Letter to the Editor-in-Chief and Author Response: The Repetitive Strain Injury Process: Alterations in Physiology vis-a-vis Symptoms

J Orthop Sports Phys Ther 2012;42(7):660-661. doi:10.2519/jospt.2012.0204 

STUDY DESIGN: Case-control study. OBJECTIVES: To investigate whether oxygen consumption and blood flow at rest and after exercise are lower in the affected arm of patients with repetitive strain injury (RSI) compared to controls, and lower in the healthy nonaffected forearm within patients with unilateral RSI. BACKGROUND: RSI is considered an upper extremity overuse injury. Despite the local presentation of complaints, RSI may be represented by systemic adaptations. Insight into the pathophysiology of RSI is important to better understand the development of RSI complaints and to develop effective treatment and prevention strategies. METHODS: Twenty patients with unilateral RSI and 20 gender-matched control subjects participated in this study. Forearm muscle blood flow and oxygen consumption were measured using near-infrared spectroscopy at baseline and immediately after isometric handgrip exercises at 10%, 20%, and 40% of the individual maximal voluntary contraction. RESULTS: Unilateral RSI resulted in a lower oxygen consumption and blood flow in the affected forearm at baseline and lower oxygen consumption after incremental handgrip exercises compared to controls (P<.05). In addition, exercise-induced blood flow and oxygen consumption in the nonaffected forearm in patients with RSI were similarly reduced. CONCLUSION: Blood flow and oxygen consumption after exercise are similarly attenuated in the affected and nonaffected arms of patients with unilateral RSI. Our findings suggest that, despite the unilateral character in clinical symptoms, RSI demonstrates systemic adaptations in forearm blood flow and oxygen consumption at rest and after exercise.

J Orthop Sports Phys Ther 2012;42(4):371-378. doi:10.2519/jospt.2012.3751

KEY WORDS: overuse injuries, pain, upper extremity