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February 10, 2022 5 min read

If you’re an avid gym-goer, you may have heard of the “burn” and the “pump” many times. When you train hard, especially when you train to failure, you will feel a burning sensation in your muscles — the “burn,” and/or experience a transient appearance of fullness or swelling of your muscles — the “pump.” 


When you’ve already worn yourself out in weight lifting and you’re no longer able to complete a repetition through a full range of motion, you’ll start to feel a burning sensation in your muscles. This burning or warmth sensation, which is also experienced following strenuous activities, such as sprinting or cycling, means that your body has used all available oxygen for energy (aerobic system) and enters the anaerobic (no oxygen) metabolism.

Buildup of Lactic Acid or Hydrogen Ions?

Previously, the feeling of the burn is thought to be the result of lactic acid buildup. That is, lactic acid is produced when we exercise at an intensity high enough to exhaust all the body’s supply of oxygen. Our muscles need oxygen to break down glucose, creating fuel for our muscles — ATP or adenosine triphosphate. When the body runs out of oxygen, it breaks down glucose (through liver enzymes) but with lactic acid as a by-product. The muscles can become saturated with lactic acid, and are believed to be what’s causing the feeling of a “burn.” The more strenuous your workout is, the more lactic acid is spilled over into the bloodstream, leading to a more burning sensation.

However, it is lactate, not lactic acid, that is produced when we exercise at a high intensity — When our bodies rely on glucose for energy, hydrogen ions are released along with a buildup of pyruvate, an end product of broken-down glucose. When the supply of oxygen to our muscles is limited, our body can’t keep up with breaking down the hydrogen ions fast enough. The pyruvate absorbs hydrogen ions and forms lactate. Studies showed that the production of lactate increases the number of hydrogen ions which creates an acidic environment, and in turn causes the “burn.” Lactate acts as a buffer to the acidic hydrogen ions and delays muscle fatigue.


Feeling the sensation of a “burn” may mean that your muscles are correctly responding to your exercise and are working hard to produce the force needed to lift a given load. Your body should feel it during exercises but should go away once the intensity of an exercise is reduced or the physical activity is stopped.

The feeling of a “burn,”  however, should be something like a “good” pain, or else, you could be risking yourself an injury. A rule of thumb is to perform as many reps as you can, and then give yourself a break once you feel a slight burning sensation in your muscles.

Also, you may be feeling the “burn” but could be dealing with more than just a muscle burn. Sometimes exercise can lead to muscle injury, especially if you train too soon, too long, or too vigorously, or when you perform an exercise with poor form and technique. Symptoms of muscle injury include pain and swelling, as well as a burning sensation.

So, in this sense, the “feeling of a burn” is not at all absolute advice, although it can be a good gauge of your cardiovascular fitness level as it reflects the amount of effort you can exert for a particular exercise and allows you to know your limits so that you’ll be able to adjust and pace yourself with the routine. It also means that when training a specific muscle group, the feeling of the “burn” means that you’re performing a particular exercise correctly and activating these muscles precisely.


Your muscles often feel warm after exercise, which is a common reaction of the body following strenuous training. First, it means that the body is properly responding to the exercise-induced muscle damage and sets off a cascade of events to begin the repair process.

When the body senses damage, it triggers an inflammatory response, which could lead to a burning or warm sensation. The feeling of warmth serves to speed up the repair and recovery process and prevent infection. Certain types of white blood cells stimulate the release of histamine, which causes the blood vessels to dilate to increase blood flow to the damaged site and induces redness, warmth, and swelling. The increased blood flow allows the removal of damaged cells and other waste products, as well as ensures the availability of fuel and nutrients to further support the body’s reactions.

DELAYED ONSET MUSCLE SORENESS: If the burning sensation persists after exercise, you might be experiencing delayed-onset muscle soreness or DOMS, which typically occurs after performing a new routine that your muscles are not yet accustomed to or when your muscle has performed too much too soon, causing microtears in their fibers.


You may feel the “burn” either due to  muscle overload or localized muscular fatigue.

  • MUSCLE OVERLOAD: overloading occurs when your muscles are made to perform more than they’re used to, like lifting heavy weights.
  • MUSCULAR FATIGUE:muscle fatigue happens when a muscle gets tired and is unable to produce a maximal force or power to perform an activity.

Muscle "burn" does not stimulate growth; muscle overloaddoes. Muscle overload means that the workout intensity is high enough to produce physiological adaptations, such as an increase in strength and muscle growth. The "feeling of the burn" is an indicator that you’re performing an exercise correctly and targeting specific muscle groups properly. It is not an indicator of an optimum workout but is a result of hydrogen ions build-up. You can experience "burn" by performing high-repetition workouts. However, this may not sufficiently overload the muscle and cause hypertrophy.


Muscle injuries can occur at any time an exercise is performed with a poor form or technique, or simply when the body hasn’t quite adapted yet to the demands of an exercise. This puts a novice lifter more likely to experience a greater amount of muscle burn, or worse even a muscle injury. That is why it’s important to start an exercise program as lightly as possible and progress slowly so that your body begins to respond safely and effectively.

Performing a post-workout cool down and active recovery can speed up the clearing of excess lactic acid from the body while providing your muscles with a good supply of oxygen through increased blood flow for repair and recovery.

Keeping yourself hydrated throughout the training and refueling your body with water during cool-down can also help get rid away of the “burn.”