Effects of Mind-Muscle Connection on Muscle Activity During Machine-Based Shoulder Press in Untrained Individuals

Background/Objectives: Mind-muscle connection (MMC) refers to a strategy in which an individual intentionally focuses attention on specific muscles to enhance the neural activation of those muscles. The purpose of this study was to examine the acute effects of MMC directed toward a specific muscle during a machine-based shoulder press exercise on the muscle activity of untrained individuals. Methods: Thirty-one healthy young adults with no athletic or resistance training experience participated in this single-session study. Participants performed machine-based shoulder presses at 40% of one-repetition maximum intensity under three MMC conditions. The three conditions were: no-focus condition, deltoid (DT)-focused condition, and triceps brachii (TB)-focused condition. Muscle activities of the DT, TB, and upper trapezius (UT) were measured during exercise under each MMC condition. Differences in muscle activity across conditions were analyzed using a two-way repeated-measures analysis of variance. Results: A total of 31 participants were included in the final analysis. A significant interaction between muscle and MMC condition was observed (p < 0.001). Post hoc analysis showed that DT activity was higher in the DT-focused condition, whereas TB activity was higher in the TB-focused condition (p < 0.001). UT activity did not differ across conditions (p > 0.05). Conclusions: MMC selectively enhanced target muscle activity without changing non-target muscle activity, indicating its potential for selective neuromuscular recruitment. These findings suggest that MMC may serve as a practical strategy for selective muscle activation during machine-based resistance training. Further study is needed to determine whether these findings translate into long-term improvements in muscle strength and functional performance.