The effectiveness of training and retraining at various frequencies on the aerobic capacity and intrinsic cardiovascular dynamics (systolic time intervals) in South African employees

Abstract

Cardiovascular disease (CVD) remains a serious health threat in most countries globally, placing a severe burden on the workforce in the corporate environment. Physical activity intervention has already been indicated as an effective regime against CVD. The purpose of this study therefore, was to examine the effect of training and retraining, following different exercise programme frequencies on the aerobic capacity, and some intrinsic cardiovascular dynamics (systolic time intervals) in a cohort of male employees. In this study, 60 employees (28 and 49 years) from an academic environment were randomly assigned to 3 groups namely; experimental (A and B), and control (C) groups. Groups A and B trained 3 times/week for 12 weeks, detrained for 12 weeks and retrained (A=2 times/week and B=4 times/week) for another 12 weeks. Aerobic capacity, myocardial function (double product) and systolic time intervals were determined at baseline and at the end of each phase. Experimental groups showed significant improvement in aerobic capacity (VO₂-peak) and myocardial function after 12 weeks of training. Furthermore, the results showed a significant increase in aerobic capacity for groups A (2 times/week) and B (4 times/week). Systolic time intervals (STIs) namely, Pre-ejection period (PEP_c), Left ventricular ejection time (LVET_c) and Intra-ventricular contraction time (IVCT) showed inconsistent responses during rest, while 30 and 120 seconds during recovery from a standardized workload, PEP_c peak _ratio and LVET_c peak _ratio showed the same tendency as the aerobic capacity. Physical intervention can improve both the aerobic function and selected cardiovascular dynamics (PEP_c and LVET_c). These responses of the STIs were clearer after a standardized physical exercise test than at rest. Programme frequency remains an important factor, which determines the outcomes.

Keywords: Training, retraining, aerobic capacity, systolic time intervals