Muscle mass, muscle strength, functional performance, and physical impairment in women with the hypermobility type of Ehlers-Danlos syndrome

Objective: To investigate lower extremity muscle mass, muscle strength, functional performance, and physical impairment in women with the Ehlers-Danlos syndrome hypermobility type (EDS-HT).

Methods: Forty-three women with EDS-HT and 43 sex- and age-matched healthy control subjects participated. Muscle mass was determined by dual x-ray absorptiometry. Muscle strength and muscle strength endurance were measured with isokinetic dynamometry at angular velocities of 60, 180, and 240°/second. Static muscle endurance during posture maintenance was also assessed. Pain and fatigue were simultaneously evaluated by visual analog scale and the Borg scale, respectively. In addition, the chair rise test for assessment of functional performance and the Arthritis Impact Measurement Scales (AIMS) for physical impairment evaluation were used.

Results: Compared to control subjects, EDS-HT patients showed substantial lower extremity muscle weakness, reflected by significantly reduced knee extensor and flexor muscle strength and endurance parameters, with differences ranging from -30% to -49%; reduced static muscle endurance time; and diminished functional performance. Lower extremity muscle mass was similar in both groups and unlikely to affect the muscle strength results. By contrast, pain and fatigue were omnipresent and increased remarkably due to the tests. Furthermore, the EDS-HT group was physically impaired, especially in the AIMS domain walking and bending.

Conclusion: This study demonstrates severely reduced quantitative muscle function and impairment in physical function in patients with EDS-HT compared to age- and sex-matched controls. The muscle weakness may be due to muscle dysfunction rather than reduced muscle mass. Whether muscle strength and endurance can be improved by appropriate exercise programs needs evaluation in further studies.