PURPOSE/HYPOTHESIS: The stabilizing action of the serratus anterior (SA) muscle is vital in maintaining proper scapulothoracic rhythm.1,2 Poor activation of SA muscle could lead to many shoulder dysfunctions.1,3 This warrants for exercises that are best to activate the SA muscle. Kinetic-chain recruitment during exercises has demonstrated increased SA activation due to the myofascial connections between various segments of the body.4–6 Variation of surfaces during an exercise has been shown to alter the muscle recruitment patterns.7–9 The primary purpose of this study was to determine if the unstable surface can influence SA muscle activity during the kinetic chain recruitment while performing the forward punch plus (FPP) exercise. The secondary purpose was to compare the effects of stable versus unstable surface during these exercises.
NUMBER OF SUBJECTS: Twenty-one healthy men between the ages of 23 and 35 years with no history of neck and upper extremity (UE) injury or surgery were recruited for the study.
MATERIALS/METHODS: Surface electromyographic (EMG) activity of the SA, latissimus dorsi (LD), external oblique (EB) on the dominant, and femoral adductor (FD) muscles on the non dominant side were analyzed in FPP and its 2 variations: FPP with closed chain serape (CS), FPP with open chain serape (OS) on stable and unstable surface. The percentage of maximum voluntary isometric contraction (percent MVIC) for each muscle was compared across 3 exercises using a separate 1-way repeated-measures ANOVA with Sidak pairwise comparison as post hoc test for stable and unstable surface. Multiple paired t tests were run for 3 exercises to compare percent MVIC of stable versus unstable surface for each muscle (P≤.05).
RESULTS: Statistically significant main effects existed among all the exercises for the SA, EB, and FD within the same surface but not for LD. Pairwise comparisons within the same surface showed EMG activity of the SA to be significantly higher for the CS and the OS compared to the FPP. Regardless of the surface, there was no significant difference for the SA between the CS and the OS exercises. There was no significant difference in the mean EMG activity of any muscle on a stable surface when compared with the same exercise performed on an unstable surface.
CONCLUSIONS: The variations of the FPP exercises designed to incorporate the kinetic chain (CS and OS) does increase the activation of the SA muscle when performed on both stable and unstable surface. However, the type of surface did not influence the activation of any muscle when compared to each other during FPP or its variations.
CLINICAL RELEVANCE: The results of this study will further strengthen the concept of recruitment of kinetic chain during exercises. During rehabilitation of the UE muscles, it is recommended to recruit the lower extremity and trunk muscles regardless of the surface person stands on during exercises. Clinicians also need to be aware that adding an unstable surface to an exercise does not always imply higher activation of those muscles
