Background Little is known about the clinical management of persons with generalized joint hypermobility (GJH). Affected persons are often restricted in performing sports or leisure activities, as well as during work, due to pain and disability (1). Adequate muscle strength for movement control might be an important issue to overcome these restrictions. Resistance training has the possibility to improve muscle strength (2), but so far no study investigated how resistance training influences strength and muscle size in women with GJH.
Objectives To evaluate the effects of a 12-week resistance training program on muscle properties of women with GJH.
Methods This pragmatic randomised controlled trial included 51 hypermobile women (mean age 26.5, sd 4.5 years) with a Beighton-score of six or more (3). 27 women performed for 12 weeks a guided resistance training twice weekly and 24 women did not exercise. Before and after the 12 weeks maximum isometric strength of knee extensors and flexors was measured, which was the primary outcome. Additionally muscle cross-sectional-area (mCSA) of the thigh was measured at 33% above the knee, using peripheral quantitative computer tomography (pQCT). Data were analysed on an intention-to-treat basis. Differences between groups were tested with independent t-test at a significance level of p=0.05.
Results The groups were comparable at baseline. Change of maximum strength of knee extensors in the training group was 6.3 N (sd 57.7, CI -16.5 to 29) and in the control group 8.3 N (sd 42.1, CI -9.4 to 26.1), with no significant difference between groups. Similar results were seen for knee flexors: change in training group was 8.0 N (sd 59.8, CI -15.6 to 31.7) and in control group 16.1 N (sd 42.8, CI -2.0 to 34.2). Muscle CSA of the thigh in the training group showed a significant increase (194 mm2, CI 78 to 310 mm2), compared to the control group (46 mm2, CI -25 to 118 mm2; p=0.031). Muscle mass at the thigh significantly increased 19.1 mg (sd 27.3, CI 8.3 to 29.9) in the training group, compared to the control group with 4.3 mg (sd 14.4, CI -1.8 to 10.33) mean change. Muscle density, however, showed no change in both groups.
Conclusions The 12-week resistance training did not change isometric knee muscle strength, but led to a significant increase of mCSA of the thigh in women with GJH. However, this difference was only 2.4% and thus may not be clinically significant. In strength testing possibly no change was seen because the dynamic training could not be transformed to the isometric test condition and the intensity of the training might not have been high enough. The detailed analysis of the training protocols will provide further details concerning this issue. However, the small increase in muscle area may indicate that strength training is a possible option for these hypermobile women. Further analysis of the additional measurements in this trial, may give more insight into changes in pain or disability. Further research should investigate if the muscle increase could be optimized by a more intense or better supervised training.
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Acknowledgement The study was approved by the Ethics Committee of Canton Bern (222/12).
Disclosure of Interest None declared