The goal was to examine the acute effects of five sets of variable loading (VL) on the post-activation performance enhancement (PAPE) response during a live training session in highly trained athletes. PAPE is the phenomenon where acute improvements in power production in light loaded movements occur post near maximal loaded muscle contraction. PAPE may be induced with VL where resistance in the form of chains or bands is added to the bar as it displaces in the concentric phase. Participants were American football players from a variety of field positions (n=12, height =188 ± 0.01 cm, total body mass = 114.4 ± 24.3 kg) preparing for the 2023 National Football League draft representing during a lower body training session. They performed a contrast PAPE protocol consisting of 2 baseline vertical jumps (VJ) on dual-force plates followed by five sets of heavy VL half-squats using chains alternated with 2 VJs. PAPE did produce practical increases in reactive strength (baseline, 0.66±0.15, set 5, 0.67±0.17 m/s) and decreases in jump height (baseline, 20.3±2.9, set 5, 19.5±2.9 in), absolute peak power (baseline, 8125±1116, set 5, 7988±1038 W), and normalized peak power (baseline, 72.0±6.3, set 5, 71.1±8.7 W/kg). Findings suggest that power was at least maintained over multiple sets of VL induced PAPE. Acute post-activation performance enhancement through variable loading with chains in the strength-speed zone appeared to preserve power output across multiple sets but does not increase power in highly trained athletes.


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