Of the key physiological determinants of performance, VO2max has received the most attention with well-documented reductions across the lifespan of approximately 1% per year. By comparison, the influence of ageing on exercise efficiency has received little attention. However, recent publications (Venturelli et al., 2012) and a point-counterpoint (Venturelli & Richardson, 2012; Ortega, 2012) have demonstrated that there is considerable debate on the effects of ageing, exercise efficiency and performance. Consequently, the aim of this study was to assess the effect of training status, age and muscle fiber composition on cycling gross efficiency (GE) and exercise performance.
Forty males were recruited into one of 4 groups: young and old trained cyclists, young and old untrained individuals. In a series of laboratory visits all participants completed an incremental ramp test to measure their VO2max, maximal heart rate (HRmax) and MMP, a submaximal test of GE at a series of relative work rates, and in trained participants only, a 1-hour cycling time trial. Finally, all participants underwent a muscle biopsy of their right vastus lateralis muscle.
A univariate general linear model of VO2max and MMP data demonstrated significant main effects of training status (P<0.01), and age (P<0.01), whereas HRmax was only affected by age (P<0.01). At relative work rates of 50% and 60% MMP, 60% MMP 60 rev.min-1, and 60% MMP 120 rev.min-1 there was an effect of training status on GE (P<0.01), the effect of age was only significant at 50% MMP and 60% MMP (P<0.01). The proportion of type I muscle fibers in the vastus lateralis muscle was higher in the trained groups (P<0.01), with no effect of age. Further, performance power output was predicted by performance VO2 and GE with standardized beta coefficients of 0.94 and 0.34 respectively. Independently, only age significantly added to the prediction for parameters in the model where MMP was included (standardized beta coefficients of 1.21 for MMP and 0.45 for age).
These data demonstrate that key physiological factors influencing endurance exercise performance are detrimentally affected by ageing, although exercise training can potentially moderate some of these effects. Further, even though biological ageing provides an influence, oxygen cost is the main factor affecting exercise performance. Therefore, the reductions in exercise performance with age are mostly likely influenced by lower exercise efficiency.
Ortega JD. (2012). J Appl Physiol, doi: 10.1152/japplphysiol.01438.2012. Venturelli M, Richardson RS. (2012). J Appl Physiol, doi:10.1152.japplphysiol.01438.2012. Venturelli M, Schena F, Scarsini R, Muti E & Richardson RS. (2012). Age, doi:10.1007/s11357-011-9379-1.