Effects of Resistance Training and Protein Supplementation on Body Composition, Muscular Strength, and Physical Function in Breast Cancer Survivors

Breast cancer survivors (BCS) encounter side effects from cancer treatments that negatively affect muscular strength and body composition, particularly the loss of lean mass. Studies have shown that resistance training (RT) can maintain lean mass, but few have observed increases in lean mass. This may be due to the lower intensities of RT used or the inadequate protein intake of the participants in these studies. PURPOSE: To evaluate the efficacy of higher intensity RT (n=16) and RT+protein (n=17) interventions to improve muscular strength and body composition in BCS over 12 weeks. METHODS: Thirty-three (59 ± 8 years) BCS were measured pre and post RT for the following variables: muscular strength (chest press and leg extension) via one-repetition maximal (1-RM) and handgrip (HG) strength via HG dynamometer, physical function via the Continuous Scale of Physical Functional Performance, body composition (lean mass, fat mass) via dual-energy X-ray absorptiometry (DXA), blood biomarkers of muscle and fat metabolism [insulin-like growth factor-1 (IGF-1) and adiponectin] and total body inflammation [human C-reactive protein (CRP)]. RT consisted of two days/wk using ten exercises performed for three sets of 10-12 repetitions at ~65-85% of 1-RM. RT+protein also consumed 20g of a protein supplement twice a day. Data were reported as means and standard deviations. Dependent variables at baseline were analyzed by one-way analysis of variance (ANOVA). When group differences in baseline variables were observed, an analysis of covariance (ANCOVA) was performed with the baseline variable as the covariate. Dependent variables were analyzed by a 2 by 2 factorial ANOVA (group x time) with repeated measures on the last factor. One-way ANOVA post hoc tests were used to compare group or time differences. An intent-to-treat analysis was used to evaluate pre and posttest scores to address the effects of the interventions on all randomized participants regardless of whether they completed the study or not by using the principle of last observation carried forward. Significance was accepted at p<0.05. RESULTS: The total weight training volume (weight lifted x repetitions x sets) over the 12 weeks for the upper body exercises was 227,673 ± 65,732 kg for the RT+protein group and 185,760 ± 62,932 kg for the RT group and was approaching significance (p= 0.071). The total training volume for lower body exercises was not different between the RT+protein and RT groups (258,877 ± 75,997 vs. 219,274 ± 73,906 kg). Average RT intensity was not different between the RT+protein and RT groups during weeks 1-6 for upper body (70 ± 7% vs. 71 ± 4%) and lower body (69 ± 5% vs. 70 ± 6%) percent of baseline 1-RM and during weeks 7-12 for upper body (77 ± 7% vs. 75 ± 8%) and lower body (80 ± 9% vs. 83 ± 9%) percent of the 6-week 1-RM. No group x time interactions were detected for variables measured except upper body lean mass, which was higher in the RT+protein group compared to the RT group at 12 weeks. Both groups (n=33) significantly increased upper (86 ± 22 to 115 ± 29 kg), lower body (97 ± 25 to 116 ± 31 kg), HG (51 ± 9 to 54 ± 8 kg) strength and total physical function (69 ± 14 to 72 ± 15 units). Lean mass (40.4 ± 6.2 to 41.3 ± 6.5 kg), fat mass (29.4 ± 9.3 to 28.9 ± 9.4 kg), percent body fat (41.4 ± 5.4 to 40.4 ± 5.6%) significantly improved over the 12 weeks of RT. There were no group by time interactions for any of the blood biomarkers. Serum levels of IGF-1 significantly increased from baseline to 12 weeks in both the RT+protein group (110 ± 40 to 119 ± 37 ng/ml) and the RT group (102 ± 34 to 115 ± 33 ng/ml) but adiponectin and CRP did not change. At baseline, the RT group had a significantly greater percent difference in upper extremity volume, a measurement of lymphedema, than the RT+protein group (9.5 ± 11.2 vs 1.8 ± 10.2%, respectively. The percent difference in upper extremity volume significantly decreased from baseline to week 5 to a greater extent in the RT group (9.5 ± 11.2 to 0.18 ±7.7%) than the RT+protein group (1.8 ± 10.2 to 1.87 ± 7.4%). The average percent difference in upper extremity volume of all the BCS significantly decreased from 5.6 ± 11.2% at baseline to 2.0 ± 5.6% in week 9. CONCLUSIONS: Twelve weeks of RT at 65-81% of 1-RM was well tolerated and significantly improved muscular strength, physical function, body composition and lymphedema in BCS. RT significantly increased IGF-1, the blood biomarker of muscle metabolism in both groups, but the values did not exceed the normal range. Although the protein supplement was well tolerated and adhered to, supplementing with 40g/day did not provide additional benefits to RT. The greater increments in upper body lean mass were likely due to the somewhat higher training volume in the upper body exercises in the RT+protein group and not the daily protein supplementation. RT at higher intensities can help counteract the cancer related changes and significantly improve muscular strength and body composition without exacerbating lymphedema or causing any musculoskeletal injuries.