Design: Cross-sectional observational.
Setting: The Anglo-European College of Chiropractic.
Subjects: A convenience sample of 27 non-low back pain subjects who met the exclusion criteria.
Methods: Each subject performed four repetitions of prone hip extension for each leg, alternating their left and right sides. One of two examiners classified the subject as “Positive” or “Negative” based on the presence or absence of “abnormal” lumbar spine motion patterns. Activity within the four muscles was recorded using surface electromyography, and a foot switch was used to determine the onset of leg movement. The frequency with which each of the 24 possible activation orders was used by each group was compared. The mean onset time of each muscle, relative to the onset of leg movement and contraction of the other muscles, was calculated for each group and compared.
Results: The same six activation orders were the most prevalent in the “Positive” and “Negative” groups and accounted for the majority of each group's total repetitions. No between-group differences were found in the frequency with which each of these six orders was used. The only significant between-group difference in the onset times of the muscles was that the GM was delayed relative to the onset of leg movement (difference = 188.9 ms; 95% CI = 99.6 to 278.2 ms; p = 0.0001) and the contraction of each of the other three muscles in the “Positive” group.
Conclusions: The PHE test may be a potential tool for clinicians to determine whether the GM is a “weak link” in the motor control strategies of a patient and as such could be used as an indicator for the prescription of therapy aimed at restoring a “normal” motor pattern for this muscle. However, there are several issues which challenge the clinical importance and effectiveness of such an approach, and further research needs to be performed to address these before any definite recommendations can be made.
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