title: Effects of altering pedal frequency on the slow component of pulmonary VO2 kinetics and EMG activity.
abstract: This study investigated the effects of pedal frequency on the slow component of pulmonary oxygen uptake ( V O(2)) kinetics during heavy exercise at the same relative intensity. We hypothesized that higher pedal frequency (expected to enhance fast-twitch muscle fiber recruitment) would be associated with greater slow component amplitude (A' (s)), surface electromyography (normalized root mean square; RMS) and blood lactate concentration ([lactate]). Eight subjects performed square-wave transitions to heavy exercise at 35 and 115 rpm. Furthermore, alternated cadences square-wave transitions (35-115 rpm) were performed to examine the potential effects of additional fast-twitch muscle fiber recruitment on the slow component. Significance was accepted when P<0.05. The A' (s) was greater at higher cadences (0.58+/-0.08 and 0.70+/-0.09 L.min (-1) at 115 and 35-115 rpm, respectively) than at 35 rpm (0.35+/-0.04 L.min (-1)). Greater EMG increase over time (DeltaRMS ((10-3 min))) and [lactate] were observed at 115 and 35-115 rpm compared with 35 rpm. There was a significant correlation between A' (s) and overall DeltaRMS ((10-3 min)) for all pedal frequencies combined (r=0.63; P=0.001). Pedal frequency had no effect on time constants or time delays. These findings are consistent with the concept that progressive recruitment of muscle fibers is associated with the V O(2) slow component.
authors.affiliation: Department of Physical Education, State University of Londrina, Londrina, Brazil.
authors.forename: D M
authors.initials: DM
authors.lastname: Hirai
authors.forename: B T
authors.initials: BT
authors.lastname: Roseguini
authors.forename: F
authors.initials: F
authors.lastname: Diefenthaeler
authors.forename: F P
authors.initials: FP
authors.lastname: Carpes
authors.forename: M A
authors.initials: MA
authors.lastname: Vaz
authors.forename: E L
authors.initials: EL
authors.lastname: Ferlin
authors.forename: J P
authors.initials: JP
authors.lastname: Ribeiro
authors.forename: F Y
authors.initials: FY
authors.lastname: Nakamura
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D004576:Electromyography; D005080:Exercise Test / Q000379:methods*; D006801:Humans; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism; D010101:Oxygen Consumption; D013997:Time Factors