Tired and sore muscles are expected after a challenging workout. While muscle fatigue and muscle soreness are often thought of as the same, they are actually two different aspects of muscle physiology. Being able to tell the difference helps in dealing with their associated symptoms.
Muscle fatigue refers to how repetitive use of a muscle can affect its ability to contract. Muscle fatigue is more likely to occur immediately after extensive use of said muscle. A person lifting weights will find it harder to do their last repetition (“rep”) when compared to their first because the muscle is fatigued.
Types of Fatigue
Muscle fatigue is likely due to conduction failure or lactic acid build-up. In conduction failure, the repetitive firing of electrical signals through muscle fibers leads to a temporary and local electrolyte imbalance. Potassion ions buildup outside muscle fibers, and aren’t given enough time to move back in where they are needed to create an electrical signal. This prevents muscle fibers from contracting and inhibits the muscle from working properly.
Fatigue from lactic acid build-up results from the extensive use of muscle fibers that produce it. The buildup leads to a drop in pH that then alters the shape (and function) of proteins needed for muscle contraction. This leads to a temporary and partial loss of muscle function until the body neutralizes the pH and brings it back up to normal.
A good way to counteract muscle fatigue is to properly warm-up before your workout and take breaks in between sets. This allows for electrolyte balance inside muscles to be restored.
Proper breathing is essential to minimizing lactic acid build-up. This is because the natural chemical reaction that neutralizes lactic acid creates excess carbon dioxide, which we expel through exhalation. Special workout equipment, known as vascular performance machines (or “vasper”), are specially designed to aid in lactic acid recover. Vasper machines provide a high-intensity workout while simultaneously promoting natural muscle recovery by maintaining cool compression around arm and leg muscles.
Lactic acid build-up is often blamed for causing muscle soreness after a workout, but the low (acidic) pH it causes actually gets neutralized rather quickly. Delayed onset muscle soreness (DOMS) is due to microtears in the muscle that happens as a result of exercise. These microtears lead to low-grade local inflammation that makes the muscle sore and stiff. This inflammation and soreness take a while to disperse.
Muscle soreness is normal, especially after a challenging workout. As muscles get used to performing certain exercises, the level of resulting sourness decreases. This may be due to training adaptations in muscles in response to exercise. Stretches and massage may help speed up recovery from sore muscles by reducing fluid buildup and increasing circulation to muscles.
- Fox, Stuart Ira. Human Physiology. 15th ed., McGraw-Hill, 2019. “Muscle Fatigue” pg. 381
- Cheung, Karoline, et al. “Delayed Onset Muscle Soreness: Treatment Strategies and Performance Factors.” Sports Medicine (Auckland, N.Z.), U.S. National Library of Medicine, 2003, www.ncbi.nlm.nih.gov/pubmed/12617692.