Trapezius Muscle Electromyographic Activity in Lawn-Mower Exercise: Standing Versus Quadruped

In shoulder rehabilitation, exercises that reduce upper trapezius (UT) activity and optimize the trapezius muscle activation rate reduce the symptoms of shoulder pathologies. One such exercise, the lawn-mower (LM) exercise, is frequently used in scapular rehabilitation protocols due to its multijoint, multiplanar, and kinetic chain-based nature. Design/Objective: This study aimed to compare trapezius muscle activation levels and ratios during the LM exercise in standing and quadruped positions through a randomized controlled trial.

Eighteen healthy volunteers (mean age [SD] = 25 [5] y, 10 women and 8 men, mean body mass index [SD] = 22.91 [2.59] kg/m2) participated in the study, and surface electromyography was employed to measure trapezius muscle activity during quadruped LM (QLM) and standing LM (SLM) exercises. The data were normalized as a percentage of maximal voluntary contraction.

The study revealed significantly lower UT activity (percentage of maximal voluntary contraction) during QLM compared with SLM (P < .05) in concentric and isometric phases. Conversely, QLM exhibited significantly higher activation of the middle trapezius (MT) and lower trapezius (LT) in all phases when compared with SLM (P < .05). UT/MT and UT/LT ratios were also significantly lower in all QLM phases compared with SLM (P < .05).

Study findings suggest that quadruped exercises reduce UT activation while promoting more balanced MT and LT muscle activation. This balance is essential for shoulder rehabilitation, especially in cases requiring minimal UT activation and maximal MT and LT activation. In cases where a balanced trapezius muscle activation pattern is required, including QLM exercises rather than SLM exercises may be more efficient.