Age-related Differences in Shoulder Dynamic and Isometric Contractions


A cross-sectional descriptive study, in which the surface electromyographic activity of five shoulder muscles was compared in two populations: older adults and adults. The evaluation of the electromyographic data offers a suitable foundation to understand aging process. This supports that surface electromyography provide information about the aged shoulder muscles. Loss of functionality is suffered by a high percentage of older adults, which greatly limits their physical activity. In this sense, this paper presents findings that might be related with possible therapeutic approaches in subsequent studies.

Full Title of Study: “Age-related Differences in Motor Recruitment Patterns of the Shoulder in Dynamic and Isometric Contractions. A Cross-sectional Study”

Study Type

  • Study Type: Observational [Patient Registry]
  • Study Design
    • Time Perspective: Cross-Sectional
  • Study Primary Completion Date: January 2019

Detailed Description

Aging processes in the musculoskeletal system lead to functional impairments that restrict participation. Purpose: To assess differences in force and motor recruitment patterns of shoulder muscles between age groups to understand functional disorders. A cross-sectional study comparing thirty adults (20-64) and 30 older adults (>65). Surface-electromyography (sEMG) of the middle deltoid, upper and lower trapezius, infraspinatus and serratus anterior muscles was recorded. Maximum isometric voluntary contraction (MIVC) was determined at 45° glenohumeral abduction. For the sEMG signal registration, concentric and excentric contraction with and without 1 kg and isometric contraction were requested. Participants abducted the arm from 0° up to an abduction angle of 135° for concentric and excentric contraction; and from 0º to 45º and remained there at 80% of the MIVC level while isometrically pushing against a handheld dynamometer. Differences in sEMG amplitudes (root mean square, RMS) of all contractions, but also onset latencies during concentric contraction of each muscle between age groups were analyzed. Statistical differences in strength (Adults>Older adults;0.05) existed between groups. No significant differences in RMS values of dynamic contractions were detected, except for serratus anterior, but there were for isometric contraction of all muscles analyzed (Adults>Older adults;0.05). The recruitment order varied between age groups, showing a general tendency towards delayed onset times in Older Adults, except for the upper trapezius muscle. Age differences in muscle recruitment patterns were found, which underscores the importance of developing musculoskeletal data to prevent and guide geriatric shoulder pathologies.


  • Device: Surface Electromyography
    • SEMG was used to measure the amplitude and onset of five shoulder muscle electrical signal, performing glenohumeral abduction. In this movement, the middle deltoid muscle was selected because it is a main motor. The infraspinatus muscle represented the rotator cuff muscle group. The middle deltoid muscle was selected as the representative of shoulder abduction because it is a main motor in this movement. The trapezius muscle and the serratus anterior muscle were chosen as representative established of the ascending scapular rotator muscles.

Arms, Groups and Cohorts

  • Older adults
    • Participants, without symptoms in the shoulder and / or cervical area (at least the last year), were assigned to the Older adult group: over 65 years.
  • Adults
    • Participants, without symptoms in the shoulder and / or cervical area (at least the last year), were assigned to the Adult groups: 20 to 64 years.

Clinical Trial Outcome Measures

Primary Measures

  • The mean Root Mean Square (RMS) value
    • Time Frame: day 1
    • The electromyographic data were captured simultaneously on a computer by using the LabChart® software. Within the time interval from 2 to 4 seconds after contraction initiation a power spectrum analysis was performed together with the determination of RMS values. The mean RMS values were automatically obtained from the software.
  • onset muscle contraction
    • Time Frame: day 1
    • The onset was obtained as the time distance of the interception between the level of pre-activation relative to the onset of arm displacement during dynamic contraction and the linearly interpolated RMS slope

Secondary Measures

  • Maximal isometric voluntary contraction
    • Time Frame: day 1
    • Using hand-held dynamometer
  • body mass index
    • Time Frame: day 1
    • is a measure of body fat based on height and weight that applies to adult men and women. Enter your weight and height using standard or metric measures.

Participating in This Clinical Trial

Inclusion Criteria

  • Healthy subjects – No previously manifested symptoms in the shoulder joint and/or the neck during the past year, Exclusion Criteria:

  • Moderate or severe cognitive impairment – Rheumatologic diseases – Massive osteoarthritis – Tumors – Shoulder joint instability – Circulatory disorders (hemophilia clotting problems) – Dermatological problems exacerbated by contact with skin.

Gender Eligibility: All

Minimum Age: 20 Years

Maximum Age: N/A

Are Healthy Volunteers Accepted: Accepts Healthy Volunteers

Investigator Details

  • Lead Sponsor
    • University of Castilla-La Mancha
  • Collaborator
    • University of Alcala
  • Provider of Information About this Clinical Study
    • Principal Investigator: Cristina Lirio, Principal Investigator, PhD – University of Castilla-La Mancha
  • Overall Official(s)
    • Cristina Lirio-Romero, PhD, Principal Investigator, University of Castilla-La Mancha


Lirio-Romero C, Anders C, De La Villa-Polo P, Torres-Lacomba M. Implications on older women of age- and sex-related differences in activation patterns of shoulder muscles: A cross-sectional study. J Women Aging. 2019 Nov-Dec;31(6):492-512. doi: 10.1080/08952841.2018.1521654. Epub 2018 Sep 25.

McManus L, De Vito G, Lowery MM. Analysis and Biophysics of Surface EMG for Physiotherapists and Kinesiologists: Toward a Common Language With Rehabilitation Engineers. Front Neurol. 2020 Oct 15;11:576729. doi: 10.3389/fneur.2020.576729. eCollection 2020.

Medved V, Medved S, Kovač I. Critical Appraisal of Surface Electromyography (sEMG) as a Taught Subject and Clinical Tool in Medicine and Kinesiology. Front Neurol. 2020 Oct 26;11:560363. doi: 10.3389/fneur.2020.560363. eCollection 2020. Review.

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