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Comparison of Muscle Activation Levels During Arm Abduction in the Plane of the Scapula vs. Proprioceptive Neuromuscular Facilitation Upper Extremity Patterns

Youdas, James W.; Arend, David B.; Exstrom, Jada M.; Helmus, Taylor J.; Rozeboom, Jessica D.; Hollman, John H.

Journal of Strength & Conditioning Research:
doi: 10.1519/JSC.0b013e31822e597f
Original Research

Abstract: Youdas, JW, Arend, DB, Exstrom, JM, Helmus, TJ, Rozeboom, JD, and Hollman, JH. Comparison of muscle activation levels during arm abduction in the plane of the scapula vs. proprioceptive neuromuscular facilitation upper extremity patterns. J Strength Cond Res 26(4): 1058–1065, 2012—This study quantified activation of 8 muscles of the shoulder, trunk, and back during standing performance of (a) arm abduction in the plane of the scapula (scaption), (b) proprioceptive neuromuscular facilitation (PNF) diagonal 1 flexion (D1F), and (c) PNF diagonal 2 flexion (D2F) while lifting a dumbbell with the dominant hand. Twelve men (26.1 ± 4.4 years) and 13 women (24.5 ± 1.9 years) volunteered to participate. Electromyographic signals were collected with DE-3.1 double-differential surface electrodes at a sampling frequency of 1,000 Hz. Electromyographic signals were normalized to peak activity in the maximum voluntary isometric contraction (MVIC) trial and expressed as a percentage. One-way repeated-measures analysis of variance with Bonferroni corrections (α = 0.05) examined muscle activation patterns across the 3 conditions. For the middle trapezius, average activation was greater (p < 0.001) for D2F (70.5 ± 23.4% MVIC) than D1F (46.4 ± 19.6% MVIC). Lower trapezius average activation was greater (p < 0.001) for D2F (55.3 ± 23.8% MVIC) than D1F (40.1 ± 16% MVIC). The anterior deltoid showed greater activation (p = 0.009) for scaption (92.4 ± 26% MVIC) than D1F (74.4 ± 21.4% MVIC). The erector spinae showed greater activation for D2F (34.2 ± 12% MVIC; p < 0.001) and D1F (41.7 ± 21.4% MVIC; p < 0.001) than scaption (14.5 ± 12.3% MVIC). During D2F and scaption, all 6 muscles of the shoulder complex demonstrated very high activation levels (>60% MVIC) with the exception of the lower trapezius (55% MVIC). In contrast, erector spinae and external oblique muscles exhibited moderate activation (21–40% MVIC) during arm elevation. The 6 muscles of the shoulder complex displayed high to very high muscle activation at a level appropriate for strength training during all 3 exercise conditions.

Author Information

Program in Physical Therapy, Mayo Clinic, Rochester, Minnesota

Address correspondence to James W. Youdas,

Copyright © 2012 by the National Strength & Conditioning Association.