THE COMMON INFRASPINATUS MUSCLE TRAINING POSITION IS NOT THE MOST FUNCTIONAL

Fujitake, S., Takemura, M., Ishida, T., Dehara, C., & Tsujita, J. (2012). Electromyographic analysis of the infraspinatus muscle during several shoulder elevation tasks. Presentation 3276 at the 59th Annual Meeting of the American College of Sports Medicine, San Francisco, California; May 29-June 2, 2012.

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This study compared the activity in shoulder muscles, particularly the infraspinatus muscle, during shoulder elevation at several initial arm positions in adults (M = 7; F = 3). Ss performed maximal voluntary isometric contractions of shoulder flexion, abduction, and external rotation (first position). Ss then performed three 5-second isometric contractions of shoulder elevation at 30 with 3 kg weight loads, within the frontal plane (abduction; [ABD]), scapula plane [Scaption], sagittal plane (flexion; [Flex]), the diagonal plane (flexion and abduction) with shoulder external rotation [DiaER], the diagonal plane with shoulder internal rotation [DiaIR], and external rotation with therapeutic band load of equivalent of 3 kg weight loads at first position (0 of shoulder flexion and abduction, with elbow flexion; [1stER]). Surface EMG was recorded from the muscle belly of the infraspinatus (the upper portion; [ISup], and the lower portion; [ISlo]), supraspinatus [SS], upper trapezius [T], anterior deltoid [DA], and middle deltoid [DM] muscles, and mean integrated EMG [iEMG; normalized as MVIC; (%)] were analyzed.

The EMG activity (%iEMG) of ISlo was 37.6 (24.9) at ABD, 41.9 (19.6) at Scaption, 47.3 (14.9) at Flex, 57.5 (15.8) at DiaER, 80.5 (29.6) at DiaIR, and 48.7 (12.7) at 1stER. DiaIR was significantly higher than other positions. In the activity of ISup, DiaIR [47.2 (17.8)] and 1st ER [48.7 (12.0)] were significantly higher than ABD [35.9 (16.2)], Scaption [39.3 (13.5)], Flex [41.3 (12.3)], and DiaER [39.5 (13.2)]. DiaIR and 1stER were not different.

Implication. This study showed that ISlo activity at DiaIR was higher than at 1stER. Although 1stER exercise is a popular training method, the diagonal (flexion and abduction) and spiral (internal to external rotation) patterns are more useful as a functional exercise pattern for the infraspinatus muscle.

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