Mark Stone

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.

Central and peripheral fatigue in male cyclists after 4-, 20-, and 40-km time trials.

PURPOSE Few studies have assessed neuromuscular fatigue after self-paced locomotor exercise; moreover, none have assessed the degree of supraspinal fatigue. This study assessed central and peripheral fatigue after self-paced exercise of different durations. METHODS Thirteen well-trained male cyclists completed 4-, 20-, and 40-km simulated time trials (TTs). Pre- and immediately post-TT (<2.5 min), twitch responses from the knee extensors to electrical stimulation of the femoral nerve and transcranial magnetic stimulation of the motor cortex were recorded to assess neuromuscular and corticospinal function. RESULTS Time to complete 4-, 20-, and 40-km TTs was 6.0 ± 0.2, 31.8 ± 1.0, and 65.8 ± 2.2 min at average exercise intensities of 96%, 92%, and 87% of maximum oxygen uptake, respectively. Exercise resulted in significant reductions in maximum voluntary contraction, with no difference between TTs (-18%, -15%, and -16% for 4-, 20-, and 40-km TTs, respectively). Greater peripheral fatigue was evident after 4-km (40% reduction in potentiated twitch) compared with that after 20-km (31%) and 40-km TTs (29%). In contrast, longer TTs were characterized by more central fatigue, with greater reductions in voluntary activation measured by motor nerve (-11% and -10% for 20- and 40-km TTs vs -7% for 4-km TTs) and cortical stimulation (-12% and -10% for 20- and 40-km vs -6% for 4-km). CONCLUSIONS These data demonstrate that fatigue after self-paced exercise is task dependent, with a greater degree of peripheral fatigue after shorter higher-intensity (6 min) TTs and more central fatigue after longer lower-intensity TTs (>30 min).

A pilot investigation into the effect of maca supplementation on physical activity and sexual desire in sportsmen.

AIMS OF THE STUDY Maca (Lepidium meyenii Walp) is consumed both as a sports supplement by strength and endurance athletes, and as a natural stimulant to enhance sexual drive. However, whether or not the postulated benefits of maca consumption are of scientific merit is not yet known. The aim of the study was therefore to investigate the effect of 14 days maca supplementation on endurance performance and sexual desire in trained male cyclists. MATERIALS AND METHODS Eight participants each completed a 40 km cycling time trial before and after 14 days supplementation with both maca extract (ME) and placebo, in a randomised cross-over design. Subjects also completed a sexual desire inventory during each visit. RESULTS ME administration significantly improved 40 km cycling time performance compared to the baseline test (P=0.01), but not compared to the placebo trial after supplementation (P>0.05). ME administration significantly improved the self-rated sexual desire score compared to the baseline test (P=0.01), and compared to the placebo trial after supplementation (P=0.03). CONCLUSIONS 14 days ME supplementation improved 40 km cycling time trial performance and sexual desire in trained male cyclists. These promising results encourage long-term clinical studies involving more volunteers, to further evaluate the efficacy of ME in athletes and normal individuals and also to explore its possible mechanisms of action.

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.

Response to: Reproducibility of 24-h ambulatory blood pressure and measures of autonomic function

The aim of our study was to assess the reproducibility of 24-h ambulatory blood pressure, 24-h heart rate variability (HRV) and short-term resting measurements of both HRV and blood pressure variability. We reported the magnitude of between-day variability in these measures and the appropriateness of familiarisation sessions before experimental data collection. Findings revealed that ambulatory blood pressure became more reproducible following repeated recordings. In addition, 24-h HRV was more reproducible than resting measures. Consecutive pairs of measurements (days 1–2, 2–3, 3–4) were analysed for the determination of the typical error and coefficient of variation as described by Hopkins [2]. These statistical methods provide a point estimate of absolute and relative reliability and reflect the ability of a measure to detect systematic changes between repeated measurements within a participant [3]. These methods also quantify the degree of uncertainty surrounding this point estimate and can be used by researchers to evaluate the likelihood that observed changes following an intervention in a sample population are attributable to the experimental conditions and not a manifestation of error inherent within the test. The effect of a therapeutic intervention on autonomic function and blood pressure is a fertile area of contemporary research [4], and the data presented in our manuscript are appropriate to inform practitioners making population-wide health recommendations based on the outcomes of experimental research.