Does flexibility training influence the biomechanics of the sit-to-stand for people with multiple sclerosis
Bowser, Bradley J.
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For people with multiple sclerosis (MS), compromised neuromuscular control, muscle weakness and balance impairments can reduce their ability to perform activities that require them to rise from a seated position. To date no research has examined how people with MS perform the sit-to-stand (STS) movement. Furthermore, no research has examined the possible influence of flexibility training on the performance of the STS for people with MS. Therefore the purpose of this study was to first determine the biomechanical differences between an MS and non-MS control group for the STS movement and second, to determine whether16 weeks of flexibility training would improve the functional performance and biomechanics exhibited by individuals with MS during the STS. A series of t-tests and repeated measures ANOVAs were used for analysis (α = 0.05). Compared to controls, MS participants exhibited decreased leg extensor strength and increased movement time, maximum trunk flexion, and maximum trunk flexion velocity. Decreased muscle activation of rectus femoris and hamstrings were found for the leg affected more by MS when compared to the leg affected less my MS for both the control and MS groups. No differences for peak magnitudes for joint kinetics were found. However, MS participants did employ the ‘trunk flexion’ strategy commonly exhibited by other clinical populations with neuromuscular deficits. This strategy is suggested to both reduce joint moment requirements as well as simplify the motor coordination of the sit-to-stand movement. Following 16 weeks of flexibility training participants increased ROM for knee flexion, ankle dorsiflexion and plantarflexion by 8%, 31%, and 19%, respectively. Additionally, maximum posterior ground reaction force and maximum hip extensor moments occurred approximately 5.5% earlier. No other differences were detected. MS participants were able to increase ROM at the ankle and knee joints and exhibit some biomechanical changes with low-intensity flexibility training. In summary, ambulatory individuals with relapsing-remitting MS display strength and functional deficits (slower STS movement times) and demonstrate an adaptation that is commonly used to compensate for impaired muscle function, a common symptom of MS. Although no changes to muscle strength and spasticity were detected following 16 weeks of flexibility training, static stretching programs may be beneficial in maintaining current functional levels as well as improve joint ROM in people with MS. To improve flexibility of other joints, increase muscle strength and increase function of the STS movement, that is, movement time, and reduce atypical movement kinematics and kinetics, a more intense flexibility training program may be needed.