a Research Institute for Sport and Exercise Sciences , Liverpool John Moores University , Liverpool , UK.
b Sports Science Department , Aspire Academy , Doha , Qatar.
Chronobiol Int. 2019 Mar;36(3):392-406. doi: 10.1080/07420528.2018.1552596. Epub 2018 Dec 26.
The present study investigated the magnitude of diurnal variation in back squat and bench press using the MuscleLab linear encoder over three different loads and assessed the benefit of an active warm-up to establish whether diurnal variation could be negated. Ten resistance-trained males underwent (mean ± SD: age 21.0 ± 1.3 years, height 1.77 ± 0.06 m, and body mass 82.8 ± 14.9 kg) three sessions. These included control morning (M, 07:30 h) and evening (E, 17:30 h) sessions (5-min standardized warm-up at 150 W, on a cycle ergometer), and one further session consisting of an extended active warm-up morning trial (M, 07:30 h) until rectal temperature (T) reached previously recorded resting evening levels (at 150 W, on a cycle ergometer). All sessions included handgrip, followed by a defined program of bench press (at 20, 40, and 60 kg) and back squat (at 30, 50, and 70 kg) exercises. A linear encoder was attached to an Olympic bar used for the exercises and average force (AF), peak velocity (PV), and time to peak velocity (tPV) were measured (MuscleLab software; MuscleLab Technology, Langesund, Norway) during the concentric phase of the movements. Values for T were higher in the E session compared to values in the M session (Δ0.53 °C, P < 0.0005). Following the extended active warm-up in the morning (M), T and T values were no different to the E values (P < 0.05). Values for T were lower in the M compared to the E condition throughout (P < 0.05). There were time-of-day effects for hand grip with higher values of 6.49% for left (P = 0.05) and 4.61% for right hand (P = 0.002) in the E compared to the M. Daily variations were apparent for both bench press and back squat performance for AF (3.28% and 2.63%), PV (13.64% and 11.50%), and tPV (-16.97% and -14.12%, where a negative number indicates a decrease in the variable from morning to evening). There was a main effect for load (P < 0.0005) such that AF and PV values were larger at higher masses on the bar than lower ones and tPV was smaller at lower masses on the bar than at higher masses for both bench press and back squat. We established that increasing T in the M-E values did not result in an increase of any measures related to bench press and back squat performance (P > 0.05) to increase from M to E levels. Therefore, MuscleLab linear encoder could detect meaningful differences between the morning and evening for all variables. However, the diurnal variation in bench press and back squat (measures of lower and upper body force and power output) is not explained by time-of-day oscillations in T.
本研究使用 MuscleLab 线性编码器在三种不同负荷下测量了深蹲和卧推的昼夜变化幅度，并评估了主动热身的益处，以确定是否可以消除昼夜变化。十名接受过阻力训练的男性进行了三次测试：（平均 ± 标准差：年龄 21.0 ± 1.3 岁，身高 1.77 ± 0.06 米，体重 82.8 ± 14.9 公斤），包括对照晨（M，07:30 h）和傍晚（E，17:30 h）测试（5 分钟标准化热身，在自行车测力计上，150 W），以及一次额外的测试，包括扩展的主动热身晨试（M，07:30 h），直到直肠温度（T）达到之前记录的傍晚静息水平（在自行车测力计上，150 W）。所有测试均包括握力测试，然后进行规定的卧推（20、40 和 60 公斤）和深蹲（30、50 和 70 公斤）测试。一根线性编码器被连接到用于测试的奥林匹克杠铃上，在运动的向心阶段测量平均力（AF）、峰值速度（PV）和达到峰值速度的时间（tPV）（MuscleLab 软件；MuscleLab Technology，Langesund，挪威）。E 测试中的 T 值高于 M 测试中的 T 值（Δ0.53°C，P < 0.0005）。经过清晨的扩展主动热身（M），T 和 T 值与 E 值没有差异（P < 0.05）。M 测试中的 T 值全天低于 E 测试（P < 0.05）。握力有时间效应，E 测试中的左手（P = 0.05）和右手（P = 0.002）握力分别高出 6.49%和 4.61%。AF（3.28%和 2.63%）、PV（13.64%和 11.50%）和 tPV（-16.97%和-14.12%，负数表示变量从早晨到傍晚的下降）的昼夜变化在卧推和深蹲表现中均很明显。负载有主要影响（P < 0.0005），即杠铃上的质量较高时，AF 和 PV 值较大，质量较低时 tPV 值较小，杠铃上的质量较低时 tPV 值较小，杠铃上的质量较高时，杠铃上的质量较高。我们发现，在 M-E 值中增加 T 并没有导致与卧推和深蹲表现相关的任何测量值（P > 0.05）从 M 增加到 E 水平。因此，MuscleLab 线性编码器可以检测到所有变量在早晨和傍晚之间的有意义差异。然而，昼夜变化（下半身和上半身力量和功率输出的测量值）不能用 T 的时间波动来解释。
