Exercise therapy for runners with chronic low back pain - back or lower limb exercise?

Abstract

One in seven recreational runners were reported to suffer from non-specific chronic low back pain (LBP), and the condition could be long lasting and debilitating. However, this group of chronic LBP patients have not received sufficient attention in biomechanical, physiological and clinical studies. This thesis reviews the prevalence of non-specific chronic LBP in recreational runners, low back injury mechanism during running, and 3 different exercise therapy concepts for chronic LBP management: lumbar extensor exercises, lumbar stabilization exercises and lower limb exercises. For each exercise concept, the basic knowledge of anatomy, biomechanics and physiology, current exercise regime and effectiveness of the exercise are described. The measurement reliability and validity of relevant instruments are also examined. Two studies were conducted to investigate muscle functional characteristics and the treatment effectiveness of the abovementioned 3 exercise therapy concepts among recreational runners with non-specific chronic LBP.<br><br>First, a cross-sectional study was performed to compare the functional characteristics of back and lower limb muscles between recreational runners with and without non-specific chronic LBP. In this study, the diminished knee extension isokinetic strength was observed in runners with non-specific chronic LBP. Additionally, male runners with the LBP condition were found to have altered activation of lumbar multifidus. The study results also suggest that lumbar extensors fatigability and hip muscles strength may have little clinical relevance in the management of non-specific chronic LBP among recreational runners, since there was no difference in these functional characteristics between runners with and without chronic LBP.<br><br>Second, a single-blinded randomised trial was conducted on recreational runners with non-specific chronic LBP to evaluate the treatment effectiveness of the lower limb exercise therapy, compared with conventional lumbar extensor and lumbar stabilization exercises. In this study, the lower limb exercise therapy was found to be a more effective and specific approach for managing non-specific chronic LBP in recreational runners. Compared with the conventional exercise therapies, this novel approach has shown to be more favourable in improving participants’ self-rated running capability, knee extension strength and increasing running step length. For outcomes including running induced pain and lumbar stabilizing muscle activation, where improvements were not specific to any exercise approach, the lower limb exercise therapy was as effective as the conventional exercise therapies. There was also no significant change in lumbar extensors fatigability and hip muscles strength observed in all 3 exercise therapy groups despite substantial improvements in self-rated running capability and reduction in pain. The same is also true for most spatiotemporal variables of running including running flight time, contact time, and between-leg asymmetry of running step length, flight time and contact time.<br><br>In conclusion, the current thesis has revealed diminished knee extension strength as a major muscle functional deficit in recreational runners with chronic LBP. Further, the thesis has provided empirical evidence to recommend lower limb exercise therapy, a specific and effective approach, as a new treatment option for non-specific chronic LBP in recreational runners.