title: Artificial gravity as a countermeasure to microgravity: a pilot study examining the effects on knee extensor and plantar flexor muscle groups.
abstract: The goal of this project was to examine the effects of artificial gravity (AG) on skeletal muscle strength and key anabolic/catabolic markers known to regulate muscle mass. Two groups of subjects were selected for study: 1) a 21 day-bed rest (BR) group (n = 7) and 2) an AG group (n = 8), which was subjected to 21 days of 6 degrees head-down tilt bed rest plus daily 1-h exposures to AG (2.5 G at the feet). Centrifugation was produced using a short-arm centrifuge with the foot plate approximately 220 cm from the center of rotation. The torque-velocity relationships of the knee extensors and plantar flexors of the ankle were determined pre- and posttreatment. Muscle biopsy samples obtained from the vastus lateralis and soleus muscles were used for a series of gene expression analyses (mRNA abundance) of key factors implicated in the anabolic vs. catabolic state of the muscle. Post/pre torque-velocity determinations revealed greater decrements in knee extensor performance in the BR vs. AG group (P < 0.04). The plantar flexors of the AG subjects actually demonstrated a net gain in the torque-velocity relationship, whereas in the BR group, the responses declined (AG vs. BR, P < 0.001). Muscle fiber cross-sectional area decreased by approximately 20% in the BR group, whereas no losses were evident in the AG group. RT-PCR analyses of muscle biopsy specimens demonstrated that markers of growth and cytoskeletal integrity were higher in the AG group, whereas catabolic markers were elevated in the BR group. Importantly, these patterns were seen in both muscles. We conclude that paradigms of AG have the potential to maintain the functional, biochemical, and structural homeostasis of skeletal muscle in the face of chronic unloading.
authors.affiliation: Dept. of Orthopaedics, College of Health Sciences, Univ. of California, Irvine, CA 92697, USA. vjcaiozz@uci.edu
authors.forename: V J
authors.initials: VJ
authors.lastname: Caiozzo
authors.forename: F
authors.initials: F
authors.lastname: Haddad
authors.forename: S
authors.initials: S
authors.lastname: Lee
authors.forename: M
authors.initials: M
authors.lastname: Baker
authors.forename: William
authors.initials: W
authors.lastname: Paloski
authors.forename: K M
authors.initials: KM
authors.lastname: Baldwin
mesh_terms: D000328:Adult; D001510:Bed Rest / Q000009:adverse effects; D005080:Exercise Test; D015870:Gene Expression; D018470:Gravity, Altered; D018475:Head-Down Tilt; D006801:Humans; D007717:Knee / Q000033:anatomy & histology / Q000502:physiology; D007866:Leg / Q000033:anatomy & histology / Q000502:physiology; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology*; D009133:Muscular Atrophy / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D020966:Muscular Disorders, Atrophic / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism; D010865:Pilot Projects; D012333:RNA, Messenger / Q000378:metabolism; D016059:Range of Motion, Articular; D014893:Weightlessness / Q000009:adverse effects*; D018544:Weightlessness Countermeasures; D018474:Weightlessness Simulation
chemical_list: D012333:RNA, Messenger; D018995:Myosin Heavy Chains