(Public Library of Science, 2012) Gorostiaga Ayestarán, Esteban; Navarro Amezqueta, Ion; Calbet, José A. L.; Hellsten, Ylva; Cusso, Roser; Guerrero, Mario; Granados, Cristina; González Izal, Miriam; Ibáñez Santos, Javier; Izquierdo Redín, Mikel; Ciencias de la Salud; Osasun Zientziak
This investigation examined the influence of the number of repetitions per set on power output and muscle metabolism
during leg press exercise. Six trained men (age 3466 yr) randomly performed either 5 sets of 10 repetitions (10REP), or 10
sets of 5 repetitions (5REP) of bilateral leg press exercise, with the same initial load and rest intervals between sets. Muscle
biopsies (vastus lateralis) were taken before the first set, and after the first and the final sets. Compared with 5REP, 10REP
resulted in a markedly greater decrease (P,0.05) of the power output, muscle PCr and ATP content, and markedly higher
(P,0.05) levels of muscle lactate and IMP. Significant correlations (P,0.01) were observed between changes in muscle PCr
and muscle lactate (R2 = 0.46), between changes in muscle PCr and IMP (R2 = 0.44) as well as between changes in power
output and changes in muscle ATP (R2 = 0.59) and lactate (R2 = 0.64) levels. Reducing the number of repetitions per set by
50% causes a lower disruption to the energy balance in the muscle. The correlations suggest that the changes in PCr and
muscle lactate mainly occur simultaneously during exercise, whereas IMP only accumulates when PCr levels are low. The
decrease in ATP stores may contribute to fatigue.
