Athletics
Currently there is great interest in the relation between nutrition and sports and physical fitness; nutritionists, physicians, and trainers are exchanging ideas and studying the nutritional implications of various types of physical activity associated with different sports. One area of common interest has been muscle physiology and the metabolic processes within muscle cells. Muscles are made up of many filamentous cells or fibers. Each cell contains many nuclei lying between the cell membrane (sarcolemma) and the cytoplasm (sarcoplasm). Embedded in the sarcoplasm and running the entire length ofthe cell are many fine fibers called myofibrils. Within each myofibril are long parallel rows of contractile proteins, actin, and myosin. The smallest contractile unit in a myofibril is called a sarcomere. During muscle contraction, brought about by the release of acetylcholine at the synapse of the neuromuscular junction, actin filaments slide into spaces between myosin filaments, pulling in the ends ofthe sarcomere. Cell membrane permeabilit:· to sodium and calcium is increased, and potassium leaks out of the cell. Immediately after this contraction acetylcholinesterase breaks dovm the acetylcholine, readying the muscle for reactivation.
ATP (adenosine triphosphate) is the source of energy for the actin-myosin contractile process. Both glucose ane fatty acids are metabolized in the muscle cell to produce the ATP. The proportion of each depends on the metabolic state and nutrient supply to the muscle, the type of physical exercise, and the type of muscle cell. After a meal when plenty of glucose is available, it is taken up by the muscle cell in quantity, both
'erted to glycogen and, along with fatty acids, used to uce ATP. In the postabsorptive state when blood cose levels drop, more fatty acid is taken into the cell and oxidized at the same time glucose uptake and utilization decrease.
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Currently there is great interest in the relation between nutrition and sports and physical fitness; nutritionists, physicians, and trainers are exchanging ideas and studying the nutritional implications of various types of physical activity associated with different sports. One area of common interest has been muscle physiology and the metabolic processes within muscle cells. Muscles are made up of many filamentous cells or fibers. Each cell contains many nuclei lying between the cell membrane (sarcolemma) and the cytoplasm (sarcoplasm). Embedded in the sarcoplasm and running the entire length ofthe cell are many fine fibers called myofibrils. Within each myofibril are long parallel rows of contractile proteins, actin, and myosin. The smallest contractile unit in a myofibril is called a sarcomere. During muscle contraction, brought about by the release of acetylcholine at the synapse of the neuromuscular junction, actin filaments slide into spaces between myosin filaments, pulling in the ends ofthe sarcomere. Cell membrane permeabilit:· to sodium and calcium is increased, and potassium leaks out of the cell. Immediately after this contraction acetylcholinesterase breaks dovm the acetylcholine, readying the muscle for reactivation.
ATP (adenosine triphosphate) is the source of energy for the actin-myosin contractile process. Both glucose ane fatty acids are metabolized in the muscle cell to produce the ATP. The proportion of each depends on the metabolic state and nutrient supply to the muscle, the type of physical exercise, and the type of muscle cell. After a meal when plenty of glucose is available, it is taken up by the muscle cell in quantity, both
'erted to glycogen and, along with fatty acids, used to uce ATP. In the postabsorptive state when blood cose levels drop, more fatty acid is taken into the cell and oxidized at the same time glucose uptake and utilization decrease.
Continue>>
