Jogging kinematics after lumbar paraspinal muscle fatigue

Journal of Athletic Training, Sept-Oct, 2009 by Joseph M. Hart, D. Casey Kerrigan, Julie M. Fritz, Christopher D. Ingersoll

Low back pain (LBP) remains a significant health care issue, with more than 70% of people in the United States experiencing at least 1 episode during their lifetime. (1) The annual incidence of LBP has been estimated to involve up to 45% of the population, resulting in more than $40 billion in economic costs in the form of medical treatment and lost wages. (2,3) Individuals who want to maintain a healthy lifestyle may be restricted because of recurring and disabling nonspecific LBP. (4) Those who must continue with normal and necessary activities of daily living may choose an adaptive mechanism to preserve function. Some may use an unfavorable adaptive strategy, possibly exposing muscles and joints to injury or long-term degenerative processes. Kinematic changes during activities and gait may help to explain the recurrent nature of LBP.

Poor lumbar extension endurance, measured as the duration of sustained isometric contraction of the lumbar paraspinals muscles (ie, the Biering-Sorensen test), has been identified as a risk factor for developing LBP. (5-7) Similarly, persons with current LBP (8) or a history of LBP (9) exhibit poor lumbar extension endurance compared with controls. Thus, the rate of fatigue in these muscles may be different during exercise in persons with lumbar paraspinal weakness and poor endurance. Research (10-13) using models of isolated lumbar paraspinal fatigue recreates a condition of poor core stability in order to study potential adaptations during exercise in controlled settings. The core describes the active and passive structures comprising and providing stability to the lumbo-pelvic-hip complex. (14)

Isolated lumbar paraspinal fatiguing exercise has been used to compare postural control and neuromuscular response in healthy persons and in those with recurrent LBP. (10-13) In healthy persons, similar localized lumbar paraspinal fatigue resulted in deteriorated postural sway and caused participants to exhibit a forward-flexed position while standing (10,13) Recreationally active persons with recurrent LBP and healthy controls experienced reduced quadriceps voluntary activation (11,12) after isolated lumbar paraspinal fatiguing exercise. Isolated lumbar paraspinal fatigue may cause kinematic adaptations during jogging gait that may affect persons with recurrent LBP differently than uninjured individuals. Difficulty maintaining appropriate positioning and stability of the trunk as a result of excessive fatigue may affect lower extremity joints during activities and may help to describe lower extremity injury risk in persons with poor core and trunk stability.

Therefore, the purpose of our study was to compare 3-dimensional trunk and lower extremity joint kinematics during jogging gait before and after lumbar paraspinal fatiguing exercise in persons with a history of recurrent episodes of LBP and controls.

METHODS

A 2 x 2 repeated-measures, time-series design (pretest, posttest) with static group comparison was used to compare lower extremity and trunk kinematics during jogging gait after fatiguing isometric lumbar extension exercise. The independent variables were group (history of LBP, control) and time (baseline, post-fatiguing exercise set). The dependent variables were peak sagittal-plane, frontal-plane, and transverse-plane angles of the knee, hip, lumbar spine, and trunk during the loading phase of jogging.

Twenty-five participants with a history of recurrent LBP, including 12 females (age = 22.3 [ or -] 2.7 years, height = 169.2 [ or -] 6.5 cm, mass = 64.5 [ or -] 6.2 kg) and 13 males (age = 22.9 [ or -] 3.5 years, height = 183.4 [ or -] 7.8 cm, mass = 83.5 [ or -] 11.8 kg), were matched for sex, height, and mass with 12 healthy females (age = 20.8 [ or -] 1.0 years, height = 169.5 [ or -] 7.2 cm, mass = 64.6 7.3 kg) and 13 healthy males (age = 24.5 4.5 years, height = 182.4 [ or -] 6.1 cm, mass = 81.8 [ or -] 11.0 kg). All volunteers provided informed consent before participating. This study was approved by our university's institutional review board.

All participants were recreationally active, had healthy knees (no current pain, no history of knee injury or surgery), and denied history of lower extremity surgery or recent injury (within 6 months). Volunteers were excluded from participating if they reported a history of intervertebral disc injury, cancer, neurologic injury, or radicular symptoms in the lower extremity; vertebral fracture; or spine surgery. The group with recurrent LBP group consisted of persons who met the above inclusion criteria but reported at least 3 LBP episodes within the past 3 years or at least 5 LBP episodes in their lifetime. An episode was defined as LBP sufficient to impose limitations or modifications to daily activities, (11,12) Persons in the control group reported never having had LBP.

Instruments

Joint angles were calculated during jogging gait with a 10-camera motion analysis system (model 624; Vicon Motion Systems Inc, Lake Forest, CA) in conjunction with a multiaxis strain gauge force plate embedded beneath the moving belt of a custom-built treadmill (AMTI; Watertown, MA) (Figure 1). Force and video were sampled at 120 Hz.