Power Fatigue Across Five Sets For Three Different Lifting Protocols

Abstract

Power development is a common training goal for many resistance exercisers. Because strength coaches attempt to meet these goals by manipulating the number of repetitions, sets, and intensity, it is important to understand how each of these variables alter movement power. The purpose of this study is to determine how average power changes across 5 sets of squats in 3 different lifting protocols. Seven healthy recreationally trained males (21.4 ± 1.67 years, 72.1 ± 2.0 in., 202.9 ± 21.4 lbs.), who had squatted regularly, completed each of three speed squat (emphasizing speed of the concentric phase) protocols in randomized order and on non-consecutive days. The three testing protocols consisted of 5 sets of 10 repetition at 30% of 1RM; 5 sets of 5 repetitions at 70% of 1RM; and 5 sets of 3 repetitions at 90% of 1RM. Power measures accounted for system mass (bar weight + body mass) instead of merely the bar mass. Set average power (SAP) was calculated as the mean of the repetition average power. Resting and post exercise lactate was also measured. Two way repeated measures ANOVA examined the effect of load and set number for SAP. Post hoc tests of within-subject contrasts using Tukey's LSD procedure were also performed. A separate repeated measures ANOVA tested for differences in lactate measures between the three protocols. Lactate measures were not significantly different between the three testing protocols. Mean SAp ± SE was 1040 ± 78.9 for the 90% load, 1301 ± 87.4 for 70% load, and 1518.5 for the 30% load. There was a significant main effect for load (F = 10.23, p = 0.004), but not for set (F= 0.883, p= 0.520). The average power was lower for the 90% protocol than for the 30% protocol (F= 28.96, p<0.01), but there was no difference between average power produced at the 70% and 30% loads or the 70 % and 90% protocol. A significant interaction (F= 4.98, p< 0.001) was found. A post hoc analysis indicated that at the 90% load the average power for each set decreased from sets 1 to set number 5, while in the 30% protocol SAP significant increased in set 5 compared to set 1. Resistance load appears to affect power fatigue across five sets of resistance exercise. The heaviest load had the highest power fatigue, while the moderate or 70% load did not show any evidence of power fatigue. It should also be noted that five sets at 30% 1RM produced a warm-up effect in that SAP increased from set 1 to set five. At the intensities most frequently utilized to develop power, there is no evidence of decreased power over 5 sets of speed squats. Practitioners attempting to train for power at higher loads (i.e. 90%) may wish to limit the number of sets of such exercises in the training program.