Class 12 Physical Education Chapter 7 Physiology and Injuries in Sports

Exercise physiology is a study of the body’s response to exercise. In the human body we majorly study skeletal, muscular, nervous, endocrine, cardiovascular, metabolic, respiratory, digestive, urinary and reproductive systems which are somehow affected by exercises. During exercise, all systems of our body work jointly but responses of these systems are independent.

Cardiovascular system controls circulation, transports oxygen and energy to muscles and waste products from muscles. Respiratory system takes in air, diffuses oxygen to lungs and muscle tissue and removes carbon dioxide from body. Neuroendocrine and Immune system help to maintain homeostasis of the body. To develop fitness, each component has different exercise, intensity and volume, so the responses of systems are different.

Skeletal muscles are made up of muscles fibres which are divided into two categories Slow twitch fibres or Type I fibres and Fast twitch fibres or Type II fibres. Composition of fibres in muscles plays a dominant role in development of strength, endurance, and speed performance. Skeletal muscles have four properties contractility, excitability, extensibility and elasticity and four contractile characteristics namely maximal force production, speed contraction, maximal power output and efficiency of contraction. These characteristics existing in muscles determine different components of fitness.

Type I fibres or slow twitch fibres or slow oxidative fibres contain large numbers of oxidative enzymes, have more capillaries, higher concentration of myoglobin and mitochondrial enzyme than fast twitch fibres which promote aerobic activity and resistance against fatigue. Due to higher concentration of capillaries the colour of fibres becomes red and has greater supply of blood. Such types of fibres contract at low rate and keep contracting for longer duration without fatigue; thus, producing large amounts of energy slowly.

Cellular respiration is a process in which ATP is formed through food. Main source of energy in food is in form of carbohydrates, proteins and fats. Each has different complex chemical process to form ATP energy. During exercise, the load on metabolic system increases manifold because of increase in demand of energy by different systems. In this process, carbohydrates give instant energy as compared to fats and proteins, but fats give a larger amount of energy as compared to carbohydrates and proteins.

Higher intensity aerobic activity requires carbohydrates in the form of glucose and glycogen as fuel. Carbohydrates work as a fuel for short duration exercise, fats are utilized for long duration exercises and proteins contribute a small but important proportion of nourishment. Basically, three energy system works in our body ATP-CP system, anaerobic system and aerobic system.

ATP- CP system provides energy if the activity is less than 10 second. Such activities are dynamic in nature and of very short duration and very intensive. They include jumps, throws, sprints, weightlifting, powerlifting etc. Anaerobic system provides energy for less than two minutes, in activities like 200m, 400m races. Aerobic system provides energy for long duration activities like marathon, football, hockey etc. Aerobic and anaerobic systems work simultaneously, but which system is predominant depends upon type, duration, intensity of exercise, long and short-term nutritional status, proportions of types of muscle fibres etc.

Cardiorespiratory system is combination of respiratory and cardiovascular systems which jointly work to transport oxygen to the cells and support metabolism by delivering nutrients, which provide energy to neuromuscular system and neuroendocrine system. During exercise, the demand for energy increases and to meet the demand, oxygen is required in appropriate volume, to achieve the same. Demand of energy depends on intensity, duration and type of activity. To match the same, the respiratory system parameters: pulmonary ventilation, external respiration and internal respiration work together.

The cardiovascular response to exercise is directly proportional to the demands of the skeletal muscles for Oxygen. Maximal oxygen consumption (VO2 Max), Blood pressure, blood volume, oxygen diffusion and extraction, muscle and arterial blood flow etc. simultaneously increase as per activity.