What’s going on within your body when you are 47 reps deep into curls and have had zero rest time? Is it lactic acid? Ruptured biceps? Soul combustion? Or something else? Let’s take a look at the body science behind the burning sensation in your muscles.
Lactic Acid is Not Your Enemy
Lactic acid – everyone wants to prevent its presence. It’s what you’ve been taught all of your life. What if we told you that you’ve been living in a lie? What if we said that lactic acid is not your mortal enemy, but a good friend that supports you in a time of need? We know you’re thinking that’s absurd, but hear us out.
Exercise Physiology 101
The duration and intensity in which you exercise dictate which metabolic pathways your body utilizes to derive energy from to fuel your activity. For the purpose of this blog, we care about the pathway that is tapped into during moderate to intense exercise lasting from 30 seconds up to 3 minutes.
During those circumstances, your body’s favorite substrate to burn for fuel is stored carbs. These stored carbs cannot be burned for fuel without being broken down first. There are always byproducts when metabolic reactions take place. In this specific scenario, lactate is a byproduct of the breakdown process. Lactate can be used to provide additional fuel during exercise (read more here).
The accumulation of lactate is positively associated with fatigue and the “burning” sensation felt after doing an abundance of reps with little rest periods, such as what is commonly experienced in the kettlebell circuit classes at Elite. However, correlation does not equal causation. In fact, it is suggested that lactate may have protective properties against fatigue. As discussed earlier, metabolic reactions have by-products. Lactate is not the only byproduct of the breakdown of carbs. Hydrogen (H+) ions are also positively associated with fatigue and the burning sensation. The accumulation of this metabolite is said to be the prime suspect, not lactate (lactic acid).
Lactic Acid and Muscle Soreness
Is lactic acid build-up present during delayed onset muscle soreness? Several studies have shown that lactic acid levels return to normal about 1 hour after exercise. It’s unlikely the soreness you feel a day or two later is caused by lactic acid build-up, but rather microtrauma of the muscle fibers.
For a more in-depth look into the subject, check out this article. If you’re ready to take your fitness to the next level, come see a personal trainer for a free fitness consultation and they’ll develop a program based on your goals!
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