title: Comparison of muscle activation levels during arm abduction in the plane of the scapula vs. proprioceptive neuromuscular facilitation upper extremity patterns.
abstract: 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.
authors.affiliation: Program in Physical Therapy, Mayo Clinic, Rochester, Minnesota, USA. youdas.james@mayo.edu
authors.forename: James W
authors.initials: JW
authors.lastname: Youdas
authors.forename: David B
authors.initials: DB
authors.lastname: Arend
authors.forename: Jada M
authors.initials: JM
authors.lastname: Exstrom
authors.forename: Taylor J
authors.initials: TJ
authors.lastname: Helmus
authors.forename: Jessica D
authors.initials: JD
authors.lastname: Rozeboom
authors.forename: John H
authors.initials: JH
authors.lastname: Hollman
mesh_terms: D000328:Adult; D001132:Arm / Q000502:physiology*; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D052580:Muscle Stretching Exercises; D018482:Muscle, Skeletal / Q000502:physiology*; D012540:Scapula / Q000502:physiology; D012782:Shoulder / Q000502:physiology; D014891:Weight Lifting / Q000502:physiology; D055815:Young Adult