The influence of shoulder position during multi-joint exercises in the relative scapular muscles activity in symptomatic and asymptomatic conditions

Article type: Research Article

Authors: Melo, Ana S.C.^{a; b; c; d} | Vilas-Boas, J. Paulo^{c; e} | Cruz, Eduardo B.^{f; g} | Macedo, Rui M.^a | e Ferreira, Sílvia B.^h | Sousa, Andreia S.^{a; *}

Affiliations: [a] Center for Rehabilitation Research – Human Movement System (Re)habilitation Area, Department of Physiotherapy, ESS, Polytechnic of Porto, Porto, Portugal | [b] Research Centre in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal | [c] Porto Biomechanics Laboratory (LABIOMEP), University of Porto, Porto, Portugal | [d] Center for Interdisciplinary Applied Research in Health, Health School of the Setubal Polytechnic Institute, Campus do IPS Estefanilha, Setúbal, Portugal | [e] Centre of Research, Education, Innovation and Intervention in Sport (CIFI2D), Faculty of Sport, University of Porto, Porto, Portugal | [f] Department of Physiotherapy, Escola Superior de Saúde, Instituto Politécnico de Setúbal, Campus do IPS Estefanilha, Setúbal, Portugal | [g] Comprehensive Health Research Center (CHRC), Universidade Nova de Lisboa, Lisbon, Portugal | [h] ESS, Polytechnic of Porto, Porto, Portugal

Correspondence: [*] Corresponding author: Andreia S. Sousa, Department of Physiotherapy, Center for Rehabilitation Research – Human Movement System (Re)habilitation Area, ESS, Polytechnic of Porto, Porto, Portugal. E-mails: asp@ess.ipp.pt or andreia.asps@gmail.com.

Abstract: BACKGROUND: Scapular muscles changes, as increased upper trapezius activity and decreased middle and lower trapezius and serratus anterior muscle activity, have been demonstrated in shoulder pain specific or non-specific conditions. Shoulder external rotation exercises have been recommended to improve scapular activity in shoulder pain. OBJECTIVE: To evaluate the relative scapular muscles activity during multi-joint exercises combining shoulder external rotation, trunk rotation and scapular squeeze. METHODS: Forty-one participants with and without shoulder pain were assessed in a cross-sectional study. They performed isometric multi-joint exercises at 0∘ and 90∘ of shoulder abduction with and without support. The relative activity of upper, middle, and lower trapezius and serratus anterior (upper/middle and lower portions) was measured through electromyography. The scapular muscular balance was assessed by the ratio between relative activity of the upper trapezius and the other muscles. RESULTS: Both groups presented similar results. The exercise at 90∘ abduction led to increased relative muscle activity against maximal voluntary contraction in both groups for upper trapezius (with support: 4% MVIC, p= 0.001 or 15% MVIC, p< 0.0001; and without support: 11% MVIC, p< 0.0001 or 13%, p< 0.0001, for asymptomatic and symptomatic group, respectively) and lower trapezius (with support: 66% MVIC, p< 0.0001 or 62% MVIC, p< 0.0001, for asymptomatic and symptomatic group,

DOI: 10.3233/BMR-220056

Journal: Journal of Back and Musculoskeletal Rehabilitation, vol. 36, no. 4, pp. 883-893, 2023