Original ResearchSerratus anterior and trapezius muscle activity during knee push-up plus and knee-plus exercises performed on a stable, an unstable surface and during sling-suspension

•The knee-plus was found to be just as effective in activating the SA muscle as the knee push-up plus exercise.•The knee-plus may be favored when the goal is isolated SA activity and low UT activity at the same time.•Unstable bases of support did not elicit greater SA muscle activity compared to stable conditions.

ObjectivesPush-up plus variations are commonly prescribed to clients during shoulder rehabilitation. The purpose of this study was to compare electromyographic (EMG) activities of the serratus anterior (SA), upper (UT), and lower trapezius (LT) during a knee push-up plus and knee-plus exercise performed on various surfaces.Study designWithin-subjects Repeated-Measure Design.Participants19 healthy, young female participants performed both exercises on a stable and unstable surface and during sling-suspension.Outcome measuresSurface EMG activities were recorded and average amplitudes were presented as a percentage of the maximal voluntary contraction. A two-way repeated-measures ANOVA was performed to determine differences in activity for each muscle.ResultsSA showed no significant differences between exercises and was independent of the base of support (p > 0.05). Muscle activity of UT (95% CI [1.2, 1.4]) and LT (95% CI [2.4, 3.5]) showed slightly greater values when performing the knee push-up plus compared to the knee-plus exercise.ConclusionsThe isolated protraction of the shoulder girdle in a kneeling position is as sufficient as the push-up plus in activating the SA selectively. Therefore, we recommended this exercise for clients who are unable to perform an entire push-up or should avoid detrimental stress on the shoulder joint.