• Resting heart rate
• Stroke volume and cardiac output
• Oxygen uptake and lung capacity
• Hemoglobin level
• Muscle hypertrophy
• effect on fast/slow twitch muscle fibers

Resting Heart Rate

• Refers to the number of contractions the heart makes in 1 minute while the body is at rest after a workout rep.
• Trained athletes have a lower resting heart rate than those without proper training due to higher efficiency of the cardiovascular system.
• Athletes with a lower resting heart rate do not get exhausted easily, because of sufficient oxygen supply in the cells.
• Allows athletes to recover even in small resting periods.

Stroke Volume and Cardiac Output

• Stroke volume refers to the amount of blood the heart pumps/contraction.
• Cardiac output refers to the total amount of blood pumped/minute.
  Cardiac output = heart rate x stroke volume
• Trained athletes have a cardiac output of 20-25L/minute facilitating in oxygen transport at a higher rate.

Oxygen Uptake and Lung Capacity

• The amount of O₂ an individual’s body uses in 1 minute is called oxygen uptake.
• For an individual, their maximum body intake of oxygen is denoted by VO2 max; which is measured using the 12 minute run and beep test.
• VO2 max is representative of an athlete’s cardiorespiratory endurance.
• VO2 max will increase if the number of oxidative enzymes, capillaries and mitochondria increase.
• Lung capacity refers to the amount of oxygen that can be inhaled and exhaled by an individual.
• It relatively remains unchanged during training.
• Over time with training the lung capacity might increase due to increase in capillary density and number of mitochondria.

Hemoglobin Level

• Hemoglobin is the oxygen-transporting protein in our blood.
• With anaerobic training, athletes are capable of producing more hemoglobin (20% increase) which then helps in transporting oxygen at higher levels.
• Increased hemoglobin levels reduces the possibilities of early fatigue onset in athletes.

Muscle Hypertrophy

• Increase in the size of muscles.
• Muscle fibers grow from stimuli obtained from physical activity during training programs.
• Muscle atrophy occurs if training intensity is lowered or training sessions are skipped.
• Increase in muscle size increases the strength, endurance and power of muscles.

Effect on Fast/Slow Twitch Muscle Fibers

• For slow twitch, contraction of red fibers occurs for prolonged time periods.
• Endurance activities like marathons, swimming, cycling demand slow twitch muscle fibers.
• Slow twitch fibers also make muscles resistant to fatigue.
• Fast twitch (white) muscle fibers quickly reach the tension threshold, and contract quickly.
• Fast twitch muscle fibers last for shorter time periods and are susceptible to fatigue.
• Fast twitch fibers enhance explosive movements that require a combination of power and strength (example: weight lifting).
• Both aerobic and anaerobic activities are allowed by fast twitch fibers.