The Effect of Low Back Pain on Hip Range of Motion and Gluteus Medius Function in Field Hockey Players

Low back pain is a highly disabling musculoskeletal condition that often does not have a specific diagnosis. Low back pain has a high incidence rate in athletes who participate in sports that involve repetitive rotation about the hips and trunk such as field hockey and can be severe enough to cause many of these athletes to miss trainings and/or games. The main skills in rotational sports require repetitive rotations about the hips and spine, while in a position of lumbar flexion, for them to be performed. This combination of laterality, repetitive nature and asymmetrical positioning is thought to putatively increase the likelihood of low back pain occurrence. The gluteus medius is a lateral pelvic stabiliser whose main role is to abduct and medially rotate the hip. Previous work has linked reduced gluteus medius endurance, as well as high magnitudes of gluteus medius coactivation with the development of low back pain during prolonged static standing. The purpose of this study was to explore the relationship between gluteus medius function and low back pain in a group of young female field hockey players to better understand the potential link between asymmetrical rotational sports and non-specific low back pain. Forty one premier level female field hockey players who were grouped according to the presence of a reported history of low back pain within the last two years (15 in the history of low back pain group and 26 in the no history of low back pain group) completed a hip abduction range of motion test, gluteus medius strength and endurance tests and a 70 minute prolonged static stand to assess bilateral gluteus medius coactivation and median frequency through electromyography. During the prolonged stand, back pain was monitored using a visual analogue scale and recorded in 10 minute intervals. The study showed that field hockey players with a history of low back pain had significantly reduced hip abduction range of motion (p < .001) compared to those who were asymptomatic. Time had a significant effect on VAS score (p < .001) and gluteus medius coactivation (p = .037), however there was only a significant group x time effect on VAS score (p < .001). Group also had a significant effect on the total change in VAS score from the start to the end of the prolonged stand (p < .001) and gluteus medius median frequency (p = .004). Percentage change in bilateral gluteus medius coactivation and Oswestry low back pain disability score were observed to have a significant association with the development of back pain during the prolonged standing (p < .001, η = .83). Findings from this study show that female field hockey players are a unique population that differs significantly from an asymptomatic population. An over rotation of the spine may be used to compensate for reduced lead hip mobility. The excessive spinal rotation potentially places abnormal loads on the lower back, which through repetitive use causes pain to occur. There is an indication that a history of low back pain and the level of disability associated with the pain are more important than the magnitude of gluteus medius coactivation in the development of back pain while standing. Preliminary findings suggest that participants with a history of low back pain appear to either recruit a higher proportion of fast twitch motor units or have their slow twitch fibres firing at peak firing rate to help stabilise the pelvis while standing for prolonged periods of time. There are two important areas for future research: (1) the effect of improving hip range of motion in field hockey players on low back pain, the baseline gluteus medius frequency and associated pain with prolonged standing and, (2) the role of the posterior, medial and anterior subdivisions of the gluteus medius in pelvic stabilisation during prolonged standing