What is Aerobic Exercise?
Aerobic exercise is dynamic physical activity that uses large muscle groups in a rhythmic, sustained manner to increase the body's ability to use oxygen for energy production, resulting in improved cardiovascular fitness. 1
Physiological Definition
Aerobic exercise is characterized by the availability of oxygen for the muscle contraction process, distinguishing it from anaerobic exercise which occurs without sufficient oxygen. 1 The term "aerobic" refers specifically to the metabolic pathway used during the activity, where muscles derive energy through oxygen utilization. 1
Key Physiological Responses
During aerobic exercise, the body demonstrates specific cardiovascular adaptations:
- Increased oxygen uptake (VO2), cardiac output, and heart rate that parallel the intensity of activity 1
- Progressive increase in systolic blood pressure with maintenance or slight decrease in diastolic blood pressure 1
- Decreased peripheral vascular resistance as blood is shunted to active skeletal muscles 1
- Widening of the arteriovenous oxygen difference through increased oxygen extraction by working muscles 1
Aerobic exercise imposes primarily a volume load on the cardiovascular system, in contrast to resistance exercise which creates a pressure load. 1
Intensity Classification
Moderate-intensity aerobic exercise is defined as activity performed at 40-59% of VO2 max or heart rate reserve, corresponding to a rate of perceived exertion of 5-6 on the CR10 Borg scale. 1, 2
The absolute energy expenditure varies by age:
- 4.8-7.1 METs in young adults 1, 2
- 4.0-5.9 METs in middle-aged adults 1, 2
- 3.2-4.7 METs in older adults 1, 2
- 2.0-2.9 METs in very old adults 1, 2
Vigorous-intensity aerobic exercise occurs at 60-85% of VO2 max or heart rate reserve, typically exceeding 6 METs. 1, 3
Common Examples of Aerobic Activities
Sport-related aerobic activities include hiking, running, jogging, skating, cycling, rowing, swimming, and cross-country skiing. 1
Lifestyle-based aerobic activities include brisk walking, climbing stairs, housework, gardening, and active recreational pursuits. 1, 2 These everyday activities can contribute meaningfully to total aerobic exercise volume when performed at appropriate intensity. 1
Cardiovascular Benefits and Mechanisms
Regular aerobic exercise results in improved myocardial perfusion through increased diameter of major coronary arteries, augmented microcirculation, and improved endothelial function. 1
Additional cardiovascular benefits include:
- Decreased myocardial oxygen demands for the same level of external work, demonstrated by reduction in the product of heart rate × systolic blood pressure 1
- Antithrombotic effects including increased plasma volume, reduced blood viscosity, decreased platelet aggregation, and enhanced thrombolytic ability 1
- Reduction of arrhythmic risk through favorable modulation of autonomic balance 1
- 20-30% reduction in all-cause and cardiovascular mortality in a dose-response fashion 1
Recommended Volume and Frequency
The volume of moderate-intensity aerobic exercise that provides reduction in all-cause and cardiovascular mortality ranges from 2.5 to 5 hours per week, with greater benefits observed at longer durations. 1
Alternatively, 1-1.5 hours per week of vigorous-intensity aerobic exercise provides similar mortality benefits, or an equivalent combination of moderate and vigorous intensities can be used. 1
Exercise should be distributed over most days of the week, and the total weekly volume can be accumulated through multiple daily bouts of at least 10 minutes each. 1
Distinction from Resistance Exercise
Aerobic exercise differs fundamentally from resistance (strength) exercise in both mechanical and metabolic characteristics. 1 While resistance exercise involves lifting heavier weights with longer rest periods (greater anaerobic component), aerobic exercise involves sustained activity with continuous oxygen utilization. 1
Most physical activities involve both aerobic and anaerobic metabolism, but activities are classified based on their dominant metabolic characteristic. 1 The physiological responses during dynamic-aerobic exercise differ markedly from heavy dynamic resistance exercise, necessitating separate exercise recommendations for each type. 1