AbstractIn the following thesis, I investigate the effectiveness of lumbar mobilisations on characteristics of the lumbar and hamstring unit. Part 1: Investigating the effect of lumbar mobilisations on the hamstring unit. In STUDY 1, the effects of mobilisation of the L4/5 zygapophyseal joint on two hamstring extensibility outcomes were quantified in elite footballers. Two measures of hamstring extensibility; the straight leg-raise test and the passive knee extension test were assessed. Lumbar mobilisations had a very likely small beneficial effect on the straight leg raise test (6.3%; 90% confidence limits, 3.6 to 9.0%) and a likely small beneficial effect on the passive knee extension test (-23%; -36.6 to -8.7%). STUDY 2 in addition to range of motion testing, investigated the electrical activity of the erector spinae and biceps femoris following lumbar mobilisations. Lumbar mobilisations had a most likely beneficial effect on active lumbar flexion 18.6% (90% CL, 11.8 to 25.8%) and active knee extension range 22.8% (–29.6 to 15.2%). Mobilisations had a possible beneficial effect on sEMG activation reduction of the erector spinae –4.7% (–10.5 to 1.4%) and bicep femoris –6.1% (–13.1% to 1.6%) during lumbar flexion. Likely beneficial effects of reduced sEMG were observed following mobilisations during the active knee extension test for the erector spinae –18.3% (–27.7 to -7.6%) and biceps femoris muscle activity –20.8% (–30.9 to -9.2%).
Part 2: Investigating the most effective lumbar mobilisation technique and the duration of hamstring unit adaption. In STUDY 3, the acute effects of two mobilisation techniques central posterior-anterior (CPA) and unilateral posterior-anterior (UPA) were examined on previously investigated measures of the lumbar and hamstring unit. Both CPA and UPA mobilisations increased lumbar and hamstring range of motion whilst reducing local muscle activity. UPA mobilisation had a greater ability to increase hamstring extensibility (–5.5% ±3.8%) and reducing biceps femoris muscle activity (–11.2% ±8.0%) compared to CPA mobilisations. In STUDY 4, the post-intervention time-course changes of lumbar and hamstring extensibility were examined following UPA mobilisations. A likely moderate effect on the active lumbar flexion (ALF) test was found at 5 minutes (mean 16 ± SD 1.1) and possible moderate/most likely small at 10 minutes (16 ± 1.1). For the active knee extension test (AKE), most likely/likely moderate effects were recorded for 5- (-28.8 ± 10.3) and 10-minutes (-29.3 ± 10.7) post treatment The magnitude of the associated effect substantially reduced following these time points. Interindividual differences displayed moderate changes for up to 10 minutes post and small to the 30-minute duration. Increases in lumbar mobility were large until 5 minutes post, moderate until 15- and small to 60 minutes post application.
Part 3: Investigating the extent to which lumbar mobilisations affect hamstring extensibility and performance during an eccentric strength exercise. In STUDY 5, the final paper in this thesis, the primary aim was to quantify the effects of UPA on force production, failure point and muscle activity of the hamstring unit during the Nordic hamstring exercise (NHE). The second aim of this study was to quantify individual differences in responses using a replicated crossover approach. The data indicated immediate changes in bilateral hamstring force production and peak torque during the NHE following UPA mobilisations. Lumbar mobilisations increased mean (95% CI) left limb force by 18.7 (4.6 to 32) N, right limb force by 22.0 (3.4 to 40.6) N, left peak torque by 0.14 (0.06 to 0.22) Nm and right peak torque by 0.14 (0.05 to 0.23) Nm. Both peak sEMG activity (p=0.002; mean 16.8mV; CI 95% 7.1 to 26.4), and sEMG at the angle of downward force right (0.02; 8.8; 1.5 to 16.1) also increased. The effect on the NHE failure point was unclear, with slight decreases in the point of downward force on the side of application 4.1° (0.5 to 7.6) but the angle of downward acceleration, another measure of failure point, was small and not statistically significant. Intervention response heterogeneity was found only for force right, with a statistically significant participant x intervention interaction (P=0.04) and response heterogeneity SD of 34.5 (5.7 to 48.4) N. No other interindividual differences were detected. The replicated design allowed, for the first time in this research domain, quantification of individual response heterogeneity to the intervention.
With this thesis, I have demonstrated that applying UPA lumbar mobilisations can increase range of motion of the hamstring unit and decrease its muscle electrical activity for up to 15 to 20 minutes. Additionally, mobilisation application prior to an NHE, an eccentric exercise aimed to increase hamstring muscle strength, can increase hamstring force production and peak torque. This body of work presents novel clinically relevant research to inform manual therapists of the role lumbar mobilisations may play in the prevention of hamstring strain injury.
|Date of Award||18 Feb 2022|
|Supervisor||Gregory Atkinson (Supervisor)|