Introduction

1. Does Hip Flexibility Influence Lumbar Spine and Hip Joint Excursions during Forward Bending and Reaching Tasks. Erica Johnson, Ashley McCallum, Brian Sabo and James S. Thomas. School of Physical Therapy, Ohio University, Athens, OH Table 1: Correlation values between hamstring flexibility and lumbar excursions and mean joint excursions data. Introduction Low back pain (LBP) is a prevalent and costly health concern. However, there is no clear consensus on the best treatment for this condition. Conservative treatment may include manipulation, myofascial release, exercise, modalities, and a number of other treatment options. Conservative treatment also often includes flexibility exercises, especially of the hamstrings. Many clinicians support this practice based on the theory that normal hamstring length will prevent excessive lumbar flexion during postures that place the hamstrings in a lengthened position such as forward bending. However, there are few studies that have examined the influence of hamstring flexibility on hip and lumbar spine joint excursions during forward reaching or bending tasks. Therefore, we performed a retrospective examination of data from our lab to evaluate the influence of hamstring flexibility as measured by hip flexion with the knee extended (i.e. straight leg raise) on hip and lumbar spine joint excursions. Methods Data from participants of two prior investigations were analyzed for this study. Study 1 consisted of one group of participants: Recovered - currently pain free after an acute episode of low back pain (n= 42 men, 44 women). While the original study consisted of 88 participants, complete range of motion (ROM) data was only available for 86. Study 2 consisted of two groups of participants: Healthy- no history of low back pain (n=8 men, 10 women) and Chronic Low Back Pain- back pain greater than 3 months duration (n=8 men, 10 women) (Unpublished findings). In these two prior studies, hamstring flexibility was assessed with the knee straight (SLR) using a bubble goniometer following standard methods found in physical therapy textbooks. Hip flexion ROM was also assessed with the knee bent to evaluate the full flexion range available at the hip. No movement restrictions were found with hip flexion in any of the participants that would limit evaluation of hamstring flexibility. In both studies, participants performed reaching tasks to two target locations based on their individual anthropometric characteristics. Targets were positioned in the mid-sagittal plane such that the participant could reach the high and low targets with 15º and 60º of hip flexion, respectively, while maintaining 90º of shoulder flexion (Figure 1). Participants in Study 1 then performed a maximum forward bending task (FBT) by starting in a standing position and bending forward as far as possible as if to touch the toes while keeping the legs and arms straight to assess maximum lumbar and hip joint flexion excursion. Joint motions were measured using The Motion Monitor™, a magnetic based kinematic system. The change in joint angle from initial to final posture (i.e. target contact or end range flexion) was extracted using custom software. Healthy participant with right SLR=96º reaching to low target and exhibiting an average lumbar excursion of 43.5º Figure 2: Joint excursions of the lumbar spine averaged over three trials during forward reaching task to the high target in the Healthy group. Correlation value = -.172 Figure 3: Joint excursions of the lumbar spine averaged over three trials during forward reaching task to low target in the Healthy group. Correlation value = -.585 (p<.05) Results Excursions of the lumbar spine and hip during the reaching tasks and FBT were not significantly correlated with SLR for the Recovered or LBP groups (Table 1). A significant negative correlation was found in the Healthy group between SLR and lumbar spine flexion excursion only during the forward reaching task to the low target (Table 1). For the Recovered group, mean(SD) SLR for the right side was 56.3°(±9.3) and 61.3°(±10.3) for the left side. Mean(SD) SLR for the Healthy group was 80.7°(12.3) for the right side and 77.2°(±13.7) for the left side. For the LBP group, mean(SD) SLR was 72.3°(±10.5) for the right side and 68.2°(±12.2) for the left side. Mean SLR in the Healthy group was significantly greater than the mean SLR in the Recovered and LBP groups (p<.05). However, there was no corresponding significant difference between the Healthy and LBP group for amount of lumbar excursion during the forward reaching tasks. Conclusions Contrary to expectations, individuals with LBP or a history of LBP did not exhibit a significant correlation between hamstring flexibility, as clinically measured by the SLR, and the amount of lumbar flexion excursion used to complete forward reaching tasks. It was theorized that increased hamstring flexibility would decrease the amount of lumbar flexion used during forward reaching tasks. Therefore, individuals with greater hamstring flexibility would have been expected to exhibit less lumbar flexion excursion (i.e. maintaining the lumbar spine in a more neutral position) when completing forward reaching tasks than those with limited hamstring flexibility. This relationship was only demonstrated in the Healthy group with a significant negative correlation between hamstring flexibility and the lumbar flexion excursion used to reach to low target. However, no correlation between lumbar excursion and hamstring flexibility was found in the Recovered or LBP group for forward reaching, nor was there a correlation between total lumbar excursion and hamstring flexibility in the Recovered group during the FBT. These results indicate that hamstring flexibility is not strongly related to the amount of lumbar flexion used to perform these tasks in these individuals. In light of these findings, it may be reasonable to assume that increasing hamstring length would not affect the amount of lumbar excursion exhibited during forward bending tasks in individuals with LBP or who have a history of LBP. It remains to be determined if there is a lower limit of hamstring flexibility at which forward bending patterns would be altered, but that is outside of the scope of this study. More research needs to be conducted to examine the influence of hamstring flexibility on observed movement patterns to further evaluate the efficacy of flexibility training in the rehabilitation of patients with low back pain. This research was supported by The National Institutes of Health Grant R01-HD045512 to J.S. Thomas Figure 4: Joint excursions of the lumbar spine averaged over three trials during forward reaching to the high target in the LBP group. Correlation value =.248 Figure 5: Joint excursions of the lumbar spine averaged over three trials during forward reaching to the low target in the LBP group. Correlation value =.025 LBP participant with right SLR=81º reaching to low target and exhibiting an increased amount of lumbar flexion excursion of 62.2º Data Analysis Separate bivariate correlation analyses were performed between SLR measures and hip and lumbar spine joint excursions used during the standardized reaching tasks and the FBT to assess the influence of hamstring flexibility on joint excursions. These analysis were performed separately for the right and left sides. Figures 2-7 are the scatterplots correlating each participant’s right SLR measurement with the amount of lumbar flexion excursion observed during reaching tasks to the high and low targets separated by group. Figure. 1Targets were positioned in the mid-sagittal plane such that the participant could reach the high and low targets with 15º and 60º of hip flexion, respectively, while maintaining 90º of shoulder flexion. LBP participant with a right SLR=64º reaching to the low target using an average lumbar flexion excursion of 48.3º Figure 7: Joint excursions of the lumbar spine averaged over three trials during forward reaching to the high target in the Recovered group. Correlation value = .081 Figure 6: Joint excursions of the lumbar spine averaged over three trials during forward reaching to the high target in the Recovered group. Correlation value = -.015