Everyone has heard of lactic acid (“LA”), so what’s all the excitement about?  Does it cause muscle soreness?  How does it affect your training program?

Technically, LA is an end product of glucose metabolism.  In an oxygen rich environment, like an easy 20 minute workout, LA production is kept to a minimum, thus your working muscles feel fresh.  As the intensity increases and the cellular environment becomes oxygen deficient, like during a maximum 20 minute effort, LA production increases and the efficiency of your working muscles to contract decreases.  LA production and/or accumulation does not cause muscle soreness.  But it is the gateway to better endurance, maximum calorie burn, and higher performance.

As your intensity during a workout increases, so does your LA production.  The good news is that with proper training the cells of your working muscles develop the ability to recycle LA.  And so, even though LA production is increasing, concentration in your blood remains the same.

Even with trained muscles however, there is a point when LA production overcomes your cells’ ability to deal with it.  The point when LA overwhelms your system is called your lactate threshold (“LT”).  Muscle burn is generally, but not specifically, associated with this point, and the time clock starts ticking!  Just beyond LT, you have about 30 minutes of sustainable effort left before your glycogen is depleted and lactic acid claims victory.  The further your intensity climbs beyond LT, the less time you have before “hitting the wall”.  Proper LT training increases the point where LA production overwhelms your working muscles.

The key to improving your LT is to push the intensity to the edge of LA overproduction, and sustain it.  The next obvious question: where’s the edge?  There are numerous ways to answer that.  Here’s the short list of objective and subjective answers you’ll find on the web:

1. A comfortably hard pace
2. 85-90% of your maximum heart rate
3. If running, your 10k race pace + 30-60 seconds per mile
4. Your average heart rate in a 1 hour maximum effort
5. Your heart rate when lactic acid production is at 4.0 mmol per liter of blood
6. Suffer a Conconi test

Training in the Zone!

Frustrating, yes?  As a former professional triathlete, I fully appreciate the “feel-it-out” method, and the reluctance to trust science over personal experience.  Yet, as an Exercise Physiologist, I have seen the pitfalls of the “feel-it-out” method too.  Overtraining, for example, is what happens when you let your senses dictate your training program.  Your brain wants to do a hard workout because such a workout is cathartic.  Plus, it feels good to sweat!  Your body, on the other hand, may be tired and on the brink of injury.  It’s the delicate mixture of experience and science that leads to big results.  An organic middle ground is what I suggest:

1. Get your LT tested by a real Exercise Physiologist, not because the test is difficult to conduct, but because an accurate interpretation requires an understanding of the whole system.  The Denver Athletic Club, of course, offers such a test with such a scientist. J
2. Your LT test should present your training zones in terms of heart rate, perceived exertion, and pace (i.e., speed on a treadmill, watts on a bike, steps per minute on a step mill, etc.).
3. Your training program should incorporate your goals, likes and dislikes, family, work, and social commitments, your previous injuries, and your current conditioning level.

Here are a couple examples of typical LT-improving workouts:

Running, Cross Country Skiing, or Swimming

Progressive warm up followed by 3 intervals of 5 minutes @ LT with a 1 minute walk between intervals.

Biking

Progressive warm up followed by 3 intervals of 10 minutes @ LT with a 2 minute “walk” between intervals.

In conclusion, your pace at LT is moderate-hard, so the risk of injury is real.  Progress into this type of training slowly over 6 weeks to 3 months considering your current conditioning level.

If you have the patience, then you will not find a more affective workout!

Train Smart!