Stretching with a constant force immediately increases range of motion more than holding a joint in a fixed position, research by movement scientist Guido Geusebroek has shown. In the longer term, this finding could contribute to improving treatments for people recovering from a stroke or living with spastic muscle disorders.
Conditions such as stroke, paralysis and prolonged bed rest can cause muscles and tendons to become shorter and stiffer. ‘As a result, joints become less mobile and may be less able to bend or straighten. This can severely restrict everyday activities such as walking and getting dressed,’ Geusebroek explains.
‘At present, treatment for joint stiffness includes stretching shortened and stiffened muscles using splints, physiotherapy and automated stretching devices. However, there is still little scientific consensus on the most effective way to stretch,’ says the researcher.
‘My research therefore focuses on how different stretching methods affect joint range of motion and the properties of muscle and tendon tissue.’
Contant force provides greater range of motion
The research consisted of a literature review on ankle stiffness and three experiments using animal models. Geusebroek: ‘The results of previous literature reviews involving patients showed that stretching with a constant force immediately produces a greater range of motion in the ankle joint than other methods. However, there was not enough clearly described data available to analyse the long-term effects.’
New animal model for research into joint stiffness
The first animal experiment confirmed that stretching with a constant force has a greater short-term effect than stretching while maintaining a constant joint position, at both muscle and tendon level. The second experiment examined how the stretch was distributed at a microscopic level across a calf muscle and tendon.
Geusebroek: ‘In the third experiment, we developed a new contracture model in the ankle of the rat in which the ankle joint is not completely immobilised and the paw can still bear some weight. This allows joint stiffness to be modelled more accurately in rats. The model can be used in future research to investigate the effectiveness of stretching and other treatment methods.’
Potential implications for rehabilitation
According to Geusebroek, the findings are relevant to physiotherapists, rehabilitation physicians and developers of medical devices. ‘Splints and automated stretching devices may be able to stretch more effectively when they apply a continuous, constant force, rather than fixing the joint at a single position,’ says Geusebroek.
He emphasises that further research is needed to establish the long-term effects of stretching with a constant force. ‘Ultimately, the results could contribute to optimising treatment guidelines and splints used in rehabilitation practice and potentially to a better quality of life for people recovering from a stroke or living with spastic muscle disorders,’ the researcher concludes.