a School for Sport and Biological Sciences , University of Bolton , Bolton , UK.
b Research Institute for Sport and Exercise Sciences , Liverpool John Moores University , Liverpool , UK.
Chronobiol Int. 2018 Sep;35(10):1391-1401. doi: 10.1080/07420528.2018.1485685. Epub 2018 Jun 26.
We have investigated the magnitude of diurnal variation in back squat and bench press performance using the MuscleLab force velocity transducer. Thirty resistance-trained males (mean ± SD: age 21.7 ± 1.4 years; body mass 80.5 ± 4.5 kg; height 1.79 ± 0.06 m) underwent two sessions at different times of day: morning (M, 07:30 h) and evening (E, 17:30 h). Each session included a period when rectal temperature (T) was measured at rest, a 5-min standardized 150 W warm-up on a cycle ergometer, then defined programme 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 at rest were higher in the evening compared to morning values (0.48°C, P < 0.0005). Daily variations were apparent for both bench press and back squat performance for AF (1.9 and 2.5%), PV (8.3 and 12.7%) and tPV (-16.6 and -9.8%; where a negative number indicates a decrease in the variable from morning to evening). There was a main effect for load where AF and tPV increased and PV decreased from the lightest load to the heaviest for both bench press and back squat (47.1 and 80.2%; 31.7 and 57.7%; -42.1 and -73.9%; P < 0.0005 where a negative number indicates a decrease in the variable with increasing load). An interaction was found only for tPV, such that the tPV occurs earlier in the evening than the morning at the highest loads (60 and 70 kg) for both bench press and back squat, respectively (mean difference of 0.32 and 0.62 s). In summary, diurnal variation in back squat and bench press was shown; and the tPV in complex multi-joint movements occurs earlier during the concentric phase of exercise when back squat or bench press is performed in the evening compared to the morning. This difference can be detected using a low cost, portable and widely available commercial instrument and enables translation of past laboratory/tightly controlled experimental research in to main-stream coaching practice.
我们使用 MuscleLab 力速度传感器研究了深蹲和卧推的日常变化幅度。30 名经过阻力训练的男性（平均 ± SD：年龄 21.7±1.4 岁；体重 80.5±4.5 公斤；身高 1.79±0.06 米）在不同的时间进行了两次测试：上午（M，07:30 h）和晚上（E，17:30 h）。每次测试都包括直肠温度（T）在休息时测量的时间段，在循环测功计上进行 5 分钟的标准化 150 W 热身，然后按照规定的程序进行卧推（20、40 和 60 公斤）和深蹲（30、50 和 70 公斤）练习。在练习过程中，将线性编码器连接到用于练习的奥林匹克杠铃上，并使用 MuscleLab 软件（MuscleLab Technology，Langesund，挪威）测量了在运动的向心阶段的平均力（AF）、峰值速度（PV）和达到峰值速度的时间（tPV）。晚上休息时的 T 值比早上高（0.48°C，P<0.0005）。对于 AF（1.9%和 2.5%）、PV（8.3%和 12.7%）和 tPV（-16.6%和-9.8%；负数表示变量从早上到晚上减少），无论是在卧推还是深蹲，都表现出明显的日常变化。在从最轻的负荷到最重的负荷时，对于卧推和深蹲，AF 和 tPV 增加，PV 减少（47.1%和 80.2%；31.7%和 57.7%；-42.1%和-73.9%；P<0.0005，负数表示变量随负荷增加而减少），均有主要负荷效应。仅在 tPV 中发现了交互作用，即与早上相比，在最高负荷（60 和 70 公斤）时，晚上的 tPV 更早地出现在向心阶段（分别为 0.32 和 0.62 秒）。总的来说，在深蹲和卧推中发现了昼夜变化，并且当在晚上进行深蹲或卧推时，在向心阶段，复杂的多关节运动中的 tPV 会更早发生。这种差异可以使用低成本、便携式且广泛可用的商用仪器检测到，并使过去在实验室/严格控制的实验研究中的翻译能够应用于主流教练实践。
