The Effects of Exercise on Ligamentous Stiffness in the Wrist Joseph J. Crisco, PhD, MD, Providence, Ri, Sudahkar Chelikani, MS, Robert K. Brown, MD, Scott W. Wolfe, MD, New Haven, CT The purpose of this study was to determine if exercise alters wrist joint laxity, as measured by the mechanical behavior of the scaphoid bone. The load-displacement behavior of the scaphoid was studied in the palmar-dorsal direction in both wrists of 7 healthy volunteers (n = 14) before and after 2 exercise protocols (grip and push-up). When compared to the rested values, both exercise protocols significantly increased the displacement at 40 N by 47% (grip) and by 34% (push-up). Accordingly, the stiffness decreased significantly by 36% (grip) and by 32% (push-up). Partial recovery was documented after 1 hour of rest and there were no differences between any of the groups after 24 hours of rest. The increase in laxity docu- mented during these exercise protocols reduces the ligament loads at comparable wrist posi- tions and may thereby reduce the likelihood of traumatic ligamentous injury during partici- pation in strenuous activity or sports. (J Hand Surg 1997;22A:44-48.) Via its stout ligamentous connections to the proxi- mal and distal carpal rows, the scaphoid helps to sta- bilize the carpus throughout a wide range of wrist motion and variations in external load. l Injuries to the scaphoid ligaments are not infrequent in sports that involve extremes of wrist position, such as rac- quet sports, golf, hockey, and platform diving.= In an attempt to minimize these and other soft tissue injuries, warm-up or loosening-up exercises are over- whelmingly recommended prior to strenuous physi- cal activity, though no studies have documented the efficacy of such exercise. Previous studies have doc- umented that the ligamentous laxity (looseness) of the knee joint increases following repetitive exer- cises. 3-5 To the best of our knowledge, the effects of exercise on joint laxity have been examined only in the knee. We hypothesize that exercise would also From the Departmentof Orthopaedicsand Rehabilitation, Yale Uni- versitySchool of Medicine,New Haven,CT. Receivedfor publicationJuly 5, 1995;acceptedin revisedformJuly 15, 1996. No benefitsin any formhave been receivedor will be received from a commercial party related directlyor indirectly to the subject of this article. Reprintrequests:J. J. TreyCrisco,PhD, Orthopaedic ResearchSWP- 3, RhodeIsland Hospital,593 EddyStreet,Providence, R102903. increase wrist joint laxity. The purpose of this study was to determine the effects of exercise on the load- displacement behavior of the scaphoid bone. Materials and Methods We recruited 7 healthy men (average age, 27; range, 23-33) for this study. Written consent was obtained from all subjects in accordance with our institution's policies. None of the subjects had a known history of wrist injury or dysfunction. Both wrists of each subject were tested independently (n = 14) to determine the mechanical behavior of the scaphoid in response to a dorsally directed load. Each wrist was tested on 3 separate days with 1 of 3 different protocols, randomized to the day of testing. Each protocol consisted of an initial test (t = 0) that was repeated after 5 minutes (t = 5 minutes) and then repeated again after 1 hour (t = 65 minutes). The testing methodology is defined below. The type of exercise that the subject performed defined the protocol. The first protocol served as the control protocol to establish the variability within a single day of test- ing. In this protocol, defined as rest, the volunteers were asked to refrain from any strenuous activities, including keyboard activity, prior to or during the 44 The Journal of Hand Surgery