Jogging kinematics after lumbar paraspinal muscle fatigue.

CONTEXT Isolated lumbar paraspinal muscle fatigue causes lower extremity and postural control deficits. OBJECTIVE To describe the change in body position during gait after fatiguing lumbar extension exercises in persons with recurrent episodes of low back pain compared with healthy controls. DESIGN Case-control study. SETTING Motion analysis laboratory. PATIENTS OR OTHER PARTICIPANTS Twenty-five recreationally active participants with a history of recurrent episodes of low back pain, matched by sex, height, and mass with 25 healthy controls. INTERVENTION(S) We measured 3-dimensional lower extremity and trunk kinematics before and after fatiguing isometric lumbar paraspinal exercise. MAIN OUTCOME MEASURE(S) Measurements were taken while participants jogged on a custom-built treadmill surrounded by a 10-camera motion analysis system. RESULTS Group-by-time interactions were observed for lumbar lordosis and trunk angles (P < .05). A reduced lumbar spine extension angle was noted, reflecting a loss of lordosis and an increase in trunk flexion angle, indicating increased forward trunk lean, in healthy controls after fatiguing lumbar extension exercise. In contrast, persons with a history of recurrent low back pain exhibited a slight increase in spine extension, indicating a slightly more lordotic position of the lumbar spine, and a decrease in trunk flexion angles after fatiguing exercise. Regardless of group, participants experienced, on average, greater peak hip extension after lumbar paraspinal fatigue. CONCLUSIONS Small differences in response may represent a necessary adaptation used by persons with recurrent low back pain to preserve gait function by stabilizing the spine and preventing inappropriate trunk and lumbar spine positioning.