WISE 2005: Aerobic and resistive countermeasures prevent paraspinal muscle deconditioning during 60-days bed rest in women

Microgravity-induced lumbar paraspinal muscle deconditioning may contribute to back pain commonly experienced by astronauts, and may increase the risk of postflight injury. We hypothesized that a combined resistance and aerobic exercise countermeasure protocol that included spinal loading would mitigate lumbar paraspinal muscle deconditioning during 60-days of bed rest in women. METHODS: Sixteen women underwent 60-day, 6° head-down-tilt bed rest and were randomized into control and exercise groups. During bed rest, the control group performed no exercise. The exercise group performed supine treadmill exercise within lower body negative pressure (LBNP) for 3-4 d/wk and flywheel resistive exercise for 2-3 d/wk. Paraspinal muscle cross-sectional area (CSA) was measured using a lumbar spine MRI sequence before and after bed rest (BR). In addition, isokinetic spinal flexion and extension strengths were measured before and after BR. Data are presented as mean ± SD. RESULTS: Total lumbar paraspinal muscle CSA decreased significantly more in controls (10.9 ± 3.4%) than in exercisers (4.3 ± 3.4%; p <0.05). The erector spinae was the primary contributor (76%) to total lumbar paraspinal muscle loss. Moreover, exercise attenuated isokinetic spinal extension loss (-4.3 ± 4.5%), as compared to controls (-16.6 ± 11.2%; p <0.05). CONCLUSIONS: LBNP treadmill and flywheel resistive exercises during simulated microgravity mitigates decrements in lumbar paraspinal muscle structure and spine function. Therefore, space flight exercise countermeasures that attempt to reproduce spinal loads experienced on Earth may mitigate spinal deconditioning during long-duration space travel.

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