Optimal cut-off values of the active knee extension test for diagnosing hamstring tightness

Area of Science:

• Biomechanics
• Kinesiology
• Sports Medicine

Background:

• Active Knee Extension (AKE) is a common clinical measure for hamstring muscle length.
• The diagnostic criterion of 'AKE >20°' for hamstring tightness lacks robust scientific validation.

Purpose of the Study:

• To analyze Active Knee Extension (AKE) measurements in relation to sex and exercise participation levels.
• To evaluate the appropriateness of current diagnostic criteria for hamstring tightness.

Main Methods:

• AKE was measured in participants with varying exercise levels, positioned supine with 90° hip and knee flexion.
• Cut-off values for hamstring tightness were calculated using 'mean-1SD', 'mean-2SD', and 'mean-3SD' statistical methods.
• Goniometric measurements assessed maximal knee extension.

Main Results:

• Significant differences in AKE were observed between exercise groups and sexes.
• For healthy adults (Group A), AKE cut-off values (mean-1SD, mean-2SD) were 33.5°/19.7° for males and 28.0°/15.7° for females.
• AKE showed a weak correlation with Body Mass Index, but not with height or weight.

Conclusions:

• Exercise participation level significantly influences Active Knee Extension (AKE) measurements.
• Female participants demonstrated consistently high hamstring flexibility irrespective of their exercise habits.
• The widely accepted AKE cut-off value of >20° may not be a universally suitable criterion for diagnosing hamstring tightness.