RESULTS The physiological effects of stretches may contribute to reducing discomfort and pain .
However , if other measures are not in place to remediate their causes , stretches may suppress awareness of risks , result ing in more debilitating injuries .
If inadequately performed , stretches may also cause or aggravate injuries .
The studies provided mixed findings , but demonstrated some beneficial effect of stretching in preventing work-related musculoskeletal disorders .
OBJECTIVE This article review ed the literature to clarify the physiological effects and benefits of , and misconceptions about , stretches used to reduce musculoskeletal disorders .
Mechanical and physical responses to stretching with and without preisometric contraction in human skeletal muscle.
OBJECTIVE To examine electromyography ( EMG ) activity , passive torque , and stretch perception during static stretch and contract-relax stretch . DESIGN Two separate r and omized crossover protocol s : ( 1 ) a constant angle protocol on the right side , and ( 2 ) a variable angle protocol on the left side . SUBJECTS 10 male volunteers . INTERVENTION Stretch-induced mechanical response in the hamstring muscles during passive knee extension was measured as knee flexion torque ( Nm ) while hamstring surface EMG was measured . Final position was determined by extending the knee to an angle that provoked a sensation similar to a stretch maneuver . Constant angle stretch : The knee was extended to 10 degree below final position , held 10sec , then extended to the final position and held for 80 sec. Variable angle stretch : The knee was extended from the starting position to 10 degrees below the final position , held 10sec , then extended to the onset of pain . Subjects produced a 6-sec isometric contraction with the hamstring muscles 10 degrees below the final position in the contract-relax stretch , but not in the static stretch . MAIN OUTCOME MEASURES Passive torque , joint range of motion , velocity , and hamstring EMG were continuously recorded . RESULTS Constant angle contract-relax and static stretch did not differ in passive torque or EMG response . In the final position , passive torque declined 18 % to 21 % in both contract-relax and static stretch ( p<.001 ) , while EMG activity was unchanged . In the variable angle protocol , maximal joint angle and corresponding passive torque were significantly greater in contract-relax compared with static stretch(p<.01 ) , while EMG did not differ . CONCLUSION At a constant angle the viscoelastic and EMG response was unaffected by the isometric contraction . The variable angle protocol demonstrated that PNF stretching altered stretch perception
RESULTS The physiological effects of stretches may contribute to reducing discomfort and pain .
However , if other measures are not in place to remediate their causes , stretches may suppress awareness of risks , result ing in more debilitating injuries .
If inadequately performed , stretches may also cause or aggravate injuries .
The studies provided mixed findings , but demonstrated some beneficial effect of stretching in preventing work-related musculoskeletal disorders .
OBJECTIVE This article review ed the literature to clarify the physiological effects and benefits of , and misconceptions about , stretches used to reduce musculoskeletal disorders .