Since Meyerhoff and Hill (separately) published their Nobel Prize winning work on lactic acid and skeletal muscle fatigue in 1922, it has been an accepted fact that the accumulation of lactic acid in training or exercise is detrimental to performance. We have been told by coaches, trainers, and books that the build-up of lactic acid is to be avoided as long as possible while running or training. Even the phrase lactic threshold has become synonymous with with fatigue, breakdown of form, muscle soreness, and possible eventual collapse. Training plans for endurance athletes in particular have revolved around threshold levels and raising/changing these levels. We train below lactate threshold levels in long runs, at lactate threshold levels in steady state runs, and above lactate threshold levels in interval training all to teach our bodies how to avoid producing lactate and then how to dissipate it faster when levels get too high. Lactate has been blamed for post-exercise soreness, muscle fatigue, and impaired recovery process. Lots of athletes get massages and rubdowns to help the body get rid of or 'flush' lactate after high intensity training. But what do we really know about lactate? Is it really as detrimental on performance as we think? If so, why do we produce it at all? Let's look at some of the "facts" we have learned over the years about lactate.

1. Lactic acid is produced as a byproduct by the muscles during exercise. This is not true. What muscles DO produce is a compund called lactate. Furthermore this compound is NOT a waste byproduct of anaerobic metabolism but is actually a link between the aerobic and anaerobic systems. It helps with the transition from one system to the other.

2. Lactate (proper term) causes muscle fatigue. Research in 2006, conclusively proved that this once popular belief is simply not true. In fact, quite the opposite is true. The build-up of lactate DELAYS muscle fatigue by diminishing the effects of depolarization. Simply explained, your muscles lose power in the same way as a battery does. The cell membrane potential becomes more positive and results in an action potential. This process is called depolarization. Lactate counteracts this process, delaying the onset of muscle fatigue.

3. Lactate causes muscle soreness. Once again, false. Research has shown that during prolonged, low intensity exercise (the type of exercise that causes the most soreness) there are minimal amounts of lactate produced. Post-exercise soreness or delayed onset muscle soreness (DOMS) is the result of simple mechanical damage to the muscle during the activity and the inflammation associated with tissue repair.

4. Muscles have no functional use for lactate. This is false as well. Lactate is metabolized by mitochondria in an aerobic reaction and used as a direct fuel for muscle contraction. Also, de Paoli et al, 2007, found that lactate and adrenaline, working together, led to increased muscle excitability through a decrease in intracellular pH (role of lactate) and an increase in the sodium-potassium pump (role of adrenaline).

5. Lactate production does not contribute to exercise performance. Like the previous four facts, this is now shown to be untrue. Lactate production during exercise initiates a process called mitochondrial biogenesis. Lactate stimulates an increase in mitochondria within the cell. Mitochondria are organelles inside the cell responsible for aerobic metabolism (i.e. oxygen breaking down fats and glucose to yield energy). So, in fact, lactate stimulates the very process which allows our muscles and bodies to adapt to training and improve fitness and endurance performance.

At the end of all this, your question is, What does this mean for my training? Research notes that a combination of training phases is the best way to maximize how your body uses lactate efficiently. Those training phases are discussed below.

1. High volume. Tried and trusted long runs and base work, the mainstay of any endurance athlete's training. Even in this phase research shows that introducing 2-3 miles of marathon paced running during your long run can be beneficial for lactate training. Take your fastest 10K and apply it to the marathon. Add approximately 12% to the time to get your marathon pace.

2. Maximum steady state run. This is your tempo run. Be aware that research has indicated that maximum benefit from tempo runs is achieved with one tempo run per week.

3. Interval training. Needs no explanation. Every distance runner is familiar with the pain of interval training.

I guess what I'm saying is that, in the end of the day, little will change with your training schedules. It is the reason we do them that has changed.

There was a recent study done by Rashidi et al in 2013 that showed the effectiveness of the cooldown as well in terms of lactate. Their study used 60 endurance athletes and placed them in 4 random groups. Group 1 exercised and then performed no cooldown. Groups 2, 3, 4 did the the same exercise and then cooled down at 55%, 60%, and 65% of maximum heart rate. They found that the group that cooled down at 60% MHR had significantly less lactate in their blood after 20 minutes than the other groups. Moral of the story? Do your cooldown because it serves a purpose, not because the coach tells you to.

Run long. Play hard.