Insert Richard Simmons quotation here
Many attribute the burning feeling in their muscles during exercise to lactic acid. Most have been told something like this: "Lactic acid is a waste product excreted in muscle during anaerobic exercise." Or: "Lactic acid makes muscles acidic and unable to contract." This information isn't dead-wrong, but it's not spot-on.
It is now accepted that muscle fatigue from anaerobic exercise is caused by a lack of fuel to muscles and an increase in muscle and blood acidity due to hydrogen ion byproducts of glucose metabolism. Here is a very diluted description of what goes down:
- When exercise is performed without oxygen to generate ATP (the body's currency of energy), sugar metabolism (glycolysis) gets kicked into high gear.
- Hydrogen ions build up as a by-product of anaerobic glycolysis. These ions make muscle acidic and reduce its ability to contract.
- Pyruvate, another product of glycolysis, binds to these hydrogen ions to buffer them, from this, lactate is formed.
- Lactate is the proper terminology for what is colloquially referred to as lactic acid. Lactate allows exercise to continue by buffering acid and providing fuel for muscles and the brain.
It is true that as blood lactate levels rise, exercise performance decreases, this is a case of correlation, not causation. Trained athletes benefit from lower blood lactate levels during exercise because this means they are able to use lactate as a fuel more efficiently.
Here is a short video that highlights the key points about lactate and muscle fatigue:
How do I apply this?
Now you can impress everyone at your next dinner party. Oh, you mean apply the information to your training? This information should change the way you think about exercise fatigue. Know that if you're feeling 'the burn,' during your workout, your body is learning to to utilize fuel more efficiently.
There are many complicated ways of training your lactate threshold, increasing the amount of work or time before muscle fatigue occurs. You do not have to worry about these complex methods unless you are an extremely elite athlete. The process of energy utilization and muscle fatigue is complicated, applying it to your workout is simple. The next time you repeat a workout, it should take longer, or you should have to work harder to fatigue. Work harder or longer to feel the same feeling of fatigue and you know you are progressing.
If you are a novice exerciser, you should only concern yourself with lactate and muscle fatigue when you're trying to impress or correct someone.
What about muscle soreness?
Delayed onset muscle soreness, or DOMS peaks 12-72 hours after a new or especially tough workout. The fact that muscle soreness is delayed severs its previous ties to lactate, as lactate clears muscle within an hour after activity.
Here are a few key points on soreness:
- Eccentric exercise (the stretch or lowering phase of a movement) causes micro-trauma to muscle.
- Muscle micro-trauma triggers your body's inflammatory response.
- This inflammatory response (which takes hours to fully ramp up) draws water and nutrients into to the muscle to repair it, but also heightens pain and sensitivity.
- Soreness is not linearly correlated with muscle hypertrophy or strength, but it should happen every once-in-a-while during a solid training phase.
Soreness = Rest day?
Many believe that DOMS is protecting their muscle, that they should not workout until their soreness is gone, so as not injure themselves further. Soreness is not a sign of injury, it is a display of your body adapting to stimulus. Exercising with sore muscles won't make soreness worse or cause damage to your muscle. In fact, most experience a decrease in soreness after exercise. This is likely because an increase in blood flow from exercise helps to reduce muscle inflammation. Ironically, increased blood flow to muscle is another type of inflammatory response, but it triggers the body to reduce inflammation. Talk about self sabotage.
The only reason you should not exercise with sore muscles is if you are so sore that you cannot perform full range of motion. In this case, you won't harm yourself by exercising, but you won't do anything very productive either. If you must to get to the gym (I feel you), you may perform movements that are not affected by your soreness. Concentric exercises, like rowing, pushing a prowler or airdyne biking are great 'sore day' options because they have no loaded eccentric component (the part of the exercise related to soreness).
What makes soreness better?
Time and love, just like everything else in life. There are no concrete ways to prevent or heal exercise induced soreness. Anecdotally, essential amino acid supplementation before training works well for me and my circle of clients, friends and family. Moving around, getting a massage or taking an Epsom salt bath can help decrease the pain from DOMS that has already set in. Nothing has been proven to mitigate the actual mechanism of soreness, yet.
One more rep
This information is not going to make you bigger, stronger, faster or leaner. However, you may now go about your training with two fewer things to worry about. Muscle fatigue and soreness are natural occurrences in the training process, chasing or fearing them is pointless. Ponder your form, nutrition and progress instead.
