Post-activation Potentiation in Moderately Heavy Squats following a Heavy Pre-load Squat

Post-activation potentiation (PAP) is a phenomenon where force output is acutely enhanced following muscular contraction. Previous research has documented enhanced performance in power-type light exercise following a heavy pre-load, such as vertical jumps following heavy squats. To date, the effect of PAP on moderately heavy exercise following a heavy pre-load has not been investigated. Purpose: The purpose was to examine whether PAP could be elicited in moderately heavy squats following a heavy squat pre-load, and if so, what intensity (as percentage of one repetition-maximum [1RM]) of pre-load elicited the highest PAP effect (measured as mean power, mean force and number of repetitions performed). Subjects: Seventeen resistance-trained males (age 24±2 years, length 182±8 cm, body mass 84.7±13.1 kg, squat 1RM 147.6±29.6 kg) with at least 2 years of experience of the squat exercise. Methods: After testing parallel squat 1RM at a separate session, subjects performed three testing sessions in a randomized order in a cross-over design; performance test at 80% of parallel squat 1RM (control), one repetition at 85% of 1RM followed 8 minutes later by the same performance test (PAP85), and one repetition at 93% of 1RM followed 8 minutes later by the same performance test (PAP93). Sessions were separated by six days. Force and power output was recorded using a linear encoder. Friedman’s test was used to reveal differences between conditions, and a Wilcoxon signed rank test was used to identify these differences. Results: There was an increase in number of repetitions performed for PAP85 (p=0.009) and PAP93 (p=0.001) compared to control, but not for mean power or mean force. There was no significant difference between PAP85 and PAP93 for number of repetitions (p=0.091). Conclusion: PAP can be elicited to improve performance in moderately heavy squats following a heavy squat pre-load in trained subjects, but only measured as number of repetitions performed, not force or power. PAP could therefore be useful not only for designing power training, but also for strength and hypertrophy training.