Abstract and Introduction
Introduction: Menopause is accompanied by body composition changes that include a decrease in lean mass and aerobic fitness and an increase in fat mass. Sprint interval training (SIT) may be able to reverse these changes.
Purpose: To examine the effect of an 8-wk SIT program on body composition and aerobic fitness of overweight postmenopausal women.
Methods: Forty postmenopausal women were randomized into SIT (n = 20) or control (n = 20) groups. The SIT group completed three SIT sessions a week for 8 wk with each session consisting of 20 min of alternating 8-s sprints and 12-s of light pedaling. Total mass, regional lean mass, and fat mass were assessed using dual-energy x-ray absorptiometry. Maximal oxygen uptake (V̇O2max) was predicted using a submaximal test.
Results: Total lean mass was significantly increased from pretest (48.1 ± 5.81 kg) to posttest (48.8 ± 5.96 kg) and fat mass was significantly reduced (pre, 29.5 ± 7.29 kg; post, 29.1 ± 7.61 kg) for the SIT group. Lean mass was mostly increased in the trunk (pre, 24.4 ± 2.79 kg; post, 24.8 ± 2.93 kg) and legs (pre, 15.6 ± 2.31 kg; post, 15.9 ± 2.34 kg). V̇O2max was significantly increased from pretest (21.7 ± 4.89 mL·kg−1·min−1) to posttest (24.4 ± 5.96 mL·kg−1·min−1) for the SIT group only.
Conclusions: The SIT intervention increased total lean mass, decreased fat mass, and increased aerobic fitness of postmenopausal women after only 8 h of actual exercise over 8 wk.
Menopause is marked by a decline in endogenous estrogen production and is accompanied by a decrease in lean mass, an increase in body fat, and a reduction in aerobic fitness. As these changes are strongly associated with an abnormal metabolic profile overweight postmenopausal women are at high risk for developing insulin resistance, type 2 diabetes, and cardiovascular disease. Consequently, interventions should be developed to enhance the body composition and metabolic health of postmenopausal women. One such intervention is aerobic exercise which typically consists of moderate-intensity steady-state exercise, repeated about 30 to 40 min·d−1 for 3 to 4 d·wk−1, up to a 6-month period. Disappointingly, aerobic exercise programs have typically resulted in minimal fat loss and no gain in the lean mass of postmenopausal women.
In contrast to aerobic exercise, sprint interval training (SIT) has resulted in decreased fat loss and increased lean mass in young overweight men and women. For example, a 15-wk SIT program was conducted with premenopausal women that included three 20-min sessions per week. Women performed an 8-s sprint followed by 12 s of low-intensity pedaling, continuously for 20 min. A control group carried out a 40-min aerobic exercise cycling protocol each session. Women in the SIT group lost 2.5 kg of subcutaneous fat, whereas no change occurred with steady state aerobic exercise. Importantly, exercising women also showed a significant 0.6 kg increase in lean mass, whereas lean mass of the steady state exercise group remained unchanged. Similar results using the same SIT protocol have been found with young overweight women and young overweight men.[9,10] Also, in postmenopausal women, a significant reduction in total fat mass (0.8 kg) was found after 16 wk of SIT. The mechanisms underlying the SIT-induced fat loss decrease effect most likely involve increased fat oxidation during and after exercise,[12,13] whereas it has been suggested that mechanisms driving lean mass increase involve an increase in muscle protein synthesis. Numerous studies have also found that a variety of SIT protocols have resulted in significant increases in aerobic fitness probably brought about by SIT-induced central and peripheral adaptations. Interestingly, major changes in body composition and aerobic fitness have typically occurred after 8 wk or 8 h of SIT. The effect of 8 wk of SIT on the body composition and aerobic fitness of overweight postmenopausal women, however, is yet to be determined.
Therefore, the purpose of this study was to examine the effects of 20-min bouts of SIT, repeated three times weekly for 8 wk, on body composition and aerobic fitness of overweight postmenopausal females. It was predicted that SIT would result in significantly increased total lean mass, decreased fat mass, and increased aerobic fitness of postmenopausal women after 8 h of actual exercise over 8 wk.
Med Sci Sports Exerc. 2019;51(7):1413-1419. © 2019 American College of Sports Medicine