Aerobic Exercises and Its Physiological Effects

Aerobic Exercise, Definition, Physiological effects of Aerobic exercises
Definition:
American College of Sports Medicine (ACSM): Aerobic exercise is any activity that uses large muscle groups, can be maintained continuously, and is rhythmic in nature.
World Health Organization (WHO): Activity in which the body’s large muscles move in a rhythmic manner for a sustained period of time. Aerobic activity—also called endurance activity—improves cardiorespiratory fitness.
PHYSIOLOGICAL RESPONSE TO AEROBIC EXERCISE:
1. Exercise stimulates sensory nerve fibers in skeletal muscles, activating the sympathetic nervous system (SNS).
SNS activation causes:
a. Increased heart rate
b. Increased myocardial contractility (stronger heart contractions)
c. Increased systolic blood pressure
d. Vasoconstriction in nonworking tissues
These changes increase and redistribute cardiac output to active muscles
2. Cardiac Effects
a. Heart rate increases due to:Reduced vagal (parasympathetic) activity
b. Increased sympathetic stimulation
c. Myocardial contractility increases, leading to stronger heart contractions and greater stroke volume.
3. Peripheral Effects
a. Reduction in Total Peripheral Resistance
b. Blood vessels in inactive organs and muscles constrict.
c. Blood flow is redirected to active muscles.
d. Local metabolites (Mg²⁺, Ca²⁺, ADP, CO₂) cause vasodilation in working muscles.
e. Veins remain constricted, helping return blood to the heart.
4. Increased Cardiac Output Caused by:
a. Increased heart rate
b. Increased stroke volume
c. Increased blood flow to active muscles
d. Increased venous return
e. Increased Systolic Blood Pressure
5. Respiratory Response to Exercise
a. Breathing increases rapidly, often before exercise begins.
b. Exercise increases oxygen demand and carbon dioxide production.
c. Factors stimulating respiration include:Increased CO₂ and H⁺ levels
d. Increased body temperature
e. Increased epinephrine
6. Joint and muscle receptor stimulation
7. Ventilatory Changes
a. Respiratory rate and tidal volume increase.
b. Minute ventilation rises significantly.
c. Alveolar ventilation can increase 10–20 times during heavy exercise.
d. A steady state is usually reached within 3–4 minutes if exercise intensity remains constant.

Author: Notes are prepared by Expert Physical Therapist
Ref: Kisner C, Colby LA, Borstad J. Therapeutic Exercise: Foundations and Techniques. 5th ed. Philadelphia: F.A. Davis; 2018
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