Effects of a Third Year of Exercise Training Preceded by Two Years of Exercise Training with Isoflavone Supplementation on Bone in Postmenopausal Women

Osteoporosis is a chronic disease characterized by low bone mineral density (BMD) and micro-architectural deterioration and is especially prevalent in postmenopausal women. Soy isoflavones (i.e. “phytoestrogens”) have been proposed as a safe alternative to hormone replacement therapy for preventing loss of BMD. Exercise is also recommended for slowing the loss of BMD. The present research is a one year extension of a previous randomized controlled trial which measured bone loss in women who did or did not take isoflavone or exercised for two years. The present study consisted of 86 participants from the same previous groups with: n=28 exercised and did not take isoflavone; n=26 stopped isoflavone supplementation but continued to exercise; n=18 stopped isoflavone supplementation and did not exercise; and n=14 controls who did not exercise or take isoflavone. Exercise training included two one-hour resistance training sessions and four 20-30 min brisk walking sessions per week. Areal BMD (aBMD) of the hip and lumbar spine, and fat and lean tissue mass were measured at baseline, and at one, two, and three years. There were exercise group x time interactions for total hip and lumbar spine BMD with it decreasing in the exercise groups compared to non-exercise groups (p<0.05). There were no changes in lean tissue mass but fat mass was reduced from a baseline of 25 ± 6.6 kg in the exercise group after year one and this was maintained into year three (24 ± 7.1 kg) (p < 0.01). The fat mass in the non-exercise groups increased from baseline (28.9 ± 6.7 kg) to year three (30.3 ± 7.1 kg) (p < 0.01). There were also exercise group x time interactions for trunk and percent fat with more decreases in the exercise compared to non-exercise groups. There were exercise x time interactions for muscular strength, with chest press (upper body) and hack squat (lower body) strength 33% and 88% higher in exercise groups than non-exercise groups by the end of three years (p