Browsing by Subject "Resistance exercise"
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Item The effects of carbohydrate and HMB supplementation on glycogen synthesis post-exercise(2013-08) Choi, Ran Hee; Farrar, Roger P.Carbohydrate plus additional protein supplementation provided immediately after exercise has been found to increase the rate of muscle glycogen restoration compared to carbohydrate alone. To examine whether leucine, and/or β-hydroxy-β-methylbutyrate (HMB) to carbohydrate plus protein supplementation affects short-term recovery (45 min) of muscle glycogen, we compared plasma glucose and insulin, the muscle glycogen concentration, and the cellular signaling proteins controlling muscle glycogen synthesis 45 min after supplementation. Rats (n=35) underwent high-intensity resistance exercise followed by supplementation with carbohydrate (CHO: 1.2g/kg body weight), carbohydrate with whey protein (CP: 1.2g CHO + 375mg whey protein/kg body weight), carbohydrate with whey protein plus HMB (CPH: 1.2g CHO + 375mg whey protein + 400mg HMB/kg body weight), carbohydrate with whey protein, HMB plus leucine (CPHL: 1.2g CHO + 375mg whey protein + 400mg HMB + 444mg leucine/kg body weight) or exercise only (CON). Blood samples were collected immediately after exercise and 45 min after supplementations. Muscle samples of plantaris were excised immediately and 45 min post-exercise. Plasma glucose was increased by CHO and CPH supplementation and reduced by CPHL at 45 min post-exercise. Plasma insulin was elevated by CP and CPHL treatments compare to CHO. Muscle glycogen concentration was unaffected by all treatments and did not differ from CON. Phosphorylation of Akt/PKB, GSK3α/β, and GS at 45 min of recovery for all supplements was not significant difference from CON. Phosphorylation of mTOR was significantly increased by CPHL and CP supplementation compared to CON, CHO, and CPH. Phosphorylation of AS160 was markedly reduced by CPH supplementation compared to CON. These results suggest that supplementing with carbohydrate plus protein with or without leucine and its metabolite, HMB, to enhance muscle glycogen replenishment following exercise may not provide an advantage during the early phase of recovery (45 min). Furthermore, there is some indication that HMB may elicit insulin resistance, and this needs further evaluation.Item New models of regenerating VML injured rat skeletal muscle : single muscle fiber injection and resistance exercise(2015-12) Song, Taejeong, 1978-; Farrar, Roger P.; Baker, Aaron; Castelli, Darla M; Suggs, Laura; Brothers, Robert Matt; Thompson, WesleyVolumetric muscle loss (VML) is a traumatic soft tissue injury that is common in recent battle fields and causes permanent losses of muscle mass and function in affected muscle. Since a new VML injury model has been developed in our lab which defects large mass of rat lateral gastrocnemius (LGAS), several sources of extracellular matrix (ECM) and stem cells including adipose tissue derived stem cells and mesenchymal stem cells have been utilized to enhance the regeneration of defected muscle. In the current study, regenerative effects of resistance exercise and satellite cells injection after the VML injury were tested. Satellite cells transplanted via single muscle fiber injection significantly enhanced generation of a specific force of defected muscle possibly via suppressing fibrotic tissue build-up and inducing significant hypertrophy of regenerating muscle at the sites of injury. However it did not increase muscle mass and tetanic force of the defected LGAS. Resistance exercise intervention after the injury improved all morphological and functional recoveries. Defected muscle mass and functions (tetanic and specific forces) were significantly increased in the resistance exercised group compared to the non-exercised. Cross sectional area (CSA) of mature and regenerating muscle fibers in injured muscle were also significantly increased by the resistance training. Single muscle fiber injection with resistance exercise did not further increase muscle mass or functions, but it had an impact on decreasing accumulation of the non-functional (fibrotic tissue and residual injured) area. These results indicate that resistance exercise is a great rehabilitative intervention after traumatic muscle injury to enhance muscle mass and function with or without satellite cells injection.Item Stiffening of the extracellular matrix in skeletal muscle of aged rats and the effect on muscle fiber mechanotransduction(2011-08) Eklund, Kyrstin; Domire, Zachary; Hart, Melanie A.; Park, YoonjungSarcopenia is a growing problem and will continue as the aging population of the United States increases. Reduced adaptation of elderly skeletal muscle to exercise is likely to contribute to sarcopenia. The mechanism by which response to exercise is reduced is unclear, but altered mechanotransduction could be occurring. The extracellular matrix of muscle become stiffer with age and this could impair normal mechanotransduction. This could impair elderly individuals from responding to exercise programs, but may also contribute to strength loss. It was hypothesized that age, muscle stiffness, and glycation would be significant predictors of gene expression, and that muscle stiffness would best predict gene expression. Male Fisher Brown Norway hybrid rats aged 6 to 37 months completed 3 sets of 10 concentric contractions of the dorsiflexor muscles on a rat dynamometer through stimulation of the peroneal nerve. Rats were sacrificed eight hours post exercise, and the tibialis anterior and extensor digitorum longus muscles of both hindlimbs were excised. A significant inverse relationship was found between age and myogenin gene expression (myogenin = -0.502*(age) + 2.180, p=0.012). An interesting finding was that muscle stiffness of elderly rats was highly variable with five out of eleven old rats far outside the normal range. While muscle stiffness was not shown to be a significant predictor of response to exercise, this could have been from the generally small response. Future studies should investigate higher intensity exercise or more sensitive measures of response.Item The effects of carbohydrate and amino acids on muscle protein synthesis after acute resistance exercise and muscle adaptation following chronic resistance training(2016-05) Wang, Wanyi; Farrar, Roger P.; Ivy, John, 1945-; Brothers, Robert M; Wilcox, Richard E; Jolly, Christopher A; Bray, Molly SResistance exercise (RE) is purported to induce muscle protein accretion primarily by stimulating muscle protein synthesis (MPS), with its effect potentiated by providing a protein or amino acid (AA) supplement post exercise. Glutamine, a conditionally essential AA, is increasingly recommended to improve exercise performance, but it is poorly soluble and unstable in sports drinks. This limitation can be overcome by combining L-glutamine with L-alanine to form a dipeptide (AlaGln). The first study demonstrated that AlaGln supplementation post resistance exercise significantly reduced the phosphorylation of AMPK and NF-kB p65 without activating intracellular signals for MPS. This study also showed that whey protein (WP) activated the mTOR signaling pathways without affecting signaling proteins that controls muscle protein breakdown (MPB). The results provide indirect evidence that AlaGln blocks MPB via suppressing the activation of AMPK-FOXO3A and NF-kB p65, while WP promotes MPS. Recent research suggests that adding carbohydrate (CHO) to a protein supplement post exercise can produce greater protein accretion and subsequently increase the magnitude of resistance training adaptation relative to protein supplementation alone. Early studies from our laboratory found that co-ingestion of CHO and protein, as compared with CHO or protein intake individually, had a greater effect on the activation of anabolic signaling proteins. However, the effect of CHO plus protein on MPS and muscle adaptation is controversial. The second study demonstrated that adding CHO to a protein supplement (CP) accelerated MPS via activating the mTOR-signaling pathway in comparison with placebo (PLA) and WP during early exercise recovery, but CP did not affect signaling proteins that regulate MPB. The third study found that CP enhanced muscle strength relative to PLA and WP. The greater strength development in CP appeared due to increased myofibrillar protein content. Increased muscle hypertrophy occurred without an increase in myonuclei suggesting satellite cell activation was not required for muscle fiber development. Taken together, the results of this series of studies suggest that 1) AlaGln inhibits MPB following acute RE; 2) Adding CHO to a protein supplement accelerates muscle recovery by stimulating MPS, and increases the magnitude of muscle strength by accumulating more myofibrillar protein in comparison with PLA and WP.