What Causes The Burn In Your Muscles During a Workout?

What Causes The Burn In Your Muscles During a Workout?

Have you ever wondered what causes that painful burn in your muscles during an intense workout? Whether your workout involves the utilization of weights or your own body weight as resistance, repetition after repetition often causes a burning sensation in the isolated muscle.  The burn is caused by a substance called lactic acid which is produced by the body when glucose is broken down for energy during intense anaerobic exercise.

The body prefers to generate most of its energy using aerobic methods, meaning with oxygen.  But when we lift weights, the body has to generate energy anaerobically, without oxygen.  The energy comes from glucose through a process called glycolysis, in which glucose is broken down into a substance called pyruvate through a series of steps.  When oxygen is limited, the body temporarily converts pyruvate into a substance called lactate which allows glucose breakdown to continue.  The working muscle cells can continue this type of anaerobic energy production for one to three minutes, during which time lactate can accumulate to high levels.

A side effect of high lactate levels is and increase of acidity in the muscle cells, commonly known as lactic acid.  When lactic acid builds up in the muscle cells it becomes very difficult for the body to continue the breakdown of glucose as a source of energy.    So you see, lactic acid is the body’s natural defense mechanism in order to prevent permanent damage during extreme exertion by slowing the key systems needed to maintain muscle contraction. Once the body slows down and oxygen becomes available, lactate reverts back into pyruvate and the burn goes away.

So, to all of my personal training clients out there that insist on stopping their reps short of completion because the burn is too great, push yourself to keep going because the burn is only temporary and will subside as soon as the set is completed. For more information on nutrition, health and fitness, or if you’re frustrated with your current level of fitness and have been thinking about hiring a personal trainer, contact us.