Microgravity and inactivity due to prolonged
bed rest have been shown to result in
atrophy of spinal extensor muscles such as the multifidus, and either no
atrophy or
hypertrophy of flexor muscles such as the abdominal group and psoas muscle. These effects are long-lasting after
bed rest and the potential effects of rehabilitation are unknown. This two-group intervention study aimed to investigate the effects of two rehabilitation programs on the recovery of lumbo-pelvic musculature following prolonged
bed rest. 24 subjects underwent 60 days of head down tilt
bed rest as part of the 2nd Berlin
BedRest Study (BBR2-2). After
bed rest, they underwent one of two exercise programs, trunk flexor and general strength (TFS) training or specific motor control (SMC) training. Magnetic resonance imaging of the lumbo-pelvic region was conducted at the start and end of
bed rest and during the recovery period (14 and 90 days after re-ambulation). Cross-sectional areas (CSAs) of the multifidus, psoas, lumbar erector spinae and quadratus lumborum muscles were measured from L1 to L5. Morphological changes including disc volume, spinal length,
lordosis angle and disc height were also measured. Both exercise programs restored the multifidus muscle to pre-
bed-rest size, but further increases in psoas muscle size were seen in the TFS group up to 14 days after
bed rest. There was no significant difference in the number of
low back pain reports for the two rehabilitation groups (p=.59). The TFS program resulted in greater decreases in disc volume and anterior disc height. The SMC training program may be preferable to TFS training after
bed rest as it restored the CSA of the multifidus muscle without generating potentially harmful compressive forces through the spine.