Precision of 7 Commercially Available Devices for Predicting the Bench Press 1-Repetition Maximum From the Individual Load-Velocity Relationship.

OBJECTIVE This study aimed to compare the accuracy of different devices to predict the bench press 1-repetition maximum (1RM) from the individual load-velocity relationship modelled through the multiple- and 2-point methods. METHODS 11 men performed an incremental test on Smith machine against 5 loads (45-55-65-75-85%1RM), followed by 1RM attempts. The mean velocity was simultaneously measured by 1 linear velocity transducer (T-Force), 2 linear position transducers (Chronojump and Speed4Lift), 1 camera-based optoelectronic system (Velowin), 2 inertial measurement units (PUSH band and Beast sensor), and 1 smartphone application (PowerLift). The velocity recorded at the 5 loads (45-55-65-75-85%1RM) or only at the 2 most distant loads (45-85%1RM) were considered for the multiple- and 2-point methods, respectively. RESULTS An acceptable and comparable accuracy in the estimation of the 1RM was observed for the T-Force, Chronojump, Speed4Lift, Velowin and PowerLift when using both the multiple- and 2-point methods (effect size [ES] ≤ 0.40; Pearson's correlation coefficient [r] ≥ 0.94; standard error of the estimate [SEE] ≤ 4.46 kg), while the accuracy of the PUSH (ES = 0.70-0.83; r = 0.93-0.94; SEE = 4.45-4.80 kg) and especially the Beast sensor (ES = 0.36-0.84; r = 0.50-0.68; SEE = 9.44-11.2 kg) was lower. CONCLUSIONS These results highlight that the accuracy of 1RM prediction methods based on movement velocity are device-dependent with the inertial measurement units providing the least accurate estimate of the 1RM.