger relationships at both the ankle and hip in older adults may suggest that older adults rely more on motion at these joints, and constrain other degrees-of-freedom, in an attempt to maintain gait velocity for successful task execution and/or safety on the treadmill. This study statistically quantifies the effects of age on the relationships between spatiotemporal and kinematic domains while accounting for stride-to-stride variations during gait, which provides insight into the control of spatiotemporal variables in healthy individuals across adulthood, and may inform strategies for identifying gait dysfunction with aging.

Changes in shooting accuracy among basketball players under fatigue: a systematic review and meta-analysis

Objective

To investigate the influence of physical and mental fatigue of different intensities (mild, moderate or severe) on basketball shooting accuracy, with the aim of informing more effective training protocols and competition strategies.

Methods

Literature searches were conducted on Web of Science, PubMed, and EBSCO databases up to 25 June 2024. Inclusion and exclusion criteria were specified, and data extraction sheets were prepared. Study quality was assessed by using the Cochrane Risk of Bias Tool in Review Manager 5.4, and Stata18.0 software was used for heterogeneity analysis, subgroup analysis, forest plots, stratification analysis, and bias assessment.

Results

Moderate physical fatigue affected two-point shooting accuracy (P < 0.01),severe physical fatigue affected both two-point (P = 0.02) and three-point shooting accuracy (p < 0.01),with severe physical fatigue showing a greater detrimental impact on three-point shooting accuracy, while two-point shooting accuracy may vary under specific conditions. Additionally, adolescent athletes were less affected by severe physical fatigue compared to adult athletes or those with longer training experience. Moderate mental fatigue also significantly reduced free-throw accuracy (p < 0.01).

Conclusion

The shooting accuracy of basketball players was significantly affected by moderate and severe physical fatigue. Severe physical fatigue notably adversely affected the accuracy of three-point shooting relative to moderate fatigue; Additionally, moderate mental fatigue significantly reduced free-throw accuracy, which may be attributed to a decline in cognitive executive functions, highlighting the importance of fatigue management in sports training.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/#myprospero, identifier CRD42024539553.

Translation and Validation of the Portuguese Version of the Rating-of-Fatigue Scale

BACKGROUND

The Rating-of-Fatigue (ROF) scale is a validated tool to measure changes in perceived fatigue in sports and everyday contexts; thus, this study aimed to translate and validate the Portuguese version of the ROF scale. For this, the study was composed of three phases. Phase 1 involved a comprehensive translation of the ROF scale into Portuguese, followed by a back-translation and a consolidation process to obtain the final version of the ROF scale in Portuguese. In phase 2, the face validity of the scale was assessed. Seventy-three native Portuguese speakers responded to a series of Likert scale items designed to evaluate the purpose of the scale and assess whether it accurately measured the intended construct. In the final phase, the convergent and divergent validity of the scale was assessed during an incremental cycling test to exhaustion, followed by 10 min of passive recovery and a subsequent repetition of the initial 5 min of the test. The study was conducted between October 2023 and June 2024 in Portugal.

RESULTS

The results from phase 1 indicated a high level of comparability and interpretability between the original and back-translated versions, with only minor adjustments made to finalize the Portuguese version of the ROF scale. In phase 2, a high level of face validity was observed. The median score for the item "measures fatigue" was (median [IQR]) was 3.0 [3.0, 4.0] out of 4. After participants were provided with the scale instructions, the face validity score improved significantly (4.0 [3.0, 4.0]; p = 0.001). In phase 3, during the incremental test, very large correlations were observed between ROF, and key physiological and performance indicators, including rating of perceived exertion (RPE), heart rate, oxygen consumption, and power output. Discriminant validity between ROF and RPE was found during the recovery.

CONCLUSIONS

The present study indicates that the Portuguese version of the ROF maintains the properties of the original version and can be used effectively in the Portuguese language.

Risk of crashes among self-employed truck drivers: Prevalence evaluation using fatigue data and machine learning prediction models

INTRODUCTION

Transportation companies have increasingly shifted their workforce from permanent to outsourced roles, a trend that has consequences for self-employed truck drivers. This transition leads to extended working hours, resulting in fatigue and an increased risk of crashes. The present study investigates the factors contributing to fatigue and impairment in truck driving performance while developing a machine learning-based model for predicting the risk of traffic crashes.

METHOD

To achieve this, a comprehensive questionnaire was designed, covering various aspects of the participants' sociodemographic characteristics, health, sleep, and working conditions. The questionnaire was administered to 363 self-employed truck drivers operating in the State of São Paulo, Brazil. Approximately 63% of the participants were smokers, while 17.56% reported drinking alcohol more than four times a week, and also admitted to being involved in at least one crash in the last three years. Fifty percent of the respondents reported consuming drugs (such as amphetamines, marijuana, or cocaine).

RESULTS

The surveyed individuals declared driving for approximately 14.62 h (SD = 1.97) before they felt fatigued, with an average of approximately 5.92 h of sleep in the last 24 h (SD = 0.96). Truck drivers unanimously agreed that waiting times for truck loading/unloading significantly impact the duration of their working day and rest time. The study employed eight machine learning algorithms to estimate the likelihood of truck drivers being involved in crashes, achieving accuracy rates ranging between 78% and 85%.

CONCLUSIONS

These results validated the construction of accurate machine learning-derived models.

PRACTICAL APPLICATIONS

These findings can inform policies and practices aimed at enhancing the safety and well-being of self-employed truck drivers and the broader public.

Work-Related Fatigue: Relationship Between Perceived and Performance Fatigability in Career Firefighters

OBJECTIVE

The purpose of this study was to (1) examine the relationship between perceived work-related fatigue and performance fatigability, and (2) assess the impact of percent body fat (%BF) on perceived fatigue constructs in career firefighters.

METHODS

Thirty-nine career firefighters completed body composition testing, the Occupational Fatigue Exhaustion Recovery (OFER15) scale assessing three subscales of work-related fatigue (acute fatigue, chronic fatigue, and inter-shift recovery), and maximal leg extensor isometric strength testing prior to and following an isotonic fatiguing protocol.

RESULTS

Performance fatigability was not associated with any of the OFER15 perceived work-related fatigue variables ( P ≥ 0.513). Greater %BF was associated with greater %∆ peak torque ( r = -0.41, P = 0.010) but none of the OFER15 perceived work-related fatigue variables ( P ≥ 0.638).

CONCLUSIONS

Performance fatigability was not associated with OFER15 perceived work-related fatigue, and greater adiposity negatively impacted performance fatigability but not perceived fatigability.

Muscle endurance, neuromuscular fatigability, and cognitive control during prolonged dual-task in people with chronic obstructive pulmonary disease: a case-control study

PURPOSE

Recent studies suggest that, compared to healthy individuals, people with chronic obstructive pulmonary disease (pwCOPD) present a reduced capacity to perform cognitive-motor dual-task (CMDT). However, these studies were focused on short-duration CMDT offering limited insight to prolonged CMDT inducing fatigue, which can be encountered in daily life. The present study aimed to explore the effect of adding a cognitive task during repeated muscle contractions on muscle endurance, neuromuscular fatigability, and cognitive control in pwCOPD compared to healthy participants.

METHODS

Thirteen pwCOPD and thirteen age- and sex-matched healthy participants performed submaximal isometric contractions of the knee extensors until exhaustion in two experimental sessions: (1) without cognitive task and (2) with a concurrent working memory task (i.e., 1-back task). Neuromuscular fatigability (as well as central and peripheral components measured by peripheral magnetic stimulation), cognitive performance, and perceived muscle fatigue were assessed throughout the fatiguing tasks.

RESULTS

Independently to the experimental condition, pwCOPD exhibited lower muscle endurance compared to healthy participants (p = 0.039), mainly explained by earlier peripheral fatigue and faster attainment of higher perceived muscle fatigue (p < 0.05). However, neither effect of cognitive task (p = 0.223) nor interaction effect (group × condition; p = 0.136) was revealed for muscle endurance. Interestingly, cognitive control was significantly reduced only in pwCOPD at the end of CMDT (p < 0.015), suggesting greater difficulty for patients with dual tasking under fatigue.

CONCLUSION

These findings provide novel insights into how and why fatigue develops in COPD in dual-task context, offering a rationale for including such tasks in rehabilitation programs.

Simulated breathing in virtual reality does not affect perceived effort during the physical rehabilitation of people with long COVID

OBJECTIVE

To assess the effectiveness of simulated breathing in virtual reality (VR) for manipulating the level of perceived effort of people with long COVID during sessions of physical rehabilitation.

METHODS

We conducted a within-participants randomized prospective study during a cycling exercise in immersive VR with three counterbalanced conditions of simulated breathing: slower breathing, neutral breathing, and faster breathing compared to theirs. 37 participants with long COVID and deconditioning were included in the study, 36 of which could finish the experiment.

RESULTS

The study did not show any influence of the rate of the simulated breathing on participants' perceived effort, which was the primary judgment criterion. We did not find any effect of simulated breathing rate on perceived fatigue, cybersickness and embodiment (VR metrics), and preference. However, higher actual breathing rates were observed in the condition with faster simulated breathing.

CONCLUSION

The study did not show the effectiveness of using simulated breathing in VR to manipulate perceived effort during the physical rehabilitation of people with long COVID. Nevertheless, our results suggest that this technique is feasible, as only one participant dropped out due to their symptoms, as most participants had a good appreciation of the system, and reported feeling rather strong embodiment and weak cybersickness.

On Your Mark, Get Set, Choose! A Randomized Cross-Over Study Comparing Fixed and Self-Selected Rest Periods in Interval Running Among Professional Female Soccer Players

BACKGROUND

Studies on rest durations during high-intensity interval training (HIIT) often compare fixed and self-selected (SS) rest allocation approaches. Frequently, the rest duration under SS conditions is unlimited, leading to inconsistent total rest durations compared to fixed rest conditions. To address this limitation, we recently compared fixed and SS rest conditions during cycling HIIT sessions, while keeping the total rest duration equivalent. However, our protocol required athletes to divide a long total rest duration (720 s) across nine intervals, which may have been overly cognitively demanding. The current study aimed to explore the effects of the SS approach with a simplified rest allocation task on performance, physiological, and psychological outcomes.

METHODS

Following a familiarization session, 24 professional female soccer players completed two running HIIT sessions on a non-motorized treadmill. Each session consisted of twelve 15 s intervals, divided into three blocks, with the goal of maximizing the distance covered. In both conditions, the between-interval rest duration per block amounted to 270 s. In the fixed condition, the rest was uniformly allocated to 90 s between each interval, whereas in the SS condition, the athletes chose how to allocate the entirety of the 270 s of rest. We compared the following outcomes: distance, heart rate, perception of fatigue, effort, autonomy, enjoyment, boredom, and athletes' preferences. Outcomes were compared using aggregated measures via paired univariate tests, and across the intervals via mixed-effects models.

RESULTS

We observed comparable results in most outcomes with the exception of higher autonomy (1-15 points) in the SS condition (mean difference = 2.1, 95%CI (0.9, 3.3) points) and a negligibly higher heart rate in the SS condition when comparing the observations across intervals (estimate = 2.5, 95%CI (0.9, 4.2) beats × min-1). Additionally, participants chose to rest for longer durations as the block progressed. Finally, the majority of participants (65%) favored the SS condition.

CONCLUSION

This study further solidifies that SS and fixed approaches with matched total rest durations result in similar performance, physiological, and psychological responses. This effect persists even when the total rest duration required to be allocated is relatively short. Therefore, coaches and trainees can choose either approach based on their preferences and training goals.

Brain activation patterns in normal hearing adults: An fNIRS Study using an adapted clinical speech comprehension task

OBJECTIVES

Understanding brain processing of auditory and visual speech is essential for advancing speech perception research and improving clinical interventions for individuals with hearing impairment. Functional near-infrared spectroscopy (fNIRS) is deemed to be highly suitable for measuring brain activity during language tasks. However, accurate data interpretation also requires validated stimuli and behavioral measures.

DESIGN

Twenty-six adults with normal hearing listened to sentences from the Oldenburg Sentence Test (OLSA), and brain activation in the temporal, occipital, and prefrontal areas was measured by fNIRS. The sentences were presented in one of the four different modalities: speech-in-quiet, speech-in-noise, audiovisual speech or visual speech (i.e., lipreading). To support the interpretation of our fNIRS data, and to obtain a more comprehensive understanding of the study population, we performed hearing tests (pure tone and speech audiometry) and collected behavioral data using validated questionnaires, in-task comprehension questions, and listening effort ratings.

RESULTS

In the auditory conditions (i.e., speech-in-quiet and speech-in-noise), we observed cortical activity in the temporal regions bilaterally. During the visual speech condition, we measured significant activation in the occipital area. Following the audiovisual condition, cortical activation was observed in both regions. Furthermore, we established a baseline for how individuals with normal hearing process visual cues during lipreading, and we found higher activity in the prefrontal cortex in noise conditions compared to quiet conditions, linked to higher listening effort.

CONCLUSIONS

We demonstrated the applicability of a clinically inspired audiovisual speech-comprehension task in participants with normal hearing. The measured brain activation patterns were supported and complemented by objective and behavioral parameters.

Wearable heart rate sensing and critical power-based whole-body fatigue monitoring in the field

Whole-body fatigue (WBF) presents a concerning risk to construction workers, which can impact function and ultimately lead to accidents and diminished productivity. This study proposes a new WBF monitoring technique by applying the Critical Power (CP) model, a bioenergetic model, with a wrist-worn heart rate sensor. The authors modified the CP model to calculate WBF from the percentage of heart rate reserve (%HRR) and generated a personalized model via WBF perception surveys. Data were collected for two days from 33 workers at four construction sites. The results showed that the proposed technique can monitor field workers' perceived WBF with a mean absolute error of 12.8% and Spearman correlation coefficient of 0.83. This study, therefore, demonstrates the viability of wearable WBF monitoring on construction sites to support programs aimed at improving workplace safety and productivity.

Influence of running on incidental and integral vitality and fatigue: An intensive longitudinal intervention in young Women's daily life

Exercise intensity and perceived autonomy are important factors for the affective response toward exercise and adherence. Dual-mode theory suggests an inverted-J response curve of affect with increased exercise intensity, but little is known about how different running programs affect the affective response and subsequent incidental affect in daily life. This ambulatory assessment study examines the short- to long-term effects of two 8-week running interventions (affect-based vs. polarized-prescribed) on subjective vitality and perceived fatigue in young female novices. Participants engaged in 3 × 30 minute running sessions weekly in their natural environments and completed electronic diaries three times daily. Autoregressive multilevel models indicate small effects of training intensity on immediate affective subjective vitality (ß = -2.37; p = .03; f2 = 0.02) but negligible non-significant effects on fatigue (ß = 0.26; p = 0.12; f2 = 0.002). Novices experienced increased vitality throughout the day when their running was evaluated positively (ß = 0.23; p = .03; f2 = 0.04), with effects lasting over two days before returning to baseline (ß = -0.26; p < .001; f2 = 0.004). However, no significant long-term effects were observed over 8 weeks in vitality or fatigue. Results indicate between- and within-person variations, but limited sample power does not allow differentiating between programs. This study supports the dual-mode theory and highlights the importance of distinguishing affective response from incidental affect.

Immediate but not prolonged effects of submaximal eccentric vs concentric fatiguing protocols on the etiology of hamstrings' motor performance fatigue

PURPOSE

Our study aimed to compare the immediate and prolonged effects of submaximal eccentric (ECC) and concentric (CON) fatiguing protocols on the etiology of hamstrings' motor performance fatigue.

METHODS

On separate days, 16 males performed sets of 5 unilateral ECC or CON hamstrings' contractions at 80% of their 1 Repetition Maximum (1 RM) until a 20% decrement in maximal voluntary isometric contraction (MVC) torque was reached. Electrical stimulations were delivered during and after MVCs at several time points: before, throughout, immediately after (POST) and 24 h (POST 24) after the exercise. Potentiated twitch torques (T100 and T10, respectively) were recorded in response to high and low frequency paired electrical stimulations, and hamstrings' voluntary activation (VA) level was determined using the interpolated twitch technique. For statistical analysis, all indices of hamstrings' motor performance fatigue were expressed as a percentage of their respective baseline value.

RESULTS

At POST, T100 (ECC: -13.3%; CON: -9.7%; p < 0.001), T10 (ECC: -5.1%; CON: -11.8%; p < 0.05) and hamstrings' VA level (ECC: -3.0%; CON: -2.4%; p < 0.001) were significantly reduced from baseline, without statistical differences between fatigue conditions. At POST24, all indices of hamstrings' motor performance fatigue returned to their baseline values.

CONCLUSION

These results suggest that the contribution of muscular and neural mechanisms in hamstrings' motor performance fatigue may not depend on contraction type. This may have implications for practitioners, as ECC and CON strengthening could be similarly effective to improve hamstrings' fatigue resistance.

Sex-Based Effects of Branched-Chain Amino Acids on Strength Training Performance and Body Composition

BACKGROUND

Branched-chain amino acids (BCAAs) are widely studied for their effects on muscle recovery and performance.

AIMS

This study examined the effects of BCAA supplementation on anthropometric data, physical performance, delayed onset muscle soreness (DOMS), and fatigue in recreational weightlifters.

METHODS

The trial involved 100 participants (50 men and 50 women), randomized into BCAA and placebo groups. Subjects in the BCAA group took five daily capsules of 500 mg L-leucine, 250 mg L-isoleucine, and 250 mg L-valine for six months. A two-way ANOVA was used to analyze the main and interaction effects of sex and treatment.

RESULTS

Notable findings include significant improvements in muscle recovery, as indicated by reduced DOMS, particularly in women who showed a decrement of 18.1 ± 9.4 mm compared to 0.8 ± 1.2 mm in the placebo group of a horizontal 100 mm line. Fatigue perception was also significantly lower in the BCAA group, with women reporting a greater decrease (2.6 ± 1.5 scores) compared to the placebo group (0.6 ± 0.7 scores). Strength gains were prominent, especially in men, with a 10% increase in bench press maximum observed in the BCAA group. The interaction between sex and treatment was significant, suggesting sex-specific responses to BCAA supplementation.

CONCLUSIONS

These results underscore the effectiveness of BCAA supplementation in enhancing muscle recovery, reducing fatigue, and improving strength. This study also highlights sex-specific responses, with women benefiting more in terms of DOMS and fatigue reduction, while men experienced greater strength gains, suggesting a need for tailored supplementation strategies.

Acute psycho-physiological responses to submaximal constant-load cycling under intermittent hypoxia-hyperoxia vs. hypoxia-normoxia in young males

Background

Hypoxia and hyperoxia can affect the acute psycho-physiological response to exercise. Recording various perceptual responses to exercise is of particular importance for investigating behavioral changes to physical activity, given that the perception of exercise-induced pain, discomfort or unpleasure, and a low level of exercise enjoyment are commonly associated with a low adherence to physical activity. Therefore, this study aimed to compare the acute perceptual and physiological responses to aerobic exercise under intermittent hypoxia-hyperoxia (IHHT), hypoxia-normoxia (IHT), and sustained normoxia (NOR) in young, recreational active, healthy males.

Methods

Using a randomized, single-blinded, crossover design, 15 males (age: 24.5 ± 4.2 yrs) performed 40 min of submaximal constant-load cycling (at 60% peak oxygen uptake, 80 rpm) under IHHT (5 × 4 min hypoxia and hyperoxia), IHT (5 × 4 min hypoxia and normoxia), and NOR. Inspiratory fraction of oxygen during hypoxia and hyperoxia was set to 14% and 30%, respectively. Heart rate (HR), total hemoglobin (tHb) and muscle oxygen saturation (SmO2) of the right vastus lateralis muscle were continuously recorded during cycling. Participants' peripheral oxygen saturation (SpO2) and perceptual responses (i.e., perceived motor fatigue, effort perception, perceived physical strain, affective valence, arousal, motivation to exercise, and conflict to continue exercise) were surveyed prior, during (every 4 min), and after cycling. Prior to and after exercise, peripheral blood lactate concentration (BLC) was determined. Exercise enjoyment was ascertained after cycling. For statistical analysis, repeated measures analyses of variance were conducted.

Results

No differences in the acute perceptual responses were found between conditions (p ≥ 0.059, ηp 2 ≤ 0.18), while the physiological responses differed. Accordingly, SpO2 was higher during the hyperoxic periods during the IHHT compared to the normoxic periods during the IHT (p < 0.001, ηp 2 = 0.91). Moreover, HR (p = 0.005, ηp 2 = 0.33) and BLC (p = 0.033, ηp 2 = 0.28) were higher during IHT compared to NOR. No differences between conditions were found for changes in tHb (p = 0.684, ηp 2 = 0.03) and SmO2 (p = 0.093, ηp 2 = 0.16).

Conclusion

IHT was associated with a higher physiological response and metabolic stress, while IHHT did not lead to an increase in HR and BLC compared to NOR. In addition, compared to IHT, IHHT seems to improve reoxygenation indicated by a higher SpO2 during the hyperoxic periods. However, there were no differences in perceptual responses and ratings of exercise enjoyment between conditions. These results suggest that replacing normoxic by hyperoxic reoxygenation-periods during submaximal constant-load cycling under intermittent hypoxia reduced the exercise-related physiological stress but had no effect on perceptual responses and perceived exercise enjoyment in young recreational active healthy males.

The effect of fatigue on peak Achilles tendon force in Irish dancing-specific landing tasks

Achilles tendinopathy is prevalent among Irish dancers, believed to be due to aesthetic technical requirements and high-impact landing tasks. However, the peak Achilles tendon force during Irish dancing-specific landing tasks has not been quantified. Furthermore, the influence of fatigue is unclear. This study aimed to quantify the peak Achilles tendon force during three common Irish dancing landing tasks and investigate the effects of fatigue on this force. Twelve nationally competitive Irish dancers completed the landing tasks prior to and following a fatigue protocol. A Vicon motion analysis system and AMTI force plates were used to calculate sagittal plane ankle joint kinematics during landing to estimate peak Achilles tendon force. Three independent measures (Rating-of-Fatigue scale, Flight time: Contraction during a counter movement jump and jump height during the landing trials) were used to evaluate participant fatigue between conditions. Results revealed a significant difference in peak Achilles tendon force between the three landing tasks, however, no significant difference was observed between pre- and post-fatigue. Further research is required to investigate the effects of the landing technique used in Irish Dancing on peak Achilles tendon force with the aim to reduce peak Achilles tendon force and the risk of developing Achilles tendinopathy.

Hematological and performance adaptations to altitude training (2,320 m) in elite middle-distance and distance swimmers

Purpose

Elite swimmers often schedule altitude training camps ahead of major events in an attempt to maximize performance. However, the relationships between altitude-induced hematological changes, markers of training adaptation, and performance changes in such context are unclear. This study assessed hematological status, markers of daily adaptation, and swimming performance in elite middle-distance and distance swimmers during a 22-day altitude training camp at 2,320 m, 2 weeks prior to World Championship qualification competition.

Methods

Venous blood was obtained and total hemoglobin mass (tHbmass) measured (CO rebreathing) in 7 elite swimmers (4 females, 3 males) 8 days before and on day 22 of the altitude camp. Resting heart rate, peripheral oxygen saturation, urinary specific gravity, body mass, fatigue and self-reported sleep duration and quality were monitored daily during the altitude camp. Swimming performance was assessed through a standardized set (6 sets of 4 maximal repetitions of 100 m front crawl) on days 3, 10 and 17 of the camp, and at sea level competitions (200 m-1,500 m) immediately after the camp, and 2 weeks later.

Results

tHbmass (+5.6 ± 3.3%; range: 2.1%-11.0%; p < 0.05), red blood cell count, hemoglobin concentration, hematocrit increased at the end of the training camp (p < 0.05). Performance at altitude improved throughout the camp (+1.4 ± 0.4%; range: 0.7%-2.5%; p < 0.05). No significant relationship was noted between hematological changes, the change in altitude performance and any of the monitored daily markers of adaptation during the camp. Compared to the swimmers' previous personal best, competition performances did not improve immediately (2.5% ± 1.9% slower times) and 2 weeks after altitude (1.2% ± 1.4% slower times).

Conclusion

The 22-day altitude training camp at 2,320 m was beneficial for elite swimmers' tHbmass, hematological status and performance at altitude, but these benefits did not clearly translate into enhanced sea level performance immediately after or 2 weeks later. The present study confirms the large inter-individual variability in hematological responses to altitude training, and that the improvement in performance at altitude and sea level may depend on factors other than the increase in tHbmass alone.

Multicomponent Support Program for Secondary Prevention of Stroke Using Digital Health Technology: Co-Design Study With People Living With Stroke or Transient Ischemic Attack

BACKGROUND

Few individuals (<2%) who experience a stroke or transient ischemic attack (TIA) participate in secondary prevention lifestyle programs. Novel approaches that leverage digital health technology may provide a viable alternative to traditional interventions that support secondary prevention in people living with stroke or TIA. To be successful, these strategies should focus on user needs and preferences and be acceptable to clinicians and people living with stroke or TIA.

OBJECTIVE

This study aims to co-design, with people with lived experience of stroke or TIA (referred to as consumers) and clinicians, a multicomponent digital technology support program for secondary prevention of stroke.

METHODS

A consumer user needs survey (108 items) was distributed through the Australian Stroke Clinical Registry and the Stroke Association of Victoria. An invitation to a user needs survey (135 items) for clinicians was circulated via web-based professional forums and national organizations (eg, the Stroke Telehealth Community of Practice Microsoft Teams Channel) and the authors' research networks using Twitter (subsequently rebranded X, X Corp) and LinkedIn (LinkedIn Corp). Following the surveys, 2 rounds of user experience workshops (design and usability testing workshops) were completed with representatives from each end user group (consumers and clinicians). Feedback gathered after each round informed the final design of the digital health program.

RESULTS

Overall, 112 consumers (male individuals: n=63, 56.3%) and 54 clinicians (female individuals: n=43, 80%) responded to the survey; all items were completed by 75.8% (n=85) of consumers and 78% (n=42) of clinicians. Most clinicians (46/49, 94%) indicated the importance of monitoring health and lifestyle measures more frequently than current practice, particularly physical activity, weight, and sleep. Most consumers (87/96, 90%) and clinicians (41/49, 84%) agreed that providing alerts about potential deterioration in an individual's condition were important functions for a digital program. Intention to use a digital program for stroke prevention and discussing the data collected during face-to-face consultations was high (consumers: 79/99, 80%; clinicians 36/42, 86%). In addition, 7 consumers (male individuals: n=5, 71%) and 9 clinicians (female individuals: n=6, 67%) took part in the user experience workshops. Participants endorsed using a digital health program to help consumers manage stroke or TIA and discussed preferred functions and health measures in a digital solution for secondary prevention of stroke. They also noted the need for a mobile app that is easy to use. Clinician feedback highlighted the need for a customizable clinician portal that captures individual consumer goals.

CONCLUSIONS

Following an iterative co-design process, supported by evidence from user needs surveys and user experience workshops, a consumer-facing app that integrates wearable activity trackers and a clinician web portal were designed and developed to support secondary prevention of stroke. Feasibility testing is currently in progress to assess acceptability and use.

An Integrated Perspective of Effort and Perception of Effort

Effort and the perception of effort (PE) have been extensively studied across disciplines, resulting in multiple definitions. These inconsistencies block scientific progress by impeding effective communication between and within fields. Here, we present an integrated perspective of effort and PE that is applicable to both physical and cognitive activities. We define effort as the energy utilized to perform an action. This definition can be applied to biological entities performing various voluntary or involuntary activities, irrespective of whether the effort contributes to goal achievement. Then, we define PE as the instantaneous experience of utilizing energy to perform an action. This definition builds on that of effort without conflating it with other subjective experiences. We explore the nature of effort and PE as constructs and variables and highlight key considerations in their measurement. Our integrated perspective aims to facilitate a deeper understanding of these constructs, refine research methodologies, and promote interdisciplinary collaborations.

Effects of acute simulated altitude on the maximal lactate steady state in humans

We sought to determine the effects of acute simulated altitude on the maximal lactate steady state (MLSS) and physiological responses to cycling at and 10 W above the MLSS-associated power output (PO) (MLSSp and MLSSp+10, respectively). Eleven (4 females) participants (means [SD]; 28 [4] yr; V̇o2max: 54.3 [6.9] mL·kg-1·min-1) acclimatized to ∼1,100 m performed 30-min constant PO trials in simulated altitudes of 0 m sea level (SL), 1,111 m mild altitude (MILD), and 2,222 m moderate altitude (MOD). MLSSp, defined as the highest PO with stable (<1 mM change) blood lactate concentration ([BLa]) between 10 and 30 min, was significantly lower in MOD (209 [54] W) compared with SL (230 [56] W; P < 0.001) and MILD (225 [58] W; P = 0.001), but MILD and SL were not different (P = 0.12). V̇o2 and V̇co2 decreased at higher simulated altitudes due to lower POs (P < 0.05), but other end-exercise physiological responses (e.g., [BLa], ventilation [V̇e], heart rate [HR]) were not different between conditions at MLSSp or MLSSp + 10 (P > 0.05). At the same absolute intensity (MLSSp for MILD), [BLa], HR, and V̇E and all perceptual variables were exacerbated in MOD compared with SL and MILD (P < 0.05). Maximum voluntary contraction, voluntary activation, and potentiated twitch forces were exacerbated at MLSSp + 10 relative to MLSSp within conditions (P < 0.05); however, condition did not affect performance fatiguability at the same relative or absolute intensity (P > 0.05). As MLSSp decreased in hypoxia, adjustments in PO are needed to ensure the same relative intensity across altitudes, but common indices of exercise intensity may facilitate exercise prescription and monitoring in hypoxia.NEW & NOTEWORTHY This study demonstrates the power output and metabolic rate associated with the maximal lactate steady-state (MLSS) decline in response to simulated altitude; however, common indices of exercise intensity remained unchanged when cycling was performed at the work rate associated with MLSS at each simulated altitude. These results support previous studies that investigated the effects of hypoxia on alternative measures of the critical intensity of exercise and will inform exercise prescription/monitoring across altitudes.

Fatigue and Performance Rates as Decision-Making Criteria in Pacing Control During CrossFit®

We investigated fatigue and performance rates as decision-making criteria in pacing control during CrossFit®. Thirteen male regional-level competitors completed conditions of all-out (maximum physical work from beginning to end) and controlled-split (controlled physical work in the first two rounds but maximum work in the third round) pacing throughout the Fight Gone Bad workout separated by one week. We assessed benchmarks, countermovement jumps and ratings of fatigue after each round. Benchmarks were lower in round 1 (99 vs. 114, p < .001) but higher in rounds 2 (98 vs. 80, p < .001) and 3 (97 vs. 80, p < .001) for controlled-split compared with all-out pacing. Reductions in countermovement jumps were higher after rounds 1 (-12.6% vs. 1.6%, p < .001) and 2 (-12.7% vs. -4.0%, p = .014) but similar after round 3 (-13.2% vs. -11.3%, p = .571) for all-out compared with controlled-split pacing. Ratings of fatigue were higher after rounds 1 (7 vs. 5 a.u., p < .001) and 2 (8 vs. 7 a.u, p = .023) but similar after round 3 (9 vs. 9 a.u., p = .737) for all-out compared with controlled-split pacing. During all-out pacing, countermovement jump reductions after round 2 correlated with benchmark drops across rounds 1 and 2 (r = .78, p = .002) and rounds 1 and 3 (r = -.77, p = .002) and with benchmark workout changes between pacing strategies (r = -.58, p = .036), suggesting that the larger the countermovement jump reductions the higher the benchmark drops across rounds and workouts. Therefore, benchmarks, countermovement jumps and ratings of fatigue may assess exercise-induced fatigue as decision-making criteria to improve pacing strategy during workouts performed for as many repetitions as possible.

First-Generation OTC Antihistamine Use and Voice Function in Individuals with Allergic Rhinitis: A Preliminary Report of Clinically Impactful Findings

PURPOSE

The primary goal of this investigation was to characterize the effect of the first-generation, over-the-counter antihistamine Chlor-Trimeton on laryngeal structure and function in a previously unstudied population - individuals diagnosed with allergic rhinitis who routinely take over-the-counter antihistamines and deny the experience or diagnosis of voice disorder.

STUDY DESIGN

Prospective within-participant multimodality repeated measures design.

METHODS

Eight consented participants (seven females, one male) previously diagnosed with allergic rhinitis and without history of voice disorder who routinely took over-the-counter antihistamines completed the study. Volunteers completed the following measures before and 2hours after antihistamine administration: perceptual vocal function measures, phonation threshold pressure (PTP), acoustic measures, and laryngeal imaging. All pre- and post-administration data were descriptively analyzed for clinically significant change.

RESULTS

No clinically significant differences were identified for any acoustic or aerodynamic measures taken. Analyses of laryngeal imaging data indicated that all participants had evidence of mucosal changes in one or more of the following parameters: increased vascularity, mucus in the anterior commissure, and vocal fold color changes, all of which are consistent with prior descriptions of allergy larynx.

CONCLUSIONS

Empirical study of laryngeal appearance in individuals diagnosed with allergic rhinitis, affirmed clinical observations of laryngeal tissue changes consistent with allergy larynx. Stable PTP suggests potential vocal fold cover adaptations from routine use of over-the-counter antihistamines that may buffer the typical desiccating effect on voice function observed in prior studies of healthy individuals.

Association between Mid-Term Functionality and Clinical Severity in Patients Hospitalized for Pulmonary Embolism

The aim of this study is to evaluate the relationship between clinical severity and functionality, occupational performance, and health-related quality of life in patients hospitalized with pulmonary embolism. Pulmonary embolism patients were grouped by clinical severity using the Pulmonary Embolism Severity Index. Those scoring ≥160 were in the high-severity group (HSG); those scoring < 160 in the low-moderate group (LMSG). The main variables were functionality assessed by the World Health Organization Disability Assessment Schedule (WHODAS), self-perception of occupational performance assessed by the Canadian Occupational Performance Measure (COPM), pain and fatigue assessed by a Visual Analogue Scale (VAS), and health-related quality of life assessed by the EuroQol-5Dimensions (EQ-5D). Patients were evaluated at hospital admission and at 1-month and 3-month follow-up. At admission, there were significant differences between groups in the WHODAS and health-related quality of life in favor of the LMSG. At 1-month and at 3-month follow-up, there were significant differences between the LMSG and HSG in WHODAS, COMP, NRS pain, fatigue and EQ-5D scores in favor of the LMSG. An association exists between clinical severity and mid-term functionality, self-perception of occupational performance, pain, fatigue, and health-related quality of life in PE patients.

The Autoregulation Rest-Redistribution Training Method Mitigates Sex Differences in Neuromuscular and Perceived Fatigue During Resistance Training

PURPOSE

To examine the sex differences in performance and perceived fatigue during resistance training prescribed using traditional (TRA) and autoregulation rest-redistribution training (ARRT) approaches.

METHODS

Twelve resistance-trained men and 12 women completed 2 sessions including the bench-press exercise matched for load (75% of 1-repetition maximum), volume (24 repetitions), and total rest (240 s). Sessions were performed in a counterbalanced randomized design with TRA consisting of 3 sets of 8 repetitions with 120-second interset rest and ARRT employing a personalized combination of clusters, repetitions per cluster, and between-clusters rest regulated with a 20% velocity-loss threshold. The effects of TRA and ARRT on velocity loss, unilateral isometric peak force, and rating of fatigue (ROF) were compared between sexes.

RESULTS

The velocity loss was generally lower during ARRT compared with TRA (-0.47% [0.11%]), with velocity loss being mitigated by ARRT to a greater extent among males compared with females (-0.37% [0.15%]). A smaller unilateral isometric peak force decline was observed after ARRT than TRA among males compared with females (-38.4 [8.4] N). Lower ROF after ARRT than TRA was found among males compared to females (-1.97 [0.55] AU). Additionally, males reported greater ROF than females across both conditions (1.92 [0.53] AU), and ARRT resulted in lower ROF than TRA overall (-0.83 [0.39] AU).

CONCLUSIONS

The ARRT approach resulted in decreased velocity loss, peak force impairment, and ROF compared with TRA in both sexes. However, male subjects exhibited more pronounced acute within-session benefits from the ARRT method.

Exploring sex differences in blood-based biomarkers following exhaustive exercise using bioinformatics analysis

This study examined the acute effects of exercise testing on immunology markers, established blood-based biomarkers, and questionnaires in endurance athletes, with a focus on biological sex differences. Twenty-four healthy endurance-trained participants (16 men, age: 29.2± 7.6 years, maximal oxygen uptake (V ˙ O 2 max ): 59.4 ± 7.5 ml · min-1 · kg-1; 8 women, age: 26.8 ± 6.1 years,V ˙ O 2 max : 52.9 ± 3.1 ml · min-1 · kg-1) completed an incremental submaximal exercise test and a ramp test. The study employed exploratory bioinformatics analysis: mixed ANOVA, k-means clustering, and uniform manifold approximation and projection, to assess the effects of exhaustive exercise on biomarkers and questionnaires. Significant increases in biomarkers (lymphocytes, platelets, procalcitonin, hemoglobin, hematocrit, red blood cells, cell-free DNA (cfDNA)) and fatigue were observed post-exercise. Furthermore, differences pre- to post-exercise were observed in cytokines, cfDNA, and other blood biomarkers between male and female participants. Three distinct groups of athletes with differing proportions of females (Cluster 1: 100% female, Cluster 2: 85% male, Cluster 3: 37.5% female and 65.5% male) were identified with k-means clustering. Specific biomarkers (e.g., interleukin-2 (IL-2), IL-10, and IL-13, as well as cfDNA) served as primary markers for each cluster, potentially informing individualized exercise responses. In conclusion, our study identified exercise-sensitive biomarkers and provides valuable insights into the relationships between biological sex and biomarker responses.

The effects of affect-guided interval training on pleasure, enjoyment, and autonomy: A registered report

This registered report tested the effects of a novel exercise protocol, namely affect-guided interval training, on motivationally relevant variables of remembered pleasure, forecasted pleasure, enjoyment, and autonomy. Affect-guided interval training (AIT) consisted of 60-s intervals that alternated between the highest pleasant intensity and lowest pleasant intensity for 20 min; this was intended to minimize the potential displeasure of traditional high-intensity interval training. The novel protocol was compared to self-selected exercise intensity (30 min) and high-intensity interval training (60-s intervals for 20 min). All sessions were, on average, vigorous in intensity (80-89% peak heart rate). Data indicate that the AIT session was experienced as the most pleasant, had the most pleasant slope of affect, was remembered as the most pleasant, resulted in the most positive affective forecasts, and was the most enjoyable. Both the affect-guided interval session and self-selected exercise session resulted in greater autonomy than high-intensity interval training. Several evaluative and motivationally relevant variables, including (a) remembered pleasure, (b) enjoyment, and (c) forecasted pleasure were predicted by (a) experienced pleasure, the (b) pleasure experienced at the end of exercise, and (c) the slope of pleasure experienced throughout the exercise session. Overall, this study suggests that affect-guided interval training is a feasible and positive alternative that can be included as a viable option for exercise programming.

Influence of voluntary isocapnic hyperpnoea on recovery after high-intensity exercise in elite short-track speedskaters - randomized controlled trial

Respiratory muscle training plays a significant role in reducing blood lactate concentration (bLa) and attenuating negative physiological stress reactions. Therefore, we investigated if voluntary isocapnic hyperpnoea (VIH) performed after a maximum anaerobic effort influences bLa and perceived fatigue level in well-trained speedskaters. 39 elite short-track speedskaters participated in a trial with two parallel groups: experimental and control. All the participants performed the Wingate Anaerobic Test (WAnT). The experimental group performed a VIH-based recovery protocol 20 min after exercise, the control group used passive recovery only. Blood samples were taken 3 and 30 min after the WAnT to measure bLa. Fatigue was self-appraised on a 0-10 perceived rating-of-fatigue (ROF) scale 3 and 30 min after the WAnT. Noteworthy, but not statistically significant changes between the experimental and control groups were observed for changes in bLa (p = 0.101). However, statistically significant changes between the groups were found for ROF (p = 0.003, ηp2 = 0.211, ω2 = 0.106). Moreover, statistically significant interactions between post-exercise bLa clearance and VO2max (p = 0.028) and inspiratory muscle strength (p = 0.040) were observed. Our findings provided preliminary insight that VIH may be an efficient recovery protocol after anaerobic exercise performed by elite athletes. The association between VO2max and post-exercise bLa clearance indicates the vital role of aerobic fitness in repeated-efforts ability in short-track speedskaters. The study was registered at ClinicalTrials.gov as NCT05994092 on 15th August 2023.

Oxygen therapy for exercise capacity in fibrotic interstitial lung disease: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Fibrotic interstitial lung disease (fILD) is characterised primarily by impaired lung function and quality of life. The present study investigated whether oxygen therapy could improve exercise capacity among patients with fILD.

METHODS

Previously published randomised controlled trials (RCTs) were surveyed. A systematic review and meta-analysis was conducted to evaluate the effectiveness of oxygen therapy in improving the exertional capacity of patients with fILD. The primary outcome was peripheral oxygen saturation (SpO2) during exercise. The effects of oxygen therapy on fatigue, dyspnoea, heart rate, and exercise duration or distance were also analysed.

RESULTS

Fourteen RCTs involving 370 patients were included. Oxygen therapy improved SpO2 during exercise (mean difference, MD = 6.26 %), exercise duration (MD = 122.15 s), fatigue (standard mean difference, SMD = -0.30), and dyspnoea (MD = -0.75 Borg score units). High-flow oxygen systems tended to be more effective than low-flow systems in improving exercising SpO2, duration, fatigue, dyspnoea, and heart rate. High-flow nasal cannulas (HFNCs) yielded better outcomes regarding SpO2 and fatigue than did high-flow Venturi masks (MD = 1.60 % and MD = -1.19 Borg score units, respectively). No major adverse events were reported.

CONCLUSION

The evidence from RCTs supports the short-term use of oxygen supplementation to improve SpO2, exercise capacity, fatigue, and dyspnoea among patients with fILD. Further analyses demonstrates that HFNCs yield more favourable outcomes, yet not reaching statistical significance except for improving SpO2 and fatigue. However, the long-term effects of oxygen therapy on quality of life and mortality remain unclear.

Performance and perceived fatigability across the intensity spectrum: role of muscle mass during cycling

The role of muscle mass in modulating performance and perceived fatigability across the entire intensity spectrum during cycling remains unexplored. We hypothesized that at task failure (Tlim), muscle contractile function would decline more following single- (SL) versus double-leg (DL) cycling within severe and extreme intensities, but not moderate and heavy intensities. After DL and SL ramp-incremental tests, on separate days, 11 recreationally active males (V̇o2max: 49.5 ± 7.7 mL·kg-1·min-1) completed SL and DL cycling until Tlim within each intensity domain. Power output for SL trials was set at 60% of the corresponding DL trial. Before and immediately after Tlim, participants performed an isometric maximal voluntary contraction (MVC) coupled with one superimposed and three resting femoral nerve stimulations [100 Hz; 10 Hz; single twitch (Qtw)] to measure performance fatigability. Perceived fatigue, leg pain, dyspnea, and effort were collected during trials. Tlim within each intensity domain was not different between SL and DL (all P > 0.05). MVC declined more for SL versus DL following heavy- (-42 ± 16% vs. -30 ± 18%; P = 0.011) and severe-intensity cycling (-41 ± 12% vs. -31 ± 15%; P = 0.036). Similarly, peak Qtw force declined more for SL following heavy- (-31 ± 12% vs. -22 ± 10%; P = 0.007) and severe-intensity cycling (-49 ± 13% vs. -40 ± 7%; P = 0.048). Except for heavy intensity, voluntary activation reductions were similar between modes. Similarly, except for dyspnea, which was lower for SL versus DL across all domains, ratings of fatigue, pain, and effort were similar at Tlim between exercise modes. Thus, the amount of muscle mass modulates the extent of contractile function impairment in an intensity-dependent manner.NEW & NOTEWORTHY We investigated the modulatory role of muscle mass on performance and perceived fatigability across the entire intensity spectrum. Despite similar time-to-task failure, single-leg cycling resulted in greater impairments in muscle contractile function within the heavy- and severe-intensity domains, but not the moderate- and extreme-intensity domains. Perceived fatigue, pain, and effort were similar between cycling modes. This indicates that the modulatory role of muscle mass on the extent of performance fatigability is intensity domain-dependent.

Acute anodal transcranial direct current stimulation improves the performance of professional rowers

Introduction

The aim of the present study was to evaluate the influence of acute transcranial direct current stimulation (tDCS) on physical and subjective responses in professional rowing during the 2,000-m time trial test.

Methods

Seven rowers (age 20.86 ± 4.49 years; weight 71.66 ± 7.97 kg) participated in this randomized triple-blind trial with a crossover experimental design. The protocol consists of 2 days with different conditions (anodal and sham). The tDCS anodic stimulation conducted was 2 mA for 20 min in the left temporal cortex (2.5 cm from the F7 zone and 2.5 cm from the T3 zone), targeting the left insular cortex. In the sham moment, the participants experienced 30 s of stimulation. Afterward, they performed a standardized progressive warm-up for 15 min, following the Brazilian Rowing Confederation's assessment protocols, and rested for 3 min before the test started. All procedures were made on an indoor rowing machine, which allowed the capture of performance variables such as time performed, power in watts (W), pace (m/min), and stroke rate (strokes/min). The ratings of perceived exertion [Borg scale (CR-20)] were recorded in each 2-min during the test.

Results

The results presented differences in power [Z: -2.371; p = 0.018; effect size (ES) = -0.896 (large)] and pace [Z: -2.371; p = 0.018; ES = -0.896 (large)] and time performance [Z: -1.612; p = 0.107; ES = -0.609 (large)] throughout the protocol for the anodal moment.

Discussion

However, no differences for the other variables were found. According to the results, the current tDCS with the present protocol improved the physical performance at the 2,000-m time trial Test providing ergogenic aid.

Validation of the Borg CR10 Scale for the evaluation of shoulder perceived fatigue during work-related tasks

Work-related upper extremity disorders (WRUEDs) are highly prevalent and costly. Development of fatigue is thought to be one of the causes of WRUEDs. Perceived fatigue can be assessed with the Borg CR Scale® (Borg CR10). The objective was to validate the Borg CR10 for the evaluation of shoulder perceived fatigue during lifting tasks. Seventy adults in working age performed three rhythmic lifting tasks with two loads (15% and 30% of maximal voluntary contraction). Using generalized repeated-measures ANOVA (Generalized Estimating Equations), statistically significant Task and Load effects (p < 0.001), as well as Task × Load interaction effects (p < 0.0001) were observed on Borg CR10, without any influence of sex. The Borg CR10 is a valid tool to assess shoulder perceived fatigue as it can discriminate between tasks of different difficulty levels in term of complexity, height, and resistance, regardless of sex.

Effects of carbohydrate availability on cycling endurance at the maximal lactate steady state

The impacts of carbohydrate (CHO) availability on time to task failure (TTF) and physiological responses to exercise at the maximal lactate steady state (MLSS) have not been studied. Ten participants (3 females, 7 males) completed this double-blinded, placebo-controlled study that involved a ramp incremental test, MLSS determination, and four TTF trials at MLSS, all performed on a cycle ergometer. With the use of a combination of nutritional (CHO, 7 g/kg, and placebo, PLA, 0 g/kg drinks) and exercise interventions [no exercise (REST) and glycogen-reducing exercise (EX)], the four conditions were expected to differ in preexercise CHO availability (RESTCHO > RESTPLA > EXCHO > EXPLA). TTF at MLSS was not improved by CHO loading, as RESTCHO (57.1 [16.6] min) and RESTPLA (57.1 [15.6] min) were not different (P = 1.00); however, TTF was ∼50% shorter in EX conditions compared with REST conditions on average (P < 0.05), with EXCHO (39.1 [9.2] min) ∼90% longer than EXPLA (20.6 [6.9] min; P < 0.001). There were effects of condition for all perceptual and cardiometabolic variables when compared at isotime (P < 0.05) and task failure (TF; P < 0.05), except for ventilation, perceptual responses, and neuromuscular function measures, which were not different at TF (P > 0.05). Blood lactate concentration was stable in all conditions for participants who completed 30 min of exercise. These findings indicate that TTF at MLSS is not enhanced by preexercise CHO supplementation, but recent intense exercise decreases TTF at MLSS even with CHO supplementation. Extreme fluctuations in diet and strenuous exercise that reduce CHO availability should be avoided before MLSS determination.NEW & NOTEWORTHY Carbohydrate (CHO) loading did not increase participants' ability to cycle at their maximal lactate steady state (MLSS); however, performing a glycogen depletion task the evening before cycling at MLSS reduced the time to task failure, even when paired with a high dose of CHO. These diet and exercise interventions influenced blood lactate concentration ([BLa]) but not the stability of [BLa]. Activities that reduce CHO availability should be avoided before MLSS determination.

Immediate crossover fatigue after unilateral submaximal eccentric contractions of the knee flexors involves peripheral alterations and increased global perceived fatigue

After a unilateral muscle exercise, the performance of the non-exercised contralateral limb muscle can be also impaired. This crossover fatigue phenomenon is still debated in the literature and very few studies have investigated the influence of eccentric contractions. This study was designed to assess neuromuscular adaptations involved in the crossover fatigue of the non-exercised contralateral knee flexor muscles. Seventeen healthy young men performed a unilateral submaximal eccentric exercise of the right knee flexors until a 20% reduction in maximal voluntary isometric contraction torque was attained in the exercised limb. Before (PRE), immediately after exercise cessation (POST) and 24 hours later (POST24), neuromuscular function and perceived muscle soreness were measured in both the exercised limb and non-exercised limb. In addition, global perceived fatigue was assessed at each measurement time. At POST, significant reductions in maximal voluntary isometric contraction were observed in the exercised limb (-28.1%, p < 0.001) and in the non-exercised limb (-8.5%, p < 0.05), evidencing crossover fatigue. At POST, voluntary activation decreased in the exercised limb only (-6.0%, p < 0.001), while electrically evoked potentiated doublet torque was impaired in both the exercised limb and the non-exercised limb (-11.6%, p = 0.001). In addition, global perceived fatigue significantly increased at POST (p < 0.001). At POST24, all measured variables returned to PRE values, except for perceived muscle soreness scores exhibiting greater values than PRE (p < 0.05). A possible cumulative interaction between peripheral alterations and global perceived fatigue may account for the immediate crossover fatigue observed in the non-exercised limb.

Effects of Acute Physical Fatigue on Gaze Behavior in Expert Badminton Players

Perceptual cognitive skills in real game settings, under conditions of fatigue, such as the ability to gather relevant visual information, are key factors in achieving motor goals in sports. The objectives were to evaluate the effects of acute physical fatigue on gaze behavior during a badminton game (Study 1) and in an unfavorable force ratio situation (Study 2). Six international-level badminton players played two sets and unfavorable force ratio situations while wearing eye-tracking glasses before and after a fatiguing task. During the set, fatiguing physical exercise led to fewer fixations per exchange and more fixations on one area of interest. During unfavorable force ratio situations, fatiguing physical exercise led to shorter fixation durations per exchange, shorter fixation durations on two areas of interest, and longer fixation durations on one area of interest. The results showed that gaze behaviors were adapted in acute physical fatigue conditions to maintain performance.

Thoracic-Worn Accelerometers Detect Fatigue-Related Changes in Vertical Stiffness During Sprinting

ABSTRACT

Horsley, BJ, Tofari, PJ, Halson, SL, Kemp, JG, Johnston, RD, and Cormack, SJ. Thoracic-worn accelerometers detect fatigue-related changes in vertical stiffness during sprinting. J Strength Cond Res 38(2): 283-289, 2024-Thoracic-mounted accelerometers are valid and reliable for analyzing gait characteristics and may provide the opportunity to assess running-related neuromuscular fatigue (NMF) during training and competition without the need for additional tests, such as a countermovement jump (CMJ). However, their sensitivity for detecting fatigue-related changes in gait across different speeds is unclear. We, therefore, assessed the changes in accelerometer-derived gait characteristics, including vertical stiffness (K vert ), following a repeated sprint protocol (RSP). Sixteen recreationally active subjects performed single and repeated CMJs on a force plate and 40 m run throughs overground at 3-4, 5-6, and 7-8 m·s -1 pre-post a 12 × 40 m RSP. Gait characteristics (contact time, step frequency, step length, K vert , etc.) were derived from an accelerometer contained within a global navigation satellite system unit on the thoracic spine using a validated algorithm. Changes in running gait and CMJ performance were assessed using a linear mixed-effects model (95% confidence interval [95% CI]; effect size [ES]). Significance was set at p < 0.05. A significant reduction in K vert occurred at 7-8 m·s -1 following the RSP (-8.51 kN·m -1 [-13.9, -3.11]; p = 0.007; ES [95% CI] = -0.39 [-0.62, -0.15]) which coincided with a decreased jump height (-0.03 m [-0.04, -0.01]; p = 0.002; ES [95% CI] = -0.87 [-1.41, -0.30]). However, all other gait characteristics were not significantly different irrespective of speed. Thoracic-worn accelerometers can detect changes in K vert at 7-8 m·s -1 which may be useful for monitoring NMF during sprinting. However, a RSP does not result in altered gait mechanics in subsequent running at lower speeds.

Effect of sportswear on performance and physiological heat strain during prolonged running in moderately hot conditions

INTRODUCTION

This study examined the impact of different upper-torso sportswear technologies on the performance and physiological heat strain of well-trained and national-level athletes during prolonged running in moderately hot conditions.

METHODS

A randomized crossover design was employed in which 20 well-trained (n = 16) and national-level (n = 4) athletes completed four experimental trials in moderately hot conditions (35°C, 30% relative humidity). In each trial, participants ran at 70% of their peak oxygen uptake (70% V̇O2peak ) for 60 min, while wearing a different upper-body garment: cotton t-shirt, t-shirt with sweat-wicking fabric, compression t-shirt, and t-shirt with aluminum dots lining the inside of the upper back of the garment. Running speed was adjusted to elicit the predetermined oxygen consumption associated with 70% V̇O2peak . Physiological (core and skin temperatures, total body water loss, and urine specific gravity) and perceptual (thermal comfort and sensation, ratings of perceived exertion, and garment cooling functionality) parameters along with running speed at 70% V̇O2peak were continuously recorded.

RESULTS

No significant differences were observed between the four garments for running speed at 70% V̇O2peak , physiological heat strain, and perceptual responses (all p > 0.05). The tested athletes reported larger areas of perceived suboptimal cooling functionality in the cotton t-shirt and the t-shirt with aluminum dots relative to the sweat-wicking and compression t-shirts (d: 0.43-0.52).

CONCLUSION

There were not differences among the tested garments regarding running speed at 70% V̇O2peak , physiological heat strain, and perceptual responses in well-trained and national-level endurance athletes exercising in moderate heat.

Thermoregulatory and perceptual implications of varying torso soft armour coverage during treadmill walking in dry heat

Modular armour allows soldiers to adjust the level of coverage according to the threat level. We hypothesized that armour configurations with lower levels of torso soft armour coverage attenuate physiological and perceptual responses during exercise in the heat. Fifteen adults (5 females/10 males, 26 ± 5 years) walked (5 km/h, 1% incline, 1h) in dry heat (38 °C, 20% humidity) while wearing body armour that provided; i) high coverage (HC: 0.57 ± 0.09 m2, 18.5 ± 0.3 kg), ii) moderate coverage (MC: 0.44 ± 0.07 m2, 18.1 ± 0.3 kg), iii) low coverage (LC1: 0.21 ± 0.03 m2, 17.4 ± 0.1 kg), or iv) low coverage with weight equalization (LC2: 0.21 ± 0.03 m2, 18.6 ± 0.2 kg). Core temperature (Tcore), heart rate (HR), metabolic heat production (M-W), whole-body sweat rate (WBSR), and perceptual responses were measured. M-W during exercise (629 ± 126 W) did not differ between configurations (p = 0.30). The change in Tcore (HC: 0.88 ± 0.37 °C, MC: 0.85 ± 0.32 °C, LC1: 0.91 ± 0.38 °C, LC2: 0.89 ± 0.42 °C, p = 0.93), HR (HC: 97 ± 14 bpm, MC: 103 ± 16 bpm, LC1: 96 ± 15 bpm, LC2: 97 ± 20 bpm, p = 0.08), and WBSR (HC: 10.2 ± 3.4 g/min, MC: 10.3 ± 4.3 g/min, LC1: 9.9 ± 4.7 g/min, LC2: 10.4 ± 4.5 g/min, p = 0.84) did not differ between configurations. Perceptual responses did not differ between configurations (all p ≥ 0.15). Reducing torso soft armour coverage, with minimal reductions in armour load, does not reduce physiological or perceptual strain during walking in dry heat.

The effect of transcutaneous auricular vagus nerve stimulation on cycling ergometry and recovery in healthy young individuals

BACKGROUND

It is aimed to examine the potential benefits and effects of the use of transcutaneous auricular vagus nerve stimulation (VNS) for sporting purposes on recovery, fatigue, and sportive performance level.

METHODS

In this study, 90 people between the ages of 18-23 were participated. They were randomly divided into three groups as bilateral sham, unilateral left, and bilateral VNS. A 4-day protocol was applied to the participants. Cycling exercise was performed with maximum performance for 30 min under the same watt load. Pulse, systolic and diastolic blood pressure, distance, pain, fatigue, lactic acid level, and autonomic nervous system were evaluated.

RESULTS

Within the groups, there was a statistically significant difference between the data (p < .05) except for the distance covered parameter. When we compare the groups, in addition to the distance traveled in all groups, there is no statistically significant difference in the 1st day 1st measurement and 2nd measurement data of all parameters (p > .05 When we compared the data according to days, there was a statistically significant difference between bilateral stimulation (BS) and unilateral stimulation, only pain and fatigue levels (p < .05).

CONCLUSION

In our study, we saw that BS application gave positive results in reducing pain and fatigue due to cycling exercise compared to other applications. Similar results were obtained when we evaluated the data on a daily basis. We believe that VNS will be beneficial in reducing pain and fatigue, especially during and after the competition halftime.

The influence of skeletal muscle mitochondria and sex on critical torque and performance fatiguability in humans

Critical torque (CT) represents the highest oxidative steady state for intermittent knee extensor exercise, but the extent to which it is influenced by skeletal muscle mitochondria and sex is unclear. Vastus lateralis muscle biopsy samples were collected from 12 females and 12 males -matched for relative maximal oxygen uptake normalized to fat-free mass (FFM) (F: 57.3 (7.5) ml (kg FFM)-1  min-1 ; M: 56.8 (7.6) ml (kg FFM)-1  min-1 ; P = 0.856) - prior to CT determination and performance fatiguability trials. Males had a lower proportion of myosin heavy chain (MHC) I isoform (40.6 (18.4)%) compared to females (59.5 (18.9)%; P = 0.021), but MHC IIa and IIx isoform distributions and protein markers of mitochondrial content were not different between sexes (P > 0.05). When normalized to maximum voluntary contraction (MVC), the relative CT (F: 42.9 (8.3)%; M: 37.9 (9.0)%; P = 0.172) and curvature constant, W' (F: 26.6 (11.0) N m s (N m)-1 ; M: 26.4 (6.5) N m s (N m)-1 ; P = 0.962) were not significantly different between sexes. All protein biomarkers of skeletal muscle mitochondrial content, as well as the proportion of MHC I isoform, positively correlated with relative CT (0.48 < r < 0.70; P < 0.05), and the proportion of MHC IIx isoform correlated positively with relative W' (r = 0.57; P = 0.007). Indices of performance fatiguability were not different between males and females for MVC- and CT-controlled trials (P > 0.05). Greater mitochondrial protein abundance was associated with attenuated declines in potentiated twitch torque for exercise at 60% MVC (P < 0.05); however, the influence of mitochondrial protein abundance on performance fatiguability was reduced when exercise was prescribed relative to CT. Whether these findings translate to whole-body exercise requires additional research. KEY POINTS: The quadriceps critical torque represents the highest intensity of intermittent knee extensor exercise for which an oxidative steady state is attainable, but its relationship with skeletal muscle mitochondrial protein abundance is unknown. Matching males and females for maximal oxygen uptake relative to fat-free mass facilitates investigations of sex differences in exercise physiology, but studies that have compared critical torque and performance fatiguability during intermittent knee extensor exercise have not ensured equal aerobic fitness between sexes. Skeletal muscle mitochondrial protein abundance was correlated with critical torque and fatigue resistance for exercise prescribed relative to maximum voluntary contraction but not for exercise performed relative to the critical torque. Differences between sexes in critical torque, skeletal muscle mitochondrial protein abundance and performance fatiguability were not statistically significant. Our results suggest that skeletal muscle mitochondrial protein abundance may contribute to fatigue resistance by influencing the critical intensity of exercise.

Sodium Bicarbonate Ingestion in a Fasted State Improves 16.1-km Cycling Time-Trial Performance

PURPOSE

The use of sodium bicarbonate (SB) as a preexercise ergogenic aid has been extensively studied in short-duration high-intensity exercise. Very few studies have considered the effects of SB ingestion before prolonged high-intensity exercise. The aim of the present study was to determine the effects of a 0.3 g·kg -1 body mass dose of SB ingested before the start of a 16.1-km cycling time trial in cyclists.

METHOD

Ten trained male cyclists (age, 31.1 ± 9 yr; height, 1.84 ± 0.05 m; body mass, 82.8 ± 8.5 kg; and V̇O 2peak , 60.4 ± 3.1 mL·kg -1 ·min -1 ) completed this study. Participants ingested 0.3 g·kg -1 in gelatine (SB-G) and enteric capsules (SB-E) 1 wk apart to determine individualized time-to-peak alkalosis for each ingestion form. Using a randomized crossover design, participants then performed simulated 16.1-km time trials after ingestion of SB-G, SB-E, or a placebo.

RESULTS

There were significant differences in performance between the SB and placebo ingestion strategies ( f = 5.50, P = 0.014, p η2 = 0.38). Performance time was significantly improved by SB ingestion (mean improvement: 34.4 ± 42.6 s ( P = 0.031) and 40.4 ± 45.5 s ( P = 0.020) for SB-G and SB-E, respectively) compared with the placebo. Gastrointestinal symptoms were lower after SB-E compared with SB-G (36.3 ± 4.5 vs 5.6 ± 3.1 AU, P < 0.001, g = 7.09).

CONCLUSIONS

This study demonstrates that increased buffering capacity after acute preexercise SB ingestion can improve endurance cycling time-trial performances. The use of SB could be considered for use in 16.1-km cycling time trials, but further work is required to establish these effects after a preexercise meal.

Development and validation of the pandemic fatigue scale

The existence and nature of pandemic fatigue-defined as a gradually emerging subjective state of weariness and exhaustion from, and a general demotivation towards, following recommended health-protective behaviors, including keeping oneself informed during a pandemic-has been debated. Herein, we introduce the Pandemic Fatigue Scale and show how pandemic fatigue evolved during the COVID-19 pandemic, using data from one panel survey and two repeated cross-sectional surveys in Denmark and Germany (overall N = 34,582). We map the correlates of pandemic fatigue and show that pandemic fatigue is negatively related to people's self-reported adherence to recommended health-protective behaviors. Manipulating the (de)motivational aspect of pandemic fatigue in a preregistered online experiment (N = 1584), we further show that pandemic fatigue negatively affects people's intention to adhere to recommended health-protective behaviors. Combined, these findings provide evidence not only for the existence of pandemic fatigue, but also its psychological and behavioral associations.

Effects of different cluster-set rest intervals during plyometric-jump training on measures of physical fitness: A randomized trial

The optimal intra-set rest for cluster sets (CLS) during plyometric-jump training (PJT) to improve physical fitness remains unclear. The objective of this quasi-experimental study was to compare the effects of PJT with traditional (TRS) vs. CLS structures, using different intra-set rests, on the physical fitness of healthy participants. Forty-seven recreationally active young men performed 3-5 sets of 10-12 repetitions of upper- and lower-body PJT exercises twice a week for six weeks using different set configurations: TRS group (no intra-set rest), and the CLS10, CLS20 and CLS30 groups with 10, 20 and 30 s of intra-set rest, respectively, while the total rest period was equated. Pretest-posttest measurements were carried out 48 h before and after the intervention and the rating of fatigue (ROF) was also assessed using a numerical scale (0-10 points) 20 min after the first and last (i.e., 12th) session. There was no significant difference in the mean energy intake between groups (p > 0.05). The repeated measures ANOVA revealed that all groups showed similar improvements (p < 0.05) in body mass, body mass index, fat-free mass, one repetition maximum (dynamic strength) and repetitions to failure (muscular endurance) in back squat and chest press, handgrip strength, standing long jump, 20 m sprint, 9-m shuttle run (change of direction speed), and ROF. Of note, the ROF was lower for the CLS20 and CLS30 groups, independent from the training effect. The physical fitness of recreationally active young men improved after 6 weeks of PJT involving intra-set rest intervals of 0 s, 10 s, 20 s, or 30 s. However, an intra-set rest of 20 s and 30 s seems to induce lower exercise-induced fatigue perception.

Beyond the Lungs: O 2 Supplementation Improves Cerebral Oxygenation and Fatigue during Exercise in Interstitial Lung Disease

PURPOSE

Cerebral hypoxia may exacerbate the perception of fatigue. We previously demonstrated that exercise-related hypoxemia, a hallmark of fibrotic interstitial lung disease ( f -ILD), dose dependently impairs cerebral oxygenation in these patients. It is unknown whether normalizing cerebral oxygenation with O 2 supplementation would be associated with positive changes in a relevant patient-centered outcome during exercise in f -ILD, such as improved perceived fatigue.

METHODS

Fourteen patients (12 males, 72 ± 8 yr, 8 with idiopathic pulmonary fibrosis, lung diffusing capacity for carbon monoxide = 44% ± 13% predicted) performed a constant-load (60% peak work rate) cycle test to symptom limitation (Tlim) breathing medical air. Fourteen controls cycled up to Tlim of an age- and sex-matched patient. Patients repeated the test on supplemental O 2 (fraction of inspired O 2 = 0.41 ± 0.08) for the same duration. Near-infrared spectroscopy and the rating-of-fatigue (ROF) scale assessed prefrontal cortex oxygenation and perceived fatigue, respectively.

RESULTS

Patients showed severe exertional hypoxemia (Tlim O 2 saturation by pulse oximetry = 80% ± 8%); they had poorer cerebral oxygenation (e.g., oxy-deoxyhemoglobin difference [HbDiff] = -3.5 ± 4.7 [range = -17.6 to +1.9] vs +1.9 ± 1.7 μmol from rest) and greater fatigue (ROF = 6.2 ± 2.0 vs 2.6 ± 2.3) versus controls under air ( P < 0.001). Reversal of exertional hypoxemia with supplemental O 2 led to improved HbDiff (+1.7 ± 2.4 μmol from rest; no longer differing from controls) and lower ROF scores (3.7 ± 1.2, P < 0.001 vs air) in patients. There was a significant correlation between O 2 -induced changes in HbDiff and ROF scores throughout exercise in f -ILD ( rrepeated-measures correlation = -0.51, P < 0.001).

CONCLUSIONS

Supplemental O 2 improved cerebral oxygenation during exercise in f -ILD, which was moderately associated with lower ratings of perceived fatigue. Reversing cerebral hypoxia with O 2 supplementation may thus have positive effects on patients' disablement beyond those expected from lower ventilation and dyspnea in this patient population.