Quantitating the capillary supply and the response to resistance training in older men

Resistance training (RT) has been shown to increase aerobic power in older 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 the lower body. Following RT, peak O-2 uptake (VO2,peal) increased by 7% (P<.01). Needle biopsies (vastus lateralis muscle) revealed significant increases (mean +/- SE) in fibre area (3,874 +/- 314 mu m(2) to 4,778 +/- 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 individual capillary-to-fibre ratio (C:F-i, 1.33 +/- .32 to 1.61 +/- .37, P<.005). To evaluate the potential for blood-tissue exchange, both fibre area-based and perimeter-based measures of the capillary supply were compared. While the area-based measures were maintained, C:F-i/P was increased, 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 the 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 population.