The Effects of Lifting Lighter and Heavier Loads on Subjective Measures

Background: Despite the progress made in the study of subjective measures in resistance-training, some questions remain unanswered. Here we investigated if ratings of perceived effort (RPE) can predict task-failure and bar-velocity across exercises and loads as a primary outcome, and whether a battery of subjective measures differs as a function of the lifted loads as a secondary outcome.

Methods: In this preregistered study, twenty resistance-trained subjects (50% females) first completed one repetition-maximum (RM) test of the barbell-squat and bench-press. In the second and third sessions, subjects completed two sets of squats followed by two sets of bench-press to task-failure, using 70% or 83% of 1RM, while bar-velocity was recorded. RPE scores were recorded after every repetition. In addition to RPE, rating-of-fatigue, affective-valence, enjoyment, and load-preferences were collected after sets- and sessions-completion.

Results: Across conditions, RPE was strongly correlated with reaching task-failure (r= .86) and moderately correlated with bar-velocity (r= -.58). Our model indicates that an increase in one RPE unit is associated with an 11% shift towards task-failure, and a 4% reduction in bar-velocity, with steeper slopes observed in the heavier condition. Negligible differences were observed between the load-conditions in rating-of-fatigue, affective-valence, enjoyment, and load-preference.

Conclusion: RPE scores, collected on a repetition-by-repetition basis, accurately reflected reaching task-failure across loads and conditions. Hence, RPE can be used to prescribe repetition numbers during ongoing sets. The negligible differences between load conditions in rating-of-fatigue, affective-valence, enjoyment, and load-preference indicate that when sets are taken to task-failure, loads can be selected based on individual preferences.