• Within-session Post-activation Performance Enhancement for Countermovement Jump performance in Morning vs. Evening: A pilot study

Post-activation performance enhancement (PAPE) is a phenomenon following acute conditioning activity (CA) that transiently enhances neuromuscular performance. However, it is unclear if PAPE is influenced by time-of-day. Methods: 15 resistance-trained participants (27.1 ± 5.1years, 11M/4F, relative 1-RM back squat = 1.81x BW) were recruited. Using a crossover, counterbalanced study design, participants completed 2 trials at different times-of-day: 8-10 a.m. and 4-6 p.m. The conditioning activity (CA) included 3 sets of barbell back squat at 85%1-RM. Countermovement jump (CMJ) performance, such as jump height (JH), modified reactive strength index (RSImod), peak power (Ppeak) and average concentric power (CPavg) were measured on a force plate prior to the CA, and again at 10s, 4, 8, 12 and 16 min post-CA. A two-way ANOVA was performed to compare the effects of CA and time-of-day effect on CMJ performance. Results: Analysis of absolute Pre-Postmax changes in CMJ performance variables indicates significant improvements in RSImod (p = 0.04, d = 0.9) in the morning only and non-significant changes in JH, Ppeak and CPavg (p > 0.05) in both morning and evening conditions. CMJ height was higher at baseline (p = 0.30, d = 0.63) in the evening but this difference was not maintained in subsequent jumps post-CA. The magnitude of PAPE observed in morning and evening sessions exhibited considerable variability among individuals. Conclusion: Results suggests a diurnal amplitude of PAPE in the morning, particularly RSImod, and practitioners should monitor the individual response during complex training at different times of day to optimise performance.