title: Short-term exercise training improves diaphragm antioxidant capacity and endurance.
abstract: These experiments tested the hypothesis that short-term endurance exercise training would rapidly improve (within 5 days) the diaphragm oxidative/antioxidant capacity and protect the diaphragm against contraction-induced oxidative stress. To test this postulate, male Sprague-Dawley rats (6 weeks old) ran on a motorized treadmill for 5 consecutive days (40-60 min x day(-1)) at approximately 65% maximal oxygen uptake. Costal diaphragm strips were excised from both sedentary control (CON, n=14) and trained (TR, n=13) animals 24 h after the last exercise session, for measurement of in vitro contraction properties and selected biochemical parameters of oxidative/antioxidant capacity. Training did not alter diaphragm force-frequency characteristics over a full range of submaximal and maximal stimulation frequencies (P > 0.05). In contrast, training improved diaphragm resistance to fatigue as contraction forces were better-maintained by the diaphragms of the TR animals during a submaximal 60-min fatigue protocol (P < 0.05). Following the fatigue protocol, diaphragm strips from the TR animals contained 30% lower concentrations of lipid hydroperoxides compared to CON (P < 0.05). Biochemical analysis revealed that exercise training increased diaphragm oxidative and antioxidant capacity (citrate synthase activity +18%, catalase activity +24%, total superoxide dismutase activity +20%, glutathione concentration +10%) (P < 0.05). These data indicate that short-term exercise training can rapidly elevate oxidative capacity as well as enzymatic and non-enzymatic antioxidant defenses in the diaphragm. Furthermore, this up-regulation in antioxidant defenses would be accompanied by a reduction in contraction-induced lipid peroxidation and an increased fatigue resistance.
authors.affiliation: Department of Exercise and Sport Sciences and Physiology and Center for Exercise and Sports Science, 25 Florida Gym, University of Florida, Gainesville, FL 32611, USA.
authors.forename: H K
authors.initials: HK
authors.lastname: Vincent
authors.forename: S K
authors.initials: SK
authors.lastname: Powers
authors.forename: D J
authors.initials: DJ
authors.lastname: Stewart
authors.forename: H A
authors.initials: HA
authors.lastname: Demirel
authors.forename: R A
authors.initials: RA
authors.lastname: Shanely
authors.forename: H
authors.initials: H
authors.lastname: Naito
mesh_terms: D000818:Animals; D003964:Diaphragm / Q000201:enzymology* / Q000502:physiology; D008054:Lipid Peroxides / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology; D010088:Oxidoreductases / Q000378:metabolism*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013997:Time Factors
chemical_list: D008054:Lipid Peroxides; D013438:Sulfhydryl Compounds; D010088:Oxidoreductases