Author(s): MATTA, T., PEREIRA, Y. AND OLIVEIRA, L., Institution: UNIVERSIDADE FEDERAL DO RIO DE JANEIRO, Country: BRAZIL, Abstract-ID: 1397

INTRODUCTION:
The latissimus dorsi (LD) exhibits a broad architecture and multiple lines of action and, according to biomechanical muscle models, enables its contribution to different shoulder movements such as extension and horizontal abduction. Previous studies have shown that large muscles may present region-specific activation depending on task demands and joint kinematics, particularly when assessed using high-density electromyography (HDEMG) [1,2]. However, evidence regarding how changes in shoulder movement planes during rowing exercises affect the spatial distribution and magnitude of LD activation remains limited. Therefore, this study aimed to compare the activation barycenter position and neural demand of the LD during close-grip and wide-grip rowing exercises.
METHODS:
Fourteen resistance-trained men performed three sets of 12-repetition maximum of a close-grip row (CGR) and a wide-grip row (WGR) on separate days. LD muscle activity was recorded using a 32-electrode HDEMG array. The spatial distribution of activation was quantified by the normalized position of the activation barycenter along the superior–inferior axis of the LD, while neural demand was assessed by the root mean square amplitude normalized (RMS%) to maximal voluntary isometric contraction (MVIC). Linear mixed models were applied for statistical analyses.
RESULTS:
The activation barycenter was consistently positioned more inferiorly during CGR (≈ 23% of LD length) compared with WGR (≈ 13%) across all repetitions and sets (p < 0.001; η²p ≈ 0.41), indicating greater recruitment on the lower LD region. RMS% was significantly higher in CGR (≈ 60% of MVIC) than in WGR (≈ 36%) for all repetitions and sets (p < 0.001; η²p ≈ 0.36–0.37).
CONCLUSION:
Changes in shoulder movement planes during rowing exercises influence both the spatial distribution and magnitude of latissimus dorsi activation. The close-grip row elicits a more inferior activation pattern and greater neural demand than the wide-grip row, reinforcing the concept of task-dependent regional muscle activation described in previous HDEMG studies [2,3]. These findings highlight the relevance of exercise configuration for maximizing LD recruitment and provide mechanistic insight into region-specific muscle activation during resistance exercise.