Repeated bouts of exercise alter the blood lactate-RPE relation. Med. Sci. Sports Exerc., Vol. 30, No. 7, pp. 1113-1117, 1998.
Purpose: To examine the effects of repeated bouts of exercise on the blood lactate [HLa]-ratings of perceived exertion (RPE) relation.
Methods: Six moderately trained males were studied on two occasions: a sequential exercise bouts day (SEB: 1000 h, 1130 h, and 1300 h) and a delayed exercise bouts day (DEB: 1000 h, 1400 h, and 1800 h). Each of the three exercise bouts within a given condition were 30 min in duration at the power output (PO) associated with 70% of V˙O2peak on a cycle ergometer. A standardized meal was provided at 0600 h. V˙O2, PO, HR, and RER were recorded every min during exercise and blood [HLa] and RPE were measured every 5 min during exercise.
Results: A 2 × 3 analysis of variance with repeated measures revealed that blood [HLa] decreased significantly with each repeated exercise bout (X¯ ± SEM: bout 1: SEB = 3.5 (0.3), DEB = 3.8 (0.4); bout 2: SEB = 2.6 (0.3), DEB = 2.8 (0.3); bout 3: SEB = 2.0 (0.2), DEB = 2.1 (0.4); mM). No differences were observed in the blood [HLa] response to repeated bouts of exercise between SEB and DEB. RPE-peripheral (legs, RPE-L) was higher during bout 3 compared with bout 1 (P < 0.05) (bout 1: SEB = 11.8 (0.8), DEB = 12.3 (0.2); bout 2: SEB = 12.3 (0.5), DEB = 13.3 (0.4); bout 3: SEB = 13.5 (0.8), DEB = 14.0 (0.7)); RPE-central (chest and breathing, RPE-C) was not affected by repeated bouts of exercise, whereas RPE-Overall (RPE-O) was higher during bout 3 compared with bouts 1 and 2 (P < 0.05) (bout 1: SEB = 12.5 (0.2), DEB = 12.3 (0.4); bout 2: SEB = 12.8 (0.4), DEB = 12.7 (0.4); bout 3: SEB = 13.7 (0.7), DEB = 13.2 (0.3)). No interaction for RPE × condition was observed. HR increased with repeated bouts of exercise with HR during exercise bout 3 being higher than HR during exercise bout 1 (164 vs. 156 bpm, P < 0.05). There was also a strong trend for HR during exercise bout 3 to be higher than HR during exercise bout 2 (P < 0.06). A trend for a reduction in V˙O2 with repeated exercise was observed (P < 0.07), with the reduction apparently related to the SEB condition (P < 0.12 for V˙O2 × condition). PO and kcal·min−1 were not affected by repeated bouts of exercise. RER decreased significantly with each repeated bout of exercise (from RER = 0.96 to RER = 0.89, P < 0.05) with no difference observed between SEB and DEB.
Conclusions: We conclude that the blood [HLa]-RPE relation is altered by repeated bouts of exercise and that this alteration does not appear to be affected by recovery time between exercise bouts (up to 3.5 h of recovery). These data suggest that, after the first exercise bout, RPE should not be used to produce a specific blood [HLa] on subsequent exercise bouts.
Department of Internal Medicine, Department of Pediatrics, General Clinical Research Center, University of Virginia Health Sciences Center, Department of Human Services, University of Virginia, Charlottesville, VA 22908
Submitted for publication May 1997.
Accepted for publication January 1998.
This work was supported by an NIH grant to the General Clinical Research Center RR 00847 and NIH grant RO1 AG10997 (to M. L. Hartman).
Present address for J. A. Kanaley: Department of Health and Physical Education at Syracuse University, Syracuse, NY 13244.
Address for correspondence: Arthur Weltman, Ph.D., Exercise Physiology Laboratory Memorial Gymnasium, University of Virginia, Charlottesville, VA 22903. E-mail: firstname.lastname@example.org.