If lactate values at a given HR increase it can be a warning sign of a potential problem. With aerobic adaptation we should see a decrease in [La-] at given HR assuming the speed is constant. However, we are learning to be detectives here, I’ll direct your attention to the speeds the athlete is holding at the 160 HR (third red point and fifth green point from the left on the top graph) and this will help.
From this we learn that while an increase in lactate may indicate more muscular work is being done, there can be reasons for this. In this case the reason is that the athlete can now run almost 30 seconds / kilometer faster at a HR of 160 than they could in March. In a 6 mile run this is about 3 minutes faster, although holding this pace for 6 miles may be tricky as their individual anaerobic threshold is probably about 150. As you can see, there is no clear point where their lactate levels rise fast, although it is obvious it is somewhere between HR 150 and 160. A different individual anaerobic threshold test would help us estimate the iAnT. My favorite these days is one called the Maximal Lactate Steady State (MLSS) test. This test works very nicely with trained athletes, although non-athletes find it mentally challenging to work as hard as is necessary.
As a coach you need to ask and answer questions about the results you see, no matter what the test being performed. In this case I have an unfair advantage, as I know that the athlete did no intensity work for three months as a means to minimze the risk of re-injury. All their training was at an aerobic threshold pace of 125-145 beats per minute. The training adaptation we are looking at is that all sub-maximal speeds (where maximal is equal to a HR of ~180) are faster than in March.
For the next month we are focusing on easier “race pace” intensity intervals to prepare them for a race at the end of June. Not an ideal situation as far as training goes, but as a coach I should help my athletes achieve their goals despite the challenges they face. In this case, the challenge was an injury which required 10 weeks off from running, followed by a walk-run program, then gradual increases in running volume prior to any intensity. There is no doubt this athlete is behind the 8 ball for the June race, which incidentally is an Ironman triathlon. The swim and bike training progressed well through the stress fracture, so all we need now is the run to hold together at a sub-iAnT pace which is what most mid-pack Ironman triathletes accomplish. Our goal is to run at a HR of 145.
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