Soy isoflavones and exercise to improve physical capacity in postmenopausal women

ABSTRACT

Aim In postmenopause, ovarian decline along with sedentary lifestyle could contribute to the loss of lean body mass (LBM) and muscle strength. This study aimed to verify whether exercise and isoflavones could have additive effects on muscle quality, muscle mass index, relative strength and physical capacity in overweight sedentary postmenopausal women.

Method We recruited 70 overweight-to-obese (body mass index 32.2±4.8 kg/m²) postmenopausal women (59±5 years old) to participate in a 6-month clinical study combining isoflavones (70 mg/day) and exercise (resistance and aerobic training) treatments. Subjects were divided into four groups: (1) placebo (n =15), (2) isoflavones (n =15), (3) exercise and placebo (n =20), and (4) exercise and isoflavone (n =20). Principal outcome variables included maximal muscle strength (1RM) at the leg press and the bench press, muscle mass index, muscle quality in the legs and relative strength.

Results After 6 months of training, exercise produced 49% and 23% increases, respectively, in leg press and bench press 1RM (p ≤0.01). Leg relative strength and muscle quality increased by more than 50% (both p <0.01), while muscle mass index increased by 7% (p <0.05) in both exercise groups only.

Conclusion Exercise training can improve muscle tissue strength, function and quality in sedentary postmenopausal women. Isoflavones, irrespective of exercise, did not produce changes in these variables. From a clinical perspective, these results suggest that overweight women could reduce the risks of mobility impairments, even in the absence of weight loss, by following a sound exercise intervention that includes both resistance and aerobic training at a high intensity.

Key words::

• SARCOPENIA
• HANDGRIP STRENGTH
• RESISTANCE TRAINING
• AEROBIC TRAINING
• FUNCTIONAL CAPACITY
• MUSCLE STRENGTH

ACKNOWLEDGEMENTS

The authors wish to thank all the participants in this study, with a very special thank you to Martine Fisch, research nurse, and Karine Perreault, research assistant, for their invaluable help in every aspect of this project.

Conflict of interest The authors of this study state that they have no conflicts of interest. The Canadian Institutes of Health Research took no part in any aspects of this study, including elaboration, recruitment or interpretation of the results. The contributions of the authors are: S.C.: study design, data collection, analyses, figure preparation and manuscript preparation; T.D.: data collection and manuscript preparation; M.B.: study design and manuscript preparation; I.J.D.: principal investigator, senior writer, study design and manuscript preparation.

Source of funding This research project was funded by the Canadian Institutes of Health Research (CIHR).