Effect of task familiarisation on distribution of energy during a 2000 m cycling time trial

A self-paced 15-minute cycling time trial is a reliable performance measure in recreationally active individuals

Cycling time trial (TT) protocols have been shown to be reliable in trained cyclists, but their reproducibility in lesser-trained individuals is unknown. This study examined the reliability of a self-paced 15-minute cycling TT in recreationally active individuals. Twelve recreationally active males (age 27 ± 3 y; body mass 75.2 ± 8.9 kg; V ˙ O2peak = 51.10 ± 7.53 ml∙kg∙min-1) completed a V ˙ O2peak test and four experimental trials, separated by > 48 h. Experimental trials consisted of 10 min cycling at 60% Wmax, followed by a self-paced 15-min TT. Heart rate and work done were recorded every 5 min during the TT; and coefficient of variation (CV) was calculated. Work done was not different (P = 0.706) between trials (193.2 ± 45.3 kJ; 193.2 ± 43.5 kJ; 192.0 ± 42.3 kJ; 193.9 ± 42.8 kJ). Within participant CV ranged from 0.5-4.9% for the four TTs, with a mean CV of 2.1%. Mean CV decreased from 2.0% (range 0.1-5.0%) for the first two TTs to 1.7% (range 0.2-5.6%) for the second and third TTs, and further decreased to 1.0% (range 0.2-1.8%) for the third and fourth TTs. In conclusion, the use of a short-duration self-paced cycling TT in recreationally active individuals is a reliable performance measure.

The effect of inspiratory muscle training and detraining on the respiratory metaboreflex

NEW FINDINGS

What is the central question of this study? Is the attenuation of the respiratory muscle metaboreflex preserved after detraining? What is the main finding and its importance? Inspiratory muscle training increased respiratory muscle strength and attenuated the respiratory muscle metaboreflex as evident by lower heart rate and blood pressure. After 5 weeks of no inspiratory muscle training (detraining), respiratory muscle strength was still elevated and the metaboreflex was still attenuated. The benefits of inspiratory muscle training persist after cessation of training, and attenuation of the respiratory metaboreflex follows changes in respiratory muscle strength.

ABSTRACT

Respiratory muscle training (RMT) improves respiratory muscle (RM) strength and attenuates the RM metaboreflex. However, the time course of muscle function loss after the absence of training or 'detraining' is less known and some evidence suggest the respiratory muscles atrophy faster than other muscles. We sought to determine the RM metaboreflex in response to 5 weeks of RMT and 5 weeks of detraining. An experimental group (2F, 6M; 26 ± 4years) completed 5 weeks of RMT and tibialis anterior (TA) training (each 5 days/week at 50% of maximal inspiratory pressure (MIP) and 50% maximal isometric force, respectively) followed by 5 weeks of no training (detraining) while a control group (1F, 7M; 24 ± 1years) underwent no intervention. Prior to training (PRE), post-training (POST) and post-detraining (DETR), all participants underwent a loaded breathing task (LBT) to failure (60% MIP) while heart rate and mean arterial blood pressure (MAP) were measured. Five weeks of training increased RM (18 ± 9%, P < 0.001) and TA (+34 ± 19%, P < 0.001) strength and both remained elevated after 5 weeks of detraining (MIP-POST vs. MIP-DETR: 154 ± 31 vs. 153 ± 28 cmH2O, respectively, P = 0.853; TA-POST vs. TA-DETR: 86 ± 19 vs. 85 ± 16 N, respectively, P = 0.982). However, the rise in MAP during LBT was attenuated POST (-11 ± 17%, P = 0.003) and DETR (-9 ± 9%, P = 0.007) during the iso-time LBT. The control group had no change in MIP (P = 0.33), TA strength (P = 0.385), or iso-time MAP (P = 0.867) during LBT across all time points. In conclusion, RM and TA have similar temporal strength gains and the attenuation of the respiratory muscle metaboreflex remains after 5 weeks of detraining.

Analysis of pacing and kinematics in 3000 m freestyle in elite level swimmers

This study aimed to determine elite swimmers' pacing strategy in the 3000 m event and to analyse the associated performance variability and pacing factors. Forty-seven races were performed by 17 male and 13 female elite swimmers in a 25 m pool (20.7 ± 2.9 years; 807 ± 54 FINA points). Lap performance, clean swim velocity (CSV), water break time (WBT), water break distance (WBD), stroke rate (SR), stroke length (SL) and stroke index (SI) were analysed including and excluding the first (0-50 m) and last lap (2950-3000 m). The most common pacing strategy adopted was parabolic. Lap performance and CSV were faster in the first half of the race compared to the second half (p < 0.001). WBT, WBD, SL and SI were reduced (p < 0.05) in the second half compared to the first half of the 3000 m when including and excluding the first and last laps for both sexes. SR increased in the second half of the men's race when the first and last laps were excluded. All studied variables showed significant variation between the two halves of the 3000 m, the highest variation being obtained in WBT and WBD, suggesting that fatigue negatively affected swimming kinematics.

Pacing Behaviour Development and Acquisition: A Systematic Review

BACKGROUND

The goal-directed decision-making process of effort distribution (i.e. pacing) allows individuals to efficiently use energy resources as well as to manage the impact of fatigue on performance during exercise. Given the shared characteristics between pacing behaviour and other skilled behaviour, it was hypothesized that pacing behaviour would adhere to the same processes associated with skill acquisition and development.

METHODS

PubMed, Web of Science and PsycINFO databases between January 1995 and January 2022 were searched for articles relating to the pacing behaviour of individuals (1) younger than 18 years of age, or (2) repeatedly performing the same exercise task, or (3) with different levels of experience.

RESULTS

The search resulted in 64 articles reporting on the effect of age (n = 33), repeated task exposure (n = 29) or differing levels of experience (n = 13) on pacing behaviour. Empirical evidence identifies the development of pacing behaviour starts during childhood (~ 10 years old) and continues throughout adolescence. This development is characterized by an increasingly better fit to the task demands, encompassing the task characteristics (e.g. duration) and environment factors (e.g. opponents). Gaining task experience leads to an increased capability to attain a predetermined pace and results in pacing behaviour that better fits task demands.

CONCLUSIONS

Similar to skilled behaviour, physical maturation and cognitive development likely drive the development of pacing behaviour. Pacing behaviour follows established processes of skill acquisition, as repeated task execution improves the match between stimuli (e.g. task demands and afferent signals) and actions (i.e. continuing, increasing or decreasing the exerted effort) with the resulting exercise task performance. Furthermore, with increased task experience attentional capacity is freed for secondary tasks (e.g. incorporating opponents) and the goal selection is changed from achieving task completion to optimizing task performance. As the development and acquisition of pacing resemble that of other skills, established concepts in the literature (e.g. intervention-induced variability and augmented feedback) could enrich pacing research and be the basis for practical applications in physical education, healthcare, and sports.

Uneven but Conservative Pacing Is Associated With Performance During Uphill and Downhill Running

PURPOSE

To investigate the relationship between pacing strategy and performance during uphill and downhill running-specifically, what distribution of energy corresponds to faster race finish times between and among participants.

METHODS

Eighteen years of race data from a 10.2-mile running race with an uphill first half and a downhill second half were analyzed to identify relationships between pacing and performance. A pacing coefficient (PC), equal to a participant's ascent time divided by finishing time (FT), was used to define each participant's pacing strategy. The American College of Sports Medicine metabolic running equation was used to estimate energy expenditure during the ascent, descent, and total race. Statistical analyses compared participants' PC to their FT and finishing place within their age and gender category. Additionally, FT and finishing place were compared between groups of participants who exhibited similar pacing strategies.

RESULTS

PCs were positively associated with faster FTs (r2 = .120, P < .001) and better finishing positions (r2 = .104, P < .001). PCs above .600 were associated with the fastest average FTs and best average finishing position within age and gender categories (all P ≤ .047).

CONCLUSIONS

Participants performed the best when energy expenditure increased no more than 10.4% during the uphill portion compared to their overall average. It is not possible to state that overly aggressive uphill efforts resulted in premature fatigue and thus slower decent times and worse race performance. However, participants should still avoid overly aggressive uphill pacing, as performance was associated with larger PCs.

Impact of thermal sensation on exercise performance in the heat: a Thermo Tokyo sub-study

PURPOSE

Thermal perception, including thermal sensation (TS), influences exercise performance in the heat. TS is a widely used measure and we examined the impact of initial TS (iTS) on performance loss during exercise in simulated Tokyo environmental conditions among elite athletes.

METHODS

105 Elite outdoor athletes (endurance, skill, power and mixed trained) participated in this crossover study. Participants performed a standardized exercise test in control (15.8 ± 1.2 °C, 55 ± 6% relative humidity (RH)) and simulated Tokyo (31.6 ± 1.0 °C, 74 ± 5% RH) conditions to determine performance loss. TS was assessed ± 5 min prior to exercise (iTS) and every 5 min during the incremental exercise test (TS). Based on iTS in the Tokyo condition, participants were allocated to a neutral (iTS = 0, n = 11), slightly warm (iTS = 1, n = 50), or warm-to-hot (iTS = 2/3, n = 44) subgroup.

RESULTS

For the whole cohort iTS was 1 [1-2] and TS increased to 3 [3-3] at the end of exercise in the Tokyo condition. Average performance loss was 26.0 ± 10.7% in the Tokyo versus control condition. The slightly warm subgroup had less performance loss (22.3 ± 11.3%) compared to the warm-to-hot subgroup (29.4 ± 8.5%, p = 0.003), whereas the neutral subgroup did not respond different (28.8 ± 11.0%, p = 0.18) from the slightly warm subgroup.

CONCLUSION

iTS impacted the magnitude of performance loss among elite athletes exercising in hot and humid conditions. Athletes with a warm-to-hot iTS had more performance loss compared to counterparts with a slightly warm iTS, indicating that pre-cooling strategies and/or heat acclimation may be of additional importance for athletes in the warm-to-hot iTS group to mitigate the impact of heat stress.

Performance and thermoregulation of Dutch Olympic and Paralympic athletes exercising in the heat: Rationale and design of the Thermo Tokyo study: The journal Temperature toolbox

The environmental conditions during the Tokyo Olympic and Paralympic Games are expected to be challenging, which increases the risk for participating athletes to develop heat-related illnesses and experience performance loss. To allow safe and optimal exercise performance of Dutch elite athletes, the Thermo Tokyo study aimed to determine thermoregulatory responses and performance loss among elite athletes during exercise in the heat, and to identify personal, sports-related, and environmental factors that contribute to the magnitude of these outcomes. For this purpose, Dutch Olympic and Paralympic athletes performed two personalized incremental exercise tests in simulated control (15°C, relative humidity (RH) 50%) and Tokyo (32°C, RH 75%) conditions, during which exercise performance and (thermo)physiological parameters were obtained. Thereafter, athletes were invited for an additional visit to conduct anthropometric, dual-energy X-ray absorptiometry (DXA), and 3D scan measurements. Collected data also served as input for a thermophysiological computer simulation model to estimate the impact of a wider range of environmental conditions on thermoregulatory responses. Findings of this study can be used to inform elite athletes and their coaches on how heat impacts their individual (thermo)physiological responses and, based on these data, advise which personalized countermeasures (i.e. heat acclimation, cooling interventions, rehydration plan) can be taken to allow safe and maximal performance in the challenging environmental conditions of the Tokyo 2020 Olympic and Paralympic Games.

Exercise Performance and Thermoregulatory Responses of Elite Athletes Exercising in the Heat: Outcomes of the Thermo Tokyo Study

Objective

We examined the impact of simulated Tokyo 2020 environmental condition on exercise performance, thermoregulatory responses and thermal perception among Dutch elite athletes.

Methods

105 elite athletes from different sport disciplines performed two exercise tests in simulated control (15.9 ± 1.2 °C, relative humidity (RH) 55 ± 6%) and Tokyo (31.6 ± 1.0 °C, RH 74 ± 5%) environmental conditions. Exercise tests consisted of a 20-min warm-up (70% HR_max), followed by an incremental phase until volitional exhaustion (5% workload increase every 3 min). Gastrointestinal temperature (T_gi), heart rate, exercise performance and thermal perception were measured.

Results

Time to exhaustion was 16 ± 8 min shorter in the Tokyo versus the control condition (− 26 ± 11%, whereas peak power output decreased with 0.5 ± 0.3 W/kg (16 ± 7%). Greater exercise-induced increases in T_gi (1.8 ± 0.6 °C vs. 1.5 ± 0.5 °C, p < 0.001) and higher peak T_gi (38.9 ± 0.6 °C vs. 38.7 ± 0.4 °C, p < 0.001) were found in the Tokyo versus control condition. Large interindividual variations in exercise-induced increase in T_gi (range 0.7–3.5 °C) and peak T_gi (range 37.6–40.4 °C) were found in the Tokyo condition, with greater T_gi responses in endurance versus mixed- and skill-trained athletes. Peak thermal sensation and thermal comfort scores deteriorated in the Tokyo condition, with aggravated responses for power versus endurance- and mixed-trained athletes.

Conclusion

Large performance losses and T_gi increases were found among elite athletes exercising in simulated Tokyo conditions, with a substantial interindividual variation and significantly different responses across sport disciplines. These findings highlight the importance of an individual approach to optimally prepare athletes for safe and maximal exercise performance during the Tokyo Olympics.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40279-021-01530-w.

Sex Differences in Performance and Pacing Strategies During Sprint Skiing

Purpose: This study aimed to compare performance and pacing strategies between elite male and female cross-country skiers during a sprint competition on snow using the skating technique.

Methods: Twenty male and 14 female skiers completed an individual time-trial prolog (TT) and three head-to-head races (quarter, semi, and final) on the same 1,572-m course, which was divided into flat, uphill and downhill sections. Section-specific speeds, choice of sub-technique (i.e., gear), cycle characteristics, heart rate and post-race blood lactate concentration were monitored. Power output was estimated for the different sections during the TT, while metabolic demand was estimated for two uphill camera sections and the final 50-m flat camera section.

Results: Average speed during the four races was ∼12.5% faster for males than females (P < 0.001), while speeds on the flat, uphill and downhill sections were ∼11, 18, and 9% faster for the males than females (all P < 0.001 for terrain, sex, and interaction). Differences in uphill TT speed between the sexes were associated with different sub-technique preferences, with males using a higher gear more frequently than females (P < 0.05). The estimated metabolic demand relative to maximal oxygen uptake (V˙O_2max) was similar for both sexes during the two uphill camera sections (∼129% of V˙O_2max) and for the final 50-m flat section (∼153% of V˙O_2max). Relative power output during the TT was 18% higher for males compared to females (P < 0.001) and was highly variable along the course for both sexes (coefficient of variation [CV] between sections 4–9 was 53%), while the same variation in heart rate was low (CV was ∼3%). The head-to-head races were ∼2.4% faster than the TT for both sexes and most race winners (61%) were positioned first already after 30 m of the race. No sex differences were observed during any of the races for heart rate or blood lactate concentration.

Conclusion: The average sex difference in sprint skiing performance was ∼12.5%, with varying differences for terrain-specific speeds. Moreover, females skied relatively slower uphill (at a lower gear) and thereby elicited more variation in their speed profiles compared to the males.

Racing an Opponent: Alteration of Pacing, Performance, and Muscle-Force Decline but Not Rating of Perceived Exertion

Purpose: Performing against a virtual opponent has been shown to invite a change in pacing and improve time-trial (TT) performance. This study explored how this performance improvement is established by assessing changes in pacing, neuromuscular function, and perceived exertion. Methods: After a peak-power-output test and a familiarization TT, 12 trained cyclists completed two 4-km TTs in randomized order on a Velotron cycle ergometer. TT conditions were riding alone (NO) and riding against a virtual opponent (OP). Knee-extensor performance was quantified before and directly after the TT using maximal voluntary contraction force (MVC), voluntary activation (VA), and potentiated doublet-twitch force (PT). Differences between the experimental conditions were examined using repeated-measures ANOVAs. Linear-regression analyses were conducted to associate changes in pacing to changes in MVC, VA, and PT. Results: OP was completed faster than NO (mean power output OP 289.6 ± 56.1 vs NO 272.2 ± 61.6 W; P = .020), mainly due to a faster initial pace. This was accompanied by a greater decline in MVC (MVC pre vs post −17.5% ± 12.4% vs −11.4% ± 10.9%, P = .032) and PT (PT pre vs post −23.1% ± 14.0% vs −16.2% ±11.4%, P = .041) after OP than after NO. No difference between conditions was found for VA (VA pre vs post −4.9% ± 6.7% vs −3.4% ± 5.0%, P = .274). Rating of perceived exertion did not differ between OP and NO. Conclusion: The improved performance when racing against a virtual opponent was associated with a greater decline in voluntary and evoked muscle force than riding alone, without a change in perceived exertion, highlighting the importance of human–environment interactions in addition to one’s internal state for pacing regulation and performance.

The reproducibility of 10 and 20km time trial cycling performance in recreational cyclists, runners and team sport athletes

OBJECTIVES

This study aimed to determine the reliability of 10 and 20km cycling time trial (TT) performance on the Velotron Pro in recreational cyclists, runners and intermittent-sprint based team sport athletes, with and without a familiarisation.

DESIGN

Thirty-one male, recreationally active athletes completed four 10 or 20km cycling TTs on different days.

METHODS

During cycling, power output, speed and cadence were recorded at 23Hz, and heart rate and rating of perceived exertion (RPE) were recorded every km. Multiple statistical methods were used to ensure a comprehensive assessment of reliability. Intraclass correlations, standard error of the measurement, minimum difference required for a worthwhile change and coefficient of variation were determined for completion time and mean trial variables (power output, speed, cadence, heart rate, RPE, session RPE).

RESULTS

A meaningful change in performance for cyclists, runners, team sport athletes would be represented by 7.5, 3.6 and 12.9% improvement for 10km and a 4.9, 4.0 and 5.6% for 20km completion time. After a familiarisation, a 4.0, 3.7 and 6.4% improvement for 10km and a 4.1, 3.0 and 4.4% would be required for 20km.

CONCLUSIONS

Data from this study suggest not all athletic subgroups require a familiarisation to produce substantially reliable 10 and 20km cycling performance. However, a familiarisation considerably improves the reliability of pacing strategy adopted by recreational runners and team sport athletes across these distances.

Pacing Ability in Elite Runners with Intellectual Impairment

PURPOSE

To understand how athletes invest their energy over a race, differences in pacing ability between athletes with and without intellectual impairment (II) were explored using a novel field test.

METHODS

Well-trained runners (n = 67) participated in this study, including 34 runners with II (age = 24.4 ± 4.5 yr; IQ = 63.1 ± 7.7) and 33 runners without II (age = 31.4 ± 11.2 yr). The ability to perform at a preplanned submaximal pace was assessed. Two 400-m running trials were performed on an athletics track, with an individually standardized velocity. In the first trial, the speed was imposed by auditory signals given in 20-40 m intervals, in combination with coach feedback during the initial 200 m. The participant was instructed to maintain this velocity without any feedback during the final 200 m. In trial 2, no coach feedback was permitted.

RESULTS

Repeated-measures analyses revealed a significant between-group effect. II runners deviated more from the target time than runners without II. The significant trial-group interaction effect (F = 4.15, P < 0.05) revealed that the ability to self-regulate the pace during the final 200 m improved for runners without II (trial 1, 1.7 ± 1.0 s; trial 2, 0.9 ± 0.8 s), whereas the II runners deviated even more in trial 2 (4.4 ± 4.3 s) than that in trial 1 (3.2 ± 3.9 s).

CONCLUSION

Our findings support the assumption that intellectual capacity is involved in pacing. It is demonstrated that II runners have difficulties maintaining a preplanned submaximal velocity, and this study contributes to understanding problems II exercisers might experience when exercising. With this field test, we can assess the effect of II on pacing and performance in individual athletes which will lead to a fair Paralympic classification procedure.

Familiarization Protocol Influences Reproducibility of 20-km Cycling Time-Trial Performance in Novice Participants

Introduction: Exercise performance is reproducible in experienced athletes; however, less trained participants exhibit greater variability in performance and pacing. To reduce variability, it is common practice to complete a familiarization prior to experimental testing. However, there are no clear guidelines for familiarizing novice participants to a cycling time-trial (TT), and research findings from novice populations may still be influenced by learning effects. Accordingly, the aims of this study were to establish the variability between TTs after administering differing familiarization protocols (duration or type) and to establish the number of familiarization trials required to limit variability over multiple trials.

Methods: Thirty recreationally active participants, with no prior experience of a TT, performed a 20-km cycling TT on five separate occasions, after completing either a full (FF, 20-km TT, n = 10), a half (HF, 10-km TT, n = 10) or an equipment familiarization (EF, 5-min cycling, n = 10).

Results: Variability of TT duration across five TTs was the lowest after completing FF (P = 0.69, η_p² = 0.05) compared to HF (P = 0.08, η_p² = 0.26) and EF (P = 0.07, η_p² = 0.21). In the FF group after TT2, the effect size for changes in TT duration was small (d < 0.49). There were large differences between later TTs in HF (d = 1.02, TT3-TT4) and EF (d = 1.12, TT4-TT5). The variability in mean power output profiles between trials was lowest within FF, with a similar pacing profile reproduced between TT3-TT5.

Discussion: Familiarization of the exercise protocol influenced reproducibility of pacing and performance over multiple, maximal TTs, with best results obtained after a full experience of the exercise compared to HF and EF. The difference of TT1 to later TTs indicates that one familiarization is not adequate in reducing the variability of performance for novice participants. After the FF and an additional TT, performance changes between TTs were small, however, a reproducible pacing profile was not developed until after the FF and two additional TTs. These findings indicate that a minimum of three full familiarizations are necessary for novice participants to limit systematic error before experimental testing.

Clair Gibson A, Jones AM, Thompson KG. Exploring the performance reserve: Effect of different magnitudes of power output deception on 4,000 m cycling time-trial performance

Purpose

The aim of the present study was to investigate whether a magnitude of deception of 5% in power output would lead to a greater reduction in the amount of time taken for participants to complete a 4000 m cycling TT than a magnitude of deception of 2% in power output, which we have previously shown can lead to a small change in 4000 m cycling TT performance.

Methods

Ten trained male cyclists completed four, 4000 m cycling TTs. The first served as a habituation and the second as a baseline for future trials. During trials three and four participants raced against a pacer which was set, in a randomized order, at a mean power output equal to 2% (+2% TT) or 5% (+5% TT) higher than their baseline performance. However participants were misled into believing that the power output of the pacer was an accurate representation of their baseline performance on both occasions. Cardiorespiratory responses were recorded throughout each TT, and used to estimate energy contribution from aerobic and anaerobic metabolism.

Results

Participants were able to finish the +2% TT in a significantly shorter duration than at baseline (p = 0.01), with the difference in performance likely attributable to a greater anaerobic contribution to total power output (p = 0.06). There was no difference in performance between the +5% TT and +2% TT or baseline trials.

Conclusions

Results suggest that a performance reserve is conserved, involving anaerobic energy contribution, which can be utilised given a belief that the exercise will be sustainable however there is an upper limit to how much deception can be tolerated. These findings have implications for performance enhancement in athletes and for our understanding of the nature of fatigue during high-intensity exercise.

The behavior of an opponent alters pacing decisions in 4-km cycling time trials

INTRODUCTION

The present study aimed to explore how athletes respond to different behaviors of their opponents.

METHODS

Twelve moderately to highly physically active participants with at least two years of cycling experience completed four 4-km time trials on a Velotron cycle ergometer. After a familiarization time trial (FAM), participants performed three experimental time trials in randomized order with no opponent (NO), a virtual opponent who started slower and finished faster compared to FAM (OP-SLOWFAST), or a virtual opponent who started faster and finished slower compared to FAM (OP-FASTSLOW). Repeated-measures ANOVAs (P<0.05) were used to examine differences in pacing and performance related to power output, velocity and RPE.

RESULTS

OP-SLOWFAST and OP-FASTSLOW were completed faster compared to NO (385.5±27.5, 385.0±28.6, and 390.6±29.3s, respectively). An interaction effect for condition×distance (F=3.944, P<0.001) indicated differences in pacing profiles between conditions. Post-hoc analysis revealed that a less aggressive starting strategy was adopted in NO compared to OP-FASTSLOW and OP-SLOWFAST during the initial 1000m. Finally, a faster starting opponent evokes higher power outputs by the participants in the initial 750m compared to a slower starting opponent.

CONCLUSION

The present study is the first to show that the behavior of an opponent affects pacing-related decisions in laboratory-controlled conditions. Our findings support the recently proposed interdependence of perception and action, and emphasize the interaction with the environment as an important determinant for an athlete's pacing decisions, especially during the initial stages of a race.

Pacing accuracy during an incremental step test in adolescent swimmers

To assess pacing accuracy in a group of adolescent swimmers during an incremental step test. Fifteen well-trained swimmers (age 15±1.5 years; height 170.2±8.8 cm; mass 60.2±6.6 kg), completed two 7×200 m tests, separated by ~72 hours. They swam to a predetermined incrementally increasing pace per step and were instructed to swim at even pace. Upon completion of each step, rating of perceived exertion, heart rate and blood lactate were recorded. Significant differences observed for both trials between actual and predicted swim time (P<0.05). Significant differences also observed between the first and second 100 m of each step in trial 1 for step 1 (P=0.001, effect size [ES] =0.54), step 2 (P=0.0001, ES =0.57), step 4 (P=0.0001, ES =0.53), step 5 (P=0.005, ES =0.65), step 6 (P=0.0001, ES =0.50), and step 7 (P=0.0001, ES =0.70). Similar responses witnessed for trial 2 (P<0.05). Findings suggest that the finite anaerobic capacity was engaged sooner than would normally be anticipated, as a function of an inability to regulate pace. This is proposed to be a consequence of the volume of exposure to the biological and psychological sensations and cognitive developmental status. Given the apparent error in pacing judgment exhibited in this population group, caution should be applied when adopting such tests to monitor training responses with adolescent athletes, and alternate means of modulating pace be investigated.

Improvement of 10-km Time-Trial Cycling With Motivational Self-Talk Compared With Neutral Self-Talk

Purpose:

Unpleasant physical sensations during maximal exercise may manifest themselves as negative cognitions that impair performance, alter pacing, and are linked to increased rating of perceived exertion (RPE). This study examined whether motivational self-talk (M-ST) could reduce RPE and change pacing strategy, thereby enhancing 10-km time-trial (TT) cycling performance in contrast to neutral self-talk (N-ST).

Methods:

Fourteen men undertook 4 TTs, TT1–TT4. After TT2, participants were matched into groups based on TT2 completion time and underwent M-ST (n = 7) or N-ST (n = 7) after TT3. Performance, power output, RPE, and oxygen uptake (VO2) were compared across 1-km segments using ANOVA. Confidence intervals (95%CI) were calculated for performance data.

Results:

After TT3 (ie, before intervention), completion times were not different between groups (M-ST, 1120 ± 113 s; N-ST, 1150 ± 110 s). After M-ST, TT4 completion time was faster (1078 ± 96 s); the N-ST remained similar (1165 ± 111 s). The M-ST group achieved this through a higher power output and VO2 in TT4 (6th–10th km). RPE was unchanged. CI data indicated the likely true performance effect lay between 13- and 71-s improvement (TT4 vs TT3).

Conclusion:

M-ST improved endurance performance and enabled a higher power output, whereas N-ST induced no change. The VO2 response matched the increase in power output, yet RPE was unchanged, thereby inferring a perceptual benefit through M-ST. The valence and content of self-talk are important determinants of the efficacy of this intervention. These findings are primarily discussed in the context of the psychobiological model of pacing.

Effects of high-intensity intermittent priming on physiology and cycling performance

The pre-event warm-up or "priming" routine for optimising cycling performance is not well-defined or uniform to a specific event. We aimed to determine the effects of varying the intensity of priming on 3 km cycling performance. Ten endurance-trained male cyclists completed four 3 km time-trials (TT) on four separate occasions, each preceded by a different priming strategy including "self-selected" priming and three intermittent priming strategies incorporating 10 min of constant-load cycling followed by 5 × 10 s bouts of varying relative intensity (100% and 150% of peak aerobic power, Wpeak, and all-out priming). The self-selected priming trial (379 ± 44 W) resulted in similar mean power during the 3 km TT to intermittent priming at 100% (376 ± 45 W; -0.7%; unclear) and 150% (374 ± 48 W; -1.5%, unclear) of Wpeak, but significantly greater than all-out priming (357 ± 45 W; -5.8%, almost certainly harmful). Differences between intermittent and self-selected priming existed with regards to heart rate (6.2% to 11.5%), blood lactate (-22.9% to 125%) and VO2 kinetics (-22.9% to 8.2%), but these were not related to performance outcomes. In conclusion, prescribed intermittent priming strategies varying in intensity did not substantially improve 3 km TT performance compared to self-selected priming.

Prior low- or high-intensity exercise alters pacing strategy, energy system contribution and performance during a 4-km cycling time trial

We analyzed the influence of prior exercise designed to reduce predominantly muscle glycogen in either type I or II fibers on pacing and performance during a 4-km cycling time trial (TT). After preliminary and familiarization trials, in a randomized, repeated-measures crossover design, ten amateur cyclists performed: 1) an exercise designed to reduce glycogen of type I muscle fibers, followed by a 4-km TT (EX-FIB I); 2) an exercise designed to reduce glycogen of type II muscle fibers, followed by a 4-km TT (EX-FIB II) and; 3) a 4-km TT, without the prior exercise (CONT). The muscle-glycogen-reducing exercise in both EX-FIB I and EX-FIB II was performed in the evening, ∼12 h before the 4-km TT. Performance time was increased and power output (PO) was reduced in EX-FIB I (432.8±8.3 s and 204.9±10.9 W) and EX-FIB II (428.7±6.7 s and 207.5±9.1 W) compared to CONT (420.8±6.4 s and 218.4±9.3 W; P<0.01), without a difference between EX-FIB I and EX-FIB II (P>0.05). The PO was lower in EX-FIB I than in CONT at the beginning and middle of the trial (P<0.05). The mean aerobic contribution during EX-FIB I was also significantly lower than in CONT (P<0.05), but there was no difference between CONT and EX-FIB II or between EX-FIB I and EX-FIB II (P>0.05). The integrated electromyography was unchanged between conditions (P>0.05). Performance may have been impaired in EX-FIB I due a more conservative pacing at the beginning and middle, which was associated with a reduced aerobic contribution. In turn, the PO profile adopted in EX-FIB II was also reduced throughout the trial, but the impairment in performance may be attributed to a reduced glycolytic contribution (i.e. reduced lactate accumulation).

Effect of spatial and temporal cues on athletic pacing in schoolchildren

PURPOSE

To compare pacing and performance of schoolchildren between running tasks where the end point was defined in units of either distance or time.

METHODS

Thirty-eight schoolchildren (age = 12.6 ± 0.5 yr, mass = 46.2 ± 7.5 kg, stature = 150 ± 7 cm) first performed a best-effort 750-m running task on a 150-m running track. The schoolchildren were split into two groups, matched for sex, age, and running performance, before completing the second running trial. One group repeated the 750-m running task (distance-distance group), whereas the other completed a running task to a time that had been matched to their previous 750-m performance (distance-time group). Pace was measured every 10% segment throughout each run.

RESULTS

No difference between trials in average running speed was found among the distance-distance group (13.64 ± 1.59 vs. 13.68 ± 1.62 km·h(-1), P > 0.05); however, the distance-time group were slower during the time task compared with during the distance task (13.84 ± 1.61 vs. 13.37 ± 1.57 km·h(-1), P < 0.005). There was no difference in pacing pattern between trials among the distance-distance group (P > 0.05), but the distance-time group exhibited a slower overall slower pace with no end spurt (P < 0.0001). During the time task, children looked at their watches more frequently the nearer they got to the end point (ρ = 0.933, P < 0.0001).

CONCLUSIONS

Schoolchildren find it easier to use spatial cues during a pacing task compared with temporal cues. Running pace in all trials followed a classic U-shaped pattern; however, lap-by-lap oscillations in pacing substrategies were also evident, which may be a psychological coping strategy.

Consistency of Pacing and Metabolic Responses During 2000-m Rowing Ergometry

Purpose:

This study investigated the pacing strategy adopted and the consistency of performance and related physiological parameters across three 2000-m rowing-ergometer tests.

Methods:

Fourteen male well-trained rowers took part in the study. Each participant performed three 2000-m rowing-ergometer tests interspersed by 3–7 d. Throughout the trials, respiratory exchange and heart rate were recorded and power output and stroke rate were analyzed over each 500 m of the test. At the completion of the trial, assessments of blood lactate and rating of perceived exertion were measured.

Results:

Ergometer performance was unchanged across the 3 trials; however, pacing strategy changed from trial 1, which featured a higher starting power output and more progressive decrease in power, to trials 2 and 3, which were characterized by a more conservative start and an end spurt with increased power output during the final 500 m. Mean typical error (TE; %) across the three 2000-m trials was 2.4%, and variability was low to moderate for all assessed physiological variables (TE range = 1.4−5.1%) with the exception of peak lactate (TE = 11.5%).

Conclusions:

Performance and physiological responses during 2000-m rowing ergometry were found to be consistent over 3 trials. The variations observed in pacing strategy between trial 1 and trials 2 and 3 suggest that a habituation trial is required before an intervention study and that participants move from a positive to a reverse-J-shaped strategy, which may partly explain conflicting reports in the pacing strategy exhibited during 2000-m rowing-ergometer trials.

Effects of deception on exercise performance: implications for determinants of fatigue in humans

PURPOSE

The aim of this study was to investigate whether it was possible to reduce the time taken to complete a 4000-m cycling time trial by misleading participants into believing they were racing against a previous trial, when, in fact, the power output was 2% greater.

METHODS

Nine trained male cyclists each completed four 4000-m time trials. The first trial was a habituation and the data from the second trial was used to form a baseline (BL). During trials 3 and 4, participants raced against an avatar, which they were informed represented their BL performance. However, whereas one of these trials was an accurate (ACC) representation of BL, the power output in the other trial was set at 102% of BL and formed the deception condition (DEC). Oxygen uptake and RER were measured continuously and used to determine aerobic and anaerobic contributions to power output.

RESULTS

There was a significant difference between trials for time to completion (F = 15.3, P = 0.00). Participants completed DEC more quickly than BL (90% CI = 2.1-10.1 s) and ACC (90% CI = 1.5-5.4 s) and completed ACC more quickly than BL (90% CI = 0.5-4.8 s). The difference in performance between DEC and ACC was attributable to a greater anaerobic contribution to power output at 90% of the total distance (F = 5.3, P = 0.02, 90% CI = 4-37 W).

CONCLUSIONS

The provision of surreptitiously augmented feedback derived from a previous performance reduces time taken for cyclists to accomplish a time trial of known duration. This suggests that cyclists operate with a metabolic reserve even during maximal time trials and that this reserve can be accessed after deception.

Influence of competition on performance and pacing during cycling exercise

PURPOSE

The study's purpose was to examine the influence of head-to-head (HH) competition on performance, pacing strategy, and bioenergetics during a 2000-m cycling task.

METHODS

Fourteen participants completed three 2000-m familiarization time trials (TTs) on a Velotron cycle ergometer, before completing an additional TT and a 2000-m simulated HH competition in a counterbalanced order. During the trials, a computer-generated image of the participants completing the 2000-m course was projected onto a screen positioned in front of the participants. Although participants believed they were competing against another individual during the HH competition, they were in fact competing against their best familiarization performance (FAM), replayed on the screen by the Velotron software.

RESULTS

Performance was significantly faster in HH than in FAM or TT (184.6 ± 6.2, 187.7 ± 8.2, and 188.3 ± 9.5 s, respectively). Pacing profile in HH initially matched the FAM performance but was better maintained from 1000 m until the end of exercise. The higher power output during the latter part of the test was achieved by a greater anaerobic energy contribution, whereas the aerobic energy yield remained unchanged.

CONCLUSIONS

HH competition encourages participants to increase their performance. This occurs primarily via an increased anaerobic energy yield, which seems to be centrally mediated, and is consistent with the concept of a physiologic reserve.

Fatigue is a Brain-Derived Emotion that Regulates the Exercise Behavior to Ensure the Protection of Whole Body Homeostasis

An influential book written by A. Mosso in the late nineteenth century proposed that fatigue that “at first sight might appear an imperfection of our body, is on the contrary one of its most marvelous perfections. The fatigue increasing more rapidly than the amount of work done saves us from the injury which lesser sensibility would involve for the organism” so that “muscular fatigue also is at bottom an exhaustion of the nervous system.” It has taken more than a century to confirm Mosso’s idea that both the brain and the muscles alter their function during exercise and that fatigue is predominantly an emotion, part of a complex regulation, the goal of which is to protect the body from harm. Mosso’s ideas were supplanted in the English literature by those of A. V. Hill who believed that fatigue was the result of biochemical changes in the exercising limb muscles – “peripheral fatigue” – to which the central nervous system makes no contribution. The past decade has witnessed the growing realization that this brainless model cannot explain exercise performance. This article traces the evolution of our modern understanding of how the CNS regulates exercise specifically to insure that each exercise bout terminates whilst homeostasis is retained in all bodily systems. The brain uses the symptoms of fatigue as key regulators to insure that the exercise is completed before harm develops. These sensations of fatigue are unique to each individual and are illusionary since their generation is largely independent of the real biological state of the athlete at the time they develop. The model predicts that attempts to understand fatigue and to explain superior human athletic performance purely on the basis of the body’s known physiological and metabolic responses to exercise must fail since subconscious and conscious mental decisions made by winners and losers, in both training and competition, are the ultimate determinants of both fatigue and athletic performance.

Adaptations to aerobic interval training: interactive effects of exercise intensity and total work duration

To compare the effects of three 7-week interval training programs varying in work period duration but matched for effort in trained recreational cyclists. Thirty-five cyclists (29 male, 6 female, VO(2peak) 52 ± 6 mL kg/min) were randomized to four training groups with equivalent training the previous 2 months (∼6 h/wk, ∼1.5 int. session/wk). Low only (n=8) trained 4-6 sessions/wk at a low-intensity. Three groups (n=9 each) trained 2 sessions/wk × 7 wk: 4 × 4 min, 4 × 8 min, or 4 × 16 min, plus 2-3 weekly low-intensity bouts. Interval sessions were prescribed at the maximal tolerable intensity. Interval training was performed at 88 ± 2, 90 ± 2, and 94 ± 2% of HR(peak) and 4.9, 9.6, and 13.2 mmol/L blood lactate in 4 × 16, 4 × 8, and 4 × 4 min groups, respectively (both P<0.001). 4 × 8 min training induced greater overall gains in VO(2) peak, power@VO(2) peak, and power@4 mM bLa- (Mean ± 95%CI): 11.4 (8.0-14.9), vs 4.2 (0.4-8.0), 5.6 (2.1-9.1), and 5.5% (2.0-9.0) in Low, 4 × 16, and 4 × 4 min groups, respectively (P<0.02 for 4 × 8 min vs all other groups). Interval training intensity and accumulated duration interact to influence the adaptive response. Accumulating 32 min of work at 90% HR max induces greater adaptive gains than accumulating 16 min of work at ∼95% HR max despite lower RPE.