The impact of task (un)certainty on repeated grip force production

Many studies found that in physical tasks, reducing certainty regarding their endpoints hinders performance. However, the impact of reducing certainty regarding other aspects of physical tasks is unknown. Here we manipulated the certainty of the required effort on an unrelated, parallel task (i.e., off-task uncertainty) and examined how it impacts force production in two within-subject experiments (N = 79). In two sessions, subjects completed 20 repetitions composed of maximal forces using a gripper with their dominant hand. Between repetitions, participants applied either submaximal constant or varied grip forces, with their non-dominant arm, matched for total forces across repetitions. While we observed trivial differences in total forces between conditions, under the varied condition, participants produced a steeper decrease in forces, suggesting that off-task uncertainty impacted their effort allocation strategy. We speculate that this pattern can be attributed to cognitive overload and/or changes in motivation stemming from the imposed uncertainty.

Should I Rest or Should I Go Now? A Randomized Cross-Over Trial Comparing Fixed and Self-Selected Rest Durations in High-Intensity Interval Training Cycling Sessions

BACKGROUND

In high-intensity interval training (HIIT), the rest durations between intervals are commonly prescribed using a fixed approach (e.g., 30 s between intervals). An alternative is the self-selected (SS) approach, in which trainees select their resting durations. Studies comparing the two approaches report mixed results. However, in these studies, trainees in the SS condition rested for as little or as long as they wished, leading to dissimilar total rest durations between conditions. Here, for the first time, we compare the two approaches while controlling for total rest duration.

METHODS

Twenty-four amateur adult male cyclists completed a familiarization session, followed by two counterbalanced cycling HIIT sessions. Each session was composed of nine, 30-s intervals, in which the goal was to accumulate as many watts as possible on an SRM ergometer. In the fixed condition, cyclists rested for 90 s between intervals. In the SS condition, cyclists had 720 s (i.e., 8  × 90 s) of rest to allocate in any way they wished. We measured and compared watts, heart rate, electromyography of the knee flexors and extensors, rating of perceived effort and fatigue, perception of autonomy and enjoyment. Additionally, a subsample of ten cyclists completed a retest of the SS condition.

RESULTS

With the exception of perception of autonomy, which was higher in the SS condition, outcomes were highly similar in both conditions. For example, the average aggregated differences were: 0.57 (95% CI - 8.94, 10.09) for watts; - 0.85 (95% CI - 2.89, 1.18) for heart rate; and 0.01 (95% CI - 0.29, 0.30) for rating of perceived effort (on a 0-10 scale). Additionally, the retest of the SS condition resulted in a similar rest allocation pattern across the intervals and in similar outcomes.

CONCLUSION

Given the similarities in performance, physiological and psychological outcomes between the fixed and SS conditions, both can be equally utilized based on coaches' and cyclists' preferences and training goals.

Rating of perceived effort but relative to what? A comparison between imposed and self-selected anchors

PURPOSE

Collecting reliable and valid rating of perceived effort (RPE) data requires properly anchoring the scales' upper limits (i.e., the meaning of 10 on a 0-10 scale). Yet, despite their importance, anchoring procedures remain understudied and theoretically underdeveloped. Here we propose a new task-based anchoring procedure that distinguishes between imposed and self-selected anchors. In the former, researchers impose on participants a specific task as the anchor; in the latter, participants choose the most effortful task experienced or imaginable as the anchor. We compared the impact of these conceptually different anchoring procedures on RPE.

METHODS

Twenty-five resistance-trained participants (13 females) attended a familiarization and two randomized experimental sessions. In both experimental sessions, participants performed non-fatiguing and fatiguing isometric maximal voluntary contraction (MVC) protocols with the squat followed by the gripper or vice versa. After each MVC, participants reported their RPE on a 0-10 scale relative to an imposed anchor of the performed task (e.g., gripper MVCs anchored to a gripper MVC) or to a self-selected anchor.

RESULTS

In the non-fatiguing condition, imposed anchors yielded greater RPEs than self-selected anchors for both the squat [on average, 9.4 vs. 5.5; Δ(CI95%) = 3.9 (3.2, 4.5)] and gripper [9.4 vs. 3.9; Δ = 5.5 (4.7, 6.3)]. Similar results were observed in the fatiguing condition for both the squat [9.7 vs. 6.9; Δ = 2.8 (2.1, 3.5)] and gripper [9.7 vs. 4.5; Δ = 5.2 (4.3, 5.9)].

CONCLUSIONS

We found large differences in RPE between the two anchors, independent of exercises and fatigue state. These findings provide a basis for further development and refinement of anchoring procedures and highlight the importance of selecting, justifying, and consistently applying the chosen anchors.

Seeing Effort: Assessing Coaches' Prediction of the Number of Repetitions in Reserve Before Task-Failure

Background

A key role of resistance training (RT) coaches is to personalize programs based on their trainees’ abilities and goals. Specifically, coaches often assess how many repetitions in reserve (RIR) their trainees have until task-failure. Coaches can then modify the number of repetitions assigned per set accordingly. However, coaches’ ability to predict the number of RIR is unknown.

Methods

Certified RT coaches (n = 259) were randomly assigned to watch a video of one of eight trainees. The trainees performed two sets of barbell squats and preacher biceps-curls, using 70% or 80% of their 1RM, to task-failure. The coaches predicted trainees’ RIR at 33%, 66%, and 90% of the total number of repetitions the trainees completed in each set. We fitted a linear mixed model with various predictors to the prediction errors as the outcomes (i.e., signed and unsigned values of the predicted minus actual repetitions to task-failure).

Results

The overall average number of repetitions completed by the trainees was 13.9. The average absolute errors were 4.8, 2.0, and 1.2 repetitions for the 33%, 66%, and 90% time-points, respectively. The absolute prediction error increased for the biceps-curl compared to the squat (1.43, 95% CI [1.13, 1.74]), but decreased for heavier loads (− 1.17, 95% CI [− 2.16, − 0.19]), and in the second set of each exercise (− 1.20, 95% CI [− 1.38, − 1.02]). Surprisingly, coaches’ years of experience had a negligible effect on the absolute error (− 0.020, 95% CI [− 0.039, − 0.0007]). Finally, coaches underpredicted the RIR at early time-points but reverted to slight overprediction at later time-points.

Conclusions

Prior coaching experience seems to play a minor role in RIR predictions. However, even short-term exposures to new trainees performing different exercises can substantially improve coaches’ RIR predictions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40798-022-00526-8.

Age Differences in Recovery Rate Following an Aerobic-Based Exercise Protocol Inducing Muscle Damage Among Amateur, Male Athletes

Purpose: Compare recovery rates between active young (Y) and middle-aged (MA) males up to 48H post aerobically based, exercise-induced muscle damage (EIMD) protocol. A secondary aim was to explore the relationships between changes in indices associated with EIMD and recovery throughout this timeframe.

Methods: Twenty-eight Y (n = 14, 26.1 ± 2.9y, 74.5 ± 9.3 kg) and MA (n = 14, 43.6 ± 4.1y, 77.3 ± 12.9 kg) physically active males, completed a 60-min downhill running (DHR) on a treadmill at −10% incline and at 65% of maximal heart rate (HR). Biochemical, biomechanical, psychological, force production and muscle integrity (using MRI diffusion tensor imaging) markers were measured at baseline, immediately-post, and up to 48H post DHR.

Results: During the DHR, HR was lower (p < 0.05) in MA compared to Y, but running pace and distance covered were comparable between groups. No statistical or meaningful differences were observed between groups for any of the outcomes. Yet, Significant (p < 0.05) time-effects within each group were observed: markers of muscle damage, cadence and perception of pain increased, while TNF-a, isometric and dynamic force production and stride-length decreased. Creatine-kinase at 24H-post and 48H-post were correlated (p < 0.05, r range = −0.57 to 0.55) with pain perception, stride-length, and cadence at 24H-post and 48H-post. Significant (p < 0.05) correlations were observed between isometric force production at all time-points and IL-6 at 48H-post DHR (r range = −0.62 to (−0.74).

Conclusion: Y and MA active male amateur athletes recover in a comparable manner following an EIMD downhill protocol. These results indicate that similar recovery strategies can be used by trainees from both age groups following an aerobic-based EIMD protocol.

Prescribing Intensity in Resistance Training Using Rating of Perceived Effort: A Randomized Controlled Trial

Introduction: Rating of perceived effort (RPE) scales are used to prescribe intensity in resistance training (RT) in several ways. For instance, trainees can reach a specific RPE value by modifying the number of repetitions, lifted loads, or other training variables. Given the multiple approaches of prescribing intensity using RPE and its growing popularity, we compared the effects of two RPE prescription approaches on adherence rates, body composition, performance and psychological outcomes, in an online RT intervention.

Methods: We randomly assigned 57 healthy participants without RT experience (60% females, age range: 18–45) to one of two groups that received two weekly RT sessions using a resistance-band for 8 weeks. In the fixed-repetition group, participants adjusted the band resistance with the goal of completing 10 repetitions and reaching a 7-RPE on a 0–10 scale by the 10th repetition. In the open-repetition group, participants selected their preferred band resistance and completed repetitions until reaching a 7-RPE by the final repetition. We measured body composition, performance, and program satisfaction rates.

Results: We assessed 46 participants at post-test, 24 from the fixed-repetition group and 22 from the open-repetition group. We observed non-significant and trivial differences between groups in all outcomes (p > 0.05). We then combined the pre-post change scores of the two groups. We found that adherence rates began at 89% and gradually decreased to 42%. On average, participants increased their fat-free mass [0.3 kg (95% CI: 0.1–0.6)], isometric mid-thigh pull [5.5 kg (95% CI: 0.8–10.4)], isometric knee-extension [2.2 kg (95% CI: 0.8–3.7)], and push-ups [6.3 repetitions (95% CI: 4.5–8.2)]. We observed non-significant and trivial changes in bodyweight, grip-force, and countermovement jump. Participants reported high satisfaction rates with all components of the program.

Conclusion: Participants in both groups improved their body composition and physical capacity to a similar extent, and reported comparable satisfaction rates with the programs they followed. Accordingly, either prescription approach can be used to deliver online RT sessions based on personal preferences and logistical constraints. However, since adherences rates declined over the course of the study, future research should test additional strategies aiming to maintain adherence rates.

Longing for a Longitudinal Proxy: Acutely Measured Surface EMG Amplitude is not a Validated Predictor of Muscle Hypertrophy

Surface electromyography amplitudes are commonly measured in acute sports and exercise science studies to make inferences about muscular strength, performance, and hypertrophic adaptations that may result from different exercises or exercise-related variables. Here, we discuss the presumptive logic and assumptions underlying these inferences, focusing on hypertrophic adaptations for simplicity's sake. We present counter-evidence for each of its premises and discuss evidence both for and against the logical conclusion. Given the limited evidence validating the amplitude of surface electromyograms as a predictor of longitudinal hypertrophic adaptations, coupled with its weak mechanistic foundation, we suggest that acute comparative studies that wish to assess stimulus potency be met with scrutiny.

Accuracy in Predicting Repetitions to Task Failure in Resistance Exercise: A Scoping Review and Exploratory Meta-analysis

BACKGROUND

Prescribing repetitions relative to task failure is an emerging approach to resistance training. Under this approach, participants terminate the set based on their prediction of the remaining repetitions left to task failure. While this approach holds promise, an important step in its development is to determine how accurate participants are in their predictions. That is, what is the difference between the predicted and actual number of repetitions remaining to task failure, which ideally should be as small as possible.

OBJECTIVE

The aim of this study was to examine the accuracy in predicting repetitions to task failure in resistance exercises.

DESIGN

Scoping review and exploratory meta-analysis.

SEARCH AND INCLUSION

A systematic literature search was conducted in January 2021 using the PubMed, SPORTDiscus, and Google Scholar databases. Inclusion criteria included studies with healthy participants who predicted the number of repetitions they can complete to task failure in various resistance exercises, before or during an ongoing set, which was performed to task failure. Sixteen publications were eligible for inclusion, of which 13 publications covering 12 studies, with a total of 414 participants, were included in our meta-analysis.

RESULTS

The main multilevel meta-analysis model including all effects sizes (262 across 12 clusters) revealed that participants tended to underpredict the number of repetitions to task failure by 0.95 repetitions (95% confidence interval [CI] 0.17-1.73), but with considerable heterogeneity (Q₍₂₆₁₎ = 3060, p < 0.0001, I² = 97.9%). Meta-regressions showed that prediction accuracy slightly improved when the predictions were made closer to set failure (β =  - 0.025, 95% CI - 0.05 to 0.0014) and when the number of repetitions performed to task failure was lower (≤ 12 repetitions: β = 0.06, 95% CI 0.04-0.09; > 12 repetitions: β = 0.47, 95% CI 0.44-0.49). Set number trivially influenced prediction accuracy with slightly increased accuracy in later sets (β =  - 0.07 repetitions, 95% CI - 0.14 to - 0.005). In contrast, participants' training status did not seem to influence prediction accuracy (β =  - 0.006 repetitions, 95% CI - 0.02 to 0.007) and neither did the implementation of upper or lower body exercises (upper body - lower body =  - 0.58 repetitions; 95% CI - 2.32 to 1.16). Furthermore, there was minimal between-participant variation in predictive accuracy (standard deviation 1.45 repetitions, 95% CI 0.99-2.12).

CONCLUSIONS

Participants were imperfect in their ability to predict proximity to task failure independent of their training background. It remains to be determined whether the observed degree of inaccuracy should be considered acceptable. Despite this, prediction accuracies can be improved if they are provided closer to task failure, when using heavier loads, or in later sets. To reduce the heterogeneity between studies, future studies should include a clear and detailed account of how task failure was explained to participants and how it was confirmed.

Exploring the acute affective responses to resistance training: A comparison of the predetermined and the estimated repetitions to failure approaches

BACKGROUND

In resistance-training (RT), the number of repetitions is traditionally prescribed using a predetermined approach (e.g., three sets of 10 repetitions). An emerging alternative is the estimated repetitions to failure (ERF) approach (e.g., terminating sets two repetitions from failure). Despite the importance of affective responses experienced during RT, a comparison between the two approaches on such outcomes is lacking.

METHODS

Twenty women (age range: 23-45 years) without RT experience completed estimated one repetition maximum (RM) tests in four exercises. In the next two counterbalanced sessions, participants performed the exercises using 70%1RM. Participants completed ten repetitions in all three sets (predetermined condition) or terminated the sets when perceived to be two repetitions away from task-failure (ERF condition). Primary outcomes were affective-valence, enjoyment, and approach-preference and secondary outcomes were repetition-numbers completed in each exercise.

RESULTS

We observed trivial differences in the subjective measures and an approximately even approach-preference split. Under the ERF condition, we observed greater variability in repetition-numbers between participants and across exercises. Specifically, the mean number of repetitions was slightly lower in the chest-press, knee-extension, and lat-pulldown (~1 repetition) but considerably higher in the leg-press (17 vs. 10, p<0.01).

CONCLUSIONS

Both approaches led to comparable affective responses and to an approximately even approach preference. Hence, prior to prescribing either approach, coaches should consider trainee's preferences. Moreover, under the ERF condition participants completed a dissimilar number of repetitions across exercises while presumably reaching a similar proximity to task-failure. This finding suggests that ERF allows for better effort regulation between exercises.

Beneficial Effects of Small-Sided Games as a Conclusive Part of Warm-up Routines in Young Elite Handball Players

ABSTRACT

Iacono, AD, Vigotsky, AD, Laver, L, and Halperin, I. Beneficial effects of small-sided games as a conclusive part of warm-up routines in young elite handball players. J Strength Cond Res 35(6): 1724-1731, 2021-The aim of this study was to compare the effects of small-sided games (SSGs) and traditional warm-up strategies on the mechanical, physiological, and perceptional responses of handball players. Using a randomized and counterbalanced design, 12 elite male handball players completed a general 8-minute warm-up, which was concluded with an 8-minute section of either specific handball shooting drills or 3 × 2 minutes of 3 vs. 3 SSG with a passive recovery of 1 minute between bouts. Countermovement jumps (CMJs) and plyometric press-ups (PPs) were assessed before and immediately after the warm-up regimens using a force plate. Heart rate (HR) was assessed during the warm-up regimens, and rating of perceived exertion (RPE) was assessed after the regimens. Meaningful differences favoring SSG were observed in most of the kinetic variables in the CMJs and PPs (|Hedges g| = 0.26-1.42). Conversely, no meaningful differences were found between warm-up regimens in RPE or HR responses (z-scores = 0.45 and 1.88, respectively). These results indicate that concluding warm-ups with SSGs offer greater benefits compared with a more traditional warm-up routine, despite similar HR and RPE responses even when matched for duration among elite-level handball players.

DEVELOPING twin-specific 75-g oral glucose tolerance test diagnostic thresholds for gestational diabetes based on the risk of future maternal diabetes: a population-based cohort study

OBJECTIVE

To develop twin-specific outcome-based oral glucose tolerance test (OGTT) diagnostic thresholds for GDM based on the risk of future maternal type-2 diabetes.

DESIGN

A population-based retrospective cohort study (2007-2017).

SETTING

Ontario, Canada.

METHODS

Nulliparous women with a live singleton (n = 55 361) or twin (n = 1308) birth who underwent testing for gestational diabetes mellitus (GDM) using a 75-g OGTT in Ontario, Canada (2007-2017). We identified the 75-g OGTT thresholds in twin pregnancies that were associated with similar incidence rates of future type-2 diabetes to those associated with the standard OGTT thresholds in singleton pregnancies.

RESULTS

For any given 75-g OGTT value, the incidence rate of future maternal type-2 diabetes was lower for women with a twin than women with a singleton pregnancy. Using women with a negative OGTT as reference, the risk of future maternal type-2 diabetes in twin pregnancies with a positive OGTT based on the standard OGTT thresholds (9.86 per 1000 person years, adjusted hazard ratio (aHR) 4.79, 95% CI 2.69-8.51) was lower than for singleton pregnancies with a positive OGTT (18.74 per 1000 person years, aHR 8.22, 95% CI 7.38-9.16). The twin-specific OGTT fasting, 1-hour and 2-hour thresholds identified in the current study based on correlation with future maternal type-2 diabetes were 5.8 mmol/l (104 mg/dl), 11.8 mmol/l (213 mg/dl) and 10.4 mmol/l (187 mg/dl), respectively.

CONCLUSIONS

We identified potential twin-specific OGTT thresholds for GDM that are associated with a similar risk of future type-2 diabetes to that observed in women diagnosed with GDM in singleton pregnancies based on standard OGTT thresholds.

TWEETABLE ABSTRACT

Potential twin-specific OGTT thresholds for GDM were identified.

Barbell Hip-Thrust Exercise: Test-Retest Reliability and Correlation With Isokinetic Performance

ABSTRACT

Dello Iacono, A, Padulo, J, Bešlija, T, and Halperin, I. Barbell hip-thrust exercise: Test-retest reliability and correlation with isokinetic performance. J Strength Cond Res 35(3): 659-667, 2021-The barbell hip-thrust (BHT) exercise is growing in popularity as evident by the large increase in research outputs investigating its utility as a training intervention and a testing tool. The aim of this study was to examine the test-retest reliability of the BHT and its correlation with isokinetic performance. Test-retest reliability was established by correlating the peak force and power outcomes measured with the BHT force-velocity profile test of 20 handball athletes on 2 separate days. The peak force and power measured with the BHT force-velocity profile test of 49 handball athletes were correlated with peak concentric force of the knee flexors and hip extensors measured with an isokinetic device at 2 different velocities (60-180°·s-1). The correlation between the isokinetic testing scores and the BHT force-velocity profile tests were moderate to large (Pearson r ranges: 0.45-0.86, all p values <0.001). Test-retest reliability of the BHT force-velocity profile was very high as shown with intraclass correlations of 0.94 and 0.99 for peak force and 0.97 and 0.99 for peak power measures. The BHT force-velocity profile can serve as a tentative substitute in cases that athletes do not have access to an isokinetic device, given the moderate to large correlations between them. Moreover, the BHT force-velocity profile was shown to be very reliable, thus providing coaches and scientists a range of day-to-day performance variability in this exercise.

Rating of Perceived Effort: Methodological Concerns and Future Directions

Rating of perceived effort (RPE) scales are the most frequently used single-item scales in exercise science. They offer an easy and useful way to monitor and prescribe exercise intensity. However, RPE scales suffer from methodological limitations stemming from multiple perceived effort definitions and measurement strategies. In the present review, we attend these issues by covering (1) two popular perceived effort definitions, (2) the terms included within these definitions and the reasons they can impede validity, (3) the problems associated with using different effort scales and instructions, and (4) measuring perceived effort from specific body parts and the body as a whole. We pose that the large number of interactions between definitions, scales, instructions and applications strategies, threatens measurement validity of RPE. We suggest two strategies to overcome these limitations: (1) to reinforce consistency by narrowing the number of definitions of perceived effort, the number of terms included within them, and the number of scales and instructions used. (2) Rather than measuring solely RPE as commonly done, exercise sciences will benefit from incorporating other single-item scales that measure affect, fatigue and discomfort, among others. By following these two recommendations, we expect the field will increase measurement validity and become more comprehensive.

Staying physically active during the COVID-19 quarantine: exploring the feasibility of live, online, group training sessions among older adults

The COVID-19 outbreak has led to recurring quarantines resulting in drastic reductions in physical activity (PA) levels. Given its health benefits, there is a need to explore strategies to increase PA rates during this period. Video-conferencing platforms can be used to deliver live, online, group PA sessions. However, there are only few established PA protocols on how to use such platforms. Hence, the purposes of this study were to (a) design an online PA protocol and (b) explore its feasibility among older adults during a quarantine. A group of exercise specialists developed a PA protocol while accounting for challenges that may arise when using a video-conferencing platform (“Zoom”). A special focus was placed on safety, individualization, and motivational aspects. Then, 31 community dwelling older adults (71.5 ± 4 years) were recruited via social media to follow this protocol twice a week for 8 weeks. Outcome measures included adverse events, adherence rates, and satisfaction with the protocol, its delivery, and technological aspects. Twenty-eight participants completed the protocol. No adverse events occurred, and adherence rates were high (90%). Most participants (97%) indicated they would participate in such a program in the future and highly rated all aspects of the protocol (median score >6 in 1–7 Likert scales). The PA protocol delivered live via a video-conferencing platform was found to be safe and feasible with this cohort. It can therefore be implemented in practice, and in future studies planning to utilize home-based PA sessions for older adults.

A comparison between predetermined and self-selected approaches in resistance training: effects on power performance and psychological outcomes among elite youth athletes

BACKGROUND

The aim of this study was to investigate if choice over resistance training exercise order affects motor performance and psychological outcomes among elite youth hockey players.

METHODS

Seventeen elite hockey players (male, n = 14; female, n = 3, age: 15.1 ± 1.1 years) participated in this study. In the first session, individual optimum power loads were calculated in the back squat, jump squat, bench press and bench throw exercises. Then, in four counterbalanced sessions, participants completed three sets of six repetitions in the same exercises loaded with their optimum power loads. In two sessions, athletes used a self-selected order of exercises, while in other two sessions the order was predetermined. Power outputs were estimated with a linear position transducer. Fatigue and enjoyment were measured during and after the sessions using standardized questionnaires. Repeated measures analyses of variance and a paired-sample t-test were used to compare the effects between conditions.

RESULTS

We observed trivial to small differences between conditions in power outputs (p ≥ 0.07; ES ≤ 0.21), fatigue (p ≥ 0.42; ES ≤ 0.33) and enjoyment (p = 0.72; ES = 0.05).

CONCLUSION

Given the comparable effects between approaches, both can be used when coaching youth athletes. Self-selecting the order of exercises based on preferences is a feasible and practical coaching option when working with youth athletes.

The effect of self-selecting the number of repetitions on motor performance and psychological outcomes

In resistance-training, the number of repetitions can be either fixed and predetermined (e.g., 3 sets of 10 repetitions), or selected by the trainee during ongoing sets (e.g., 3 sets of 8–12 repetitions). The first approach is more goal-focused while the latter is more autonomy-focused. Here we compared these two approaches in motor performance and psychological outcomes. Nineteen resistance-trained participants (10-males) first completed one repetition-maximum (RM) tests in the barbell-squat and bench-press, and were familiarized with the isometric mid-thigh pull (IMTP). In the next two counterbalanced sessions, participants completed two sets of the squat and bench-press using 70%1RM, and two sets of the IMTP. In the predetermined session, participants completed 10 repetitions in all sets, and in the self-selected session, participants chose how many repetitions to complete out of an 8–12 range. Bar-velocity was measured in the squat and bench-press, and force production in the IMTP. Enjoyment, perceived-autonomy, and approach-preferences were collected post-sessions. We observed comparable bar-velocity, force production, and enjoyment in both conditions (all BF₀₁ > 2.1), and an even approach-preferences split. However, in the self-selected condition, participants demonstrated considerable variability in the number of repetitions and reported greater perceived-autonomy. Given the similarities between approaches, both can be used with this cohort based on their personal-preference.

An analysis of the perceived causes leading to task-failure in resistance-exercises

Background

While reaching task-failure in resistance-exercises is a topic that attracts scientific and applied interest, the underlying perceived reasons leading to task-failure remain underexplored. Here, we examined the reasons subjects attribute to task-failure as they performed resistance-exercises using different loads.

Methods

Twenty-two resistance-trained subjects (11-females) completed one Repetition-Maximum (RM) tests in the barbell squat and bench-press. Then, in the next two counterbalanced sessions, subjects performed two sets to task-failure in both exercises, using either 70% or 83% of 1RM. Approximately 30 seconds after set-completion, subjects verbally reported the reasons they perceived to have caused them to reach task-failure. Their answers were recorded, transcribed, and thematically analyzed. The differences between the frequencies of the identified categories were then tested using a mixed logistic regression model.

Results

The most commonly reported reason was muscle fatigue (54%, p < 0.001), mostly of the target muscles involved in each exercise. However, remote muscles involved to a lesser extent in each exercise were also reported. Approximately half of the remaining reasons included general fatigue (26%), pain (12%), cardiovascular strain (11%), and negative affect (10%), with the latter three reported more often in the squat (p = 0.022).

Conclusions

In contrast to our expectations, task-failure was perceived to be caused by a range of limiting factors other than fatigue of the target muscles. It now remains to be established whether different perceived limiting factors of resistance-exercises lead to different adaptations, such as muscular strength and hypertrophy.

The effects of positive and negative verbal feedback on repeated force production

Studies indicate that providing subjects with positiveaugmented feedback (PAF) enhances motor learning and performance compared to negative- (NAF), or no-feedback. However, in the majority of these studies, the performance feedback was provided relative to a peer-group (e.g., "your performance is higher/lower than the norm"). Here we examined how different, and less explored types of PF and NF, influenced repeated force production of 22 resistance-trained subjects (50%-males). On three occasions, subjects completed 12 isometric maximal voluntary contractions (MVC) with their elbow flexors, while electromyography (EMG) was collected from their biceps and triceps brachii muscles. After every second repetition, subjects received either PF (e.g., "You are looking great."), NF (e.g., "You are not trying."), or no-feedback. All measurements were normalized to pre-test MVCs and reported aspercentages. Subjects applied greater forces in the NF condition compared to the PF (4.3%, 95%CI: 2.8, 5.8) and no-feedback (7.9%, 95%CI: 6.4, 9.4) conditions. Similarly, subjects demonstrated greater biceps EMG activity in the NF compared to the PF (6.6%, 95%CI: 3.7, 9.4) and no-feedback (2.8%, 95%CI: 9.9, 15.6) conditions. We speculate that NF can lead subjects to exert greater forces bysignaling that their efforts are lacking. These results indicate that under some circumstances, NF can have practical benefits over no-feedback and even PF; however, we note that NF should be delivered with caution since it may also hinder motivation and self-efficacy over time.

Perception of changes in bar velocity in resistance training: Accuracy levels within and between exercises

Velocity-based training is a method used to monitor resistance-training programs based on repetition velocities measured with tracking devices. Since velocity measuring devices can be expensive and impractical, trainee's perception of changes in velocity (PCV) may be used as a possible substitute. Here, 20 resistance-trained males first completed 1 Repetition Maximum (RM) tests in the bench-press and squat. Then, in three counterbalanced sessions, participants completed four sets of eight repetitions in both exercises using 60%1RM (two-sessions) or 70%1RM. Starting from the second repetition, participants reported their PCV of each repetition as a percentage of the first repetition. Accuracy of PCV was calculated as the difference between PCV and actual changes in velocity measured with a linear-encoder. Three key findings emerged. First, the absolute error in the bench-press and squat was ≈5.8 percentage-points in the second repetition, and increased to 13.2 and 16.7 percentage-points, respectively, by the eighth repetition. Second, participants reduced the absolute error in the second 60%1RM session compared to the first by ≈1.7 in both exercises (p ≤ 0.007). Third, participants were 4.2 times more likely to underestimate changes velocity in the squat compared to the bench-press. The gradual increments in the absolute error suggest that PCV may be better suited for sets of fewer repetitions (e.g., 4-5) and wider velocity-loss threshold ranges (e.g., 5-10%). The reduced absolute error in the second 60%1RM session suggests that PCV accuracy can be improved with practice. The systematic underestimation error in the squat suggests that a correction factor may increase PCV accuracy in this exercise.

The Isometric Horizontal Push Test: Test-Retest Reliability and Validation Study

PURPOSE

To investigate the test-retest reliability and criterion validity of the isometric horizontal push test (IHPT), a newly designed test that selectively measures the horizontal component of maximal isometric force.

METHODS

Twenty-four active males with ≥3 years of resistance training experience performed 2 testing sessions of the IHPT, separated by 3 to 4 days of rest. In each session, subjects performed 3 maximal trials of the IHPT with 3 minutes of rest between them. The peak force outputs were collected simultaneously using a strain gauge and the criterion equipment consisting of a floor-embedded force plate.

RESULTS

The test-retest reliability of peak force values was nearly perfect (intraclass correlation coefficient = ∼.99). Bland-Altman analysis showed excellent agreement between days with nearly no bias for strain gauge 1.2 N (95% confidence interval [CI], -3 to 6 N) and force plate 0.8 N (95% CI, -4 to 6 N). A nearly perfect correlation was observed between the strain gauge and force plate (r = .98, P < .001), with a small bias of 8 N (95% CI, 1.2 to 15 N) in favor of the force plate. The sensitivity of the IHPT was also good, with smallest worthwhile change greater than standard error of measurement for both the strain gauge (smallest worthwhile change: 29 N; standard error of measurement: 17 N; 95% CI, 14 to 20 N) and the force plate (smallest worthwhile change: 29 N; standard error of measurement: 18 N; 95% CI, 14 to 19 N) devices.

CONCLUSIONS

The high degree of validity, reliability, and sensitivity of the IHPT, coupled with its affordability, portability, ease of use, and time efficacy, point to the potential of the test for assessment and monitoring purposes.

The Effects of Cluster-Set and Traditional-Set Postactivation Potentiation Protocols on Vertical Jump Performance

PURPOSE

To compare the effects of 2 postactivation potentiation (PAP) protocols using traditional-set or cluster-set configurations on countermovement jump performance.

METHODS

Twenty-six male basketball players completed 3 testing sessions separated by 72 hours. On the first session, subjects performed barbell jump squats with progressively heavier loads to determine their individual optimum power load. On the second and third sessions, subjects completed 2 PAP protocols in a randomized order: 3 sets of 6 repetitions of jump squats using optimum power load performed with either a traditional-set (no interrepetition rest) or a cluster-set (20-s rest every 2 repetitions) configuration. After a warm-up, countermovement jump height was measured using a force platform before, 30 seconds, 4 minutes, and 8 minutes after completing the PAP protocols. The following kinetic variables were also analyzed and compared: relative impulse, ground reaction force, eccentric displacement, and vertical leg-spring stiffness.

RESULTS

Across both conditions, subjects jumped lower at post 30 seconds by 1.21 cm, and higher in post 4 minutes by 2.21 cm, and in post 8 minutes by 2.60 cm compared with baseline. However, subjects jumped higher in the cluster condition by 0.71 cm (95% confidence interval, 0.37 to 1.05 cm) in post 30 seconds, 1.33 cm (95% confidence interval, 1.02 to 1.65 cm) in post 4 minute, and 1.64 cm (95% confidence interval, 1.41 to 1.88 cm) in post 8 minutes. The superior countermovement jump performance was associated with enhanced kinetic data.

CONCLUSIONS

Both protocols induced PAP responses in vertical jump performance using jump squats at optimum power load. However, the cluster-set configuration led to superior performance across all time points, likely due to reduced muscular fatigue.

High tempo music prolongs high intensity exercise

Music has been shown to reduce rating of perceived exertion, increase exercise enjoyment and enhance exercise performance, mainly in low-moderate intensity exercises. However, the effects of music are less conclusive with high-intensity activities. The purpose of this with-participant design study was to compare the effects of high tempo music (130 bpm) to a no-music condition during repeated high intensity cycling bouts (80% of peak power output (PPO)) on the following measures: time to exercise end-point, rating of perceived exertion (RPE), heart rate (HR), breathing frequency, ventilatory kinetics and blood lactate (BL). Under the music condition, participants exercised 10.7% longer (p = 0.035; Effect size (ES) = 0.28) (increase of 1 min) and had higher HR (4%; p = 0.043; ES = 0.25), breathing frequency (11.6%; p < 0.001; ES = 0.57), and RER (7% at TTF; p = 0.021; ES = 1.1) during exercise, as measured at the exercise end-point. Trivial differences were observed between conditions in RPE and other ventilatory kinetics during exercise. Interestingly, 5 min post-exercise termination, HR recovery was 13.0% faster following the music condition (p < 0.05) despite that music was not played during this period. These results strengthen the notion that music can alter the association between central motor drive, central cardiovascular command and perceived exertion, and contribute to prolonged exercise durations at higher intensities along with a quicken HR recovery.

Case Studies in Exercise and Sport Sciences: A Powerful Tool to Bridge the Science-Practice Gap

Despite the progress made by the scientific exercise community in collaborating and communicating with non-scientist coaches, there is room for improvement. Coaches find research difficult to understand, feel that their interests are not being addressed by exercise research, and rely on peer-discussion to further their coaching knowledge base while consuming little peer-reviewed articles. One useful strategy to bridge the science-practice gap is with case-studies. In addition to furthering our understanding of the physiology, psychology, and training schedules of elite athletes, case studies can serve 1) as a useful communication channel with coaches if presented as narratives and 2) to establish and strengthen relationships between scientists and coaches leading to fruitful research collaborations. The purpose of this invited commentary is to discuss these two less-recognized benefits of case-studies, and propose a way to incorporate case-studies more frequently alongside group-based studies.

Interpreting Signal Amplitudes in Surface Electromyography Studies in Sport and Rehabilitation Sciences

Surface electromyography (sEMG) is a popular research tool in sport and rehabilitation sciences. Common study designs include the comparison of sEMG amplitudes collected from different muscles as participants perform various exercises and techniques under different loads. Based on such comparisons, researchers attempt to draw conclusions concerning the neuro- and electrophysiological underpinning of force production and hypothesize about possible longitudinal adaptations, such as strength and hypertrophy. However, such conclusions are frequently unsubstantiated and unwarranted. Hence, the goal of this review is to discuss what can and cannot be inferred from comparative research designs as it pertains to both the acute and longitudinal outcomes. General methodological recommendations are made, gaps in the literature are identified, and lines for future research to help improve the applicability of sEMG are suggested.

Acute effects of different foam rolling volumes in the interset rest period on maximum repetition performance

Background:

Foam rolling (FR) is a ubiquitous intervention utilised for the purpose of acutely increasing the range of motion without subsequent decreases in performance. Thus, it is commonly used during the periworkout period—that is, prior to, during, or after an athlete's workout.

Objective:

This study investigated how different FR durations applied to the quadriceps during the interset rest periods affects the numbers of repetitions in the knee extension exercise.

Methods:

Twenty-five females completed four sets of knee extensions with 10 repetitions of maximum load to concentric failure on four occasions. Between each set, a 4-minute rest interval was implemented in which participants either passively rested or performed FR for different durations (60 seconds, 90 seconds, and 120 seconds). The 95% confidence intervals revealed a dose-dependent relationship in which longer durations of FR resulted in fewer completed repetitions.

Results:

On average, the number of repetitions with PR was 13.8% greater than that in FR120, 8.6% greater than that in FR90, and 9.1% greater than that in FR60.

Conclusion:

For the purposes of performance and likely adaptation, interset FR seems to be detrimental to a person's ability to continually produce force, and should not be applied to the agonist muscle group between sets of knee extensions.

The Effects of Attentional Focusing Instructions on Force Production During the Isometric Midthigh Pull

Verbal instructions play a key role in motor learning and performance. Whereas directing one's attention toward bodily movements or muscles (internal focus) tends to hinder performance, instructing persons to focus on the movement outcome, or an external object related to the performed task (external focus) enhances performance. The study's purpose was to examine whether focus of attention affects maximal force production during an isometric midthigh pull (IMTP) among 18 trained athletes (8F & 10M). Athletes performed 3 IMTP trials a day for 3 consecutive days. The first day was a familiarization session in which athlete's received only control instructions. The following 2 days athletes received either control, internal, or external focus of attention instructions in a randomized, within-subject design. Compared to performance with an internal focus of attention, athletes applied 9% greater force when using an external focus of attention (p < 0.001, effect size [ES] = 0.33) and 5% greater force with control instructions (p = 0.001, ES = 0.28). A small positive 3% advantage was observed between performances with an external focus of attention compared with control instructions (p = 0.03, ES = 0.13). Focusing internally on body parts and/or muscle groups during a movement task that requires maximal force hinders performance, whereas focusing on an object external to the self leads to enhanced force production, even when using a simple multijoint static task such as the IMTP.

The Effects of Either a Mirror, Internal or External Focus Instructions on Single and Multi-Joint Tasks

Training in front of mirrors is common, yet little is known about how the use of mirrors effects muscle force production. Accordingly, we investigated how performing in front of a mirror influences performance in single and multi-joint tasks, and compared the mirror condition to the established performance effects of internal focus (IF) and external focus (EF) instructions in a two part experiment. In the single-joint experiment 28 resistance-trained participants (14 males and 14 females) completed two elbow flexion maximal voluntary isometric contractions under four conditions: mirror, IF, EF and neutral instructions. During these trials, surface EMG activity of the biceps and triceps were recorded. In the multi-joint experiment the same participants performed counter-movement jumps on a force plate under the same four conditions. Single-joint experiment: EF led to greater normalized force production compared to all conditions (P≤0.02, effect-size range [ES] = 0.46–1.31). No differences were observed between neutral and mirror conditions (P = 0.15, ES = 0.15), but both were greater than IF (P<0.01, ES = 0.79–1.84). Surface EMG activity was comparable across conditions (P≥0.1, ES = 0.10–0.21). Multi-joint experiment: Despite no statistical difference (P = 0.10), a moderate effect size was observed for jump height whereby EF was greater than IF (ES = 0.51). No differences were observed between neutral and mirror conditions (ES = 0.01), but both were greater than IF (ES = 0.20–22). The mirror condition led to superior performance compared to IF, inferior performance compared to EF, and was equal to a neutral condition in both tasks. These results provide novel and practical evidence concerning mirror training during resistance type training.

Accuracy of immunoassay and mass spectrometry urinary free cortisol in the diagnosis of Cushing's syndrome

PURPOSE

Urinary free cortisol (UFC) determination by highly specific methods as mass spectrometry instead of commercially available antibody-based immunoassays is increasingly recommended. However, clinical comparisons of both analytical approaches in the screening of Cushing's syndrome (CS) are not available. The aim of this study was to evaluate the diagnostic value of mass spectrometry versus immunoassay measurements of 24 h-UFC in the screening of CS.

METHODS

Cross-sectional study of 33 histologically confirmed CS patients: 25 Cushing's disease, 5 adrenal CS and 3 ectopic CS; 92 non-CS patients; and 35 healthy controls. UFC by immunoassay (UFCxIA) and mass spectrometry (UFCxMS), urinary free cortisone (UFCo) and UFC:UFCo ratio were measured, together with creatinine-corrected values. Sensitivity, specificity, AUC and Landis and Koch concordance index were determined.

RESULTS

AUC for UFCxIA and UFCxMS were 0.77 (CI 0.68-0.87) and 0.77 (CI 0.67-0.87) respectively, with a kappa coefficient 0.60 and strong Landis and Koch concordance index. The best calculated cutoff values were 359 nmol/24 h for UFCxIA (78 % sensitivity, 62 % specificity) and 258.1 nmol/24 h for UCFxMS (53 % sensitivity, 86 % specificity). The upper limit of UFCxIA and UCFxMS reference ranges were 344.7 and 169.5 nmol/24 h respectively. Sensitivity and specificity for CS diagnosis at these cutpoints were 84 and 56 % for UFCxIA and 81 and 54 % for UFCxMS.

CONCLUSIONS

According to our data, both methods present a very similar diagnostic value. However, results suggest that lower cutoff points for mass spectrometry may be necessary in order to improve clinical sensitivity.

Knowledge of Repetition Range Does Not Affect the Maximal Force Production Strategies of Adolescent Females

PURPOSE

Contrary to adult force reserve strategies, it is not known whether adolescent females with less experience performing maximal voluntary contractions (MVC) have specific responses to a known or unknown fatigue endpoint.

METHODS

Using a counterbalanced random crossover design, fourteen inexperienced female adolescents completed three elbow flexor (EF) fatiguing protocols. Participants were randomly assigned to a control (informed they would perform 12 MVCs), unknown (not informed of the number of MVCs to be completed, but stopped after 12) or deception condition (instructed to complete 6 MVCs, however, after the 6th repetition performed another 6 MVCs). Before and during the interventions, EF impulse, force, and biceps brachii (BB) and triceps brachii (TB) electromyography (EMG) activity were recorded.

RESULTS

Participants exhibited decreases in impulse (10.9%; p<0.05), force (7.5%; p=0.001), BB (16.2%; p<0.05) and TB (12.9%; p<0.05) EMG activity between the pre-test and the first repetition of all protocols. Knowledge of endpoint, or lack of it, did not change measures with the repeated MVCs. When informed about the final repetition, force remained depressed suggesting no physiological reserve.

CONCLUSION

Adolescent females exhibited an anticipatory response to the task of performing repeated MVCs. A lack of change with knowledge of endpoint indicates that those lacking in MVC experience do not employ the same pacing strategies as in previous studies of participants with MVC experience.

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.

Long-term remission and recurrence rate in a cohort of Cushing's disease: the need for long-term follow-up

OBJECTIVE

Transsphenoidal surgery is the procedure of choice in Cushing disease (CD), with immediate post-operative remission rates ranging between 59 and 94% and recurrence rates between 3 and 46%, both depending upon the definition criteria and the duration of the follow-up. Our aim was to assess the rate of remission, recurrence and persistence of the disease after the first treatment and to identify predictors of remission in the CD population of our center.

METHODS

Retrospective cohort study of the patients diagnosed of CD and with follow-up in our center between 1974 and 2011. We analyzed 41 patients (35 women and 6 men) with a mean age at diagnosis of 34 ± 13 years. The mean follow-up was 14 ± 10 years (range 1-37 years) and the median of follow-up period was 6.68 years.

RESULTS

Thirty-five (85.4%) patients underwent transsphenoidal surgery as first treatment option. Histopathological evidence of a pituitary adenoma was registered in 17 (48.5%) patients. Thirty-two (78%) patients achieved disease remission after the first treatment, 21 (65.6%) of them presented disease recurrence. Persistent disease was observed in 9 (22%) patients. Twelve (29.3%) subjects developed post-surgical adrenal insufficiency, 7 of which (70%) achieved stable remission. Two parameters were found to be significant predictors of remission after the first treatment: age at disease diagnosis and the development of adrenal insufficiency (cortisol <3 μg/dl) in the immediate post-operative state.

CONCLUSIONS

We report a high recurrence rate, at least partially attributable to the long follow-up time. Early post-surgery adrenal insufficiency predicts remission. Hypopituitarism was also very prevalent, and strongly associated with radiotherapy. These results lead us to the conclusion that CD needs a life-long strict follow-up.

Knowledge of repetitions range affects force production in trained females

Most studies have examined pacing strategies with cyclical activities (running and cycling). It has been demonstrated that males employ different pacing strategies during repeated maximal voluntary contractions (MVCs) dependent upon a known endpoint. Since different fatiguing mechanisms have been identified between the genders, it is not known if females use comparable pacing strategies. The purpose of this study was to examine if informing female subjects regarding the number of MVCs to perform would affect force and electromyography (EMG). Twenty well-trained females completed 3 fatiguing protocols in a randomized order. In the control condition participants were informed they would perform twelve MVCs and then actually completed twelve. In the unknown condition they were not told how many MVCs to perform but were stopped after twelve. In the deception condition they were initially informed to perform 6 MVCs, but after the 6(th) MVC they were asked to perform a few more MVCs and were stopped after twelve. During the first 6 MVCs, forces in the deception condition were greater compared to the unknown (p = 0.021, ES = 0.65, 5%) and control (p = 0.022, ES = 0.42, 3%) conditions. No differences were found between conditions in the last 6 MVCs. A main effect for repetitions showed force deficits during the first 6 MVCs (p = 0.000, ES = 1.81, 13%) and last 6 MVCs (p = 0.05, ES = 0.34, 3%). No differences were found between conditions in biceps and triceps EMG. However, EMG decreased during the first 6 MVCs for biceps (p = 0.001, ES = 1.0, 14%) and triceps (p = 0.001, ES = 0.76, 14%) across conditions. No differences were found in the last 6 MVCs. The anticipation of performing fewer MVCs led to increased force, whereas no endpoint led to decreased force production. Key pointsPacing strategies occur during repeated (fatiguing) MVCs as a function of end point expectations.Females use similar pacing strategies as previously published results with males.Without a known end point, females will tend to pace themselves by decreasing force output even when asked to perform maximal contractions.

Unilateral isometric muscle fatigue decreases force production and activation of contralateral knee extensors but not elbow flexors

Nonlocal muscle fatigue occurs when fatiguing 1 muscle alters performance of another rested muscle. The purpose of the study was to investigate if fatiguing 2 separate muscles would affect the same rested muscle, and if fatiguing the same muscle would affect 2 separate muscles. Twenty-one trained males participated in 2 studies (n = 11; n = 10). Subjects performed 2 pre-test maximum voluntary contractions (MVCs) with the nondominant knee extensors. Thereafter they performed two 100-s MVCs with their dominant knee extensors, elbow flexors, or rested. Between and after the sets, a single MVC with the nondominant rested knee extensors was performed. Subsequently, 12 nondominant knee extensors repeated MVCs were completed. Force, quadriceps voluntary activation (VA), and electromyography (EMG) were measured. The same protocol was employed in study 2 except the nondominant elbow-flexors were tested. Study 1: Compared with control conditions, a significant decrease in nondominant knee extensors force, EMG, and VA was found under both fatiguing conditions (P ≤ 0.05; effect size (ES) = 0.91-1.15; 2%-8%). Additionally, decrements in all variables were found from the first post-intervention MVC to the last (P ≤ 0.05; ES = 0.82-2.40; 9%-20%). Study 2: No differences were found between conditions for all variables (P ≥ 0.33; ES ≤ 0.2; ≤3.0%). However, all variables decreased from the first post-intervention MVC to the last (P ≤ 0.05; ES = 0.4-3.0; 7.2%-19.7%). Whereas the rested knee extensors demonstrated nonlocal effects regardless of the muscle being fatigued, the elbow-flexors remained unaffected. This suggests that nonlocal effects are muscle specific, which may hold functional implications for training and performance.

Knee extension fatigue attenuates repeated force production of the elbow flexors

Non-local muscle fatigue has been demonstrated with unilateral activities, where fatiguing one limb alters opposite limb forces. Fewer studies have examined if non-local fatigue occurs with unrelated muscles. The purpose of this study was to investigate if knee extensors fatigue alters elbow flexors force and electromyography (EMG) activity. Eighteen males completed a control and fatiguing session (randomised). Blood lactate was initially sampled followed by three maximal voluntary contractions (MVC) with the elbow flexors and two with the knee extensors. Thereafter, subjects either sat (control) or performed five sets of bilateral dynamic knee extensions to exhaustion using a load equal to the dominant limb MVC (1-min rest between sets). Immediately afterwards, subjects were assessed for blood lactate and unilateral knee extensors MVC, and after 1 min performed a single unilateral elbow flexor MVC. Two minutes later, subjects performed 12 unilateral elbow flexor MVCs (5 s contraction/10 s rest) followed by a third blood lactate test. Compared to control, knee extensor force dropped by 35% (p < 0.001; ES = 1.6) and blood lactate increased by 18% (p < 0.001; ES = 2.8). Elbow flexor forces were lower after the fatiguing protocol only during the last five MVCs (p < 0.05; ES = ∼ 0.58; ∼ 5%). No changes occurred between conditions in EMG. Elbow flexor forces significantly decreased after knee extensors fatigue. The effect was revealed during the later stages of the repeated MVCs protocol, demonstrating that non-local fatigue may have a stronger effect on repeated rather than on single attempts of maximal force production.

Pacing strategies during repeated maximal voluntary contractions

PURPOSE

Pacing strategies have been reported to occur during continuous cyclical exercises. However, currently no studies have examined if pacing takes place during repeated maximal voluntary muscle contractions (MVCs). Accordingly, the purpose of this study was to examine if informing subjects on the number of MVCs they would perform would affect force and root mean squared electromyography (EMG), during similar fatiguing protocols.

METHODS

Thirty well-trained male subjects completed three fatiguing protocols in a randomized order. In the control condition participants were informed they would perform 12 MVCs, and then completed all 12. In the unknown condition they were not told how many MVCs they would perform, but were stopped after 12. Lastly, in the deception condition they were initially told they would perform only 6 MVCs, but after the 6 contractions they were asked to perform a few more repetitions and were stopped after 12.

RESULTS

Compared to the unknown condition, subjects demonstrated greater forces (p < 0.05, ES = 0.35-1.14, 2-7.5%) and biceps EMG (p < 0.05, ES = 0.6, 6%) in the deception condition during the first six MVCs. Additionally, under all conditions subjects applied greater forces in the last repetition (#12) relative to the previous one (#11) (p < 0.06, ES = 0.36-0.5, 2.8-3.8%).

CONCLUSIONS

The anticipation of performing a certain number of MVCs led the subjects to utilize different pacing strategies. The results also question the assumption that subjects followed the instruction to exert maximal effort during repeated MVCs.

Roller massager improves range of motion of plantar flexor muscles without subsequent decreases in force parameters

BACKGROUND

Limited dorsiflexion range of motion (ROM) has been linked to lower limb injuries. Improving limited ankle ROM may decrease injury rates. Static stretching (SS) is ubiquitously used to improve ROM but can lead to decreases in force and power if performed prior to the activity. Thus, alternatives to improve ROM without performance decrements are needed.

OBJECTIVES/PURPOSE

To compare the effects of SS and self massage (SM) with a roller massage of the calf muscles on ankle ROM, maximal voluntary contraction (MVC) force F100 (force produced in the first 100 ms of the MVC), electromyography (EMG of soleus and tibialis anterior) characteristics of the plantar flexors, and a single limb balance test.

METHODS

Fourteen recreationally trained subjects were tested on two separate occasions in a randomized cross-over design. After a warm up, subjects were assessed for passive dorsiflexion ROM, MVC, and a single-limb balance test with eyes closed. The same three measurements were repeated after 10 minutes (min) of rest and prior to the interventions. Following the pre-test, participants randomly performed either SS or SM for 3 sets of 30 seconds (s) with 10s of rest between each set. At one and 10 min post-interventions the participants repeated the three measurements, for a third and fourth cycle of testing.

RESULTS

Roller massage increased and SS decreased maximal force output during the post-test measurements, with a significant difference occurring between the two interventions at 10 min post-test (p < 0.05, ES = 1.23, 8.2% difference). Both roller massage (p < 0.05, ES = 0.26, ~4%) and SS (p < 0.05, ES = 0.27, ~5.2%) increased ROM immediately and 10 min after the interventions. No significant effects were found for balance or EMG measures.

CONCLUSIONS

Both interventions improved ankle ROM, but only the self-massage with a roller massager led to small improvements in MVC force relative to SS at 10 min post-intervention. These results highlight the effectiveness of a roller massager relative to SS. These results could affect the type of warm-up prior to activities that depend on high force and sufficient ankle ROM.

LEVEL OF EVIDENCE

2c.