Chronic low back pain is a common problem among recreational runners, affecting approximately one in seven runners. Clinically, there is no specific protocol to treat low back pain for runners. Physiotherapists generally adopt exercise protocols targeting different back muscles in the same way as they treat other patients with back pain. Some exercises train the global, bigger muscle groups responsible for movements; others focus more on the core muscles to stabilise the spine.
The research team led by Associate Professor KONG Pui Wah (Veni) at the Nanyang Technological University, Singapore, offered a new perspective to treat low back pain in runners. Running is a high-impact activity, with a heavy load on the spine during each foot strike. The ankle, knee, and hip act together as a system to help reduce the force transmission to the pelvis and spine. This connection between the legs and the back urged Dr Kong and her team to postulate that weakness of the leg muscles may reduce the capacity for shock attenuation, transmitting higher forces to the back. Thus, strengthening the leg muscles may contribute to reducing loading and pain in the low back during running.
To investigate whether the new concept works, Dr Kong’s research team recruited 84 men and women who suffered from chronic low back pain and still ran regularly. The runners were randomly divided into three groups to receive 8 weeks of supervised exercise therapies, twice per week. One group tried out the new concept of training the leg muscles, while the other two groups underwent the current best practices of training various back muscles. After the therapy, the researchers followed up at 3 months and 6 months. The outcome measures included self-rated pain and running capability, lower limb strength, back muscle function, and running gait.
Pain reduction is a key rehabilitation outcome in the treatment and management of chronic low back pain. In this study, it is interesting to note that regardless of the type of exercises performed, all three groups reported less pain and demonstrated improved back muscle function. This suggests a general effect of exercise rather than a specific type of exercise for pain relief.
It is encouraging to observe that the group which was allocated to leg muscle training showed better improvement in self-rated running capability, knee strength, and running gait when compared to the other two back exercises groups. These findings support the researchers’ speculation that weak knee extensors may compromise one’s ability to absorb impact shock during running and hence transmitting higher forces to the low back. Thus, improving knee muscle strength can contribute to relieving low back pain.
Exercises targeting the leg muscles led to the greatest increase in running step length among the study participants. By the end of the 6-month follow-up period, the running step length of the leg exercises group increased by almost 10 cm when compared to the start of the study. Assuming the running speed remains the same, increased step length would have resulted in reduced step frequency or cadence. Taking fewer steps to complete the same distance may have reduced the number of impacts on the spine during ground contact, contributing to the reduced pain and improved running capability reported by the runners.
To conclude, strength training of the leg muscles could be a new therapy option for runners suffering from chronic low back pain. After 8 weeks of exercises, runners can expect positive effects such as reduced pain, improved running capability, knee extension strength, and running gait.
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