Optimizing exercise prescription during breast cancer rehabilitation in women: Analysis of the load–velocity relationship in the box squat exercise

The aims of this study were to assess (i) the load–velocity relationship during the box squat exercise in women survivors of breast cancer, (ii) which velocity variable (mean velocity [MV], mean propulsive velocity [MPV], or peak velocity [PV]) shows stronger relationship with the relative load (%1RM), and (iii) which regression model (linear [LA] or polynomic [PA]) provides a greater fit for predicting the velocities associated with each %1RM. Nineteen women survivors of breast cancer (age: 53.2 ± 6.9 years, weight: 70.9 ± 13.1 kg, and height: 163.5 ± 7.4 cm) completed an incremental load test up to one-repetition maximum in the box squat exercise. The MV, MPV, and the PV were measured during the concentric phase of each repetition with a linear velocity transducer. These measurements were analyzed by regression models using LA and PA. Strong correlations of MV with %1RM (R² = 0.903/0.904; the standard error of the estimate (SEE) = 0.05 m^.s⁻¹ by LA/PA) and MPV (R² = 0.900; SEE = 0.06 m^.s⁻¹ by LA and PA) were observed. In contrast, PV showed a weaker association with %1RM (R² = 0.704; SEE = 0.15 m^.s⁻¹ by LA and PA). The MV and MPV of 1RM was 0.22 ± 0.04 m·s⁻¹, whereas the PV at 1RM was 0.63 ± 0.18 m^.s⁻¹. These findings suggest that the use of MV to prescribe relative loads during resistance training, as well as LA and PA regression models, accurately predicted velocities for each %1RM. Assessing and prescribing resistance exercises during breast cancer rehabilitation can be facilitated through the monitoring of movement velocity.