Article

Effects of prior heavy-intensity exercise on pulmonary O2 uptake and muscle deoxygenation kinetics in young and older adult humans.

Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada N6A 3K7.
Journal of Applied Physiology (impact factor: 3.75). 10/2004; 97(3):998-1005. DOI:10.1152/japplphysiol.01280.2003 pp.998-1005
Source: PubMed

ABSTRACT Pulmonary O2 uptake (VO2p) and muscle deoxygenation kinetics were examined during moderate-intensity cycling (80% lactate threshold) without warm-up and after heavy-intensity warm-up exercise in young (n = 6; 25 +/- 3 yr) and older (n = 5; 68 +/- 3 yr) adults. We hypothesized that heavy warm-up would speed VO2p kinetics in older adults consequent to an improved intramuscular oxygenation. Subjects performed step transitions (n = 4; 6 min) from 20 W to moderate-intensity exercise preceded by either no warm-up or heavy-intensity warm-up (6 min). VO2p was measured breath by breath. Oxy-, deoxy-(HHb), and total hemoglobin and myoglobin (Hb(tot)) of the vastus lateralis muscle were measured continuously by near-infrared spectroscopy (NIRS). VO2p (phase 2; tau) and HHb data were fit with a monoexponential model. After heavy-intensity warm-up, oxyhemoglobin (older subjects: 13 +/- 9 microM; young subjects: 9 +/- 8 microM) and Hb(tot) (older subjects: 12 +/- 8 microM; young subjects: 14 +/- 10 microM) were elevated (P < 0.05) relative to the no warm-up pretransition baseline. In older adults, tauVO2p adapted at a faster rate (P < 0.05) after heavy warm-up (30 +/- 7 s) than no warm-up (38 +/- 5 s), whereas in young subjects, tauVO2p was similar in no warm-up (26 +/- 7 s) and heavy warm-up (25 +/- 5 s). HHb adapted at a similar rate in older and young adults after no warm-up; however, in older adults after heavy warm-up, the adaptation of HHb was slower (P < 0.01) compared with young and no warm-up. These data suggest that, in older adults, VO2p kinetics may be limited by a slow adaptation of muscle blood flow and O2 delivery.

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Keywords

80% lactate threshold
 
heavy warm-up
 
heavy-intensity warm-up
 
heavy-intensity warm-up exercise
 
improved intramuscular oxygenation
 
moderate-intensity cycling
 
moderate-intensity exercise preceded
 
muscle blood flow
 
muscle deoxygenation kinetics
 
O2 delivery
 
older adults consequent
 
phase 2
 
Pulmonary O2 uptake
 
slow adaptation
 
step transitions
 
tauVO2p
 
vastus lateralis muscle
 
VO2p
 
VO2p kinetics
 
warm-up pretransition baseline