The Effect of Endurance Exercise Training on Aerobic Capacity and Vascular Conductance in Healthy, Late Middle-Aged and Older Women

Abstract

Purpose: During dynamic exercise, such as cycling, rate of oxygen uptake (VO2) increases in proportion with the rates of muscular work. To support a higher VO2, there is a corresponding increase in muscle blood flow to supply active skeletal muscle with more oxygen. Therefore, it is reasonable to assume that peak whole-body oxygen uptake (VO2peak) may be partly limited by the capacity to increase muscle blood flow during exercise. Thus, the present thesis aims to test the hypothesis that there is a positive association between peak lower leg blood flow and VO2peak in that there is a proportionate increase in peak blood flow for a given increase in VO2peak. Methods: This hypothesis was tested using 2 experiments. Experiment 1 utilised a cross-sectional study to construct and characterise the relationship between peak lower leg blood flow and VO2peak in middle-aged and older women (n=34). VO2peak (cardiopulmonary exercise test) and peak lower leg blood flow (venous occlusion plethysmography) were assessed in healthy women (57.6 ± 6.9 years) with varied training histories. Experiment 2 consisted of a training study aimed at identifying the amount peak lower leg blood flow increased for a given increase in VO2peak. Sixteen healthy untrained women (HU, 59.2 ± 7.5 years) completed a 16-week exercise programme to improve VO2peak. Pre-and-post-training measurements of peak blood flow and VO2peak were compared to determine if an improved VO2peak was associated with concurrent improvement in blood flow. Results: There was a weak positive relationship between peak blood flow and VO2peak (r =0.305, p=0.079). The relationship appeared to result primarily from differences in vascular conductance. Sixteen weeks of exercise training improved VO2peak (4.7 ± 3.6 ml.kg-1.min-1, p<0.001). However, peak blood flow (31.3 ± 10.7, p=0.211) and vascular conductance (0.104 ml.min-1.100ml-1.mmHg, ± 0.11, p=0.132) were unchanged post-training. There was no correlation between change in peak vascular conductance for a given improvement in VO2peak (r=0.0078, p=0.977). Conclusion: At best, there was a weak positive association between peak blood flow and vascular conductance with VO2peak in healthy older women; however, we found no association between traininginduced improvement in VO2peak and changes in peak vascular conductance.