Physiological changes in male competitive cyclists after two weeks of intensified training

Environmental heat stress offsets adaptation associated with carbohydrate periodization in trained male triathletes

PURPOSE

Carbohydrate (CHO) intake periodization via the sleep low train low (SL-TL) diet-exercise model increases fat oxidation during exercise and may enhance endurance-training adaptation and performance. Conversely, training under environmental heat stress increases CHO oxidation, but the potential of combined SL-TL and heat stress to enhance metabolic and performance outcomes is unknown.

METHODS

Twenty-three endurance-trained males were randomly assigned to either control (n = 7, CON), SL-TL (n = 8, SLTemp ) or SL-TL + heat stress (n = 8, SLHeat ) groups and prescribed identical 2-week cycling training interventions. CON and SLTemp completed all sessions at 20°C, but SLHeat at 35°C. All groups consumed matched CHO intake (6 g·kg-1 ·day-1 ) but timed differently to promote low CHO availability overnight and during morning exercise in both SL groups. Submaximal substrate utilization was assessed (at 20°C), and 30-min performance tests (at 20 and 35°C) were performed Pre-, Post-, and 1-week post-intervention (Post+1).

RESULTS

SLTemp improved fat oxidation rates at 60% MAP (~66% VO2peak ) at Post+1 compared with CON (p < 0.01). Compared with SLTemp , fat oxidation rates were significantly lower in SLHeat at Post (p = 0.02) and Post+1 (p < 0.05). Compared with CON, performance was improved at Post in SLTemp in temperate conditions. Performance was not different between any groups or time points in hot conditions.

CONCLUSION

SL-TL enhanced metabolic adaptation and performance compared with CON and combined SL-TL and heat stress. Additional environmental heat stress may impair positive adaptations associated with SL-TL.

Aerobic Training With Blood Flow Restriction for Endurance Athletes: Potential Benefits and Considerations of Implementation

ABSTRACT

Smith, NDW, Scott, BR, Girard, O, and Peiffer, JJ. Aerobic training with blood flow restriction for endurance athletes: potential benefits and considerations of implementation. J Strength Cond Res 36(12): 3541-3550, 2022-Low-intensity aerobic training with blood flow restriction (BFR) can improve maximal oxygen uptake, delay the onset of blood lactate accumulation, and may provide marginal benefits to economy of motion in untrained individuals. Such a training modality could also improve these physiological attributes in well-trained athletes. Indeed, aerobic BFR training could be beneficial for those recovering from injury, those who have limited time for training a specific physiological capacity, or as an adjunct training stimulus to provide variation in a program. However, similarly to endurance training without BFR, using aerobic BFR training to elicit physiological adaptations in endurance athletes will require additional considerations compared with nonendurance athletes. The objective of this narrative review is to discuss the acute and chronic aspects of aerobic BFR exercise for well-trained endurance athletes and highlight considerations for its effective implementation. This review first highlights key physiological capacities of endurance performance. The acute and chronic responses to aerobic BFR exercise and their impact on performance are then discussed. Finally, considerations for prescribing and monitoring aerobic BFR exercise in trained endurance populations are addressed to challenge current views on how BFR exercise is implemented.

A Simple Model for Diagnosis of Maladaptations to Exercise Training

Background

The concept of overreaching and super compensation is widely in use by athletes and coaches seeking to maximize performance and adaptations to exercise training. The physiological aspects of acute fatigue, overreaching and non-functional overreaching are, however, not well understood, and well-defined negative physiological outcomes are missing. Instead, the concept relies heavily on performance outcomes for differentiating between the states. Recent advancements in the field of integrated exercise physiology have associated maladaptations in muscular oxidative function to high loads of exercise training.

Method

Eleven female and male subjects that exercised regularly but did not engage in high-intensity interval training (HIIT) were recruited to a 4-week long training intervention where the responses to different training loads were studied. Highly monitored HIIT sessions were performed on a cycle ergometer in a progressive fashion with the intent to accomplish a training overload. Throughout the intervention, physiological and psychological responses to HIIT were assessed, and the results were used to construct a diagnostic model that could indicate maladaptations during excessive training loads.

Results

We here use mitochondrial function as an early marker of excessive training loads and show the dynamic responses of several physiological and psychological measurements during different training loads. During HIIT, a loss of mitochondrial function was associated with reduced glycolytic, glucoregulatory and heart rate responses and increased ratings of perceived exertion in relation to several physiological measurements. The profile of mood states was highly affected after excessive training loads, whereas performance staled rather than decreased. By implementing five of the most affected and relevant measured parameters in a diagnostic model, we could successfully, and in all the subjects, identify the training loads that lead to maladaptations.

Conclusions

As mitochondrial parameters cannot be assessed without donating a muscle biopsy, this test can be used by coaches and exercise physiologists to monitor adaptation to exercise training for improving performance and optimizing the health benefits of exercise.

Clinical trial registry numberNCT04753021. Retrospectively registered 2021-02-12.

A 6-day high-intensity interval microcycle improves indicators of endurance performance in elite cross-country skiers

Purpose

The aim of this study was to compare the effects of a 6-day high-intensity interval (HIT) block [BLOCK, n = 12, maximal oxygen uptake (V̇O2max = 69. 6 ± 4.3 mL·min−1·kg−1)] with a time-matched period with usual training (CON, n = 12, V̇O2max = 69.2 ± 4.2 mL·min−1·kg−1) in well-trained cross-country (XC) skiers on physiological determinants and indicators of endurance performance. Furthermore, the study aimed to investigate the acute physiological responses, including time ≥90% of V̇O2max, and its associated reliability during repeated HIT sessions in the HIT microcycle.

Methods

Before the 6-day HIT block and following 5 days of recovery after the HIT block, both groups were tested on indicators of endurance performance. To quantify time ≥90% of V̇O2max during interval sessions in the HIT block, V̇O2 measurements were performed on the 1st, 2nd, and last HIT session in BLOCK.

Results

BLOCK had a larger improvement than CON in maximal 1-min velocity achieved during the V̇O2max test (3.1 ± 3.1% vs. 1.2 ± 1.6%, respectively; p = 0.010) and velocity corresponding to 4 mmol·L−1 blood lactate (3.2 ± 2.9% vs. 0.6 ± 2.1%, respectively; p = 0.024). During submaximal exercise, BLOCK displayed a larger reduction in respiratory exchange ratio, blood lactate concentration, heart rate, and rate of perceived exertion (p &lt; 0.05) and a tendency towards less energy expenditure compared to CON (p = 0.073). The ICC of time ≥90% V̇O2max in the present study was 0.57, which indicates moderate reliability.

Conclusions

In well-trained XC skiers, BLOCK induced superior changes in indicators of endurance performance compared with CON, while time ≥90% of V̇O2max during the HIT sessions in the 6-day block had a moderate reliability.

Four Weeks of Intensified Training Enhances On-Ice Intermittent Exercise Performance and Increases Maximal Oxygen Consumption of Youth National-Team Ice Hockey Players

PURPOSE

We investigated whether 4 weeks of intensified training consisting of speed endurance training (SET) enhanced high-intensity exercise performance in youth national-team ice hockey players.

METHODS

Utilizing a randomized crossover design, we subjected 17 players to 4 weeks of SET, comprising 6 to 10 × 20 seconds at maximal effort (>95% maximum ice skating speed) with 120-second recovery performed 3 times weekly, or maintenance of regular training (control period). Before and after each period, players completed ice-hockey-specific tests on ice, including a Yo-Yo Intermittent Recovery Level 1 test, a 30-m sprint test, and an agility test. On a separate day, players were assessed for body composition with dual-energy X-ray absorptiometry and performed countermovement jump, maximal voluntary isometric knee extensor contraction, a 15-second maximal sprint test, and a submaximal and incremental test on a bike ergometer in which pulmonary oxygen consumption was determined.

RESULTS

Yo-Yo Intermittent Recovery Level 1 test performance increased (P < .001) by 14% (95% CI, 201-496 m) during the SET period. Maximal pulmonary oxygen consumption (P < .05) and time to exhaustion (P < .05) were 4.8% and 6.5% higher, respectively, after the SET period than before. Fat-free mass increased (P < .01) during the SET period by 1.7 kg (95% CI, 1.0-2.5), whereas fat mass remained unchanged. These effects were superior to the control period.

CONCLUSIONS

These findings underpin the effectiveness of SET for improving on-ice high-intensity performance and highlight that elite ice hockey players can benefit from implementing SET.

Effect of Intensified Training on Cognitive Function, Psychological State & Performance in Trained Cyclists

AbstractAthletes often undertake intensified training loads prior to competition with the goal of functionally overreaching for temporary performance enhancement; however, little is known about the impact of this on cognitive function. The aim of this study was to investigate the effect of intensified training-induced fatigue on cognitive function, psychological state, and performance in trained cyclists. Twenty-three trained male cyclists were randomly assigned to an intensified training group or a control group for two-weeks, followed by a two-week taper period. At baseline, one-week, two-weeks and post-taper, participants undertook a series of cognitive, performance, mood, and recovery-stress assessments. The training intervention significantly increased training volume, load, and strain by 108%, 116% and 151% respectively. Peak and mean power output on a maximal test and time trial significantly decreased by 4.8% and 9.4% following the two-week training intervention compared to baseline, in addition to a 169% change in total mood disturbance and significant disruption to recovery-stress balance. No change in any cognitive measure was observed across the study period. Following a two-week taper, performance, mood, and well-being measures returned to baseline. Two weeks of intensified training resulted in overreaching as identified by performance and psychological measures. Cognitive function was not sensitive to intensified training promoting caution with its use as a measure for the early identification of overreaching.

Evaluation of nocturnal vs. morning measures of heart rate indices in young athletes

Purpose

The purpose of this study was to compare heart rate (HR) and heart rate variability in young endurance athletes during nocturnal sleep and in the morning; and to assess whether changes in these values are associated with changes in submaximal running (SRT) and counter-movement jump (CMJ) performance.

Methods

During a three-week period of similar training, eleven athletes (16 ± 1 years) determined daily HR and heart rate variability (RMSSD) during sleep utilizing a ballistocardiographic device (Emfit QS), as well as in the morning with a HR monitor (Polar V800). Aerobic fitness and power production were assessed employing SRT and CMJ test.

Results

Comparison of the average values for week 1 and week 3 revealed no significant differences with respect to nocturnal RMSSD (6.8%, P = 0.344), morning RMSSD (13.4%, P = 0.151), morning HR (-3.9 bpm, P = 0.063), SRT HR (-0.7 bpm, P = 0.447), SRT blood lactate (4.9%, P = 0.781), CMJ (-4.2%, P = 0.122) or training volume (16%, P = 0.499). There was a strong correlation between morning and nocturnal HRs during week 1 (r = 0.800, P = 0.003) and week 3 (r = 0.815, P = 0.002), as well as between morning and nocturnal RMSSD values (for week 1, r = 0.895, P<0.001 and week 3, r = 0.878, P = 0.001).

Conclusion

This study concluded that HR and RMSSD obtained during nocturnal sleep and in the morning did not differ significantly. In addition, weekly changes in training and performance were small indicating that fitness was similar throughout the 3-week period of observation. Consequently, daily measurement of HR indices during nocturnal sleep provide a potential tool for long-term monitoring of young endurance athletes.

Self-Paced Cycling at the Highest Sustainable Intensity With Blood Flow Restriction Reduces External but Not Internal Training Loads

Purpose: This study compared training loads and internal:external load ratios from an aerobic interval session at the highest perceptually sustainable intensity with and without blood flow restriction (BFR). Methods: On separate days, 14 endurance cyclists/triathletes completed four 4-minute self-paced aerobic cycling intervals at their highest sustainable intensity, with and without BFR (60% of arterial occlusion pressure). Internal training load was quantified using 3 training impulses (TRIMP; Banister, Lucia, and Edwards) and sessional ratings of perceived exertion. External load was assessed using total work done (TWD). Training load ratios between all internal loads were calculated relative to TWD. Results: Lucia TRIMP was lower for the BFR compared with non-BFR session (49 [9] vs 53 [8] arbitrary units [au], P = .020, dz = −0.71). No between-conditions differences were observed for Banister TRIMP (P = .068), Edwards TRIMP (P = .072), and training load in sessional ratings of perceived exertion (P = .134). The TWD was lower for the BFR compared with non-BFR session (223 [52] vs 271 [58] kJ, P < .001, dz = −1.27). Ratios were greater for the BFR session compared with non-BFR for Lucia TRIMP:TWD (0.229 [0.056] vs 0.206 [0.056] au, P < .001, dz = 1.21), Edwards TRIMP:TWD (0.396 [0.105] vs 0.370 [0.088] au, P = .031, dz = 0.66), and training load in sessional ratings of perceived exertion:TWD (1.000 [0.266] vs 0.890 [0.275] au, P = .044, dz = 0.60), but not Banister TRIMP:TWD (P = .306). Conclusions: Practitioners should consider both internal and external loads when monitoring BFR exercise to ensure the demands are appropriately captured. These BFR-induced changes were reflected by the Lucia TRIMP:TWD and Edwards TRIMP:TWD ratio, which could be used to monitor aerobic BFR training loads. The Lucia TRIMP:TWD ratio likely represents BFR-induced changes more appropriately compared with ratios involving either Edwards or Banister TRIMP.

Submaximal Fitness Tests in Team Sports: A Theoretical Framework for Evaluating Physiological State

Team-sports staff often administer non-exhaustive exercise assessments with a view to evaluating physiological state, to inform decision making on athlete management (e.g., future training or recovery). Submaximal fitness tests have become prominent in team-sports settings for observing responses to a standardized physical stimulus, likely because of their time-efficient nature, relative ease of administration, and physiological rationale. It is evident, however, that many variations of submaximal fitness test characteristics, response measures, and monitoring purposes exist. The aim of this scoping review is to provide a theoretical framework of submaximal fitness tests and a detailed summary of their use as proxy indicators of training effects in team sports. Using a review of the literature stemming from a systematic search strategy, we identified five distinct submaximal fitness test protocols characterized in their combinations of exercise regimen (continuous or intermittent) and the progression of exercise intensity (fixed, incremental, or variable). Heart rate-derived indices were the most studied outcome measures in submaximal fitness tests and included exercise (exercise heart rate) and recovery (heart rate recovery and vagal-related heart rate variability) responses. Despite the disparity between studies, these measures appear more relevant to detect positive chronic endurance-oriented training effects, whereas their role in detecting negative transient effects associated with variations in autonomic nervous system function is not yet clear. Subjective outcome measures such as ratings of perceived exertion were less common in team sports, but their potential utility when collected alongside objective measures (e.g., exercise heart rate) has been advocated. Mechanical outcome measures either included global positioning system-derived locomotor outputs such as distance covered, primarily during standardized training drills (e.g., small-sided games) to monitor exercise performance, or responses derived from inertial measurement units to make inferences about lower limb neuromuscular function. Whilst there is an emerging interest regarding the utility of these mechanical measures, their measurement properties and underpinning mechanisms are yet to be fully established. Here, we provide a deeper synthesis of the available literature, culminating with evidence-based practical recommendations and directions for future research.

What Is behind Changes in Resting Heart Rate and Heart Rate Variability? A Large-Scale Analysis of Longitudinal Measurements Acquired in Free-Living

The aim of this study was to investigate the relationship between heart rate and heart rate variability (HRV) with respect to individual characteristics and acute stressors. In particular, the relationship between heart rate, HRV, age, sex, body mass index (BMI), and physical activity level was analyzed cross-sectionally in a large sample of 28,175 individuals. Additionally, the change in heart rate and HRV in response to common acute stressors such as training of different intensities, alcohol intake, the menstrual cycle, and sickness was analyzed longitudinally. Acute stressors were analyzed over a period of 5 years for a total of 9 million measurements (320±374 measurements per person). HRV at the population level reduced with age (p < 0.05, r = -0.35, effect size = moderate) and was weakly associated with physical activity level (p < 0.05, r = 0.21, effect size = small) and not associated with sex (p = 0.35, d = 0.02, effect size = negligible). Heart rate was moderately associated with physical activity level (p < 0.05, r = 0.30, effect size = moderate) and sex (p < 0.05, d = 0.63, effect size = moderate) but not with age (p = 0.35, r = -0.01). Similar relationships between BMI, resting heart rate (p < 0.05, r = 0.19, effect size = small), and HRV (p < 0.05, r = -0.10, effect size = small) are shown. In response to acute stressors, we report a 4.6% change in HRV (p < 0.05, d = 0.36, effect size = small) and a 1.3% change in heart rate (p < 0.05, d = 0.38, effect size = small) in response to training, a 6% increase in heart rate (p < 0.05, d = 0.97, effect size = large) and a 12% reduction in HRV (p < 0.05, d = 0.55, effect size = moderate) after high alcohol intake, a 1.6% change in heart rate (p < 0.05, d = 1.41, effect size = large) and a 3.2% change in HRV (p < 0.05, d = 0.80, effect size = large) between the follicular and luteal phases of the menstrual cycle, and a 6% increase in heart rate (p < 0.05, d = 0.97, effect size = large) and 10% reduction in HRV (p < 0.05, d = 0.47, effect size = moderate) during sickness. Acute stressors analysis revealed how HRV is a more sensitive but not specific marker of stress. In conclusion, a short resting heart rate and HRV measurement upon waking using a smartphone app can effectively be used in free-living to quantify individual stress responses across a large range of individuals and stressors.

Effects of Including Sprints in LIT Sessions during a 14-d Camp on Muscle Biology and Performance Measures in Elite Cyclists

PURPOSE

This study investigated the effects of including sprints within low-intensity training (LIT) sessions during a 14-d training camp focusing on LIT, followed by 10-d recovery (Rec), on performance and performance-related measures in elite cyclists.

METHODS

During the camp, a sprint training group (SPR; n = 9) included 12 × 30-s maximal sprints during five LIT sessions, whereas a control group (CON; n = 9) performed distance-matched LIT only. Training load was equally increased in both groups by 48% ± 27% during the training camp and subsequently decreased by -56% ± 23% during the recovery period compared with habitual training. Performance tests were conducted before the training camp (Pre) and after Rec. Muscle biopsies, hematological measures, and stress/recovery questionnaires were collected Pre and after the camp (Post).

RESULTS

Thirty-second sprint (SPR vs CON: 4% ± 4%, P < 0.01) and 5-min mean power (SPR vs CON: 4% ± 8%, P = 0.04) changed differently between groups. In muscle, Na+-K+ β1 protein content changed differently between groups, decreasing in CON compared with SPR (-8% ± 14%, P = 0.04), whereas other proteins showed similar changes. SPR and CON displayed similar increases in red blood cell volume (SPR: 2.6% ± 4.7%, P = 0.07; CON: 3.9% ± 4.5%, P = 0.02) and V˙O2 at 4 mmol·L-1 [BLa-] (SPR: 2.5% ± 3.3%, P = 0.03; CON: 2.2% ± 3.0%, P = 0.04). No changes were seen for V˙O2max, Wmax, hematological measures, muscle enzyme activity, and stress/recovery measures.

CONCLUSIONS

Inclusion of 30-s sprints within LIT sessions during a high-volume training camp affected competition-relevant performance measures and Na+-K+ β1 protein content differently from LIT only, without affecting sport-specific stress/recovery or any other physiological measure in elite cyclists.

Behaviour of salivary testosterone and cortisol in men during an Ironman Triathlon

Endurance exercise induces notable acute hormonal responses on the gonadal and adrenal hormones. The purpose of this study was to assess the changes in salivary testosterone (Ts), salivary cortisol (Cs) and T/C ratio during long-distance triathlon. Ten well-trained male triathletes participated in the study and were assessed for hormonal changes at four time-points (pre-competition, post-swimming, post-cycling, and post-running phases). Ts decreased from pre-competition to post-swimming (from 93.37 pg/mL to 57.63 pg/mL; p < .01) and increased during two other parts of the competition to almost pre-competition values (cycling: 79.20 pg/mL, p = .02; running: 89,66 pg/mL, p = .04, respectively). Cs showed a similar behaviour; decreasing in the post-swimming phase (1.74 pg/mL) and increasing in the other transitions (post-cycling: 7.30 pg/mL; post-running: 13.31 pg/mL), with significant differences between pre-competition and post- competition values (p = .01). Conversely, T/C increased significantly from pre-competition to post-swimming phase (p = .04) to later decrease until the end of the competition. Overall, T/C significantly decreased (p < .05). In conclusion, during an Ironman triathlon, hormone values fluctuate in response to the demands of the competition. Ts and Cs decrease after-swimming, increase after-cycling and reach the maximum values after-running. T/C reflects overall catabolic status.

Overtraining Syndrome (OTS) and Relative Energy Deficiency in Sport (RED-S): Shared Pathways, Symptoms and Complexities

The symptom similarities between training-overload (with or without an Overtraining Syndrome (OTS) diagnosis) and Relative Energy Deficiency in Sport (RED-S) are significant, with both initiating from a hypothalamic-pituitary origin, that can be influenced by low carbohydrate (CHO) and energy availability (EA). In this narrative review we wish to showcase that many of the negative outcomes of training-overload (with, or without an OTS diagnosis) may be primarily due to misdiagnosed under-fueling, or RED-S, via low EA and/or low CHO availability. Accordingly, we undertook an analysis of training-overload/OTS type studies that have also collected and analyzed for energy intake (EI), CHO, exercise energy expenditure (EEE) and/or EA. Eighteen of the 21 studies (86%) that met our criteria showed indications of an EA decrease or difference between two cohorts within a given study (n = 14 studies) or CHO availability decrease (n = 4 studies) during the training-overload/OTS period, resulting in both training-overload/OTS and RED-S symptom outcomes compared to control conditions. Furthermore, we demonstrate significantly similar symptom overlaps across much of the OTS (n = 57 studies) and RED-S/Female Athlete Triad (n = 88 studies) literature. It is important to note that the prevention of under-recovery is multi-factorial, but many aspects are based around EA and CHO availability. Herein we have demonstrated that OTS and RED-S have many shared pathways, symptoms, and diagnostic complexities. Substantial attention is required to increase the knowledge and awareness of RED-S, and to enhance the diagnostic accuracy of both OTS and RED-S, to allow clinicians to more accurately exclude LEA/RED-S from OTS diagnoses.

Heart rate-based indices to detect parasympathetic hyperactivity in functionally overreached athletes. A meta-analysis

Investigations into the sensitivity of heart rate-(HR) derived indices for tracking parasympathetic nervous system (PNS) changes in functionally overreached (F-OR) endurance-trained athletes have produced equivocal findings. Lack of clarity may be a result of methodological inconsistencies. Therefore, the aims of this systematic review and meta-analysis were (a) to determine the sensitivity of resting and post-exercise vagal-related HR variability (HRV) and HR recovery (HRR) indices to detect PNS modulation in F-OR and non-overreached (non-OR) athletes, and (b) to investigate the influence of methodological factors on the sensitivity of HR-based indices to detect PNS hyperactivity in F-OR athletes. We searched CENTRAL, Scopus, PubMed, Embase, and Web of Science up to May 2020 for the following terms: male and female endurance-trained athletes, controlled and uncontrolled studies that carried out an overload training period, and PNS modulation measured in resting and post-exercise, pre- and post-overload training period. A random-effects model of standardized mean difference (SMD) was estimated for each outcome measure based on the training-induced fatigue status (F-OR vs non-OR athletes), and the influence of methodological issues to detect PNS hyperactivity in F-OR was assessed by subgroup analyses. Pooled analysis showed that resting vagal-related HRV indices did not detect PNS hyperactivity in F-OR athletes (SMD₊ = -0.01; 95% confidence interval [CI] = -0.51, 0.50), and no statistical difference (P = .600) was found with non-OR athletes (SMD₊ = 0.15; 95% CI = -0.14, 0.45). However, subgroup analysis based on HRV parameter showed a moderate statistical increase in weekly averaged HRV in F-OR athletes (SMD₊ = 0.81; 95% CI = 0.35, 1.26), while isolated HRV values did not reach statistical significance (SMD₊ = -0.45; 95% CI = -0.96, 0.06). We observed a moderate and statistically significant increase in HRR indices among F-OR athletes (SMD₊ = 0.65; 95% CI = 0.44, 0.87), no changes for non-OR athletes (SMD₊ = 0.10; 95% CI = -0.15, 0.34), and statistically significant differences between F-OR and non-OR athletes (P < .001). Insufficient data prevented meta-analysis for post-exercise vagal-related HRV indices. Our findings show that when methodological factors are considered, HR-based indices are sensitive to increased PNS modulation in F-OR.

Overtraining Syndrome as a Complex Systems Phenomenon

The phenomenon of reduced athletic performance following sustained, intense training (Overtraining Syndrome, and OTS) was first recognized more than 90 years ago. Although hundreds of scientific publications have focused on OTS, a definitive diagnosis, reliable biomarkers, and effective treatments remain unknown. The present review considers existing models of OTS, acknowledges the individualized and sport-specific nature of signs/symptoms, describes potential interacting predisposing factors, and proposes that OTS will be most effectively characterized and evaluated via the underlying complex biological systems. Complex systems in nature are not aptly characterized or successfully analyzed using the classic scientific method (i.e., simplifying complex problems into single variables in a search for cause-and-effect) because they result from myriad (often non-linear) concomitant interactions of multiple determinants. Thus, this review 1) proposes that OTS be viewed from the perspectives of complex systems and network physiology, 2) advocates for and recommends that techniques such as trans-omic analyses and machine learning be widely employed, and 3) proposes evidence-based areas for future OTS investigations, including concomitant multi-domain analyses incorporating brain neural networks, dysfunction of hypothalamic-pituitary-adrenal responses to training stress, the intestinal microbiota, immune factors, and low energy availability. Such an inclusive and modern approach will measurably help in prevention and management of OTS.

Urinary Catecholamines as Markers in Overtraining Syndrome

In this study, potential urinary markers that show the presence of overtraining syndrome (OTS) were investigated. After a hard training period without an optimal recovery, OTS could appear in athletes. This syndrome could result in a decreasing of performance, a state of chronic fatigue and a not well-being state. The search for markers that demonstrate the presence of OTS could prevent the physiological and psychological health of the athletes, improving the performance.In this chapter, we will analyze some studies that have examined biochemical, physiological, and immunological markers of overtraining in urine and the variation of the catecholamines in a situation of stressed training.

Monitoring training and recovery responses with heart rate measures during standardized warm-up in elite badminton players

Purpose

To investigate short-term training and recovery-related effects on heart rate during a standardized submaximal running test.

Methods

Ten elite badminton players (7 females and 3 males) were monitored during a 12-week training period in preparation for the World Championships. Exercise heart rate (HRex) and perceived exertion were measured in response to a 5-min submaximal shuttle-run test during the morning session warm-up. This test was repeatedly performed on Mondays after 1–2 days of pronounced recovery (‘recovered’ state; reference condition) and on Fridays following 4 consecutive days of training (‘strained’ state). In addition, the serum concentration of creatine kinase and urea, perceived recovery–stress states, and jump performance were assessed before warm-up.

Results

Creatine kinase increased in the strained compared to the recovered state and the perceived recovery–stress ratings decreased and increased, respectively (range of average effects sizes: |d| = 0.93–2.90). The overall HRex was 173 bpm and the observed within-player variability (i.e., standard deviation as a coefficient of variation [CV]) was 1.3% (90% confidence interval: 1.2% to 1.5%). A linear reduction of -1.4% (-3.0% to 0.3%) was observed in HRex over the 12-week observational period. HRex was -1.5% lower (-2.2% to -0.9%) in the strained compared to the recovered state, and the standard deviation (as a CV) representing interindividual variability in this response was 0.7% (-0.6% to 1.2%).

Conclusions

Our findings suggest that HRex measured during a standardized warm-up can be sensitive to short-term accumulation of training load, with HRex decreasing on average in response to consecutive days of training within repeated preparatory weekly microcycles. From a practical perspective, it seems advisable to determine intra-individual recovery–strain responses by repeated testing, as HRex responses may vary substantially between and within players.

A Non-Framework Multilevel Surgery May Reduce Mean Heart Rate in Patients with Very Severe Obstructive Apnea Having Confined Retroglossal Space and Framework

An elevated mean heart rate in untreated patients of obstructive sleep apnea (OSA) may lead to a higher risk of mortality and the development of various cardiovascular diseases. The elevation may positively relate to the severity of OSA and present in both wakefulness and sleep. A reduction in heart rate has been presented in reports of treating OSA patients with continuous positive airway pressure (CPAP). However, patients with very severe OSA may refuse use of CPAP devices and advocated surgeries, such as direct skeletal surgery or tracheostomy. It is unclear whether the non-framework multilevel surgery we reported previously can overcome the unfavorable anatomy and reduce mean heart rate, which serves as a risk factor of mortality. Here, we show that multilevel surgery reduced the mean heart rate from 68.6 to 62.7 with a mean reduction of 5.9 beats/min. The results suggest that the surgery may reduce the risk of consequences and mortality associated with an elevated mean heart rate, such as various cardiovascular diseases. We disclose these findings, along with the variations and possible risks to our future patients with very severe OSA who refuse or cannot use a CPAP device or reject direct skeletal surgery.

Effects of Two Different Tapering Protocols on Fitness and Physical Match Performance in Elite Junior Soccer Players

Krespi, M, Sporiš, G, and Trajković, N. Effects of two different tapering protocols on fitness and physical match performance in elite junior soccer players. J Strength Cond Res 34(6): 1731-1740, 2020-The purpose of this study was to determine the effects of 2 different tapering protocols on fitness and physical match performance in elite junior soccer players. One-hundred fifty-eight elite junior soccer players (mean age: 17.1 ± 0.79 years; mean height: 177.9 ± 6.64 cm; mean body mass: 71.3 ± 7.96 kg; and mean body mass index: 22.5 ± 1.66 kg·m) were randomly assigned to 2 groups: an exponential (n = 79) and a linear tapering (n = 79) group. Training sessions were conducted 3 times per week for 8 weeks. After 4 weeks of training and 4 weeks of tapering, participants were assessed in terms of body composition, physical fitness, and distance covered within a match. Both groups showed similar changes for body composition. The exponential group showed better improvement than the linear group in the 5- and 30-m sprints, countermovement jump, and V[Combining Dot Above]O2max (p < 0.05). The exponential tapering group had larger changes (p < 0.05) than the linear group in medium running (8-13 km·h) (6%; effect size = 0.26 compared with 5.5%; effect size = 0.22) and sprinting (>18 km·h) (26%; effect size = 0.72 compared to 21.7%; effect size = 0.60). The results show that exponential tapering produced better effects on speed, power, and endurance abilities than the linear protocol. Our results confirmed the reports of others that suggest that volume is the optimal variable to manipulate while maintaining both the intensity and the frequency of sessions.

Evaluation of a rat model of exercise-induced fatigue using treadmill running with progressively increasing load

The mechanism behind exercise-induced fatigue is a significant topic in the field of sports physiology. Therefore, establishing and evaluating an acute exercise-induced fatigue animal model that explores the limits of the motor system may provide greater insight into these mechanisms. Heart rate is an important quantitative parameter that accurately reflects the immediate change in physical function due to exercise load. And there is likely to be an important correlation between heart rate and behavioral performance. In this study, changes in heart rate and behavioral indexes during exercise-induced fatigue were quantitatively analyzed in rats using heart rate telemetry and video methods respectively. The behavioral indexes were used as independent variables and the degree of fatigue was used as the forecast value. Ternary quadratic function curve fitting was used to deduce a formula to calculate a fatigue score: Y = 15.2548+0.4346∙xa-0.1154∙xb+0.6826∙xc+0.0044∙xa∙xb-0.0021∙xb∙xc-0.0013∙xc∙xa-0.0023∙xa2-0.0016∙xb2 (r2=0.906). It identified a linear relationship between heart rate and exercise intensity, with a plateau in heart rate occurring during difference periods. It will serve as an effective reference for the modeling of exercise-induced fatigue. In addition, it also provides a theoretical method for analyzing the correlation between peripheral and central parameters.

The Influence of Exercise Intensity on the Association Between Kilojoules Spent and Various Training Loads in Professional Cycling

Purpose: A valid measure for training load (TL) is an important tool for cyclists, trainers, and sport scientists involved in professional cycling. The aim of this study was to explore the influence of exercise intensity on the association between kilojoules (kJ) spent and different measures of TL to arrive at valid measures of TL. Methods: Four years of field data were collected from 21 cyclists of a professional cycling team, including 11,716 training and race sessions. kJ spent was obtained from power output measurements, and others TLs were calculated based on the session rating of perceived exertion (sRPE), heart rate (Lucia training impulse [luTRIMP]), and power output (training stress score [TSS]). Exercise intensity was expressed by the intensity factor (IF). To study the effect of exercise intensity on the association between kJ spent and various other TLs (sRPE, luTRIMP, and TSS), data from low- and high-intensity sessions were subjected to regression analyses using generalized estimating equations. Results: This study shows that the IF is significantly different for training and race sessions (0.59 [0.03] vs 0.73 [0.03]). Significant regression coefficients show that kJ spent is a good predictor of sRPE, and luTRIMP, as well as TSS. However, IF does not influence the associations between kJ spent and sRPE and luTRIMP, while the association with TSS is different when sessions are done with low or high IF. Conclusion: It seems that the TSS reacts differently to exercise intensity than sRPE and luTRIMP. A possible explanation could be the quadratic relation between IF and TSS.

The time course of adaptations in thermoneutral maximal oxygen consumption following heat acclimation

PURPOSE

This study investigated the effects of a 10-day heat acclimation (HA) programme on the time course of changes in thermoneutral maximal oxygen uptake ([Formula: see text]O_2max) during and up to 10 days post-HA.

METHODS

Twenty-two male cyclists were assigned to a HA or control (Con) training group following baseline ramp tests of thermoneutral [Formula: see text]O_2max. Ten days of fixed-intensity (50% baseline [Formula: see text]O_2max) indoor cycling was performed in either ~ 38.0 °C (HA) or ~ 20 °C (Con). [Formula: see text]O_2max was re-tested on HA days 5, 10 and post-HA days 1, 2, 3, 4, 5 and 10.

RESULTS

[Formula: see text]O_2max initially declined across time in both groups during training (P < 0.05), before increasing in the post-HA period in both groups (P < 0.05). However, [Formula: see text]O_2max was higher than control by post-HA day 4 in the HA group (P = 0.046).

CONCLUSIONS

The non-linear time course of [Formula: see text]O_2max adaptation suggests that post-testing should be performed 96-h post-training to identify the maximal change for most individuals. In preparation for training or testing, athletes can augment their aerobic power in thermoneutral environments by performing 10 days HA, but the full effects will manifest at varying stages of the post-HA period.

Effects of short-term resistance training and tapering on maximal strength, peak power, throwing ball velocity, and sprint performance in handball players

The purpose of this study was to assess the effect of short-term resistance training and two weeks of tapering on physical performances in handball players. Following a ten-week progressive resistance training program, subjects were divided between an experimental (n = 10) and a control group (n = 10). The experimental group completed a resistance training program, followed by a two-week period when the training intensity was tapered by 60%, while the control group maintained their typical pattern of training. Muscle power (force-velocity test and squat and counter-movement jump tests), sprinting ability (10m and 30m), ability to change direction (T-half test) and throwing velocity (a 3-step throw with a run, and a jump throw) were evaluated before training, at the end of training and after tapering. The experimental group showed significantly larger interaction effects for the 10-week training period (12/15, 80%), than for the following 2 weeks of tapering (10/15, 67%), with the largest gains being in 15 m sprint times (d = 3.78) and maximal muscular strength in the snatch (d = 3.48). Although the performance of the experimental group generally continued to increase over tapering, the mean effect size for the training period was markedly higher (d = 1.92, range: 0.95-3.78) than that seen during tapering (d = 1.02, range: -0.17-2.09). Nevertheless the ten weeks of progressive resistance training followed by two weeks of tapering was an effective overall tactic to increase muscle power, sprint performance and ball throwing velocity in handball players.

Gravity-induced exercise intervention in an individual with chronic fatigue syndrome/myalgic encephalomyeltis and postural tachycardia syndrome: a case report

Background/Aims

Chronic fatigue syndrome/myalgic encephalomyeltis is a condition of complex nature, characterised by unexplained disabling fatigue and a combination of non-specific accompanying symptoms. Individuals with chronic fatigue syndrome/myalgic encephalomyeltis frequently present with debilitating orthostatic symptoms, which may fall under the umbrella of postural tachycardia syndrome. Postural tachycardia syndrome is underpinned by autonomic nervous system dysfunction. The gravitational deconditioning that occurs in those severely affected by chronic fatigue syndrome/myalgic encephalomyeltis alongside postural tachycardia syndrome has been suggested as a key focus for interventions in this group. This case report documents the evaluation and rationale behind a novel gravity-induced exercise intervention to improve the symptoms of a 44-year-old female severely affected by chronic fatigue syndrome/myalgic encephalomyeltis and postural tachycardia syndrome, who had been bedbound for 10–15 years.

Methods

An exercise intervention was designed to challenge and therefore improve key areas of autonomic nervous system regulation in the presence of gravity. It contained seven different exercises conducted once a month in a class over a 6-month period.

Results

Fatigue impact score, activity levels and heart rate upon standing, as detected by an active stand test, improved during the exercise intervention and at follow up.

Conclusions

Gravity-induced exercise intervention can have a positive effect on an individual severely affected by Chronic fatigue syndrome/myalgic encephalomyeltis alongside postural tachycardia syndrome.

Block vs. Traditional Periodization of HIT: Two Different Paths to Success for the World's Best Cross-Country Skier

In short-term studies, block periodization of high-intensity training (HIT) has been shown to be an effective strategy that enhances performance and related physiological factors. However, long-term studies and detailed investigations of macro, meso, and micro-periodization of HIT blocks in world-class endurance athletes are currently lacking. In a recent study, we showed that the world’s most successful cross-country (XC) skier used two different periodization models with success throughout her career. One including extensive use of HIT blocks, namely BP, and one using a traditional method namely TRAD. In this study, we compare BP with TRAD in two comparable successful seasons and provide a detailed description of the annual use of HIT blocks in BP. The participant is the most-decorated winter Olympian, with 8 Olympic gold medals, 18 world championship titles, and 114 world cup victories. Training data was categorized by training form (endurance, strength, and speed), intensity [low (LIT), moderate (MIT), and HIT], and mode (running, cycling, and skiing/roller skiing). No significant difference was found in the total endurance training load between BP and TRAD. However, training volume in BP was lower compared to TRAD (15 ± 6 vs. 18 ± 7 h/wk, P = 0.001), mainly explained by less LIT (13 ± 5 vs. 15 ± 5 h/wk, P = 0.004). Lower volume of MIT was also performed in BP compared to TRAD (13 vs. 38 sessions/year), whereas the amount of HIT was higher in BP (157 vs. 77 sessions/year). While BP included high amounts of HIT already from the first preparation period, followed by a reduction toward the competition period, TRAD had a progressive increase in HIT toward the competition period. In BP, the athlete performed seven HIT blocks, varying from 7 to 11 days, each including 8–13 HIT sessions. This study provides novel insights into successful utilization of two different periodization models in the worlds best XC skier, and illustrates the macro, meso and micro- periodization of HIT blocks to increase the overall amount of HIT.

DIAGNOSIS OF OVERTRAINING SYNDROME

ABSTRACT Overtraining syndrome (OTS) is a condition associated with diminished sports performance due to an increase in the volume and/or intensity of physical activity without adequate rest, and/or due to an inadequate diet. The condition often involves hormonal, nutritional, emotional, muscle, immune and neurological imbalances. Epidemiology varies considerably, affecting both sexes in different age groups. Diagnosis is still a challenge, as the syndrome resembles different diseases. The lack of specific symptoms requires a meticulous investigation in all athletes, which is often multidisciplinary. OTS can have an important repercussion on sports performance and on the quality of life of athletes. Methods: This is a mapping of scientific literature along the lines of the Systemic Review. The databases investigated were: MEDLINE and Latin American and Caribbean Health Sciences Literature – LILACS and EMBASE, in addition to printed documents. Studies describing OTS were included, prioritizing articles that report the efficacy of the different diagnostic methods, be they clinical, laboratory, or imaging. Results: We found 83 articles, of which 30 were selected. Conclusion: The only symptom present in all the different forms of manifestation of OTS is loss of performance. However, some tests assessing oxidative stress levels seem promising, even though they are not specific. Revision article.

Changes in Choice Reaction Time During and After 8 Days Exhaustive Cycling Are Not Related to Changes in Physical Performance

PURPOSE

Reaction time has been proposed as a training monitoring tool, but to date, results are equivocal. Therefore, it was investigated whether reaction time can be used as a monitoring tool to establish overreaching.

METHODS

The study included 30 subjects (11 females and 19 males, age: 40.8 [10.8] years, VO_2max: 51.8 [6.3] mL/kg/min) who participated in an 8-day cycling event. The external exercise load increased approximately 900% compared with the preparation period. Performance was measured before and after the event using a maximal incremental cycling test. Subjects with decreased performance after the event were classified as functionally overreached (FOR) and others as acutely fatigued (AF). A choice reaction time test was performed 2 weeks before (pre), 1 week after (post), and 5 weeks after (follow-up), as well as at the start and end of the event.

RESULTS

A total of 14 subjects were classified as AF and 14 as FOR (2 subjects were excluded). During the event, reaction time at the end was 68 ms (95% confidence interval, 46-89) faster than at the start. Reaction time post event was 41 ms (95% confidence interval, 12-71) faster than pre event and follow-up was 55 ms faster (95% confidence interval, 26-83). The time by class interaction was not significant during (P = .26) and after (P = .43) the event. Correlations between physical performance and reaction time were not significant (all Ps > .30).

CONCLUSIONS

No differences in choice reaction time between AF and FOR subjects were observed. It is suggested that choice reaction time is not valid for early detection of overreaching in the field.

The effects of intensified training on resting metabolic rate (RMR), body composition and performance in trained cyclists

Background

Recent research has demonstrated decreases in resting metabolic rate (RMR), body composition and performance following a period of intensified training in elite athletes, however the underlying mechanisms of change remain unclear. Therefore, the aim of the present study was to investigate how an intensified training period, designed to elicit overreaching, affects RMR, body composition, and performance in trained endurance athletes, and to elucidate underlying mechanisms.

Method

Thirteen (n = 13) trained male cyclists completed a six-week training program consisting of a “Baseline” week (100% of regular training load), a “Build” week (~120% of Baseline load), two “Loading” weeks (~140, 150% of Baseline load, respectively) and two “Recovery” weeks (~80% of Baseline load). Training comprised of a combination of laboratory based interval sessions and on-road cycling. RMR, body composition, energy intake, appetite, heart rate variability (HRV), cycling performance, biochemical markers and mood responses were assessed at multiple time points throughout the six-week period. Data were analysed using a linear mixed modeling approach.

Results

The intensified training period elicited significant decreases in RMR (F_(5,123.36) = 12.0947, p = <0.001), body mass (F_(2,19.242) = 4.3362, p = 0.03), fat mass (F_(2,20.35) = 56.2494, p = <0.001) and HRV (F_(2,22.608) = 6.5212, p = 0.005); all of which improved following a period of recovery. A state of overreaching was induced, as identified by a reduction in anaerobic performance (F_(5,121.87) = 8.2622, p = <0.001), aerobic performance (F_(5,118.26) = 2.766, p = 0.02) and increase in total mood disturbance (F_{(5, 110.61)} = 8.1159, p = <0.001).

Conclusion

Intensified training periods elicit greater energy demands in trained cyclists, which, if not sufficiently compensated with increased dietary intake, appears to provoke a cascade of metabolic, hormonal and neural responses in an attempt to restore homeostasis and conserve energy. The proactive monitoring of energy intake, power output, mood state, body mass and HRV during intensified training periods may alleviate fatigue and attenuate the observed decrease in RMR, providing more optimal conditions for a positive training adaptation.

Reliability and Seasonal Changes of Submaximal Variables to Evaluate Professional Cyclists

PURPOSE

The aim of this study was to determine the reliability and validity of several submaximal variables that can be easily obtained by monitoring cyclists' performances.

METHODS

Eighteen professional cyclists participated in this study. In a first part (n = 15) the test-retest reliability of heart rate (HR) and rating of perceived exertion (RPE) during a progressive maximal test was measured. Derived submaximal variables based on HR, RPE, and power output (PO) responses were analyzed. In a second part (n = 7) the pattern of the submaximal variables according to cyclists' training status was analyzed. Cyclists were assessed 3 times during the season: at the beginning of the season, before the Vuelta a España, and the day after this Grand Tour.

RESULTS

Part 1: No significant differences in maximal and submaximal variables between test-retest were found. Excellent ICCs (0.81-0.98) were obtained in all variables. Part 2: The HR and RPE showed a rightward shift from early to peak season. In addition, RPE showed a left shift after the Vuelta a España. Submaximal variables based on RPE had the best relationship with both performance and changes in performance.

CONCLUSION

The present study showed the reliability of different maximal and submaximal variables used to assess cyclists' performances. Submaximal variables based on RPE seem to be the best to monitor changes in training status over a season.

Decrement in Professional Cyclists' Performance After a Grand Tour

PURPOSE

To analyze professional cyclists' performance declines after, and the exercise demands during, a Grand Tour.

METHODS

Seven professional cyclists performed 2 incremental exercise tests, 1 wk before and the day after the Vuelta España. During the race the exercise demands were analyzed on the basis of heart rate (HR). Three intensity zones were established according to reference HR values corresponding to the ventilatory- (VT) and respiratory-compensation (RCT) thresholds determined during the prerace test. In addition, exercise demands for the last weeks of the Vuelta were recalculated using the reference HR determined during the postrace test for the 3rd week and averaging the change observed in the VT and RCT per stage for the 2nd week. The reference HR for the beginning of the 2nd week was estimated.

RESULTS

A significant (P-value range, .044-.000) decrement in oxygen uptake, power output, and HR at maximal exercise, VT, and RCT was found after the race. Based on the prerace test, the mean time spent daily above the RCT was 13.8 ± 10.2 min. This time decreased -1.2 min·day^-1 across the race. When the exercise intensity was corrected according to the postrace test, the time above RCT (34.1 ± 9.9 min) increased 1.0 min·day^-1.

CONCLUSION

These data indicate that completing a Grand Tour may result in a significant decrement in maximal and submaximal endurance performance capacity. This may modify reference values used to analyze exercise demands. As a consequence, the high-intensity exercise performed by cyclists may be underestimated.

HRV4Training: Large-scale longitudinal training load analysis in unconstrained free-living settings using a smartphone application

We describe an approach to support athletes at various fitness levels in their training load analysis using heart rate (HR) and heart rate variability (HRV). A smartphone-based application (HRV4Training) was developed that captures heart activity over one to five minutes using photoplethysmography (PPG) and derives HR and HRV features. HRV4Training integrated a guide for an early morning spot measurement protocol and a questionnaire to capture self-reported training activity. The smartphone application was made publicly available for interested users to quantify training effect. Here we analyze data acquired over a period of 3 weeks to 5 months, including 797 users, breaking down results by gender and age group. Our results suggest a strong relation between HR, HRV and self-reported training load independent of gender and age group. HRV changes due to training were larger than those of HR. We conclude that smartphone-based training monitoring is feasible and a can be used as a practical tool to support large populations outside controlled laboratory environments.

No Additional Benefits of Block- Over Evenly-Distributed High-Intensity Interval Training within a Polarized Microcycle

Introduction: The current study aimed to investigate the responses to block- versus evenly-distributed high-intensity interval training (HIT) within a polarized microcycle.

Methods: Twenty well-trained junior cross-country skiers (10 males, age 17.6 ± 1.5 and 10 females, age 17.3 ± 1.5) completed two, 3-week periods of training (EVEN and BLOCK) in a randomized, crossover-design study. In EVEN, 3 HIT sessions (5 × 4-min of diagonal-stride roller-skiing) were completed at a maximal sustainable intensity each week while low-intensity training (LIT) was distributed evenly around the HIT. In BLOCK, the same 9 HIT sessions were completed in the second week while only LIT was completed in the first and third weeks. Heart rate (HR), session ratings of perceived exertion (sRPE), and perceived recovery (pREC) were recorded for all HIT and LIT sessions, while distance covered was recorded for each HIT interval. The recovery-stress questionnaire for athletes (RESTQ-Sport) was completed weekly. Before and after EVEN and BLOCK, resting saliva and muscle samples were collected and an incremental test and 600-m time-trial (TT) were completed.

Results: Pre- to post-testing revealed no significant differences between EVEN and BLOCK for changes in resting salivary cortisol, testosterone, or IgA, or for changes in muscle capillary density, fiber area, fiber composition, enzyme activity (CS, HAD, and PFK) or the protein content of VEGF or PGC-1α. Neither were any differences observed in the changes in skiing economy, V˙O2max or 600-m time-trial performance between interventions. These findings were coupled with no significant differences between EVEN and BLOCK for distance covered during HIT, summated HR zone scores, total sRPE training load, overall pREC or overall recovery-stress state. However, 600-m TT performance improved from pre- to post-training, irrespective of intervention (P = 0.003), and a number of hormonal and muscle biopsy markers were also significantly altered post-training (P < 0.05).

Discussion: The current study shows that well-trained junior cross-country skiers are able to complete 9 HIT sessions within 1 week without compromising total work done and without experiencing greater stress or reduced recovery over a 3-week polarized microcycle. However, the findings do not support block-distributed HIT as a superior method to a more even distribution of HIT in terms of enhancing physiological or performance adaptions.

The Manipulation of Pace within Endurance Sport

In any athletic event, the ability to appropriately distribute energy is essential to prevent premature fatigue prior to the completion of the event. In sport science literature this is termed "pacing." Within the past decade, research aiming to better understand the underlying mechanisms influencing the selection of an athlete's pacing during exercise has dramatically increased. It is suggested that pacing is a combination of anticipation, knowledge of the end-point, prior experience and sensory feedback. In order to better understand the role each of these factors have in the regulation of pace, studies have often manipulated various conditions known to influence performance such as the feedback provided to participants, the starting strategy or environmental conditions. As with all research there are several factors that should be considered in the interpretation of results from these studies. Thus, this review aims at discussing the pacing literature examining the manipulation of: (i) energy expenditure and pacing strategies, (ii) kinematics or biomechanics, (iii) exercise environment, and (iv) fatigue development.

Supplemental Protein during Heavy Cycling Training and Recovery Impacts Skeletal Muscle and Heart Rate Responses but Not Performance

The effects of protein supplementation on cycling performance, skeletal muscle function, and heart rate responses to exercise were examined following intensified (ICT) and reduced-volume training (RVT). Seven cyclists performed consecutive periods of normal training (NT), ICT (10 days; average training duration 220% of NT), and RVT (10 days; training duration 66% of NT). In a crossover design, subjects consumed supplemental carbohydrate (CHO) or an equal amount of carbohydrate with added protein (CP) during and following each exercise session (CP = +0.94 g/kg/day protein during ICT; +0.39 g/kg/day during RVT). A 30-kilometer time trial performance (following 120 min at 50% W_max) was modestly impaired following ICT (+2.4 ± 6.4% versus NT) and returned to baseline levels following RVT (−0.7 ± 4.5% versus NT), with similar responses between CHO and CP. Skeletal muscle torque at 120 deg/s benefited from CP, compared to CHO, following ICT. However, this effect was no longer present at RVT. Following ICT, muscle fiber cross-sectional area was increased with CP, while there were no clear changes with CHO. Reductions in constant-load heart rates (at 50% W_max) following RVT were likely greater with CP than CHO (−9 ± 9 bpm). Overall it appears that CP supplementation impacted skeletal muscle and heart rate responses during a period of heavy training and recovery, but this did not result in meaningful changes in time trial performance.

Physiological profile of a professional boxer preparing for Title Bout: A case study

This study aimed to (1) profile a professional boxer (23 years and 80 kg) with boxing-specific, muscle function, aerobic capacity and body composition tests, and (2) quantify how these measures varied during an 8-week preparation phase leading to, and post a state-Title Bout fought in the 76.2-kg class. A series of boxing-specific and muscle function tests were completed on 11 occasions: 9 prior and twice after the bout, each separated by approximately 2 weeks. The boxing test included 36 maximal punches (9 of each: lead and rear straights, lead and rear hooks) to a punching integrator measuring forces and velocity. Muscle function tests included countermovement jump, drop-jumps, isometric mid-thigh pull and isometric bench-press. Body composition was assessed using skin-fold measurements on three occasions and one dual energy X-ray absorptiometry scan. Aerobic capacity was assessed using 2 VO2 max tests. Leading up to the bout, performance decreased in isometric mid-thigh pull (8%), isometric bench-press (5%), countermovement jump (15%) and impact forces in 3 of 4 punches (4%-7%). Whereas measures of dynamic and isometric muscle function remained depressed or unchanged post competition, punching forces (6%-15%) and aerobic power (6%) increased. Data suggest the athlete may have super-compensated following rest as fatigue dissipated and further adaptation occurred.

Effects of training-induced fatigue on pacing patterns in 40-km cycling time trials

INTRODUCTION

In some endurance sports, athletes complete several competitions within a short period, resulting in accumulated fatigue. It is unclear whether fatigued athletes choose the same pacing pattern (PP) as when they have recovered.

PURPOSE

This study aimed to analyze effects of fatigue on PP of cyclists during a 40-km time trial (TT).

METHODS

Twenty-three male cyclists (28.8 ± 7.6 yr) completed three 40-km TT on a cycle ergometer. TT were conducted before (TT1) and after (TT2) a 6-d training period. A third TT was carried out after 72 h of recovery (TT3). Training days consisted of two cycling sessions: mornings, 1 h at 95% of lactate threshold or 3 × 5 × 30 s all-out sprint; afternoons, 3 h at 80% individual anaerobic threshold. Four-kilometer split times (min) and RPE were recorded during TT.

RESULTS

Performance decreased from TT1 to TT2 (65.7 ± 3.5 vs 66.7 ± 3.3 min; P < 0.05) and increased from TT2 to TT3 (66.7 ± 3.3 vs 65.5 ± 3.3 min; P < 0.01). PP showed a significant difference between TT1 and TT2 (P < 0.001) as well as between TT2 and TT3 (P < 0.01). PP in TT1 and TT3 showed no significant difference (P > 0.05). In TT1 and TT3, cyclists started faster in the first 4 km compared with TT2. RPE course showed no significant difference between TT (P > 0.05).

CONCLUSIONS

Fatigue reversibly changes the PP of cyclists during a 40-km TT. Participants reduced their power output until premature exhaustion seemed very unlikely. This supports the assumption that pacing includes a combination of anticipation and feedback mechanisms.

Evidence of disturbed sleep and mood state in well-trained athletes during short-term intensified training with and without a high carbohydrate nutritional intervention

Few studies have investigated the effects of exercise training on sleep physiology in well-trained athletes. We investigated changes in sleep markers, mood state and exercise performance in well-trained cyclists undergoing short-term intensified training and carbohydrate nutritional intervention. Thirteen highly-trained male cyclists (age: 25 ± 6y, [Formula: see text]O_2max: 72 ± 5 ml/kg/min) participated in two 9-day periods of intensified training while undergoing a high (HCHO) or moderate (CON) carbohydrate nutritional intervention before, during and after training sessions. Sleep was measured each night via wristwatch actigraphy. Mood state questionnaires were completed daily. Performance was assessed with maximal oxygen uptake ([Formula: see text]. Percentage sleep time fell during intensified training (87.9 ± 1.5 to 82.5 ± 2.3%; p < 0.05) despite an increase in time in bed (456 ± 50 to 509 ± 48 min; p = 0.02). Sleep efficiency decreased during intensified training (83.1 ± 5.3 to 77.8 ± 8.6%; p < 0.05). Actual sleep time was significantly higher in CON than HCHO throughout intensified training. Mood disturbance increased during intensified training and was higher in CON than HCHO (p < 0.05). Performance in the [Formula: see text] exercise protocol fell significantly with intensified training. The main findings of this study were that 9-days of intensified training in highly-trained cyclists resulted in significant and progressive declines in sleep quality, mood state and maximal exercise performance.

Effects of a seven day overload-period of high-intensity training on performance and physiology of competitive cyclists

OBJECTIVES

Competitive endurance athletes commonly undertake periods of overload training in the weeks prior to major competitions. This investigation examined the effects of two seven-day high-intensity overload training regimes (HIT) on performance and physiological characteristics of competitive cyclists.

DESIGN

The study was a matched groups, controlled trial.

METHODS

Twenty-eight male cyclists (mean ± SD, Age: 33±10 years, Mass 74±7 kg, VO2 peak 4.7±0.5 L·min-1) were assigned to a control group or one of two training groups for seven consecutive days of HIT. Before and after training cyclists completed an ergometer based incremental exercise test and a 20-km time-trial. The HIT sessions were ∼120 minutes in duration and consisted of matched volumes of 5, 10 and 20 second (short) or 15, 30 and 45 second (long) maximal intensity efforts.

RESULTS

Both the short and long HIT regimes led to significant (p<0.05) gains in time trial performance compared to the control group. Relative to the control group, the mean changes (±90% confidence limits) in time-trial power were 8.2%±3.8% and 10.4%±4.3% for the short and long HIT regimes respectively; corresponding increases in peak power in the incremental test were 5.5%±2.7% and 9.5%±2.5%. Both HIT (short vs long) interventions led to non-significant (p>0.05) increases (mean ± SD) in VO2 peak (2.3%±4.7% vs 3.5%±6.2%), lactate threshold power (3.6%±3.5% vs 2.9%±5.3%) and gross efficiency (3.2%±2.4% vs 5.1%±3.9%) with only small differences between HIT regimes.

CONCLUSIONS

Seven days of overload HIT induces substantial enhancements in time-trial performance despite non-significant increases in physiological measures with competitive cyclists.

Evidence of parasympathetic hyperactivity in functionally overreached athletes

PURPOSE

We analyzed HR variability (HRV) to detect alterations in autonomic function that may be associated with functional overreaching (F-OR) in endurance athletes.

METHODS

Twenty-one trained male triathletes were randomly assigned to either intensified training (n = 13) or normal training (n = 8) groups during 5 wk. HRV measures were taken daily during a 1-wk moderate training (baseline), a 3-wk overload training, and a 1-wk taper.

RESULTS

All the subjects of the intensified training group demonstrated a decrease in maximal incremental running test performance at the end of the overload period (-9.0% ± 2.1% of baseline value) followed by a performance supercompensation after the taper and were therefore diagnosed as F-OR. According to a qualitative statistical analysis method, a likely to very likely negative effect of F-OR on HR was observed at rest in supine and standing positions, using isolated seventh-day values and weekly average values, respectively. When considering the values obtained once per week, no clear effect of F-OR on HRV parameters was found. In contrast, the weekly mean of each HRV parameter showed a larger change in indices of parasympathetic tone in the F-OR group than the control group in supine position (with a 96%/4%/0% chance to demonstrate a positive/trivial/negative effect on Ln RMSSD after the overload period; 77%/22%/1% on LnHF) and standing position [98%/1%/1% on Ln RMSSD; 99%/0%/1% on LnHF; 95%/1%/4% on Ln(LF + HF)]. During the taper, theses responses were reversed.

CONCLUSIONS

Using daily HRV recordings averaged over each week, this study detected a progressive increase in the parasympathetic modulation of HR in endurance athletes led to F-OR. It also revealed that due to a wide day-to-day variability, isolated, once per week HRV recordings may not detect training-induced autonomic modulations in F-OR athletes.

Effect of 24 sessions of high-intensity aerobic interval training carried out at either high or moderate frequency, a randomized trial

Purpose

The training response of an intensified period of high-intensity exercise is not clear. Therefore, we compared the cardiovascular adaptations of completing 24 high-intensity aerobic interval training sessions carried out for either three or eight weeks, respectively.

Methods

Twenty-one healthy subjects (23.0±2.1 years, 10 females) completed 24 high-intensity training sessions throughout a time-period of either eight weeks (moderate frequency, MF) or three weeks (high frequency, HF) followed by a detraining period of nine weeks without any training. In both groups, maximal oxygen uptake (VO_2max) was evaluated before training, at the 9^th and 17^th session and four days after the final 24^th training session. In the detraining phase VO_2max was evaluated after 12 days and thereafter every second week for eight weeks. Left ventricular echocardiography, carbon monoxide lung diffusion transfer factor, brachial artery flow mediated dilatation and vastus lateralis citrate maximal synthase activity was tested before and after training.

Results

The cardiovascular adaptation after HF training was delayed compared to training with MF. Four days after ending training the HF group showed no improvement (+3.0%, p = 0.126), whereas the MF group reached their highest VO_2max with a 10.7% improvement (p<0.001: group difference p = 0.035). The HF group reached their highest VO_2max (6.1% increase, p = 0.026) twelve days into the detraining period, compared to a concomitant reduction to 7.9% of VO_2max (p<0.001) above baseline in the MF group (group difference p = 0.609).

Conclusion

Both HF and MF training of high-intensity aerobic exercise improves VO_2max. The cardiovascular adaptation following a HF programme of high-intensity exercise is however delayed compared to MF training.

Trial Registration

ClinicalTrials.gov NCT00733941.

Salivary cortisol and testosterone responses to high-intensity cycling before and after an 11-day intensified training period

This study examined salivary cortisol and testosterone responses to two, different high-intensity, ∼30-min cycles separated by 2 h rest before and after an 11-day intensified training period. Twelve recreationally active, healthy males completed the study. Saliva samples were collected before, immediately after and 30 min after both bouts with salivary cortisol and testosterone concentrations assessed. Compared with pre-training blunted exercise-induced salivary cortisol, testosterone and cortisol/testosterone responses to both bouts post-training were observed (P < 0.05 for all). Comparing pre- with post-training the absolute exercise-induced salivary cortisol, testosterone and cortisol/testosterone decreased from 11.1 to 3.1 and 7.0 to 4.4 nmol · L⁻¹ (cortisol), from 407 to 258 and from 473 to 274 pmol · L⁻¹ (testosterone) and from 12 to 4 and 7 to 5 (cortisol/testosterone) for the first and second bouts, respectively (P < 0.05). No differences in the pre- and post-training rating of perceived exertion (RPE) and heart rate (HR) responses during the cycles or times to fatigue were found (P > 0.05). Fatigue and Burnout scores were higher post- compared with pre-training (P < 0.05). These high-intensity exercise bouts can detect altered hormonal responses following intensified training. This test could assess an athlete's current hormonal status, reductions in salivary cortisol and testosterone responses suggestive of increased fatigue.

Prevention, diagnosis, and treatment of the overtraining syndrome: joint consensus statement of the European College of Sport Science and the American College of Sports Medicine

Successful training not only must involve overload but also must avoid the combination of excessive overload plus inadequate recovery. Athletes can experience short-term performance decrement without severe psychological or lasting other negative symptoms. This functional overreaching will eventually lead to an improvement in performance after recovery. When athletes do not sufficiently respect the balance between training and recovery, nonfunctional overreaching (NFOR) can occur. The distinction between NFOR and overtraining syndrome (OTS) is very difficult and will depend on the clinical outcome and exclusion diagnosis. The athlete will often show the same clinical, hormonal, and other signs and symptoms. A keyword in the recognition of OTS might be "prolonged maladaptation" not only of the athlete but also of several biological, neurochemical, and hormonal regulation mechanisms. It is generally thought that symptoms of OTS, such as fatigue, performance decline, and mood disturbances, are more severe than those of NFOR. However, there is no scientific evidence to either confirm or refute this suggestion. One approach to understanding the etiology of OTS involves the exclusion of organic diseases or infections and factors such as dietary caloric restriction (negative energy balance) and insufficient carbohydrate and/or protein intake, iron deficiency, magnesium deficiency, allergies, and others together with identification of initiating events or triggers. In this article, we provide the recent status of possible markers for the detection of OTS. Currently, several markers (hormones, performance tests, psychological tests, and biochemical and immune markers) are used, but none of them meet all the criteria to make their use generally accepted.

A new overtraining protocol for mice based on downhill running sessions

1. The purpose of the present study was to verify whether a downhill running protocol was able to induce non-functional overreaching in > 75% of mice. 2. Mice were divided into control (C), trained (TR) and overtrained (OTR) groups. Bodyweight and food intake were recorded weekly. The incremental load test (ILT) and the exhaustive test (ET) were used to measure performance before and after aerobic training and overtraining protocols. 3. Although the bodyweight of the OTR group was lower than that of the C group at the end of Week 7, the food intake of the OTR group was higher than that of the C and TR groups at the end of Week 8. Evaluation of results from the ILT and ET revealed significant intra- and inter-group differences: whereas the parameters measured by both tests increased significantly in the TR group, they were significantly decreased in the OTR group. 4. In conclusion, this new overtraining protocol based on downhill running sessions induced non-functional overreaching in 100% of mice.

A multidisciplinary approach to overreaching detection in endurance trained athletes

In sport, high training load required to reach peak performance pushes human adaptation to their limits. In that process, athletes may experience general fatigue, impaired performance, and may be identified as overreached (OR). When this state lasts for several months, an overtraining syndrome is diagnosed (OT). Until now, no variable per se can detect OR, a requirement to prevent the transition from OR to OT. It encouraged us to further investigate OR using a multivariate approach, including physiological, biomechanical, cognitive, and perceptive monitoring. Twenty-four highly trained triathletes were separated into an overload group and a normo-trained group (NT) during 3 wk of training. Given the decrement of their running performance, 11 triathletes were diagnosed as OR after this period. A discriminant analysis showed that the changes of eight parameters measured during a maximal incremental test could explain 98.2% of the OR state (lactatemia, heart rate, biomechanical parameters and effort perception). Variations in heart rate and lactatemia were the two most discriminating factors. When the multifactorial analysis was restricted to these variables, the classification score reached 89.5%. Catecholamines and creatine kinase concentrations at rest did not change significantly in both groups. Running pattern was preserved and cognitive performance decrement was observed only at exhaustion in OR subjects. This study showed that monitoring various variables is required to prevent the transition between NT and OR. It emphasized that an OR index, which combines heart rate and blood lactate concentration changes after a strenuous training period, could be helpful to routinely detect OR.

Improved training tolerance by supplementation with α-Keto acids in untrained young adults: a randomized, double blind, placebo-controlled trial

Background

Exercise causes a variety of physiological and metabolic changes that can in turn reduce exercise tolerance. One of the potential mechanisms responsible for fatigue is “exercise-induced hyperammonemia”. Previous studies have shown that supplementation with amino acids can increase training tolerance. The α-keto acids are biochemical analogs of amino acids and can be converted to amino acids through transamination, thus reducing the cellular ammonia level. This double blind, placebo-controlled study was designed to investigate the effects of α-keto acid supplementation (KAS) on training tolerance, training effect, and stress-recovery state.

Methods

Thirty-three untrained young male adults underwent four weeks of training (5 sessions/week; 30 minutes running at the individual anaerobic threshold followed by 3 x 3 minute sprints/each session). Throughout the 4 weeks of training and one week of recovery, subjects took α-ketoglutarate (AKG group, 0.2 g/kg/d, n = 9), branched-chain keto acids (BCKA group, 0.2 g/kg/d, n = 12) or isocaloric placebo (control group, n = 12) daily.

Results

The 4^th week training volume, maximum power output and muscle torque were higher in the AKG group (175 ± 42 min, 412 ± 49 Watts and 293 ± 58 Newton meters, respectively, P<0.05) and the BCKA group (158 ± 35, 390 ± 29 and 273 ± 47, P<0.05) than in the control group (92 ± 70, 381 ± 67 and 233 ± 43). The general stress and emotional exhaustion as assessed by the rest-stress-questionnaire-sport after the 3^rd week of training increased significantly in the control group (P<0.05), but not in the KAS groups.

Conclusions

Under KAS, subjects could bear a higher training volume and reach a higher power output and peak muscle torque, accompanied by a better stress-recovery-state. Thus, KAS improves exercise tolerance and training effects along with a better stress-recovery state. Whether the improved training tolerance by KAS is associated with effects on ammonia homeostasis requires further observation.

Functional overreaching during preparation training of elite tennis professionals

This case study evaluated the response of objective and subjective markers of overreaching to a highly demanding conditioning training mesocycle in elite tennis players to determine 1) whether players would become functionally or non-functionally overreached, and 2) to explore how coherently overreaching markers would respond. Performance, laboratory and cardiac autonomous activity markers were evaluated in three experienced male tennis professionals competing at top 30, top 100 and top 1000 level before and after their strength and conditioning training was increased by 120, 160 and 180%, respectively, for 30 days. Every week, subjective ratings of stress and recovery were evaluated by means of a questionnaire. After 74, 76 and 55 h of training, increases in V̇O2max (+8, +5 and +18%) and speed strength indices (+9, +23 and +5%) were observed in all players. Changes of maximal heart rate (-5, -6, +4 beats per minute), laboratory markers (e.g. insulin-like growth factor -26, -17, -9%; free testosterone to cortisol ratio -63, +2, -12%) and cardiac autonomous activity markers (heart rate variability -49, -64, -13%) were variable among the players. Improved performance provides evidence that overreaching was functional in all players. However, several overreaching markers were altered and these alterations were more pronounced in the two top 100 players. The response of overreaching indicators was not coherent.