Abstract
Objective: To compare active hamstring stiffness in female subjects with and without a history of low back pain (LBP) after a standardized 20-min aerobic-exercise session. Design: Case control. Setting: Laboratory. Participants: 12 women with a history of recurrent episodes of LBP (age = 22.4 ± 2.1 y, mass = 67.1 ± 11.8 kg, height = 167.9 ± 8 cm) and 12 matched healthy women (age = 21.7 ± 1.7 y, mass = 61.4 ± 8.8 kg, height = 165.6 ± 7.3 cm). LBP subjects reported an average 6.5 ± 4.7 on the Oswestry Disability Index. Interventions: Participants walked at a self-selected speed (minimum 3.0 miles/h) for 20 min. The treadmill incline was raised 1% grade per minute for the first 15 min. During the last 5 min, participants adjusted the incline of the treadmill so they would maintain a moderate level of perceived exertion through the end of the exercise protocol. Main Outcome Measures: During session 1, active hamstring stiffness, hamstring and quadriceps isometric strength, and concurrently collected electromyographic activity were recorded before and immediately after the exercise protocol. For session 2, subjects returned 48-72 h after exercise for repeat measure of active hamstring stiffness. Results: Hamstring active stiffness (Nm/rad) taken immediately postexercise was not significantly different between groups. However, individuals with a history of recurrent LBP episodes presented significantly increased hamstring stiffness 48-72 h postexercise compared with controls. For other outcomes, there was no group difference. Conclusions: Women with a history of recurrent LBP episodes presented greater active hamstring stiffness 48-72 h after aerobic exercise.