Human Performance Laboratory, Directorate of Sport, Exercise, and Physiotherapy, University of Salford, Greater Manchester, United Kingdom.
J Strength Cond Res. 2017 Dec;31(12):3463-3473. doi: 10.1519/JSC.0000000000001765.
Dos'Santos, T, Jones, PA, Comfort, P, and Thomas, C. Effect of different onset thresholds on isometric midthigh pull force-time variables. J Strength Cond Res 31(12): 3463-3473, 2017-Various thresholds have been used to identify the onset of contraction during isometric midthigh pull (IMTP); however, no agreed onset threshold exists for this assessment. The purpose of this study was to compare relative body weight (BW) and arbitrary onset thresholds to a criterion onset threshold 5 SDs of BW for IMTP force-time variables; force at each threshold, peak force, time-specific force values (100, 150, and 200 ms), and rate of force development (RFD) during 0-100, 0-150, 0-200 ms. Academy rugby league players (n = 9, age: 18.5 ± 0.4 years; height: 1.82 ± 0.09 m; mass: 91.2 ± 13.1 kg) performed 2 IMTP trials on a force platform sampling at 1,000 Hz. The neutral force-time data pool (18 trials) was analyzed with five different thresholds and compared with criterion threshold to determine any variance in force-time variables. Five SDs of BW were significantly lower than 10% BW and 75 N for threshold force which led to significantly greater time-specific force values at 100 and 150 ms and unacceptable limits of agreements (LOA) for all force-time variables. No significant differences (p > 0.05) were observed between 2.5% and 5 SDs of BW; and between 5% and 5 SDs of BW for threshold force and all force-time variables with acceptable LOA. The 5 SDs of BW and 2.5% BW onset thresholds consistently resulted in the lowest values for threshold force, time-specific force values, and RFD, attributed to a lower onset bias. Therefore, scientists and practitioners are recommended to use a 5 SD of BW onset threshold for time-specific force values and RFD for accurate data because it accounts for signal noise during the weighing period. Subsequently, there is greater certainty that the onset of contraction identifies a true meaningful change in force, in contrast to relative BW thresholds.
多斯桑托斯、T、琼斯、PA、康福特、P 和托马斯、C. 不同起始阈值对等长大腿中部拉力时间变量的影响。J 力量与条件研究 31(12):3463-3473,2017-各种阈值已被用于确定等长大腿中部拉力 (IMTP) 期间收缩的起始；然而，对于这种评估，不存在商定的起始阈值。本研究的目的是比较相对体重 (BW) 和任意起始阈值与 BW 5 个标准差的标准起始阈值对 IMTP 力-时间变量的影响；每个阈值的力、峰值力、特定时间的力值 (100、150 和 200 ms) 和 0-100、0-150、0-200 ms 期间的力发展率 (RFD)。学院橄榄球联盟运动员 (n = 9，年龄：18.5 ± 0.4 岁；身高：1.82 ± 0.09 m；体重：91.2 ± 13.1 kg) 在力平台上进行了 2 次 IMTP 试验，采样频率为 1,000 Hz。用五种不同的阈值对中性力-时间数据池 (18 次试验) 进行了分析，并与标准阈值进行了比较，以确定力-时间变量的任何差异。BW 的 5 个标准差显著低于阈值力的 10% BW 和 75 N，这导致 100 和 150 ms 时特定时间的力值显著增加，并且所有力-时间变量的可接受协议范围 (LOA) 都不可接受。BW 的 2.5% 和 5 个标准差之间以及阈值力和所有力-时间变量之间的 5% 和 5 个标准差之间没有观察到显著差异 (p > 0.05)，LOA 可接受。BW 的 5 个标准差和 2.5% BW 起始阈值始终导致阈值力、特定时间的力值和 RFD 的最低值，这归因于起始偏差较低。因此，建议科学家和从业者使用 BW 的 5 个标准差起始阈值来获取准确数据的特定时间的力值和 RFD，因为它考虑了称重期间的信号噪声。随后，与相对 BW 阈值相比，收缩起始更有可能确定力的真正有意义的变化。
