Beta-Alanine Supplementation Improves Isotonic Strength Endurance Performance Without Altering Psychological Responses During Drop-Set and Bi-Set Resistance Exercises in Resistance-Trained Individuals.

The ergogenic effects of beta-alanine (BA) supplementation are widely recognized, yet its effects on resistance exercises remain uncertain. It is possible that previous protocols were not sufficiently 'acidotic,' such as advanced drop-set and bi-set training systems. This study investigated whether BA supplementation improves isotonic strength endurance performance and psychological responses (perceived exertion, motivation, affect) during drop-set and bi-set protocols. In a double-blind parallel-group design, 22 young resistance-trained men and women were randomly assigned to either a BA group (6.4 g·day -1 , n = 12) or a placebo (maltodextrin, n = 10). After familiarization with psychological scales, maximal strength (1-RM), and strength endurance tests, subjects' total number of repetitions and psychological responses were recorded during drop-set (three sets at 80% 1-RM, with 3 successive 20% load reductions) and bi-set (three sets at 70% 1-RM, consisting of inclined bench press followed by flat bench press) protocols before and after a 4-week supplementation period. Outcomes were analyzed using mixed models for repeated measures ( p < 0.05). The total number of repetitions increased with BA in the drop-set (+17.3%, effect size [ES] = 0.74, p = 0.007) and bi-set (+18.2%, ES = 0.98, p < 0.0001) protocols, but not with placebo (respectively, -0.98%, ES = -0.06, p = 0.988; and +5.6%, ES = 0.01, p = 0.406). Perceived exertion increased across sets during drop-set and bi-set protocols (both p < 0.0001), but without between-group differences (both p > 0.05). Other psychological responses were not influenced by set, group, or time (all p > 0.05). Four weeks of BA supplementation enhanced isotonic strength endurance performance in trained individuals performing drop-set and bi-set resistance protocols, without concurrent change in psychological responses.