Exercise Responses to Gravity-Independent Flywheel Aerobic and Resistance Training.

BACKGROUND: Although several exercise systems have been developed to mitigate the physiological deconditioning that occurs in microgravity, few have the capacity to positively impact multiple physiological systems and still meet the volume/mass requirements needed for missions beyond low Earth orbit. The purpose of this study was to test the gravity-independent Multi-Mode Exercise Device (M-MED) for both resistance (RE) and aerobic (AE) training stimuli. METHODS: Eight men and nine women (mean age 22.0 ± 0.4 yr) completed 5 wk of training on the M-MED: RE 4 × 7 squats 2 d/wk, and AE 4 × 4-min rowing bouts at ∼90% Vo2max 3 d/wk. Pre- and post-training data collection included an aerobic capacity test, MR imaging, strength testing, and vastus lateralis muscle biopsy. RESULTS: Vo2max increased 8%, 3RM strength 18%, and quadriceps femoris cross-sectional area (CSA) 10%. Knee extensor strength increased at all isokinetic speeds tested. Subjects also demonstrated improved fatigue resistance in knee extension. At the cellular and molecular level, the biopsy revealed increases in mixed myofiber CSA (13%), citrate synthase activity (26%), total RNA concentration (24%), IGF-I mRNA (77%), and Type IIa myosin heavy chain (MHC) mRNA (8%), and a concomitant decrease in Type IIx MHC mRNA (-23%). None of the changes were gender-specific. DISCUSSION: Both the functional outcomes and biomarker changes indicate that a very low volume of M-MED exercise results in robust adaptation in the cardiovascular and musculoskeletal systems. The M-MED has the potential to provide a wide range of countermeasure exercises and should be considered for testing in ground-based spaceflight simulation.

Opioids protect against substantia nigra cell degeneration under conditions of iron deprivation: a mechanism of possible relevance to the Restless Legs Syndrome (RLS) and Parkinson's disease.

Hypofunction of the endogenous opioid, dopamine and iron systems are implicated in the pathogenesis of Restless Legs Syndrome (RLS). Therefore, we probed the interrelationship of these 3 systems in an in vitro model. Cell cultures of the substantia nigra (SN) of Sprague-Dawley rats were established and the cells were determined to be primarily dopaminergic. The numbers of cells surviving under different concentrations of the iron chelator desferoxamine were reduced in a concentration and time dependent manner (p<0.01 at day 10, n=19). The cell death was determined to be apoptotic and DNA analysis revealed that 48-hour 100 µM desferoxamine exposure caused DNA fragmentation of the cells. Pre-administration of the δ-opioid peptide [D-Ala2, D-Leu5]Enkephalin (DADLE) significantly protected the SN cells from damage by iron deficiency (n=6, p<0.01). Our previous studies indicate that the DNA-damage induced apoptosis family gene P53 is activated in this model and that pre-exposure to DADLE prevents this activation. The implications of this model are that in RLS patients with iron deficiency, dopaminergic system dysfunction may result and an intact endogenous opioid system or opioid treatment may protect the dopamine system from dysfunction. Implications of this model for Parkinson's Disease are also briefly discussed.