Isokinetic arm and shoulder muscle torque-velocity characteristics in mobility limited children and adolescents with spina bifida.

Introduction: Propulsive wheelchair capacity may be influenced by arm muscle performance. To determine whether children and adolescent wheelchair-users with spina bifida show reduced arm muscle strength compared to their typically developing peers and to compare muscle strength data obtained by isokinetic and handheld dynamometry (HHD).

Methods: Participants (mean age 12.5 ± 2.5 years) were assigned to spina bifida (SB; n = 11) or control (n = 22) groups. Isokinetic dynamometry was used to measure peak torque (PT) during dynamic (60°s and 120°s) and isometric strength testing (MVIC) for shoulder and elbow flexors and extensors. HHD was used to measure MVIC of the same muscle groups.

Results: SB showed reduced isokinetic PT for shoulder extensors at 60°s and 120°s, shoulder flexor MVIC, and elbow flexors at 60°s and MVIC; higher PT for shoulder flexors and elbow flexors at 120°s; and decreased MVIC for elbow flexors but not extensors compared to controls when assessed by HHD. The SB and control groups showed strong positive correlations between MVIC data obtained by the two devices for all muscle groups (r ≥ 0.81; p < .01), except for shoulder flexor MVIC in controls (r = 0.68; p < .01).

Conclusion: SB presented reduced levels of dynamic slow-speed and isometric shoulder and elbow muscle strength and greater dynamic high-speed shoulder and elbow flexor strength than controls possibly due to the exposure to self-sustained wheelchair ambulation. Exercise-based intervention protocols to increase slow-speed arm muscle strength should be considered in youth with SB. Strong positive correlations observed between muscle strength assessed by isokinetic dynamometry and HHD support the use of HHD in this clinical population.