Skeletal Muscle Mass, Strength, and Physical Performance Gains Are Similar Between Healthy Postmenopausal Women and Postmenopausal Breast Cancer Survivors After 12 Weeks of Resistance Exercise Training

Abstract Background: Resistance exercise training (RET) has been shown to be effective in increasing skeletal muscle mass and strength in healthy postmenopausal women. In postmenopausal breast cancer survivors, however, the effects of RET on these parameters are reported as either controversial or limited. Aim: To compare the effects of a 12-week progressive whole-body RET program, on skeletal muscle mass, muscle strength and physical performance in healthy postmenopausal women versus postmenopausal women who are breast cancer survivors. Methods: Healthy (HEA, 54±3 years, BMI 26.6±2.7 kg·m2, n=13) and breast cancer survivors (BCS, 52±5 years, BMI 26.8±2.1 kg·m2, n=11) postmenopausal women were subjected to 12 weeks of progressive whole-body RET, three times per week. quadriceps muscle thickness ultrasound; one-repetition maximum (1RM) of leg extension, leg press, chest press, horizontal row, and elbow extension; grip strength and physical performance (6-minute walk test, dynamic balance test, and chair stand-up test) were assessed before and after the RET program. Results: Quadriceps muscle thickness increased from 3.6±0.6 to 3.9±0.7 cm2 (5±7%) and from 3.5±0.50 to 3.7±0.5 cm2 (7±4%), in HEA and BCS, respectively (Time, P<0.001; η2=0.44) without differences between groups. 1RM leg extension strength increased from 57±10 to 80±15 kg (41±12%) and from 54±13 to 77±18 kg (43±16 %) (Time, P<0.001; η2=0.88) in the HEA and BCS groups, respectively. Similar improvements were observed for 1RM leg press, 1RM chest press, 1RM horizontal row, and 1RM elbow extension (Time effect: all P<0.001; η2≥0.85), and grip strength (Time effect: P=0.035; η2=0.19) in the HEA and BCS groups. No differences in responses to RET were observed between groups (Time×Group, all P>0.185; all η2 ≤0.09) for all strength outcomes. Physical performance showed significant improvement (all P<0.001; η2 ≥0.45), with no differences between groups (Time×Group, P≥0.05; η2≤0.05). Conclusion: Twelve weeks of RET significantly increase skeletal muscle mass, strength, and physical performance in postmenopausal women. No differences were observed between healthy postmenopausal women and postmenopausal breast cancer survivors. These findings point out that this study's RET promotes marked skeletal muscle mass, strength, and performance gains regardless of breast cancer. Trial registration: This trial is registered on ClinicalTrials.gov: NCT05690295 as of December 22, 2022