Adaptation to a standardized training program and changes in fitness in a large, heterogeneous population: The HERITAGE Family Study

Purpose: This paper describes the variations in response to a standardized, computer-controlled training program. Methods: Steady-state heart rate (HR) and oxygen intake (V̇O₂) of 614 healthy, sedentary men and women aged 16-65 yr were measured during three cycle ergometer exercise tests. The HR associated with 55, 65, 70, and 75% of each subject's pretraining V̇O(2max) was used to prescribe exercise intensity. Subjects exercised three times a week, beginning at a HR associated with 55% V̇O(2max) for 30 min. Duration and intensity was gradually increased over 20 wk of training. The duration and HR of each training session were controlled by a computer. Results: Using the linear relationship between HR, V̇O₂ and power output (PO), PO were predicted for each of 60 training sessions at the respective programmed HR. The average ratio of the actual training HR to programmed HR was 0.99. It was hypothesized that participants whose actual training PO exceeded their predicted PO would improve V̇O(2max) more than those whose actual PO was less than their predicted PO. Using the ratio of actual/predicted PO determined after the training was over, participants were arbitrarily assigned to three groups: 128 participants had low (LO) ratios (0.65-0.84), 408 had average (AV) ratios (0.85-1.14), and 78 had high (HI) ratios (1.15-1.34). Secondary analysis showed that the training program significantly increased mean V̇O(2max) of all three groups. Those who had a smaller increase in training PO (LO) had significantly less increase in V̇O(2max) than those with larger increases in PO (HI). Conclusion: People who exercise at a HR associated with the same %V̇O(2max) can vary substantially in their training PO, in their rate of increase in PO over a 20-wk training program, and in improvement of their V̇O(2max).