Effects of Body Position and Loading Modality on Muscle Activity and Strength in Shoulder Presses

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Abstract

Saeterbakken, AH and Fimland, MS. Effects of body position and loading modality on muscle activity and strength in shoulder presses. J Strength Cond Res 27(7): 1824–1831, 2013—Little is known about the effect of performing upper-body resistance exercises with dumbbells versus barbells and standing versus seated. Therefore, this study sought to compare electromyogram activity (EMG) and one-repetition maximum (1-RM) in barbell and dumbbell shoulder presses performed seated and standing. Fifteen healthy men volunteered for 1-RM and EMG testing with a load corresponding to 80% of the 1-RM. Electromyogram activity was measured in the anterior, medial, and posterior deltoids and biceps and triceps brachii. The following EMG differences or trends were observed: For deltoid anterior: ∼11% lower for seated barbell versus dumbbell (p = 0.038), ∼15% lower in standing barbell versus dumbbell (p < 0.001), ∼8% lower for seated versus standing dumbbells (p = 0.070); For medial deltoid, ∼7% lower for standing barbell versus dumbbells (p = 0.050), ∼7% lower for seated versus standing barbell (p = 0.062), 15% lower for seated versus standing dumbbell (p = 0.008); For posterior deltoid: ∼25% lower for seated versus standing barbell (p < 0.001), ∼24% lower for seated versus standing dumbbells (p = 0.002); For biceps, ∼33% greater for seated barbell versus dumbbells (p = 0.002), 16% greater for standing barbell versus dumbbell (p = 0.074), ∼23% lower for seated versus standing dumbbells (p < 0.001); For triceps, ∼39% greater for standing barbell versus dumbbells (p < 0.001), ∼20% lower for seated versus standing barbell (p = 0.094). 1-RM strength for standing dumbbells was ∼7% lower than standing barbell (p = 0.002) and ∼10% lower than seated dumbbells (p < 0.001). In conclusion, the exercise with the greatest stability requirement (standing and dumbbells) demonstrated the highest neuromuscular activity of the deltoid muscles, although this was the exercise with the lowest 1-RM strength.

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