Lactate Curves - Various Examples
The following six charts show the relationship between lactate, heart rates and VO2 against running speed or power.
In this chart three parameters are plotted: running speed, VO2 and lactate. As running speed climbs so does the consumption of VO2. Lactate remains steady at first and then begins an exponential climb. The VO2 is a direct measure of the aerobic system, but says nothing about the anaerobic system. That is where lactate comes in. Lactate is related to both energy systems, first as the output of the anaerobic system and then as the primary fuel for the aerobic system during intense exercise. In other words, lactate is a window into both energy systems. Both systems need to be calibrated properly by appropriate training.
This particular test is not designed to assess the strength of anaerobic system per se but one can see the anaerobic system at work through the lactate curve. When the pace or effort level reaches a certain point the lactate rises quickly. This is a direct indication that the anaerobic system is being used more and more. This runner, who is a college soccer player, does not have a very high VO2 max and yet the anaerobic system is not exerting itself at moderate running paces.
The step test is mainly used to measure aerobic capacity, but it also provides an estimate of the lactate threshold or maximal lactate steady state. So at every point lactate is telling the coach something about the conditioning level of the athlete for both energy systems.
Neither heart-rate or power provides all this information. This is why neither of these measures is a replacement for lactate. It would be best if it were possible to measure the lactate in the muscle but this is a highly complex procedure. Blood lactate is an alternative that has been shown to correlate well with muscle lactate. And despite what many say, a lactate meter is a fraction of the cost of a power meter, and very thorough threshold tests for all three disciplines can be done for under $50. This is not a major expense for most triathletes.
The second chart plots lactate and heart rate against power. Here the heart rate follows a typical VO2 pattern, but it is not a direct reflection of either of the two energy systems. Heart rate represents total stress on the body and can reflect such things as heat, hydration deficiencies, lack of sleep, overall health etc. as well as the obvious demands by the body for oxygen. It has some very practical uses and one of them is to relate actual stress found during a test situation with speed or effort on a bike or during a run on the road or in the woods. Heart rates are not necessarily a good window into the two energy systems as they have no way to estimate the effort being provided by the anaerobic system. Many cyclists have now abandoned heart rates as a guide during a workout or a competition because they prefer to use power which is much easier to interpret and more relevant. But power, while a valuable measure, does not provide the same insight into the energy systems that lactate does.
This chart illustrates a very interesting trend. It compares one lactate and heart rate test (blue lines) with those at a later date (red lines). The lactate at every power level is lower. What would cause this? The amount of energy the cyclist needs at each power level is the same. Such a pattern is best explained because there is a different mixture of aerobic and anaerobic energy. This is most likely due to either an increase in aerobic capacity, or a decrease in anaerobic capacity, or both. The curve has moved to the right, which indicates a much higher threshold. The V4 has moved from approximately 330 watts to around 360 watts. This is a big jump and going over the training and past history of the athlete will tell the coach just what caused the change and whether it is mainly due to increased aerobic capacity or decreased anaerobic capacity.
The next chart represents what looks like a test of a serious, but not elite, triathlete (male 30 years old who has been doing triathlons for just 2 years). But the details are interesting.
Because There isn't any baseline and the final lactate is very high. This suggests that this athlete has a very high anaerobic capacity and is pushing out a lot of lactate at every effort level, including what should be relatively easy power levels of 175 w and 200 w. Even with his high aerobic capacity, his muscles cannot use all the lactate being produced at these relatively low power levels and it is building up from the beginning. This athlete most likely needs to lower his anaerobic capacity so that he can more fully utilize his high VO2 max. His high anaerobic capacity is getting in his way. Right now he is only able to use about 65%-70% during a race when he should be able to utilize up to 85%. This is normally a trainable situation but it may take awhile.
The lactate test indicated why he is under-performing his potential. If he had just done a normal LT power test or LT HR test, he would not have known what was happening inside his muscles.
The next chart uses a typical lactate test but also a measure of the anaerobic capacity of the athlete to provide the coach with information on what is actually happening as a result of training. This male triathlete who we will classify as a good recreational triathlete wants to get better and has started lactate testing as a way to better plan his training. The following chart shows the results of two lactate tests taken 8 weeks apart.
There is some important information that is not on these charts. The athlete completed a test of his anaerobic capacity. It was an all out test that lasted just less than a minute. After both aerobic tests the athlete rested for about 20 minutes and performed the all out test. The results were almost identical. His max lactate was 13 mmol/l and 13.1 mmol/l respectively for each test. This indicated two things
The coach and the athlete were in control of the training process, doing things he would not have been able to do with heart rates alone.
The next chart represents a situation often found in endurance athletes, a low anaerobic capacity. It is one of the main reasons why someone is an endurance athlete, they do not have the anaerobic system throwing lactate and other metabolites into their muscles and causing problems with contraction. But they are also not very fast at short races.
This athlete completed three 2000 m runs on a track at roughly 15 seconds faster for each 2000 m. Based on the lactate results of this test, this athlete should be an elite female triathlete as least in running. But she was not. She completed an anaerobic test, a 600 m all out run and only generated 3.9 mmol/l of lactate. This is extremely low and it means that her V4 was highly influenced by this low anaerobic capacity and over estimated what she was capable of doing aerobically. If she had completed a standard distance test, running all out for 30 minutes, the result would have distorted her threshold substantially and her aerobic abilities. Her training would now include more anaerobic capacity training than would be normal for a triathlete. But most of her volume would actually be lower paces than someone else with the same V4.
It is also very common to see someone at the opposite end of the anaerobic capacity spectrum. There was a recreational triathlete who just liked to compete on weekends in Olympic length triathlons. He completed a series of 2000 m runs on a track and his V4 was about 6:40 per mile pace which was not bad for someone who only trained about 8 hours a week. He then completed a 600 m all out test and generated almost 18 mmol/l of lactate. This is very high for a triathlete. So his V4 was underestimating his aerobic capabilities. He could if he wanted to become a serious triathlete and compete and do well in major events. He would have to concentrate on lowering his anaerobic threshold and that would take time and a lot of training. But he wasn't interested in that. He was just interested in doing half decent and enjoying the friends he met during the meets.