Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.
Department of Clinical and Biological Sciences, University of Turin, Turin, Italy.
Eur J Appl Physiol. 2024 Dec;124(12):3583-3591. doi: 10.1007/s00421-024-05561-9. Epub 2024 Jul 24.
This study aimed to verify whether the slowing of muscle contraction quickness, typically observed in states of fatigue, may worsen force control by decreasing the rate with which force fluctuations are modulated. Therefore, we investigated the relationship between rate of force development (RFD), and force fluctuations' magnitude (Coefficient of variation, CoV) and complexity (Approximate Entropy, ApEn; Detrended fluctuation analysis, DFAα).
Fourteen participants performed intermittent ballistic isometric contractions of the plantar dorsiflexors at 70% of maximal voluntary force until task failure (under 60% twice).
Indices of RFD (RFD, RFD, RFD, and RFD) decreased over time by approximately 46, 32, 44, and 39%, respectively (p all ≤ 0.007). DFAα increased by 10% (p < 0.001), and CoV increased by 15% (p < 0.001), indicating decreased force complexity along with increased force fluctuations, respectively. ApEn decreased by just over a quarter (28%, p < 0.001). The linear hierarchical models showed negative associations between RFD and DFAα (β = - 3.6 10, p < 0.001), CoV (β = - 1.8 10, p < 0.001), while ApEn showed a positive association (β = 8.2 × 10, p < 0.001).
The results suggest that exercise-induced reductions in contraction speed, lead to smoother force complexity and diminished force control due to slower adjustments around the target force. The fatigued state resulted in worsened force producing capacity and overall force control.
本研究旨在验证肌肉收缩速度的减缓（通常在疲劳状态下观察到）是否会通过降低力波动调制的速率而使力控制恶化。因此，我们研究了力发展速率（RFD）与力波动幅度（变异系数，CoV）和复杂性（近似熵，ApEn；去趋势波动分析，DFAα）之间的关系。
14 名参与者以最大自主力的 70%进行间歇性弹性能量收缩的足底背屈肌，直到任务失败（两次低于 60%）。
RFD 的各项指标（RFD、RFD、RFD 和 RFD）分别降低了约 46%、32%、44%和 39%（p 均≤0.007）。DFAα 增加了 10%（p<0.001），CoV 增加了 15%（p<0.001），分别表明力复杂性降低和力波动增加。ApEn 下降了四分之一以上（28%，p<0.001）。线性层次模型显示 RFD 与 DFAα（β=−3.6×10，p<0.001）和 CoV（β=−1.8×10，p<0.001）呈负相关，而 ApEn 呈正相关（β=8.2×10，p<0.001）。
结果表明，运动引起的收缩速度降低会导致力复杂性更平滑，并由于围绕目标力的调整速度较慢而导致力控制变差。疲劳状态导致产生力的能力和整体力控制恶化。
