Science Of Exercise

Energy consumption during exercise.

Principles in Exercise Physiology

Homeostasis - resting body condition and all internal factors such as blood sugar level, oxygen levels, ph level, core body temp.

A physical exercise is a shock to the homeostasis and body works towards adjusting all the internal environment as best as possible.

Overload principle - if you habitually overload a system it will respond and adapt. Regular exercise leads to permanent changes in how our body functions.

Specificity - Physical exercise only leads to changes in specific systems. For example - strength training does not have much impact on cardio vascular systems. Specific strength training only affect muscle groups involved in those exercises.

Reversibility - if you quit exercise, after a while your body will lose adaptions made in training.

Individuality - Magnitude of adaption body goes through after regular exercise depends on genetics.


  • Calculates energy cost of exercise.
  • Direct method uses fairly expensive equipment.
  • Indirect method calculates oxygen consumed during exercise compared to resting state.
  • VO2 increases linearly with exercise intensity.
  • As body adapts with regular exercise, it causes max value for VO2 to increase permanently.
  • Leading to permanent benefits to cardio vascular systems.

Respiratory exchange ration - amount of CO2 produced compared to oxygen consumed during exercise. Indicates which fuels - fat(0.7) or carbohydrate(1.0) - used during exercise.

Energy requirements

ATP - is the only high energy compound which can be directly used for muscle contraction.

Important to maintain ATP levels for endurance training.

ATP is produced by

  • Fats - Fatty acids and glycerol
  • Glucose and other sugars
  • Proteins - amino acids.

Aerobic and Anaerobic exercises

carbohydrate metabolism during exercise
  • Carbohydrates are stored in muscle(majority) and liver and blood(very small) as a form of glucose molecules - glycogen.
  • Amount of fat stored in body is 50 times more than carbohydrates.
  • During an exercise body starts burning fat for energy, but as exercise continues, it switches over to using carbohydrates.
  • Carbohydrates stored in muscle provide fuel for exercise and contribute to producing ATP required for exercise.
  • Exercise extracts glucose from blood, causing blood sugar level to drop, possible hypoglycemia.
  • Carbohydrates stored in liver are used to boost the falling blood sugar level.
  • Carbohydrate sparing - regular training helps body adapt to using fat as more fuel source as much as possible, sparing carbohydrates.
  • Regular exercise leads more mitochondria matter, which leads to utilizing glucose via aerobic methods. Aerobic methods are more efficient and produced larger amounts of ATP.
Fat metabolism during exercise
  • Free fatty acids
    • Used for immediate energy source for muscle.
    • Mitochondria uses them to produce ATP.
  • Triglycerides
    • Stored form of free fatty acids.
    • Stored in fat cells and skeletal muscle.
    • During exercise, fatty acids stored are transported to muscles and then used as energy source.
  • There is a very large amount of fat stored in our body.
  • Endurance exercises train our body to use fat as an energy source instead of carbohydrates.
Protein metabolism during exercise
  • Proteins, in their amino acids form, do contribute to providing energy during exercise.
  • Between 5-15% of energy is contributed by amino acids to produce ATP.
  • Nitrogen balance - nitrogen input vs nitrogen output. Indicates protein needs of body are being met.
  • After exercise protein synthesis increases. So ingesting proteins within first hour after workout, specially strength training, is quite useful.

Recommended protein intake - 0.8grams per kilogram of body weight. For 80kg adult it is 0.8g * 80 = 64grams