Effect of Chronic Stretching Interventions on the Mechanical Properties of Muscles in Patients with Stroke: A Systematic Review

Background: Muscle contractures are common after stroke and their treatment usually involves stretching. However, recent meta-analyses concluded that stretching does not increase passive joint amplitudes in patients with stroke. The effectiveness of treatment is usually evaluated by measuring range of motion alone; however, assessing the effects of stretching on the structural and mechanical properties of muscle by evaluating the torque-angle relationship can help in understanding the effects of stretching. Although several studies have evaluated this, the effects remain unclear.

Objective: A systematic review of the literature on the effectiveness of stretching procedures for which the outcomes included a measurement of torque associated with range of motion or muscle structure (e.g., fascicle length) in stroke survivors.

Methods: PubMed, ScienceDirect and PEDro databases were searched by 2 independent reviewers for relevant studies on the effects of chronic stretching interventions (>4 weeks) that evaluated joint angle and passive torque or muscle structure or stiffness. The quality of the studies was assessed with the PEDro scale.

Results: Eight randomized clinical trials (total of 290 participants) met the inclusion criteria, with highly variable sample characteristics (at risk/existing contractures), program objectives (prevent/treat contractures) and duration (from 4 to 52 weeks) and volume of stretching (1 to 586 hr). All studies were classified as high quality (>6/10 PEDro score). Six studies focused on the upper limb. Many programs were less than 12 weeks (n=7 studies) and did not change mechanical/structural properties. The longest intervention (52 weeks) increased muscle fascicle length and thickness (plantar flexors).

Conclusion: Long interventions involving high stretching volumes and/or loads may have effects on muscle/joint mechanical properties, for preventing/treating contractures after stroke injury, but need to be further explored before firm conclusions are drawn.