Background and Purpose
Adjuvant breast cancer therapy may reduce maximal muscle strength, muscle mass, and functional performance. Although maximal strength training (MST) has the potential to counteract this debilitating outcome and is shown to be superior to low- and moderate-intensity strength training, it is unknown if it can elicit effective adaptations in patients suffering treatment-induced adverse side effects.
Fifty-five newly diagnosed stage I to III breast cancer patients (49 ± 7 yr) scheduled for adjuvant therapy were randomized to MST or a control group. The MST group performed 4 × 4 repetitions of dynamic leg press at approximately 90% of one-repetition maximum (1RM) twice a week for 12 wk.
In the MST group, improvements in 1RM (20% ± 8%; P < 0.001) were accompanied by improved walking economy (9% ± 8%) and increased time to exhaustion during incremental walking (9% ± 8%; both P < 0.01). Moreover, the MST group increased 6-min walking distance (6MWD; 10% ± 7%), and chair rising (30% ± 20%) and stair climbing performance (12% ± 7%; all P < 0.001). All MST-induced improvements were different from the control group (P < 0.01) which reduced their 1RM (9% ± 5%), walking economy (4% ± 4%), time to exhaustion (10% ± 8%), 6MWD (5% ± 5%), chair rising performance (12% ± 12%), and stair climbing performance (6% ± 8%; all P < 0.01). Finally, although MST maintained estimated quadriceps femoris muscle mass, a decrease was observed in the control group (7% ± 10%; P < 0.001). The change in 1RM correlated with the change in walking economy (r = 0.754), time to exhaustion (r = 0.793), 6MWD (r = 0.807), chair rising performance (r = 0.808), and stair climbing performance (r = 0.754; all P < 0.001).
Lower-extremity MST effectively increases lower-extremity maximal muscle strength in breast cancer patients undergoing adjuvant therapy and results in improved work economy, functional performance, and maintenance of muscle mass. These results advocate that MST should be considered in breast cancer treatment.