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Low back pain (LBP) is a widespread musculoskeletal condition caused by various pathologies, including peripheral nervous system dysfunction, resulting in stiffness, reduced strength, and compromised neuromuscular control. Therefore, this study aimed to evaluate the influence of single-leg radicular pain on hamstring biomechanics in young adults without significant concurrent lower back symptoms while investigating the association between the functional outcome and muscle biomechanical properties.

This cross-sectional study included two groups: young adults with lower limb radicular pain (RAD, n = 15) and age-matched healthy asymptomatic individuals (CON, n = 15). Clinical characteristics were assessed using the Oswestry disability index (ODI), the numeric pain rating scale (NPRS), and the passive straight leg raise (PSLR) test. Myometric muscle analysis of the biceps femoris and semitendinosus muscles was conducted using the MyotonPRO® device, focusing on mechanical and viscoelastic properties such as frequency, stiffness, relaxation time, decrement, and creepability.

The RAD group showed around 14% higher stiffness on the symptomatic side compared to the CON group (p = 0.003), while relaxation time and creepability were by approximately 14% (p = 0.008) and 13% (p = 0.01) lower, respectively. Similarly, the RAD group exhibited approximately 13% higher stiffness on the asymptomatic side compared to the CON group (p = 0.02).

In conclusion, the biomechanical properties of the hamstrings – particularly stiffness, relaxation time, and creepability of the biceps femoris on the symptomatic side – may significantly impact pain management in individuals with radicular pain. Moreover, stiffness of the biceps femoris could be an important predictor of functional outcomes in younger adults.

Figure 1. Myoton device appliance within semitendinosus muscle (A) and biceps femoris muscle (B).

Keywords: pain, biomechanics, sciatica, myometric analysis

The results of this study reveal that in young individuals with single-leg radicular pain, the biomechanical and viscoelastic properties of the hamstring undergo changes due to neurodynamic disorders, even when no local lower back pain is evident. Notably, stiffness and relaxation time are pivotal factors in this context. This knowledge significantly enriches our understanding of this pathology. It suggests that when strategizing treatments, we must adopt a broader perspective since myometric changes are evident on both sides. Moreover, stiffness in the biceps femoris of the symptomatic leg could be a critical indicator of functional outcomes in younger adults. These insights have profound clinical implications, guiding practitioners in their treatment approach. Consequently, patients should be viewed as having a bilateral disorder, even if symptoms only manifest on one side during initial stages. Following this, interventions that incorporate two-sided or central neural techniques might be more effective. While our findings are promising, they would benefit from validation through a study with a more extensive sample size to extend our knowledge of this condition.