Fatigue indices and perceived exertion highlight ergometer specificity for repeated sprint ability testing

This study aimed to compare the timecourse of measures of performance, fatigue and perceived exertion during repeated-sprint ability (RSA) testing performed on a non-motorised treadmill (NMT) and cycling ergometer (CE). Fourteen physically-active participants performed two 10x6 sec^-1RSA tests with a 1:4 work-to-rest ratio (24 s recovery) on NMT and CE. Measures of performance (peak and mean power output [PPO and MPO], cadence and the time to reach PPO [TTP]), of fatigue (fatigue index and decrement score) and ratings of perceived exertion (RPE) were collected during each session. The level of significance was set at p<0.05. Participants completed the RSA test at a MPO of 1041±141 W on CE and 431±48 W on NMT, achieving PPO of 2310±339 W on CE and 1763±289 W on NMT. Participants’ weight was significantly correlated with PPO and MPO on CE (p<0.001), and with MPO on NMT (p<0.001). PPO on CE and NMT were significantly correlated only for absolute measures of power (p<0.01). Cadence was higher and decreased throughout the RSA on NMT compared to CE, where it decreased only at the 7^th bout. TTP was significantly shorter and more affected by fatigue on NMT than on CE. Fatigue indices were significantly greater on NMT compared to CE, with significant correlations between the decrement score and absolute and relative PPO on CE and NMT, between the fatigue index and absolute and relative PPO only on NMT, and no significant correlations with MPO. During RSA, RPE increased more on NMT compared to CE from bouts 3 to 7. During recovery, RPE was consistently higher on NMT at 1, 3 and 5 min postexercise compared to CE. These findings indicate that RSA performed on NMT induces greater fatigue and physiological load than CE, which originated in the lower resistive torque typically used on NMT compared to CE, resulting in a frontloaded power output profile from the greater acceleration and cadence. From these results, we discuss that despite providing highly correlated measures of power output, NMT and CE should not be used interchangeably to assess RSA as they elicit markedly different responses. We also discuss these results from the fundamental differences in active muscle mass and power application patterns between running and cycling, which could form the basis of future studies.

本研究旨在对比在非机动跑步机（non-motorised treadmill, NMT）与功率自行车（cycling ergometer, CE）上开展重复冲刺能力（repeated-sprint ability, RSA）测试时，运动表现、疲劳程度与自觉用力程度的时间变化进程。14名经常进行身体活动的受试者分别在NMT与CE上完成两次10组×6秒的RSA测试，功休比为1:4（恢复时长24秒）。每次测试期间均采集运动表现指标[峰值功率输出（peak power output, PPO）与平均功率输出（mean power output, MPO）、步频与踏频（cadence）以及到达峰值功率输出的时间（time to reach PPO, TTP）]、疲劳指标（疲劳指数与衰减评分）以及自觉用力程度分级（ratings of perceived exertion, RPE）数据。本研究设定显著性水平为p<0.05。受试者在CE上的平均功率输出为1041±141 W，NMT上为431±48 W；CE上的峰值功率输出为2310±339 W，NMT上为1763±289 W。受试者体重与CE上的PPO、MPO均呈显著相关（p<0.001），与NMT上的MPO亦呈显著相关（p<0.001）。CE与NMT上的PPO仅在绝对功率指标上呈显著相关（p<0.01）。相较于CE，NMT上的步频初始更高，且在整个RSA测试过程中持续下降；而CE上的踏频仅在第7组测试时出现下降。NMT上的到达峰值功率输出时间显著短于CE，且更易受疲劳影响。NMT上的疲劳指数显著高于CE：衰减评分与CE、NMT上的绝对及相对PPO均呈显著相关，疲劳指数仅与NMT上的绝对及相对PPO呈显著相关，且二者均与MPO无显著相关。在RSA测试过程中，第3至7组测试期间，NMT上的RPE上升幅度显著高于CE。在恢复阶段，运动后1、3、5分钟时，NMT上的RPE始终高于CE。上述研究结果表明，相较于CE，在NMT上开展的RSA测试会诱发更显著的疲劳与生理负荷，这源于NMT上通常使用的阻力扭矩低于CE，进而导致功率输出曲线前置——受试者加速度更大、步频与踏频更高。基于上述结果，本研究讨论认为：尽管NMT与CE的功率输出指标具有较高相关性，但二者诱发的生理反应差异显著，因此不应互换用于RSA评估。此外，本研究还从跑步与骑行的主动肌肉量、功率施加模式的本质差异出发对结果进行讨论，该差异可作为未来相关研究的切入点。