Exercise Strategy When Short on Time

Resistance training is an established method to increase muscle mass and strength, but for Americans who are short on time aerobic exercise may be a more strategic option.  Leslie H. Willis, from Duke University Medical Center (North Carolina, USA), and colleagues enrolled 234 previously sedentary overweight or obese men and women, ages 18 to 70 years, in one of three eight-month supervised protocols: aerobic training (AT), resistance training (RT), or a combination (AT/RT). Of the total, 119 participants completed the trials and had complete data for the variables of interest in the article.   Those assigned to aerobic training exercised vigorously, at about 70-85% of maximum heart rate. They exercise approximately 45 minutes three days per week throughout the study period. Individuals assigned to resistance training also exercised three days a week, completing three sets of 8-12 reps on eight resistance machines that targeted all major muscle groups. Resistance was increased throughout the study to maintain a steady level of challenge as the participants gained strength.  Individuals who were assigned to AT/RT performed all the exercises assigned to both AT and RT groups. At the end of study each enrollee was assessed for weight, body composition, waist circumference, cardiopulmonary fitness and strength compared to their baseline.   The researchers found that the groups assigned to aerobic training and aerobic plus resistance training lost more weight than those that did resistance training only. In fact, those who did resistance training only actually gained weight due to an increase in lean body mass.  Fat mass and waist circumference significantly decreased in the AT and AT/RT groups, but were not altered in RT. However, measures of lean body mass significantly increased in RT and AT/RT, but not in AT. The findings suggest that aerobic exercise is more effective in reducing these measures.  Writing that: “[To balance] time commitments against health benefits, it appears that [aerobic training] is the optimal mode of exercise for reducing fat mass and body mass, while a program including [resistance training] is needed for increasing lean mass in middle-aged, overweight/obese individuals.”