Browsing by Subject "Resistance Training"
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Item Concurrent Exercise and the Potential Role of Aquatic Treadmill Running for Promoting Rather than Impeding Skeletal Muscle Growth and Strength Development(2014-06-02) Lambert, Bradley StewartThe preservation of skeletal muscle mass, strength, and aerobic capacity have been demonstrated to be essential for maintaining one?s health, preventing a wide range of cardio-metabolic diseases, and improving quality of life. Therefore, the American College of Sports Medicine prescribes a combination of both aerobic and resistance exercise for promoting optimal health. However, previous investigators have reported that aerobic training may interfere with skeletal muscle hypertrophy and strength development when performed concurrently with resistance training as opposed to performing resistance training in isolation. Within skeletal muscle, this interference has been hypothesized to occur as a result of competing intracellular factors within skeletal muscle which are regulated by energy balance, insulin signaling, and contractile activity. However, due to inconsistencies in the literature with regards to exercise mode, frequency, intensity, training volume, and subject population, certainty about exercise interference remains unclear. Recent findings from our laboratory indicate that aquatic treadmill (ATM) running, unlike standard land treadmill (LTM) running, may enhance rather than impede skeletal muscle growth and strength while additionally providing aerobic benefits. In the investigation presented herein, we examined the exercise-induced adaptations to 12 weeks of concurrent resistance and ATM training (RT-ATM), concurrent resistance and land LTM training (RT-LTM), and resistance training (RT) alone in previously untrained subjects. Additionally, we utilized isotope labeling to analyze the acute effects of each on myofibrillar fractional synthesis rates. From our available tissue samples, we also elected to measure chronic alterations in the content of signaling proteins hypothesized to play a role in exercise interference: protein kinase B (Akt), mammailian target of rapamycin (mTOR), and tuberous sclerosis complex 2 (TSC2) content. Compared to RT and RT-LTM, concurrent RT-ATM exercise was found to enhance myofibrillar fractional synthesis when performed immediately following resistance exercise in the untrained state. These findings were concomitant with greater increases in lean mass and muscular strength following 12 weeks of training. Interestingly, RT-LTM training was found to yield greater reductions in fat mass than RT or RT-ATM training. Neither RT-LTM nor RT-ATM training was found to experience interference with strength or hypertrophy compared to the RT group. The results of this investigation challenge the view that training for both strength and endurance are universally incompatible. They also highlight the importance of exercise mode selection when prescribing exercise programs for specific health or performance outcomes. In combination with RT, the novel use of ATM running may benefit those who desire to preserve strength and muscle mass while also promoting aerobic fitness.Item Dietary Cholesterol and Resistance Training as Countermeasures to Accelerated Muscle Loss(2015-12-09) Lee, Teak VengCholesterol plays an important role in physiology, serving as a membrane constituent and steroid hormone precursor. Recently, cholesterol has also been associated with skeletal muscle homeostasis, leading to the purpose of this research, which was to examine the role of cholesterol metabolism during perturbations of skeletal muscle homeostasis. We evaluated skeletal muscle responses and proteins involved in cholesterol metabolism [sterol regulatory element-binding protein-2 (SREBP-2) and low-density lipoprotein-receptor (LDL-R)] under conditions of unloading, exercise and dietary cholesterol (D-CL) administration. We hypothesized that skeletal muscle mass, fractional synthesis rates (FSR), SREBP-2, and LDL-R would be lower in unloaded muscle while exercise and D-CL would have a positive effect. The first study examined the effect of hindlimb unloading (HU) on muscle mass, SREBP-2, and LDL-R. HU animals showed lower muscle mass and a trend towards lower gastrocnemius SREBP-2 than cage controls (CC). The second study examined the effect of D-CL and resistance training (RT) on lean mass, FSR, SREBP-2, and LDL-R in ambulatory rats. Unexpectedly, rats performing exercise without added resistance [(RT-Control (RTC)] had greater lean mass responses than the RT groups. However, RT groups had higher plantaris to body mass ratio and FSR than RTC (plantaris FSR only) and CC (both variables) animals. RT plus high D-CL administration resulted in greater plantaris FSR than the RT group consuming normal D-CL. Quadriceps SREBP-2 trended towards an increase in response to RT. The third study investigated the effect of D-CL and RT on muscle mass, FSR, SREBP-2, and LDL-R in the context of HU. HU and HU rats performing RT had lower muscle mass than CC. HU rats showed higher liver mature LDL-R than CC but showed a trend towards lower gastrocnemius SREBP-2 than CC. There was no difference in FSR among activity or D-CL groups. These studies show evidence of shifts in content of proteins related to cholesterol metabolism and muscle FSR when muscle activity is manipulated from RT to complete unloading. However, effects such as elevated FSR with RT and high D-CL were not consistent throughout the studies, leaving doubt of the effect of activity on cholesterol metabolism.