The Accuracy Of Prediction Equations For Estimating 1rm In The Press And The Deadlift

Abstract

Many of the equations used to predict the one-repetition maximum (1RM) from the number of repetitions performed to fatigue with a submaximal load have been derived from the squat and bench press exercises in which the eccentric portion precedes the concentric portion of the repetition. In the press and deadlift, the concentric phase precedes the eccentric phase which may affect performance in the number of repetitions performed to fatigue and, thus, the accuracy of existing 1RM prediction equations for these exercises. PURPOSE: To compare the actual 1RM to the predicted 1RM from seven existing prediction equations for the press and deadlift. METHODS: 30 resistance trained individuals (23±3 yrs) completed a 1RM protocol for the press and deadlift. Participants then returned to the lab on two separate occasions and completed one set of each exercise to fatigue at either 70% or 90% of their 1RM in a randomized order. The actual 1RM was compared to the predicted 1RM from seven 1RM prediction equations for each exercise at each load. A one-way repeated measures (1x8) ANOVA was used followed by Bonferroni post-hoc tests to determine pairwise differences between the actual and predicted 1RM values. RESULTS: For the press, the predicted 1RM from 70% 1RM lifted to fatigue was significantly (p≤0.002) lower than the actual 1RM from three of the seven equations (mean differences of 3.1±0.7, 5.7±0.7, and 6.2±0.7 kgs) and the predicted 1RM from 90% 1RM lifted to fatigue was significantly (p≤0.012) greater than the actual 1RM from four of the seven equations (mean differences of 3.0±0.7, 3.2±0.7, 3.5±0.6, and 4.7±0.7 kgs). For the deadlift, the predicted 1RM from 70% 1RM lifted to fatigue was significantly (p≤0.001) lower than the actual 1RM from three of the seven equations (mean differences of 13.7±2.7, 20.1±2.3, and 20.3±3.2 kgs) whereas the predicted 1RM from 90% 1RM lifted to fatigue was significantly (p≤0.012) greater than the actual 1RM from one of the seven equations (mean differences of 7.1±1.0 kg). CONCLUSIONS: Lower loads (70% 1RM) used to predict the 1RM may underestimate the actual 1RM whereas higher loads (90% 1RM) may overestimate the 1RM for the press and deadlift. The use of higher loads for 1RM prediction increases the accuracy of the 1RM prediction for the deadlift in most equations but still may lead to an overestimation of the 1RM.