Effects of 7-Week Shoulder Exercise Intervention on Joint Mobility, Strength and Function in Diabetics and Non-Diabetics

Abstract

Abbreviations: ROM, range of motion; IR, internal rotation; ER, external rotation; DASH, disabilities of the arm, shoulder and hand; SPADI, shoulder pain and disability index IntroductionIn the United States, the prevalence of diabetes has increased from 5.5% to 9.3% within past decades 1 with the disease currently affecting 29.1 million people.2 Diabetes is commonly associated with conditions such as cardiovascular disease and long-term negative effects on various organs in the body such as kidneys and eyes.3 However, diabetes has also been shown to affect the musculoskeletal system. [4][5][6][7][8][9] Diabetics are four times more likely to have musculoskeletal disorders compared to non-diabetics 6 with the shoulder being one of the joints most affected by the disease. 10 Previous studies show that diabetics have higher prevalence of shoulder pain and injuries compared to non-diabetics. 6,7,[10][11][12][13][14] Specifically, diabetics are 3-9 times more likely to have frozen capsulitis and 5 times more likely to have rotator cuff tears compared to non-diabetics. 4,12,15 Additionally, diabetics are reported to have thickened supraspinatus and biceps tendons 16 along with decreased ROM in shoulder abduction and flexion 4,5 an impaired tendon-bone healing capacity 17 and difficulty regaining range of motion (ROM) after a surgery. 18,19 The musculoskeletal symptoms described above are attributed to mechanical changes in connective tissue due to formation of advanced glycation end products (AGEs). 4 The AGEs are formed from a reaction that occurs from bonding of sugar and amino acid. 4 The AGEs cause increased crosslinking between collagen fibers and increase stiffness and brittleness of the connective tissue. This change in mechanical property makes the tissue more susceptible to failure under stress. 20While accumulation of AGEs naturally occurs with aging, the process is accelerated in diabetics due to high blood glucose concentration and decreased peripheral blood flow. 4 The insertion of the rotator cuff on the greater tubercle corresponds to an area of poor blood supply [21][22][23] which may further contribute to accumulation of AGEs.Stretching and strengthening exercises focused on improving rotator cuff strength and restoring balance between the muscles that stabilize and rotate scapula are used in prevention and treatment of shoulder pain. [21][22][23][24][25][26][27][28] Effectiveness of this approach has been demonstrated in both healthy individuals and patients with various shoulder injuries. Despite the increased prevalence of shoulder pain among diabetics, there has only been one study that examined the effect of a physiotherapy program specifically in this population. 29 The study demonstrated that implementation of a physiotherapy program resulted in decreased pain level and improved shoulder function in diabetic patients who had shoulder pain. 29 However, this study did not have a comparison group without diabetes; therefore it is unknown how changes in tissue property caused by diabetes moderates...