Ferreira Viana Bruno, Trajano Gabriel S, Ugrinowitsch Carlos, Oliveira Pires Flávio
Physical Education course, Augusto Motta University Center (UNISUAM), Rio de Janeiro, RJ, Brazil.
Physical Education course, Estácio de Sá University (UNESA), Rio de Janeiro, RJ, Brazil.
PLoS One. 2020 Aug 13;15(8):e0236592. doi: 10.1371/journal.pone.0236592. eCollection 2020.
Caffeine improves cycling time trial performance through enhanced motor output and muscle recruitment. However, it is unknown if caffeine further increases power output entropy. To investigate the effects of caffeine effects on cycling time trial performance and motor output entropy (MOEn), nine cyclists (VO2MAX of 55 ± 6.1 mL.kg.-1min-1) performed a 4 km cycling time trial (TT4km) after caffeine and placebo ingestion in a counterbalanced order. Power output data were sampled at a 2 Hz frequency, thereafter entropy was estimated on a sliding-window fashion to generate a power output time series. A number of mixed models compared performance and motor output entropy between caffeine and placebo every 25% of the total TT4km distance. Caffeine ingestion improved power output by 8% (p = 0.003) and increased MOEn by 7% (p = 0.018). Cyclists adopted a U-shaped pacing strategy after caffeine ingestion. MOEn mirrored power output responses as an inverted U-shape MOEn during the time trial. Accordingly, a strong inverse correlation was observed between MOEn and power output responses over the last 25% of the TT4km (p < 0.001), regardless of the ingestion, likely reflecting the end spurt during this period (p = 0.016). Caffeine ingestion improved TT4km performance and motor output responses likely due to a greater power output entropy.
咖啡因通过增强运动输出和肌肉募集来提高自行车计时赛成绩。然而，咖啡因是否会进一步增加功率输出熵尚不清楚。为了研究咖啡因对自行车计时赛成绩和运动输出熵（MOEn）的影响，九名自行车运动员（最大摄氧量为55±6.1 mL·kg⁻¹·min⁻¹）以平衡的顺序在摄入咖啡因和安慰剂后进行了4公里自行车计时赛（TT4km）。以2Hz的频率对功率输出数据进行采样，然后以滑动窗口方式估计熵，以生成功率输出时间序列。在TT4km总距离的每25%处，使用多个混合模型比较咖啡因和安慰剂之间的成绩和运动输出熵。摄入咖啡因使功率输出提高了8%（p = 0.003），MOEn增加了7%（p = 0.018）。摄入咖啡因后，自行车运动员采用了U形的配速策略。在计时赛期间，MOEn呈现出倒U形，反映了功率输出的响应。因此，在TT4km的最后25%距离内，无论摄入何种物质，MOEn与功率输出响应之间都观察到了强烈的负相关（p < 0.001），这可能反映了这一时期的冲刺阶段（p = 0.016）。摄入咖啡因提高了TT4km成绩和运动输出响应，这可能是由于更大的功率输出熵所致。
