In resistance-training, the number of repetitions can be either fixed and predetermined (e.g., 3 sets of 10 repetitions), or selected by the trainee during ongoing sets (e.g., 3 sets of 8-12 repetitions). The first approach is more goal-focused while the latter is more autonomy-focused. Here we compared between these two approaches on motor performance and psychological outcomes. Nineteen resistance-trained subjects (10-males) first completed one repetition-maximum (RM) tests in the barbell-squat and bench-press, and were familiarized with the isometric mid-thigh pull (IMTP). In the next two counterbalanced sessions, subjects completed two sets of the squat and bench-press using 70%1RM, and two sets of the IMTP. In the predetermined session, subjects completed 10 repetitions in all sets, and in the self-selected session, subjects chose how many repetitions to complete out of an 8-12 range. Bar-velocity was measured in the squat and bench-press, and force production in the IMTP. Enjoyment, perceived-autonomy, and approach-preferences were collected post-sessions. We observed comparable bar-velocity, force production, and enjoyment in both conditions (all BF01>2.1), and an even approach-preferences split. However, in the self-selected condition, subjects demonstrated considerable variability in the number of repetitions and reported greater perceived-autonomy. Given the similarities between approaches, both can be used with this cohort based on their personal-preference. Yet, we note that the self-selected approach has two distinct benefits: the variability in the number of repetitions completed suggests that subjects regulated their efforts, and the higher perceived autonomy could lead to long-term improvements in motor and psychological outcomes.
The effect of self-selecting the number of repetitions on motor performance and psychological outcomes