title: Effects of prior heavy-intensity exercise on oxygen uptake and muscle deoxygenation kinetics of a subsequent heavy-intensity cycling and knee-extension exercise.
abstract: This study examined the effects of prior heavy-intensity exercise on the adjustment of pulmonary oxygen uptake (VO(2p)) and muscle deoxygenation Δ[HHb] during the transition to subsequent heavy-intensity cycling (CE) or knee-extension (KE) exercise. Nine young adults (aged 24 ± 5 years) performed 4 repetitions of repeated bouts of heavy-intensity exercise separated by light-intensity CE and KE, which included 6 min of baseline exercise, a 6-min step of heavy-intensity exercise (H1), 6-min recovery, and a 6-min step of heavy-intensity exercise (H2). Exercise was performed at 50 r·min(-1) or contractions per minute per leg. Oxygen uptake (VO(2)) mean response time was ∼20% faster (p < 0.05) during H2 compared with H1 in both modalities. Phase 2 time constants (τ) were not different between heavy bouts of CE (H1, 29.6 ± 6.5 s; H2, 28.0 ± 4.6 s) or KE exercise (H1, 31.6 ± 6.7 s; H2, 29.8 ± 5.6 s). The VO(2) slow component amplitude was lower (p < 0.05) in H2 in both modalities (CE, 0.19 ± 0.06 L·min(-1); KE, 0.12 ± 0.07 L·min(-1)) compared with H1 (CE, 0.29 ± 0.09 L·min(-1); KE, 0.18 ± 0.07 L·min(-1)), with the contribution of the slow component to the total VO(2) response reduced (p < 0.05) in H2 during both exercise modes. The effective τHHb was similar between bouts for CE (H1, 18.2 ± 3.0 s; H2, 18.0 ± 3.6 s) and KE exercise (H1, 26.0 ± 7.0 s; H2, 24.0 ± 5.8 s). The ΔHHb slow component was reduced during H2 in both CE and KE (p < 0.05). In conclusion, phase 2 VO(2p) was unchanged with priming exercise; however, a faster mean response time of VO(2p) during the heavy-intensity exercise preceded by a priming heavy-intensity exercise was attributed to a smaller slow component and reduced muscle deoxygenation indicative of improved muscle O(2) delivery during the second bout of exercise.
authors.affiliation: Canadian Centre for Activity and Aging, University of Western Ontario, London, Canada.
authors.forename: Sarah Margaret
authors.initials: SM
authors.lastname: Cleland
authors.forename: Juan Manuel
authors.initials: JM
authors.lastname: Murias
authors.forename: John Michael
authors.initials: JM
authors.lastname: Kowalchuk
authors.forename: Donald Hugh
authors.initials: DH
authors.lastname: Paterson
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001642:Bicycling; D015415:Biomarkers / Q000097:blood; D005260:Female; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D007719:Knee Joint / Q000502:physiology*; D019344:Lactic Acid / Q000097:blood; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000378:metabolism*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D010807:Physical Endurance; D012123:Pulmonary Ventilation; D019265:Spectroscopy, Near-Infrared; D013997:Time Factors; D055815:Young Adult
chemical_list: D015415:Biomarkers; D006454:Hemoglobins; D019344:Lactic Acid; C100003:deoxyhemoglobin; D010100:Oxygen