Oxygen uptake kinetics for moderate exercise are speeded in older humans by prior heavy exercise

1 Centre for Activity and Aging, School of Kinesiology and 3 Department of Physiology, The University of Western Ontario, London, Ontario, Canada N6A 3K7; and 2 Department of Kinesiology, Kansas State University, Manhattan, Kansas 66506-0302 This study examined the effect of heavy-intensity warm-up exercise on O 2 uptake ( O 2 ) kinetics at the onset of moderate-intensity (80% ventilation threshold), constant-work rate exercise in eight older (65 ± 2 yr) and seven younger adults (26 ± 1 yr). Step increases in work rate from loadless cycling to moderate exercise (Mod 1 ), heavy exercise, and moderate exercise (Mod 2 ) were performed. Each exercise bout was 6 min in duration and separated by 6 min of loadless cycling. O 2 kinetics were modeled from the onset of exercise by use of a two-component exponential model. Heart rate (HR) kinetics were modeled from the onset of exercise using a single exponential model. During Mod 1 , the time constant ( ) for the predominant rise in O 2 ( O 2 ) was slower ( P