A recent study evaluated the stability of the spine and lower joints with repetitive lifting-lowering movements in healthy males and chronic low back pain patients.
Chronic low back pain (CLBP) is a major health concern that has a significant societal and economic impact. Living with CLBP can drastically reduce an individual’s quality of life by making daily activities more difficult and painful. It can be particularly troublesome for those with occupations that require repetitive movements, over a long period of time. Understanding the interaction between CLBP, fatigue, and joint stability is an ongoing challenge for researchers. To date, studies have evaluated lower trunk stability but failed to consider that both upper and lower joints contribute to the stability of the human body.
A recent study published in Human Movement Science investigated the effects of lifting-induced fatigue on the stability of the spine, hip, knees, and ankles in both healthy and chronic low back pain populations. The study recruited fourteen healthy males (average age of 23 years) and fourteen males with nonspecific CLBP (average age of 25 years). Participants lifted two equally-sized dumbbells, with a combined weight equivalent to 15% of their body weight, from the floor up to waist level and back down to the floor. This action was repeated until the participants felt fatigued. During this routine, a Vicon motion capture system was used to track the three-dimensional kinematic data of the joints. To analyze the data, researchers used the nonlinear Lyapunov exponent (LyE) to evaluate the local stability of each joint in three anatomical planes; the sagittal, transverse, and frontal planes.
The authors found that lifting-induced fatigue significantly affected the stability of the spine in the sagittal plane, whereas the hip’s stability was affected on all anatomical planes. The stability of the ankles and knees, however, was not significantly affected by progressing fatigue. This suggests that late-fatigue conditions are associated with more unstable lifting-lowering. Interestingly, no significant interaction was observed between chronic low back pain and fatigue on the stability of the joints. Hip stability was slightly compromised in the CLBP population on the frontal and transverse planes, but not on the sagittal plane. Furthermore, knee and ankle stability was not significantly different between the healthy and CLBP populations during early- and late-fatigue conditions.
In conclusion, the authors showed that both healthy and chronic low back pain patients showed decreased stability of the spine and hip with fatigue progression. The researchers reason that this is likely due to muscle fatigue; however, this was not objectively measured. Furthermore, knee and ankle stability was unaffected despite progressing fatigue. The authors argue that this is likely because participants are altering their joint control strategies as a pain-reducing mechanism. Moving forward, researchers should investigate whether different lifting techniques affect joint stability. This increased understanding of the underlying mechanisms of fatigue, chronic low back pain, and motor impairment can help physiotherapists to develop more effective program strategies and methods.
Reference
- Asgari N, Sanjari MA, Esteki A. Local dynamic stability of the spine and its coordinated lower joints during repetitive lifting: Effects of fatigue and chronic low back pain. Hum Mov Sci. 2017;54:339-346. doi:10.1016/j.humov.2017.06.007
