To examine the relationship between hamstring extensibility by use of the instrumented
straight leg raise; mechanical components of muscle contraction, including muscle
recruitment, passive torque measures of tissue stiffness, and eccentric strength;
and self-reported measures of pain and disability.
Cross-sectional study.
University laboratory.
Twenty-one individuals with chronic nonspecific axial lower back pain and 15 healthy
control subjects.
Instrumented straight leg raise, concentric and eccentric hamstring strength, self-reported
measures of pain, disability, fear avoidance, general health and well-being
Objective measures included hamstring extensibility, hamstring muscle stiffness, absolute
and relative concentric/eccentric strength, concentric/eccentric strength ratios.
Self-reported measures included Oswestry disability index, visual analog pain scale,
fear avoidance beliefs, and general health and well being.
Patients with lower back pain had lower range of motion, greater changes in muscle
stiffness, and impaired concentric-to-eccentric strength levels. Stepwise regression
identified measures of stiffness as significantly predicting hamstring extensibility
(adjusted r(2) = 0.58, F = 23.76, P < .001). Self-reported measures were not associated
with extensibility. Gender differences were noted for passive stiffness and absolute
strength. For women, later onset of the medial hamstrings also was associated with
greater hamstring extensibility.
Decreased extensibility of the hamstrings was associated with increased passive stiffness
during the common range of motion (20 to 50 degrees ). Impaired stretch tolerance
is associated with actual mechanical restriction, not behavioral measures indicating
increased pain or fear-avoidant behavior. With no relationship to actual disability
and contradictory findings in the literature for the relationship of the hamstrings
to the mechanics of the low back, it is unclear whether decreased hamstring extensibility
should be targeted in rehabilitation programs for axial lower back pain.