When we talk about endurance, many automatically think of running longer or being less out of breath during exercise. However, there are two distinct forms of endurance: muscular endurance and cardiovascular endurance.
Although they are complementary and influence each other, they do not rely on the same physiological mechanisms.
What is muscular endurance?
Muscular endurance is the ability of a muscle to produce repeated contractions or to sustain effort for a prolonged period without fatiguing quickly.
This ability is influenced by several factors, including the composition of your muscle fibers. Our muscles are mainly composed of type I and type II fibers (IIA and IIX). Type I fibers, also called slow-twitch fibers, are particularly resistant to fatigue. They are recruited during low-intensity efforts, generally below approximately 30% of our maximum capacity.
For example, when you are walking, hiking, or performing a workout with very light loads for a long period, these are primarily the fibers that are working.
Muscular endurance also depends on your body's ability to manage the by-products produced during exertion. During more demanding exercises, hydrogen ions (H⁺) gradually accumulate in the muscles. When this accumulation becomes significant, the muscle environment becomes more acidic, which makes contractions more difficult and contributes to the burning sensation many people feel during a workout.
With adapted training, the body becomes more efficient at eliminating these by-products and delaying the onset of this fatigue, thus allowing you to sustain effort longer.
What is cardiovascular endurance?
Cardiovascular endurance refers to the cardiorespiratory system's ability to supply enough oxygen to the muscles during prolonged exertion.
It primarily depends on the heart's efficiency in pumping blood, the lungs' ability to oxygenate that blood, and the muscles' ability to use that oxygen.
One of the best indicators of this ability is VO₂ max, which is the maximum amount of oxygen your body is capable of using during exercise. The higher your VO₂ max, the better you will be able to sustain high-intensity effort for a long period.
Good cardiovascular endurance also allows the body to better utilize its different energy pathways. Depending on the intensity of the effort, your body will use more lipids or carbohydrates as an energy source to support physical activity.
Two complementary physical qualities
Even though they are different, these two forms of endurance rarely work completely independently.
Take the example of a marathon runner. To run several tens of kilometers, they must obviously possess excellent cardiovascular endurance. However, their leg muscles must also be able to repeat thousands of contractions without losing efficiency, which requires excellent muscular endurance.
Conversely, a person performing long sets in weight training will primarily develop their muscular endurance, while also engaging their cardiovascular system.
In reality, each type of training develops both qualities, but with a different emphasis depending on the desired objective.
In summary
Muscular endurance and cardiovascular endurance are two distinct but complementary physical qualities.
Muscular endurance is primarily related to the muscles' ability to repeat contractions for a long period, the composition of your muscle fibers, and your ability to delay muscle fatigue.
Cardiovascular endurance, on the other hand, relies on the efficiency of the heart, lungs, and circulatory system to provide the necessary oxygen to sustain prolonged effort.
Understanding this difference allows you to better tailor your training to your goals, whether it's to improve athletic performance, physical fitness, or simply daily health.
Félix Daigle, Shop Santé Ambassador
