Fatty acid oxidation can contribute 50 to 60 per cent of the energy expenditure during a bout of low intensity exercise of long duration. Strenuous submaximal exercise requiring 65 to 80 per cent of VO2 max will utilize less fat 10 to 45 per cent of the energy expended. Exercise training is accompanied by metabolic adaptations that occur in skeletal muscle and adipose tissue and that facilitate a greater delivery and oxidation of fatty acids during exercise.
The trained state is characterized by an increased flux of fatty acids through smaller pools of adipose tissue energy. The "CP" stands for creatine phosphate , a naturally occurring compound that enables short bursts of energy. The ATP-CP pathway supplies about 10 seconds worth of energy and is used for short bursts of exercise, such as a meter sprint. This pathway first uses up any ATP stored in the muscle about 2 to 3 seconds worth.
Glycolysis is both an anaerobic and anaerobic system which creates ATP exclusively from carbohydrates, with lactic acid being a byproduct. Anaerobic glycolysis provides energy by the partial breakdown of glucose without the need for oxygen.
Glycolosis is considered both an aerobic and anaerobic pathway. This process produces energy for short, high-intensity bursts of activity lasting no more than several minutes.
After several minutes, the lactic acid build-up reaches a threshold known as the lactate threshold LT. When you reach this threshold, you experience muscle pain, burning, and fatigue, making it difficult to keep exercising at this intensity.
However, training can increase the threshold. Aerobic metabolism fuels most of the energy needed for long duration activity. It uses oxygen to convert macronutrients carbohydrates, fats, and protein to ATP.
This system is a bit slower than the anaerobic systems because it relies on the circulatory system to transport oxygen to the working muscles before it creates ATP. Aerobic metabolism is used primarily during endurance exercise , which is generally less intense and can continue for long periods of time. During exercise, an athlete will move through these metabolic pathways. As exercise begins, ATP is produced via anaerobic metabolism. With an increase in breathing and heart rate, there is more oxygen available and aerobic metabolism begins and continues until the lactate threshold is reached and anaerobic metabolism kicks in again.
Sports nutrition is built upon an understanding of how macronutrients, such as carbohydrates , fat , and protein , contribute to the fuel supply needed by the body to perform. Macronutrients contribute to the process in different ways. Because your body uses different pathways to create energy, and each pathway relies on different macronutrients, it's important to consume fat, carbohydrates, and protein in your diet.
Vitamins and minerals that make up part of enzymes are referred to as coenzymes and cofactors , respectively. Coenzymes and cofactors are required by enzymes to catalyze a specific reaction.
Coenzymes and cofactors are essential in catabolic pathways and play a role in many anabolic pathways too. Thiamine, one of the water-soluble vitamins, is especially important in glucose metabolism. The brain and heart are most affected by a deficiency in thiamine. Thiamine deficiency, also known as beriberi, can cause symptoms of fatigue, confusion, movement impairment, pain in the lower extremities, swelling, and heart failure. It is prevalent in societies whose main dietary staple is white rice.
Dutch physician Dr. Christiaan Eijkman cured chickens of beriberi by feeding them unpolished rice bran in Encyclopedia Brittanica Blog. Eijkman and Hopkins were awarded the Nobel Prize in Physiology or Medicine in for their discoveries in the emerging science of nutrition. There are two forms of beriberi, wet and dry.
Wet beriberi causes edema and heart failure while dry beriberi results in muscle wasting, weakness, and paralysis. Another deficiency syndrome is the Wernicke-Korsakoff syndrome characterized by disorientation, amnesia, jerky eye movements, and staggering gait. It is the third most common dementia in the US and is due to alcohol excess and glucose excess. Excess alcohol intake increases thiamine excretion in the urine.
Thiamine is a water-soluble vitamin, so it is not stored in the body and excess consumption increases its excretion in the urine. Thiamine need is increased with exercise. Whole grains, enriched flour, green leafy vegetables, legumes, and pork are excellent dietary sources of thiamine but you need to select an appropriate cooking method because prolonged cooking and cooking in water will destroy thiamine. The best way to cook thiamine-containing foods is in the microwave or by steaming.
Riboflavin, also a water-soluble vitamin, is an essential component of flavoproteins, which are coenzymes involved in many metabolic pathways of carbohydrate, lipid, and protein metabolism.
Flavoproteins aid in the transfer of electrons in the electron transport chain, thus the production of energy or ATP, and the active form is flavin adenine dinucleotide FAD or flavin mononucleotide FMN. Furthermore, the functions of other B-vitamin coenzymes, such as vitamin B 6 and folate, are dependent on the actions of flavoproteins. Riboflavin deficiency sometimes referred to as ariboflavinosis, is often accompanied by other dietary deficiencies most notably protein and can be common in people that suffer from alcoholism.
Its signs and symptoms are numerous and can include weakness, dry, scaly skin, mouth inflammation and sores, cracks at the corner of the mouth, painful magenta purplish-red tongue, smoothness of the tongue glossitis , sore throat, itchy eyes, and light sensitivity. Alcoholics, people with liver disease, and diabetics are particularly at risk of developing a riboflavin deficiency.
Whole grains, enriched flour products, milk and green leafy vegetables are good sources of this vitamin. Riboflavin is very sensitive to irradiation and UV light, so this is the reason milk is not sold in clear bottles. Cooking does not destroy riboflavin. Niacin is a water-soluble vitamin and is found as nicotinamide niacinamide or nicotinic acid.
NADPH is required for the anabolic pathways of fatty acid and cholesterol synthesis. In contrast to other vitamins, niacin can be synthesized by humans from the amino acid tryptophan in an anabolic process requiring enzymes dependent on riboflavin, vitamin B 6 , and iron.
Niacin is made from tryptophan only after tryptophan has met all of its other needs in the body. The contribution of tryptophan-derived niacin to niacin needs in the body varies widely and a few scientific studies have demonstrated that diets high in tryptophan have very little effect on niacin deficiency. Niacin deficiency is commonly known as pellagra and is characterized by diarrhea, dermatitis, dementia, and sometimes death Video 6.
It is still seen in poor urban US, Africa and Asia. People at risk of developing pellagra are alcoholics, people consuming a low protein diet, and people using drugs used to treat tuberculosis and leukemia. Dietary sources of niacin are whole grains, enriched flour, legumes and protein containing tryptophan such as meat and poultry. Of special note, nicotinic acid in lard amounts is used as a blood cholesterol lowering drug.
Pantothenic acid, another water-soluble vitamin, forms coenzyme A, which is the main carrier of carbon molecules in a cell. Acetyl-CoA is the carbon carrier of glucose, fatty acids, and amino acids into the citric acid cycle Figure 6. Coenzyme A is also involved in the synthesis of lipids, cholesterol, and acetylcholine a neurotransmitter. These essential nutrients are needed regardless of the intensity of activity you are doing.
If you are lying down reading a book or running the the Honolulu Marathon, these macronutrients are always needed in the body. However, in order for these nutrients to be used as fuel for the body, their energy must be transferred into the high energy molecule known as Adenosine Triphosphate ATP. The type of metabolism that is predominately used during physical activity is determined by the availability of oxygen and how much carbohydrate, fat, and protein are used.
Anaerobic metabolism occurs in the cytosol of the muscle cells. As seen in Figure Anaerobic metabolism uses glucose as its only source of fuel and produces pyruvate and lactic acid. Pyruvate can then be used as fuel for aerobic metabolism. Aerobic metabolism takes place in the mitochondria of the cell and is able to use carbohydrates, protein or fat as its fuel source. Aerobic metabolism is a much slower process than anaerobic metabolism but produces majority of the ATP. The respiratory system plays a vital role in the uptake and delivery of oxygen to muscle cells throughout the body.
Oxygen is inhaled by the lungs and transferred from the lungs to the blood where the cardiovascular system circulates the oxygen-rich blood to the muscles. The oxygen is then taken up by the muscles and can be used to generate ATP. When the body is at rest, the heart and lungs are able to supply the muscles with adequate amounts of oxygen to meet the aerobic metabolism energy needs. However, during physical activity your muscles energy and oxygen needs are increased.
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