Applied Physiology Laboratories, Department of Kinesiology, Health Promotion and Recreation, University of North Texas, Denton, Texas, USA.
J Strength Cond Res. 2011 Jul;25(7):1951-6. doi: 10.1519/JSC.0b013e31821eb67f.
Equipment with counterbalance weight systems is commonly used for the assessment of performance in explosive resistance exercise movements, but it is not known if such systems affect performance measures. The purpose of this study was to determine the effect of using a counterbalance weight system on measures of smith machine bench press throw performance. Ten men and 14 women (mean ± SD: age, 25 ± 4 years; height, 173 ± 10 cm; weight, 77.7 ± 18.3 kg) completed maximal smith machine bench press throws under 4 different conditions (2 × 2; counterbalance × load): with or without a counterbalance weight system and using 'light' or 'moderate' net barbell loads. Performance variables (peak force, peak velocity, and peak power) were measured using a linear accelerometer attached to the barbell. The counterbalance weight system resulted in significant (p < 0.001) reductions in measures of peak force (mean difference ± standard error: light: -112 ± 20 N; moderate: -140 ± 23 N), peak velocity (light: -0.49 ± 0.10 m·s; moderate: -0.33 ± 0.07 m·s), and peak power (light: -220 ± 43 W; moderate: -143 ± 28 W) compared with no counterbalance system for both load conditions. Load condition did not affect absolute or percentage reductions from the counterbalance weight system for any variable. In conclusion, the use of a counterbalance weight system reduces accelerometer-based performance measures for the bench press throw exercise at light and moderate loads. This reduction in measures is likely because of an increase in the external resistance during the movement, which results in a discrepancy between the manually input and the actual value for external load. A counterbalance weight system should not be used when measuring performance in explosive resistance exercises with an accelerometer.
带有平衡重系统的设备常用于评估抗阻运动中的运动表现，但目前尚不清楚此类系统是否会影响运动表现的测量结果。本研究旨在确定使用平衡重系统对史密斯机卧推抛球运动表现测量结果的影响。10 名男性和 14 名女性（平均值±标准差：年龄 25±4 岁；身高 173±10cm；体重 77.7±18.3kg）在 4 种不同条件（2×2；平衡重×负荷）下完成了最大史密斯机卧推抛球运动：使用或不使用平衡重系统，以及使用“轻”或“中”杠铃。使用附在杠铃上的线性加速度计测量运动表现变量（峰值力、峰值速度和峰值功率）。平衡重系统导致峰值力（轻：-112±20N；中：-140±23N）、峰值速度（轻：-0.49±0.10m·s；中：-0.33±0.07m·s）和峰值功率（轻：-220±43W；中：-143±28W）显著降低（p<0.001），与无平衡重系统相比，两种负荷条件下的所有变量均如此。负荷条件对任何变量从平衡重系统获得的绝对或百分比减少都没有影响。结论：在轻负荷和中负荷下，使用平衡重系统会降低基于加速度计的卧推抛球运动表现的测量值。这种测量值的减少可能是由于运动过程中外部阻力增加，导致输入的手动外部负荷值与实际值之间存在差异。在使用加速度计测量抗阻运动的爆发力时，不应使用平衡重系统。
