title: Prior heavy exercise increases oxygen cost during moderate exercise without associated change in surface EMG.
abstract: The aim of this study was to test the hypothesis that prior heavy exercise results in a higher oxygen cost during a subsequent bout of moderate exercise due to changes in muscle activity. Eight male subjects (25+/-2 yr, +/-SE) performed moderate-moderate and moderate-heavy-moderate transitions in work rate (cycling intensity, moderate=90% LT, heavy=80% VO(2) peak). The second bout of moderate exercise was performed after 6 min (C) or 30s (D) of recovery. Pulmonary gas exchange was measured breath-by-breath and surface electromyography was obtained from the vastus lateralis and medialis muscles. Root mean square (RMS) and median power frequency (MDPF) were computed. Prior heavy exercise increased DeltaVO(2)/DeltaWR (C: +2.0+/-0.8 ml min(-1)W(-1), D: +3.4+/-0.8 ml min(-1)W(-1); P<0.05) and decreased exercise efficiency (C: -13.3+/-5.6%, D: -22.2 +/-4.9%; P<0.05) during the second bout of moderate exercise in the absence of changes in RMS. MDPF was slightly elevated ( approximately 2%) during the second bout of moderate exercise, but MDPF was not correlated with V O(2) (r=0.17). These findings suggest that the increased oxygen cost during moderate exercise following heavy exercise is not due to increased muscle activity as assessed by surface electromyography.
authors.affiliation: Department of Kinesiology, The University of Toledo, Toledo, OH 43607, USA.
authors.forename: Joaquin U
authors.initials: JU
authors.lastname: Gonzales
authors.forename: Barry W
authors.initials: BW
authors.lastname: Scheuermann
mesh_terms: D000328:Adult; D004576:Electromyography / Q000379:methods / Q000706:statistics & numerical data; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012016:Reference Values; D013995:Time; D013997:Time Factors