Force steadiness, muscle activity, and maximal muscle strength in subjects with subacromial impingement syndrome

Abstract

We investigated the effects of the subacromial impingement syndrome (SIS) on shoulder sensory-motor control and maximal shoulder muscle strength. It was hypothesized that both would be impaired due to chronic shoulder pain associated with the syndrome. Nine subjects with unilateral SIS who remained physically active in spite of shoulder pain and nine healthy matched controls were examined to determine isometric and isokinetic submaximal shoulder-abduction force steadiness at target forces corresponding to 20%, 27.5%, and 35% of the maximal shoulder abductor torque, and maximal shoulder muscle strength (MVC). Electromyographic (EMG) activity was assessed using surface and intramuscular recordings from eight shoulder muscles. Force steadiness was impaired in SIS subjects during concentric contractions at the highest target force level only, with muscle activity largely unaffected. No between-group differences in shoulder MVC were observed. The present data suggest that shoulder sensory-motor control is only mildly impaired in subjects with SIS who are able to continue with upper body physical activity in spite of shoulder pain. Thus, physical activity should be continued by patients with SIS, if possible, to avoid the loss in neural and muscle functions associated with inactivity.

The Simple Shoulder Test Is Responsive in Assessing Change Following Shoulder Arthroplasty

“…2,9,15,[21][22][23]31 Thus, it is important to understand their responsiveness. The present results suggest that 6 months after SA most measurements of shoulder ROM are moderately to highly responsive, while measurements of isometric strength are minimally to moderately responsive.…”

Experimental muscle pain increases normalized variability of multidirectional forces during isometric contractions

“…Increased variability of force and movement have been associated with the development of musculoskeletal disorders and pain (Madeleine 2010), such as knee osteoarthritis and subacromial impingement syndrome (Hortobágyi et al 2004;Bandholm et al 2006). Multiple neuromuscular mechanisms could be responsible for the pain-induced increase in force fluctuations.…”

“…Increased force variability has been associated with muscle fatigue (Missenard et al 2009), ageing (Tracy 2007), increased risk of falls (Carville et al 2007), and in particular, higher force fluctuations were observed in patients with chronic musculoskeletal pain disorders such as knee osteoarthritis and subacromial impingement syndrome compared with healthy controls (Hortobágyi et al 2004;Bandholm et al 2006). Although it has been shown that pain may cause changes in muscle coordination (Graven-Nielsen et al 1997), it is still unclear how these changes affect the three-directional distribution of force variability.…”

Eccentric training for shoulder abductors improves pain, function and isokinetic performance in subjects with shoulder impingement syndrome: a case series

“…These assumptions generated a sample size of at least 19 subjects. The acceleration time was the variable chosen for the calculation of the sample size as some investigations have demonstrated that SIS does not affect muscle torque of the shoulder [39][40][41] , but affects scapular and rotator cuff muscle activity in subjects with SIS during arm elevation [42][43][44] . Therefore, the acceleration time may provide valuable information regarding neuromuscular readiness to produce maximal contraction.…”