Laboratory of Clinical Biomechanics, Department of Physical Therapy, Faculty of Medicine, University of Chile, Santiago, Chile.
Exercise Intervention for Health Research Group, Department of Physiotherapy, University of Valencia, Valencia, Spain.
Eur J Appl Physiol. 2020 Jun;120(6):1251-1261. doi: 10.1007/s00421-020-04357-x. Epub 2020 Apr 3.
To determine the effect of cognitive-motor dual-task load on temporal structure irregularity (complexity) of motor output and task performance of submaximal isometric contractions.
Twelve young, sedentary subjects performed handgrip isometric contractions until failure at 50% of maximal voluntary contraction under mathematical self-regulated dual-task (own pace; SDT), regulated dual-task (imposed pace; RDT), and control. Force signal complexity was calculated by sample entropy at the initial, middle, and final thirds. Task performance was assessed by muscle fatigue (time to failure and rate of median frequency of the radial flexor of the carpus), force and math task error, and self-perceived difficulty.
Only RDT decreased complexity with respect to control (17.4% ± 12.6%, p = 0.005), all conditions decreased complexity by the final third (Control: 52.8% ± 18.7%, p < 0.001; SDT: 41.1% ± 32.1%, p = 0.003; RDT: 19.1% ± 21.9%, p = 0.035). Conditions did not affect time to failure, and only RDT decreased the rate of median frequency (0.1%/s ± 0.1%/s, p = 0.020). Inferior force error rate was increased by conditions (SDT: 1.5% ± 0.8%, p < 0.001; RDT: 2% ± 1.5%, p = 0.002). Math error was only augmented by RDT (from 9.9 ± 6.7 to 51.7 ± 18.8, p < 0.001), categorized as "very hard" in 85.7% of participants (p = 0.015).
Only the RDT condition reduced complexity and neuromuscular fatigue while increasing force error rate of the handgrip's motor output, without affecting time to failure. A highly demanding dual-task may become a strategy to modify the organization of the hand force motor output, which may contribute to its motor adaptations.
确定认知-运动双重任务负荷对运动输出的时间结构不规则性（复杂性）和亚最大等长收缩任务表现的影响。
12 名年轻的久坐受试者在手握等长收缩达到最大自主收缩的 50%时，在数学自我调节双重任务（自主节奏；SDT）、调节双重任务（强制节奏；RDT）和对照组下进行。在初始、中间和最后三分之一部分，通过样本熵计算力信号复杂性。通过失败时间和腕桡侧屈肌中频频率的中位数的变化率来评估任务表现，同时评估力和数学任务误差以及自我感知的难度。
只有 RDT 与对照组相比降低了复杂性（17.4%±12.6%，p=0.005），所有条件在最后三分之一时降低了复杂性（对照组：52.8%±18.7%，p<0.001；SDT：41.1%±32.1%，p=0.003；RDT：19.1%±21.9%，p=0.035）。条件不影响失败时间，只有 RDT 降低了中频频率的变化率（0.1%/s±0.1%/s，p=0.020）。条件增加了力误差率（SDT：1.5%±0.8%，p<0.001；RDT：2%±1.5%，p=0.002）。只有 RDT 增加了数学错误（从 9.9±6.7 到 51.7±18.8，p<0.001），85.7%的参与者认为其“非常难”（p=0.015）。
只有 RDT 条件降低了复杂性和神经肌肉疲劳，同时增加了握力运动输出的力误差率，而不影响失败时间。高要求的双重任务可能成为一种策略，以改变手部力量运动输出的组织，这可能有助于其运动适应。
