Physiological factors associated with the lower maximal oxygen consumption of master runners

Abstract

We examined the hemodynamic factors associated with the lower maximal O2 consumption (VO2max) in older formerly elite distance runners. Heart rate and VO2 were measured during submaximal and maximal treadmill exercise in 11 master [66 +/- 8 (SD) yr] and 11 young (32 +/- 5 yr) male runners. Cardiac output was determined using acetylene rebreathing at 30, 50, 70, and 85% VO2max. Maximal cardiac output was estimated using submaximal stroke volume and maximal heart rate. VO2max was 36% lower in master runners (45.0 +/- 6.9 vs. 70.4 +/- 8.0 ml.kg-1.min-1, P less than or equal to 0.05), because of both a lower maximal cardiac output (18.2 +/- 3.5 vs. 25.4 +/- 1.7 l.min-1) and arteriovenous O2 difference (16.6 +/- 1.6 vs. 18.7 +/- 1.4 ml O2.100 ml blood-1, P less than or equal to 0.05). Reduced maximal heart rate (154.4 +/- 17.4 vs. 185 +/- 5.8 beats.min-1) and stroke volume (117.1 +/- 16.1 vs. 137.2 +/- 8.7 ml.beat-1) contributed to the lower cardiac output in the older athletes (P less than or equal 0.05). These data indicate that VO2max is lower in master runners because of a diminished capacity to deliver and extract O2 during exercise.

Changes in Exercise Cardiac Function With Age in Endurance-Trained Females

“…As previously reviewed, some investigators have observed age-related decreases in SVmax in NA and ET maies and females (205,222). According to the Frank-Starling mechanism, decreases in SVmax may result from decreases in diastolic filling (and thus, preload).…”

“…Both QMX and maximal snoke volume (SVmax) are signifcantly larger in younger (7, 222,234) as weii as i n younger and older ET fernales (205), compared to age and gender-matched nonnally active (NA) individuals. Penp heral adaptations in active skele t ai muscle also play an important role in the increase in V0,rna.x as a result of endurance training.…”

“…These investigators observeci a progressive increase in SV throughout inctlemental exercise to maximum without a plateau in ET males (46,67,68,105,152,220,222,285,289). nie progressive increase in SV to maximum in ET males has been associateci w i t h enhancements in both the diastolic filling rate @FR) and left venaicular emptying rate (LVER) (33, 7 1, 105, 152, 167, 186).…”

“…In addition, since the absolute levels of training intensity and/or volumes tend to decrease with age in ET males and females (69,214,226), this may aiso result in a decrease in V0,rna.x. For instance, the overail training volumes of masters athletes was shown to be only -50-60% as great as that of younger ET individuals (222). An increased prevalence of injuries or decreased levels of motivation may contx-ibute to the reduction in training (138).…”

“…Penp heral adaptations in active skele t ai muscle also play an important role in the increase in V0,rna.x as a result of endurance training. For instance, younger (1 1, 240) and older ET males (205,222), as well as younger (205) and older ET females (205) have a larger a-tD0,max than age and gender-matched NA individuals.…”