When Mike Mentzer first came out with his radical book Heavy Duty, people thought he was crazy. Mentzer preached high-intensity exercise once every five to seven days, and every training session shouldn’t last more than 20 minutes in order to achieve maximum muscle stimulation. Mentzer believed many bodybuilders were “overtraining,” so he emphasized brief, high-intensity, and infrequent workouts.
It seems that new research can validate Mentzer’s claim with clinical trials in younger adults but not with older adults. Researchers examined how strength and muscle mass were affected by cutting back on training to once a week in both younger and older adults. Seventy adults, 39 in the younger age group (between ages 20 and 35) and 31 in the older age group (between ages 60 and 75), completed the first phase of the trial, which lasted 16 weeks.
In Phase 1, participants performed three sets of three resistance-training exercises—leg press, knee extensions, and squats—three times a week. The second phase of the trial, which lasted 32 weeks, was a de-training study. Participants were divided into three groups: The first group stopped training altogether. The second group reduced training exercise days from three to one but kept the same workout. The third group decreased exercise days from three to one and also reduced training sets from three to one.
Results indicate that improvements in strength can be retained for an extended period after training ceases. While once-a-week exercise is sufficient to maintain strength, there are age-specifc differences in the required dose to maintain muscle size. Within the younger group, there was a dose-response that indicated that the group that exercised once a week but maintained the exercise volume continued to increase muscle size; however, the group that exercised once a week and reduced volume maintained size. In the older group, no group maintained muscle size.
- Once-a-week training with sufficient volume is able to increase muscle mass in younger but not older adults.
- Bodybuilders may be able to train once a week and make considerable gains in size and strength. Older adults likely require more frequent training to maintain muscle mass gained from resistance exercise.