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Metabolism During Exercise in Humans

Published on Dec 02, 2022   -  4 min read


The major benefits of exercise on metabolism are how the body converts food into energy and eliminates waste. To know more, read the article.


Exercise is important for daily life. Obesity, a common health problem, is closely associated with exercise. Exercise has the power to boost metabolism. Endurance exercise induces adaptive increases in the mitochondrial content and respiratory capacity of skeletal muscle, as well as in myoglobin concentration and capillary number. During exercise, the body converts food into energy. During metabolism, metabolites are produced. Metabolites are intermediate substrates of metabolism that signal metabolic health changes during exercise. Metabolism is a complex process that occurs during the conversion of food into energy. It helps in combining calories and oxygen to release energy which helps to perform body functions.

What Are the Factors That Affect Metabolism?

What Happens During Exercise?

  • Energy Expenditure: Humans tend to expend energy for a prolonged period of sustained exertion. However, energy expenditure varies according to age, gender, weight, and heart rate.

  • Muscle Pain: Physical exercise causes immediate and delayed pain in muscles. The immediate pain is due to the stimulation of nerve endings, and the delayed pain is due to the muscle fiber rupture. Pain may be mild to severe, depending on the intensity and level of physical activity.

What Are the Physiological Changes That Occur During Exercise?

1. Exercise-Induced Physiological Changes in the Brain:

  • Oxygen: The brain depends on oxygen to perform its function. Exercise causes a decrease in oxygen levels. If there is a demand for oxygen supply to the brain, it leads to unconsciousness within six to seven hours and disruption in motor control.

  • Cerebral Autoregulation: Cerebral autoregulation usually protects the brain during oxygen deprivation by increasing the cardiac output and producing more capillary oxygen supply to the brain. Brain autoregulation is impaired during maximal exercise since increased capillary oxygen supply alone is insufficient.

  • Glucose: Exercise reduces plasma glucose in the brain that compensates for it with lactate, which provides the required energy to the brain.

  • Hyperthermia: During exercise, more sweat causes an increase in basal body temperature. It results in cognitive impairment, reduced cerebral blood flow, and brain hyperthermia.

2. Exercise-Induced Fatigue:

  • Intense Activity: During intense exercise, there occurs disturbance in ion hemostasis and causes cellular membrane depolarization, inexcitability, and muscle weakness.

  • Endurance Failure: Intense exercise for a prolonged time causes a collapse in body hemostasis.

3. Other Factors That Cause Fatigue Include:

  • Brain hyperthermia.

  • Depletion of glycogen in brain cells.

  • Skeletal muscle function impairment.

  • Ammonia uptake by the brain.

  • Decreased glutamate level.

  • Oxygen supply impairment.

4. Exercise-Induced Cardiac Changes: Prolonged exercise (marathons) causes an increased release of cardiac biomarkers. In clinical conditions, increased release of biomarkers suggests irreversible muscle injury, whereas exertion induced is reversible (usually occurs within 24 hours).

What Are the Guidelines for Physical Activity to Burn Calories?

  • Aerobic Activity: A person should aim for at least thirty minutes of workout every day in order to lose weight and meet fitness goals. Moderate aerobic exercises include brisk walking, swimming, and biking. Heavy aerobic exercises include running and aerobic dancing.

  • Strength Training: Should perform strength training exercises at least two times a week. Strength training exercises include the use of weight machines, heavy bags, and rock climbing.

What Are the Metabolic Changes That Occur During Exercise?

  • Rapid Energy Sources: Energy required to perform physical activities come from muscle cells through anaerobic metabolism.

  • Plasma Glucose: Plasma glucose remains constant when the glucose enters the blood equals the removal of glucose from the blood. Plasma glucose level remains constant during moderate physical activity. Prolonged exercise results in a drop in blood glucose levels which leads to fatigue, and Epinephrine and growth hormones maintain the plasma glucose level by oxidizing fatty acids and utilizing glucose for the scarcity. In diabetic patients, moderate exercise results in a drop in glucose level- which maintains blood glucose within a normal range.

  • Oxygen: Exercise increases the body's oxygen demand and causes an increase in heart rate, breathing rate, and depth of breathing.

  • Dehydration: Dehydration is more common during exercise and causes an increase in basal body temperature and heart rate.

What Happens During Carbohydrate Metabolism on Exercise?

Carbohydrates, the main fuel source of energy used by working muscles, is oxidized by the skeletal muscles during prolonged exercise. This process depends on the exercise intensity and duration. There is only a limited amount of carbohydrates stored in the human body. Activation of glycolysis and glycogenolysis are regulated by multiple factors such as hormones, intramuscular calcium levels, and the energy charge. However, endurance capacity and endurance performance depend on endogenous carbohydrate availability. It is established that carbohydrate intake during prolonged exercise improves endurance performance. Taking carbohydrates during exercise is beneficial for athletes participating in team sports.

What Happens During Fat Metabolism on Exercise?

Fat is the main fuel obtained from aerobic exercise. Fat, the dominant source of energy obtained through moderate aerobic exercise, provides fifty percent of the required energy. Fat oxidation also contributes energy during recovery from a single bout of exercise. During the onset of the exercise, the activation of fat oxidation is slower. Fat metabolism is regulated in skeletal muscles.

What Happens During Protein Metabolism on Exercise?

Protein degradation increases during exercise. Certain amino acids are used as fuel for adenosine triphosphate production. Muscle protein synthesis decreases during exercise and increases during recovery. Training adaptations related to protein metabolism are task-specific and occur primarily post-exercise. Athletes initiating a training program need to be sure to maintain nitrogen balance.


Metabolism plays a vital role in the functioning of the body. Some factors, such as age, sex, and gene, affects the metabolic rate. However, faster or slower metabolism is not a concern for weight gain or loss. Also, one should not rely on dietary supplements to burn calories or lose weight.

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Last reviewed at:
02 Dec 2022  -  4 min read




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