The Onset Time of Neck and Shoulder Muscles Activation During Shoulder Elevation in Older and Young Adults

Abstract

This study examined differences in the time to onset of neck and shoulder muscle activation during arm elevation in older and younger adults. Eleven older and 10 younger adults were recruited. Data from neck and shoulder muscles were recorded as a subject elevated one arm. The mean time to onset of muscle activation was compared using an independent t-test. Older adults demonstrated significantly later onset of contraction of the ipsilateral sternocleidomastoid during shoulder flexion (p = 0.046), as well as significantly later contraction of the middle deltoid (p = 0.005), posterior deltoid (p = 0.027), contralateral splenius capitis (p = 0.008), upper trapezius (p = 0.020), middle trapezius (p = 0.012), lower trapezius (p = 0.012), and infraspinatus (p = 0.001) during shoulder abduction. These findings indicate that older adults use different neuromuscular strategies than younger adults during arm elevation. These changes could result from age-related decline in the neuromuscular system. The findings could be used to identify contributors to neck and shoulder discomfort or dysfunctionin older adults.