Age Differences in Motor Recruitment Patterns of the Shoulder in Dynamic and Isometric Contractions. A Cross-Sectional Study

Abstract

Aging processes in the musculoskeletal system lead to functional impairments that restrict participation. Purpose: To assess differences in the force and motor recruitment patterns of shoulder muscles between age groups to understand functional disorders. A cross-sectional study comparing 30 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 eccentric 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 eccentric contraction, and from 0° to 45°, 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 the serratus anterior, but there were for isometric contractions 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.

The Forgotten Flap: The Pedicled Trapezius Flap's Utility in Pediatric Head and Neck Reconstruction—A Systematic Review

“…[31][32][33][34] Regarding the upper limbs, shoulder muscle function declines with decreased use of arms and hands in daily activities, which is common with increased age. 35,36 One study sought to investigate these agerelated differences in motor recruitment patterns of the shoulder in dynamic and isometric contractions. 35 In contrast to younger adults, the upper trapezius muscle was recruited first during shoulder abduction in older adults.…”

“…In contrast, later contraction was observed in younger patients. 35 Thus, older adults tend to rely more heavily on the upper trapezius muscle for shoulder abduction. Disruption of this muscle segment is more likely to affect their overall upper extremity range of motion.…”

“…35 36 One study sought to investigate these age-related differences in motor recruitment patterns of the shoulder in dynamic and isometric contractions. 35 In contrast to younger adults, the upper trapezius muscle was recruited first during shoulder abduction in older adults. Furthermore, in older adults, the upper trapezius was recruited before the beginning of the abduction movement.…”

Exoskeletons for Elderly Activity of Daily Living Assistance: A Review of Upper Limb Exoskeletons and Assessments

“…Altered motor recruitment patterns of shoulder muscles are observed in the elderly, with a general trend towards delayed muscle onset times in the elderly population, except for the upper trapezius muscle [82], [83]. Consequently, motion intention recognition and controllers developed based on the characteristics of the young adult and adult population may not effectively cater to the unique conditions experienced by the elderly.…”

“…ML is also instrumental in modelling human locomotion control [112], [113], recognising human motion intention [114]- [117], and movement control, such as in EMG-based controller for shoulder exoskeleton [117] and neuro-muscular electrical stimulation based controller for upper limb exoskeleton [118], [119]. Considering the variations in joint kinematics and muscle activity between the elderly and adults [77], [79], [80], [82], [83], ML application potentially provides population-specific considerations for exoskeleton design and control systems. Recent ML applications include optimising exoskeleton designs in personalising the mechanical parameters of chainmail for hand exoskeletons [120].…”