title: The effect of prior heavy exercise on the parameters of the power-duration curve for cycle ergometry.
abstract: The tolerable duration (t) of high-intensity cycle ergometry is well characterized by a hyperbolic function of power output (P) with an asymptote (termed the critical power (CP)) and a curvature constant (denoted W'). The purpose of this study was to investigate the effect of prior heavy exercise (W-up) that specifically engenders an acidosis on CP and W'. Eight healthy subjects performed 2 sets of 4 high-intensity square-wave exercise bouts on a bicycle ergometer to estimate CP and W', with (W-up) and without (control) prior exercise, respectively. Exercise intensities of the 4 main bouts were selected in the range of 90% to 135% peak oxygen uptake so as to reach the limit of tolerance between approximately 1.5 and 10 min. The W-up bout was preceded by 6 min cycling at a work rate halfway between the lactate threshold and peak oxygen uptake (mean +/- SD of 153.8 +/- 29.8 W) starting 12 min before the main bout. Blood lactate levels ([La]b) just before the main exercise bouts in W-up conditions were significantly higher than those of the control (4.7 +/- 1.1 and 1.4 +/- 0.4 mEq.L(-1), respectively; p < 0.05). However, there were no significant differences in end-exercise [La]b. W-up increased significantly the tolerable duration at every work rate compared with the control, which was attributable exclusively to increased CP (176.5 +/- 34.3 and 168.7 +/- 31.3 W, respectively; p < 0.05), without any significant change in W' (11.0 +/- 3.2 and 11.0 +/- 3.1 kJ, respectively). It is concluded that the prior heavy exercise improved performance mainly because of an enhanced aerobic component of exercise energetics, as indicated by a higher CP and lower increment in the [La]b.
authors.affiliation: Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Minami-ku, Hiroshima, 734-8558 Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Miura
authors.forename: Chiaki
authors.initials: C
authors.lastname: Shiragiku
authors.forename: Yuiko
authors.initials: Y
authors.lastname: Hirotoshi
authors.forename: Asami
authors.initials: A
authors.lastname: Kitano
authors.forename: Masako Yamaoka
authors.initials: MY
authors.lastname: Endo
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Barstow
authors.forename: R Hugh
authors.initials: RH
authors.lastname: Morton
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Fukuba
mesh_terms: D000328:Adult; D001642:Bicycling; D002245:Carbon Dioxide / Q000378:metabolism; D018592:Cross-Over Studies; D016552:Ergometry / Q000379:methods*; D005080:Exercise Test / Q000379:methods; D017079:Exercise Tolerance; D005260:Female; D006339:Heart Rate; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D053580:Muscle Strength; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D012123:Pulmonary Ventilation; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide; D019344:Lactic Acid