A sex-specific relationship between capillary density and anaerobic threshold

Robbins JL, Duscha BD, Bensimhon DR, Wasserman K, Hansen JE, Houmard JA, Annex BH, Kraus WE. A sex-specific relationship between capillary density and anaerobic threshold. J Appl Physiol 106: 1181-1186, 2009. First published January 22, 2009; doi:10.1152/japplphysiol.90947.2008.-Although both capillary density and peak oxygen consumption ((V) over dotO(2)) improve with exercise training, it is difficult to find a relationship between these two measures. It has been suggested that peak (V) over dotO(2) may be more related to central hemodynamics than to the oxidative potential of skeletal muscle, which may account for this observation. We hypothesized that change in a measure of submaximal performance, anaerobic threshold, might be related to change in skeletal muscle capillary density, a marker of oxidative potential in muscle, with training. Due to baseline differences among these variables, we also hypothesized that relationships might be sex specific. A group of 21 subjects completed an inactive control period, whereas 28 subjects (17 men and 11 women) participated in a 6-mo high-intensity exercise program. All subjects were sedentary, overweight, and dyslipidemic. Potential relationships were assessed between change in capillary density with both change in (V) over dotO(2) at peak and at anaerobic threshold with exercise training. All variables and relationships were assessed for sex-specific effects. Change in peak (V) over dotO(2) was not related to change in capillary density after exercise training in either sex. Men had a positive correlation between change in (V) over dotO(2) at anaerobic threshold and change in capillary density with exercise training (r = 0.635; P < 0.01), whereas women had an inverse relationship (r = -0.636; P < 0.05) between the change in these variables. These findings suggest that, although enhanced capillary density is associated with training-induced improvements in submaximal performance in men, this relationship is different in women.