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

Abstract

chuk. Oxygen uptake kinetics for moderate exercise are speeded in older humans by prior heavy exercise. J Appl Physiol 92: 609-616, 2002; 10.1152.japplphysiol.00186. 2001.-This study examined the effect of heavy-intensity warm-up exercise on O2 uptake (V O2) kinetics at the onset of moderate-intensity (80% ventilation threshold), constantwork rate exercise in eight older (65 Ϯ 2 yr) and seven younger adults (26 Ϯ 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. V O2 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 Mod1, the time constant () for the predominant rise in V O2 (V O2) was slower (P Ͻ 0.05) in the older adults (50 Ϯ 10 s) than in young adults (19 Ϯ 5 s). The older adults demonstrated a speeding (P Ͻ 0.05) of V O2 kinetics when moderate-intensity exercise (Mod 2) was preceded by high-intensity warm-up exercise (V O2, 27 Ϯ 3 s), whereas young adults showed no speeding of V O2 kinetics (V O2, 17 Ϯ 3 s). In the older and younger adults, baseline HR preceding Mod 2 was elevated compared with Mod 1, but the for HR kinetics was slowed (P Ͻ 0.05) in Mod2 only for the older adults. Prior heavy-intensity exercise in old, but not young, adults speeded V O2 kinetics during Mod2. Despite slowed HR kinetics in Mod 2 in the older adults, an elevated baseline HR before the onset of Mod 2 may have led to sufficient muscle perfusion and O 2 delivery. These results suggest that, when muscle blood flow and O 2 delivery are adequate, muscle O 2 consumption in both old and young adults is limited by intracellular processes within the exercising muscle.aging; heart rate; oxygen transport; oxygen utilization AGING IS ASSOCIATED WITH a slowing of pulmonary O 2 uptake (V O 2 ) kinetics during the on-transition to a step increase in work rate (WR) of moderate intensity (2,7,25), implying that the rate of O 2 utilized at the muscle is also slowed with increasing age. Although it has been demonstrated that, for older adults, V O 2 kinetics responses due to exercise in muscles that are chronically active remain similar to those of young adults (8) or speed toward values seen in young adults as a consequence of chronic exercise training (1), it is unclear whether these adaptations are a consequence of improved blood flow and/or O 2 delivery or of a faster activation of the biochemical reactions in muscle, factors that have been implicated as limiting muscle O 2 consumption in young adults (20,34).Recently, it was shown in young adults that V O 2 kinetics after the start of heavy-intensity exercise became faster as a consequence of a prior "warm-up" bout of heavy-intensity exercise, whereas, in contrast, V O 2 kinetics during moderate-intensity exercise were not affected by a warm-up bout of exercise (...

Effects of Age and Long-Term Endurance Training on V·O2 Kinetics

“…Interestingly, the amount by which the slowing of VO 2 kinetics can be attenuated is dependent upon the type of training; Berger et al (2006a) examined both endurance-and sprinttrained athletes from ages 46 to 85 and found that endurance trained athletes maintained similar τVO 2 values to that of healthy younger individuals, whereas sprint trained athletes had a slowing of VO 2 kinetics with age (however all τVO 2 values in the sprint group were still below the agematched sedentary counterparts). Additionally, just one bout of heavy-priming exercise will speed VO 2 kinetics in both young and older men (DeLorey et al, 2004b;Scheuermann et al, 2002), presumably as a result of improved O 2 delivery (Scheuermann et al, 2002). …”

Kinetics of O2uptake, leg blood flow, and muscle deoxygenation are slowed in the upper compared with lower region of the moderate-intensity exercise domain

“…Gas exchange was measured breath by breath by using methods similar to those previously described (35). Briefly, inspired and expired airflow and volumes were measured by using a low-dead space (90 ml), low-resistance bidirectional turbine and volume transducer (Alpha Technologies, VMM-110).…”

Effects of short-term dietary nitrate supplementation on blood pressure, O2uptake kinetics, and muscle and cognitive function in older adults

“…Moreover, the distribution of blood flow in the microcirculation, capillary density, and capillary hemodynamics (7,8,18,30,59,60,65), as well as mitochondrial volume density and oxidative function (15,16) are compromised with aging. There is evidence that V O 2 kinetics in the transition from a lower to a higher metabolic rate is slowed in older compared with younger adults (3,14,22) and that this may be related to a limitation in muscle O 2 delivery (66). The reduction in maximal oxidative phosphorylation capacity in aged muscle (15,16,28) might also contribute toward the slower V O 2 kinetics.…”