Cardiorespiratory kinetics during exercise of different muscle groups and mass in old and young

Abstract

The purpose was to compare cardiorespiratory kinetics during exercise of different muscle groups (double-leg cycling vs treadmill walking and single-leg ankle plantar flexion) in old and young subjects. Oxygen uptake (VO2) during exercise transitions was measured breath by breath, and the phase 2 portion of the response was fit by a monoexponential for determination of the time constant (tau) of VO2. Two separate studies were performed: in study 1, 12 old (age 66.7 yr) and 16 young (aged 26.3 yr) subjects were compared during cycling and ankle plantar flexion exercise, and in the study 2, five old (aged 69.6 yr) and five young (24.4 yr) subjects were compared during cycling and treadmill walking. VO2 transients during square-wave cycling exercise were significantly slower in the old compared with the young groups. In contrast, VO2 kinetics did not differ between old and young groups during plantar flexion exercise. Heart rate (HR) kinetics followed the same pattern, with tau HR being significantly slower in the old vs young groups during transitions to cycling but not to plantar flexion. In study 2 tau VO2 and tau HR during on-transients to treadmill square-wave exercise were significantly slower in the old group compared with the young group, but tau VO2 was significantly faster during treadmill exercise than during cycling in the old group. The differences with aging between the modes of exercise may be related to the muscle mass involved and the circulatory demands. On the other hand, slowed VO2 kinetics with age appear to occur in a mode (cycling) in which the muscles are not accustomed to the activity, whereas in a mode of normal activity (walking) and with the muscle groups (plantar flexors) accustomed to the activity, VO2 kinetics are not slowed to the same degree with age.

The effects of age on kinetics of oxygen uptake and phosphocreatine in humans during exercise

“…This implies that the old can improve peripheral muscle capacity to a greater extent than central cardiovascular function, with training. This is supported by the finding that our older individuals had similar plantar flexion kinetics (Table 1), but slower 1702 kinetics during cycling compared with younger individuals, as found in a previous study (Chilibeck, Paterson, Smith & Cunningham, 1996b). Cycling exercise places a greater stress on the cardiovascular system and may be limited by central factors (i.e.…”

Left Ventricular Diastolic Filling and Cardiovascular Functional Capacity in Older Men

“…In younger subjects (Whipp et al 1982), older subjects with normal LVDF (i.e. EÏA > 1.0) (Petrella et al 1994), or active older subjects (Chilibeck et al 1996) the limitation for oxygen kinetics at sub-threshold work rates appears to be related to mechanisms of Oµ utilisation as noted by . At maximal exercise, the limiting factor appears to be Oµ delivery as described by Knight et al (1993) and as summarised by Rowell (1993).…”

“…Determination of ýOµ kinetics has been previously described (Chilibeck et al 1996). Briefly, following the measurement of the pre-study ýOµ,max, the anaerobic threshold (èL) was determined as the ýOµ at which a systematic increase in the ventilatory equivalent of Oµ and also in the end-tidal partial pressure of oxygen (PET,Oµ) was observed, without a concomitant rise in the ventilatory equivalent for COµ or a decrease in the PET,COµ.…”

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

“…Previous studies with young adults have not found faster V O 2 kinetics following NO 3 Ϫ supplementation (5,47,76). Older adults typically have slower V O 2 kinetics (3,14,22) and are more likely to evince a speeding of V O 2 kinetics following interventions designed to enhance muscle O 2 delivery (66) than their younger counterparts. The MRT for V O 2 kinetics for the older subjects tested in the present study was surprisingly fast (i.e., ϳ28 s).…”

“…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.…”