Question from M. Reith: In March 2010, I (49 years old) underwent a performance diagnosis at the Swiss Olympic Medical Centre. It revealed a maximum heart rate of 184 and an anaerobic threshold of 153. In July, I took part in a mountain bike race. After the race, which took me 98 minutes, my heart rate monitor showed an average heart rate of 179 and a maximum heart rate of 189. Compared to the diagnostics, I was well above my anaerobic threshold for most of the time. How is that possible?
Answer from Dr Stapelfeldt: The anaerobic threshold is a parameter based on a physiological theory. According to this theory, the lactic acid (lactate) content of the blood increases disproportionately at a certain intensity of exertion. The anaerobic threshold (ANS) describes the maximum performance at which the blood lactate content can just be kept constant under continuous stress. In fact, however, you can ride with significantly higher lactate levels than at the ANS because the body has buffer systems. In addition, mountain biking means a constant change in performance, so that lactate is removed from the muscle in phases of lower exertion. In this respect, the anaerobic threshold does not indicate the continuous performance limit, but the state at a defined load.
However, the endurance performance limit depends on the duration of the exercise: for example, it is higher for a 4-minute track race than for a 60-minute time trial, both in terms of performance and heart rate. The longer the race lasts - from around two hours - the better the ANS can characterise the endurance performance. You were therefore able to complete your race of around 1.5 hours with a performance beyond the anaerobic threshold. In this respect, you had significantly higher lactate values than at the ANS and ran the race in the so-called development or peak range.
