QUANTITATING THE CAPILLARY SUPPLY AND THE RESPONSE TO RESISTANCE TRAINING IN OLDER MEN

Resistance training (RT) has been shown to increase aerobic power in o lder humans. To determine the effects of RT on the capillary supply in this population, nine older men (65-74 y) engaged in 9 weeks RT of th e lower body. Following RT, peak O-2 uptake (VO2,peal) increased by 7% (P<.01). Needle biopsies (vastus lateralis muscle) revealed significa nt increases (mean +/- SE) in fibre area (3,874 +/- 314 mu m(2) to 4,7 78 +/- 309 mu m(2)), fibre perimeter (P, 262 +/- 11 mu m to 296 +/- 11 mu m), capillary contacts (3.7 +/- .2 to 4.3 +/- .3) and the individu al capillary-to-fibre ratio (C:F-i, 1.33 +/- .32 to 1.61 +/- .37, P<.0 05). To evaluate the potential for blood-tissue exchange, both fibre a rea-based and perimeter-based measures of the capillary supply were co mpared. While the area-based measures were maintained, C:F-i/P was inc reased, consistent with an increase in the size of the fibre-capillary interface and thus, an increased potential for oxygen flux following RT; Of the measurements of capillary supply, VO2,peak correlated best with C:F-i/P (r = 0.69, P<.005). These results indicate a significant increase in the capillary supply relative to the perimeter, but not th e cross-sectional area, of the muscle fibres following RT in older men , and that C:F-i/P is strongly correlated to the VO2,peak in this popu lation.