Are percentages of the one-repetition maximum (1-RM) suitable for prescribing resistance exercise in cancer survivors? - Comparability and prediction accuracy of frequently used 1-RM testing procedures

Abstract

Purpose To prescribe resistance training (RT) using percentages of (%) maximal strength (Smax), it is prerequisite that (I) methods for testing Smax are valid and (II) the relationship between %Smax and the corresponding number of repetitions (NOR) is known. This has never been investigated in cancer survivors (CS) and was the purpose of the present study. Methods Twenty breast (58 ± 10y) and 20 prostate CS (68 ± 6y), 3.6 ± 2.4 months after primary therapy, completed one one-repetition maximum (1-RM) test, one hypothetical 1-RM (h1-RM) test and three RT sessions (three sets at six different strength machines (SM)). H1-RM was calculated using two commonly used equations (after Brzycki and Epley), resulting in three Smax values for each SM, which were then compared to each other (1-RM as a reference). Each RT session was performed at a different intensity (92%, 69% and 47% of 1-RM/h1-RM). CS performed repetitions to fatigue and the resulting NOR were compared to the predicted NOR. Results Smax values differed between 1-RM and h1-RM values for each SM and between h1-RM values for some SM. Differences between performed and predicted NOR occurred among all intensities and methods. Conclusion Different strength tests yield different results for Smax and a certain %1-RM/h1-RM does not necessarily correspond to a specific NOR in all individuals, which questions the use of (I) h1-RM tests for determining Smax and (II) prescribing RT intensities based on %1-RM/h1-RM which is still the most common method used for RT intensity prescription in healthy individuals and patient populations, including CS.

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

“…However, these methods may cause significant muscle soreness and extended recovery times between sessions because of the high physical stress imposed (Shaw et al, 1995). In this line, emerging evidence questions the suitability of these methods for prescribing resistance intensity in cancer survivors (Schneider et al, 2022). Therefore, it seems important to establish training and testing procedures that maximize the benefits and minimize the risk of RT, optimizing exercise during breast cancer rehabilitation.…”