Aspects of Isometric Contractions and Static Balance in Women with Symptomatic and Asymptomatic Joint Hypermobility

Objective:
The aim of the current study was to identify the differences in strength, balance and muscle activity
between women with normal mobility and those with generalized joint hypermobility (GJH) with and without symptoms.

Methods: A total of 195 women, 67 normomobile (NM) and 128 hypermobile (HM), were included in this explorative cross-sectional study, whereby 56 were classified as symptomatically hypermobile (HM-s) and 47 as asymptomatically hypermobile (HM-as). Peak force (Fmax) and rate of force development (RFD) were measured during single-leg maximal voluntary isometric contractions of the knee extensor and flexor muscles in a sitting position. Balance was investigated on a force plate by calculating the anterior-posterior and medio-lateral sway while maintaining a single-leg stance for 15 seconds. During the sway measurements, muscle activity of six leg muscles was recorded using surface electromyography. The NM and HM groups were compared using independent samples t-tests, whereas the NM, HM-s and HM-as groups were compared using one-way ANOVAs with Tukey post-hoc tests (significance level p ≤ 0.05).

Results: While no statistically significant differences were found for Fmax, RFD and postural sway between the three groups, semitendinosus muscle activity showed a difference between the NM and HM (p=0.019) as well as between the NM and HM-as groups (p=0.020).

Conclusions: No clinically meaningful differences were found between the three groups. This might be possibly due to the fact that the performance measurements were not sensitive and the motor tasks not challenging enough to detect differences in neuromuscular behavior of the investigated groups.