P22 Involuntary hamstring muscle activity reduces passive hip range of motion during the straight leg raise test
Diong J[1], Foo Y[2], Chia L[2] and Héroux ME[3]
- Discipline of Biomedical Science, Sydney Medical School, The University of Sydney, Australia.
- Discipline of Physiotherapy, Faculty of Health Sciences, The University of Sydney, Australia.
- NeuRA (Neuroscience Research Australia), Sydney, Australia
Involuntary hamstring muscle activity is present in some people during the straight leg raise test [1], but it is not known to what extent involuntary muscle activity limits passive joint range of motion. We aimed to determine whether small amounts of involuntary hamstring activity limit passive hip range of motion during the straight leg raise test in healthy people. Thirty healthy subjects were recruited from The University of Sydney. As the hamstring muscles were continuously stimulated to generate 0, 2.5, 5, 7.5 and 10% of knee flexion maximal voluntary contraction force, an investigator blinded to the amount of simulation performed a straight leg raise test by passively raising the tested leg while keeping the knee extended. The stimulation intensities were applied in random order. The test was stopped when the knee started to flex, at which point hip range of motion was recorded. On average, passive hip range of motion decreased by 0.6° for every 1% increase in knee flexion force caused by muscle activation (95% CI 0.3 to 0.9°, p=0.0012). Correspondingly, hip range of motion decreased by 2.9° when 5% of knee flexion force was present. A small amount of involuntary muscle activity (median 2.4% of maximal activation) was present during the trial without stimulation. In conclusion, small amounts of involuntary hamstring muscle activity reduce passive hip range of motion during the straight leg raise test in healthy people. We recommend muscle activity be recorded when passive joint range is used to inform diagnoses or assess interventions.
- Göeken LN & Hof AL (1993) Arch Phys Med Rehabil 74:194-203