For years we’ve been told that as exercise intensity increases, lactic acid builds up, your muscles start to burn, and you slow down. This lactic acid then remains trapped in your muscles and causes soreness the next day unless you work it out with stretching. As I’ve mentioned before, not only does lactic acid have nothing to do with DOMS (delayed onset muscle soreness), but lactate is actually a fuel source your body uses to sustain intense activity. What’s even more interesting is lactate acts as a signal molecule that causes rapid improvements in your body and brain. It’s why one minute of high intensity interval training has been shown to be as effective as 45 minutes of steady-state training. Lactate isn’t actually a metabolic waste product, but rather an important molecule that fuels your workouts, causes rapid improvements to your health and fitness, and can even heal your brain after concussions.
Where we got it wrong
We’ve all experienced the feelings of burning muscles and exhaustion I described above so obviously something slows us down as we work harder. Early researchers tried to discover the cause, but the lactic acid theory is mainly credited to Otto Meyerhof. In his most famous experiment, he cut frogs in half, put the legs in liquid (so they were deprived of oxygen), and then stimulated the muscles to contract with electrical impulses. After a few contractions, the legs would stop responding. When he analyzed them afterwards, he discovered the muscles were full of lactate and hydrogen ions, which he termed to be lactic acid. The problem is that a live creature has all kinds of processes that remove / reuse lactate as it builds up, and the other problem is that the hydrogen ions (the acidic part) tend to come from the metabolism of ATP rather than from glycolysis breaking glucose down into pyruvate and lactate.
10 Surprising Facts About Lactate
Since the name lactic acid is a bit of a misunderstanding, I’m going to refer to it as lactate (the actual product of glycolysis) for the rest of the article.
1. We make lactate all the time
The old belief was that glycolysis in the presence of oxygen creates pyruvate, but when you workout too hard and can’t supply enough oxygen, your body switches to anaerobic glycolysis which breaks pyruvate down into lactic acid as a waste product. New research is realizing that lactate is always the product of glycolysis since it’s produced even at rest when oxygen is abundant. In fact, several organs like the heart, brain, and liver prefer it as an energy source over glucose (more on that below).
2. Lactate counteracts acidosis
As I mentioned above, the breakdown of ATP into ADP actually raises the acidity in tissue during high energy exercise. Lactate production also increases at the same time, but the presence of lactate actually delays acidosis by absorbing these extra hydrogen ions during production. If your muscles didn’t produce lactate, then in the words of one study, “acidosis and muscle fatigue would occur more quickly and exercise performance would be severely impaired.”
3. Lactate works faster than glucose for energy
Dr. George Brooks from UC Berkley is an expert in physiology and lactate metabolism. He is also the pioneer of the Lactate Shuttle Hypothesis that helped clarify how lactate works as a fast-acting bridge between the aerobic and anaerobic energy systems. One of the interesting findings in his research was how quickly consumed L-lactate was metabolized and used for energy. They used isotopes of lactate and glucose to trace how quickly it was used by test subjects for fuel during exercise. While consumed glucose took about 30 minutes to be metabolized, lactate was broken down and expelled in the breath within 5 minutes.
4. Athletes produce more lactate
Our original belief was that as your aerobic fitness improves, you have more oxygen available for energy metabolism so less lactic acid is produced. It’s why we believe that as you get more fit, you feel less of a burn, you can go longer, and you feel less sore the next day. While that part is true, it’s actually because you produce more lactate. Athletes may produce more lactate, but they are also more efficient at shuttling it into their mitochondria so it can be burned (the Lactate Shuttle Hypothesis). Athletes also have more mitochondria in general which enables them to handle more lactate before it can pile up. In this way, it would appear that athletes have less lactate circulating in their systems, but that’s only because they burn more of it up before it can be released from the cell.
5. Your brain prefers lactate
Your muscles aren’t the only cells fueled by lactate. Researchers have found that the heart, liver, and brain also take up lactate for fuel. In fact, the brain prefers lactate over glucose. Studies have used what is called a lactate clamp to infuse extra lactate into subjects to see how it effects metabolism during exercise. They found that lactate infusion spared glucose in the blood and caused glucose production to be reduced since it wasn’t being used nearly as much. Your brain is the biggest energy consumer in your body and as your energy needs during exercise increases, so do the needs of your brain. It’s actually lactate that keeps your brain working during prolonged aerobic exercise (like marathons) when your blood sugar is eventually depleted. Sports drinks containing L-lactate like Cytomax not only provide quick energy for your body and brain, but they spare the glucose for later to help extend your endurance.
6. Lactate doesn’t cause pain, it reduces it
Subjects infused with lactate also did not experience increased pain or fatigue during exercise because lactate reduced the acidosis. In fact, in one study they found that lactate infusion during exercise caused slight alkalosis. This doesn’t happen when lactate is produced naturally (or consumed in smaller quantities than provided by a lactate clamp), but the effect of reducing acidity reduces the triggering of acid-sensing ion channels in muscle tissue. The end result was the subjects did not experience any additional feelings of pain or fatigue during exercise.
7. Lactate alone signals endurance improvements (mitochondria biogenesis)
Why do short bouts of high intensity interval training cause significant improvements to long-distance endurance? Intense training may feel stressful to you, but it’s really stressful to your body (that’s why you shouldn’t do it too often). Intense training creates reactive oxygen species which can harm cells. One of the places these harmful compounds are produced is in the mitochondria, but ironically, the mitochondria are also responsible for removing reactive oxygen species from your system. When you stress your body with intense exercise, it sends signals that you will need more mitochondria in the future to not only reduce the reactive oxygen species in your system, but to make it easier to perform better during the next bout. One of the signals used to encourage mitochondrial biogenesis is lactate. Lactate is not only a fuel source utilized by the mitochondria, but it also serves as a signal molecule to up-regulate gene expression that encourages the growth of new mitochondria.
8. Lactate signals brain to release norepinephrine
People ask me all the time, “How can short, intense workouts help with weight loss if they burn so few calories?” People get too obsessed about calorie numbers. As I’ve mentioned many times before, calories in vs calories out is far too simplistic, it ignores all kinds of adaptions your body makes on a daily basis, and it tends to cause more harm than good. If you just focus on calorie numbers then high intensity interval training shouldn’t work for weight loss, but it’s been shown over and over to be more effective than long, steady-state workouts. The reason is you need to look at the whole picture. A long workout may burn a bunch of calories, but it will drop your blood sugar and you’ll eat ravenously afterwards (likely consuming more calories than you burned). Another common problem is that when people burn a lot of calories working out, they then tend to move less the rest of the day resulting in less calories burnt overall. As I mentioned above, lactate produced during high intensity spares glucose so you won’t have a blood sugar crash afterwards. It’s one of the reasons why intense workouts don’t increase appetite. Another reason is because L-lactate acts as a signal molecule to release norepinephrine from the locus coeruleus to the forebrain. This area controls the sleep-wakefulness state, vigilance, appetite, respiration, emotions, and other autonomic processes. This could explain many of the benefits we see from exercise such as improved mood, appetite control, more energy, and better focus.
9. Lactate signals brain cell growth
I’ve written before about how cardiovascular exercise improves brain function, increases neuroplasticity (the ability for your brain to restructure itself to adapt and learn), and prevents cognitive decline as you age. One of the reasons is due to the release of brain-derived neurotrophic factor (BDNF). One study infused subjects with a lactate clamp at rest and found that it stimulated the release of brain-derived neurotropic factor. Lactate not only signals positive adaptations in your body, but in your brain as well.
10. Lactate heals the brain after traumatic injuries
For me, one of the most interesting aspects of Dr. George Brooks’ research on lactate was it’s role in healing the brain after traumatic brain injuries. In his research, he found that traumatic injuries like concussions impaired glycolysis in the glial cells (the structural cells of the brain that protect the neurons). Normally these cells convert glucose into lactose so it can be used by the neurons, but after injury the neurons couldn’t receive sustenance from glucose and they starved. Other researchers found that lactate also protects neurons from excitotoxicity after a brain injury. After serious trauma like a stroke or spinal cord injury, neurons can become overstimulated by neurotransmitter signals. This barrage causes a build up of calcium ions that ultimately kills the neuron. Lactate triggers a complex series of defense mechanisms that prevent this build up and keep the neuron from dying. An observational study of 3,063 student athletes between the ages of 5 and 18 years old confirmed that activity can improve symptoms after a concussion. Students were told not to return to activity until all concussive symptoms like headaches were gone. However, the ones that ignored this advice had the best recovery. Student athletes that returned to exercising within a week were 50 percent less likely to still have concussive symptoms after a month. There are likely many other factors than just lactate that help people heal after traumatic brain injuries and more research is being done, but it was convincing enough to me that I would suggest (and have already suggested to a few people) to supplement with Cytomax for the first week post-injury and then switch to a gentle exercise program of walking, cycling, or even bodyweight squats to raise your daily lactate levels and speed up the recovery process.