Beyond Hamstring Shortness: Continuous Flexibility Is Associated With Balance and Stability but Not Sensory...

Area of Science:

• Biomechanics and Motor Control
• Human Movement Science
• Musculoskeletal Health

Background:

• Hamstring flexibility's potential impact on postural control and lower extremity function is recognized.
• The relationship between hamstring flexibility and specific motor versus sensory components of postural control requires clarification.
• Previous reliance on categorical flexibility measures may obscure functional associations.

Purpose of the Study:

• To investigate the associations between hamstring flexibility and various components of postural control in healthy young adults.
• To determine if hamstring flexibility is more strongly related to motor or sensory aspects of postural control.
• To examine the utility of analyzing flexibility as a continuous variable for functional performance studies.

Main Methods:

• Cross-sectional observational study involving 70 healthy young adults.
• Hamstring flexibility assessed via the sit-and-reach test.
• Postural control evaluated using the Y Balance Test (dynamic balance), Biodex Overall Stability Index (postural stability), joint position sense (proprioception), and two-point discrimination (tactile acuity).

Main Results:

• No significant group differences in dynamic balance, postural stability, proprioception, or tactile acuity between those with and without hamstring shortness.
• Hamstring flexibility positively correlated with right-limb Y Balance Test composite score (r = 0.298, p = 0.012) and negatively with Biodex Overall Stability Index (r = -0.241, p = 0.044).
• Hamstring flexibility independently predicted dynamic balance performance (B = 0.557, p = 0.002) in multiple linear regression.

Conclusions:

• Increased hamstring flexibility is associated with enhanced dynamic balance and better postural stability in healthy young adults.
• No robust associations were found between hamstring flexibility and sensory measures of postural control (proprioception, tactile acuity).
• Analyzing flexibility as a continuous variable revealed significant functional associations, suggesting its value over categorical approaches.