Cross-Validation of Original and Modified Equations for Estimating Bench Press One-Repetition Maximum from Repetitions to Failure in Recreationally Active Men

The purpose of this study was to cross-validate four (two original and two modified) equations (EQs) that estimate 1-repetition maximum (1RM) from repetitions to failure (RTF) for the bench press (BP). Thirty-five recreationally active men (mean SD: age = 20.5 1.4 yrs; height = 181.3 6.4 cm; body mass = 84.8 12.5 kg) with previous resistance training experience (5.0 2.9 yrs) participated in this study. Each participant completed BP 1RM testing followed by a single set of RTF at ~80% 1RM. The values from the RTF at ~80% 1RM were inputted into the EQs for estimating BP 1RM. The cross-validation analyses consisted of examining the constant error (CE) values using paired t-tests, Pearson Correlation Coefficients (r), standard error of estimate (SEE), and total error (TE) values. The RTF at 80% 1RM ranged from 4-11 repetitions. The results revealed that EQs 2, 3, and 4 significantly (p p = 0.091) from the measured 1RM values (CE = -0.57 kg). The cross-validation analyses indicated that modified EQ 3 (TE = 2.12 kg) did not improve the accuracy of BP 1RM estimations compared to original EQ 1 (TE = 1.99 kg). Modified EQ 4, however, exhibited slightly more accurate BP 1RM values (TE = 3.27 kg) than original EQ 2 (TE = 3.51). In addition, EQ 1 provided the lowest CE and TE values as well as the smallest difference between TE and SEE values (0.03 kg). Therefore, EQ1 (RTF0.1 x weight) is recommended for estimating BP 1RM with a weight that results in 4-11 RTF in recreationally active men when directly testing 1RM is not feasible or to assist in training intensity prescription.