Triathlon Magazine Canada
less than after the MT week. They dug further into this, as the body was producing the mitochondria as expected; they discovered that the mitochondria simply could not work properly.
Why were the mitochondria not functioning properly? After ET, glucose uptake (turning carbohydrate into energy) was impaired. Despite ET eliciting the training response expected (building new powerhouses in the cells), those powerhouses were cut off from glucose to turn into energy. This means athletes training frequently at a higher intensity and hoping to burn more calories are burning less than they would at moderate intensity. Creating this mitochondrial dysfunction through excessive intensity training prevents proper cellular metabolism.
One of the criticisms of this study was that this excessive training week would not actually happen in real life. I would argue that, in triathlon, athletes and coaches frequently underestimate the amount of intensity being prescribed. For example, if a Tuesday morning swim has 5 x 200 m hard repeats in the pool in the morning, followed by running intervals that evening (maybe 5 x 1 km), with a 5 x 8 minute hill repeat workout Wednesday and finally another 20 x 100 swim repeats on Thursday morning, there are four intense training sessions in three days. With four more days left in the week, this athlete is approaching excessive training.
There is a growing body of evidence suggesting that metabolic disorders, like cancer and diabetes, are related to mitochondrial dysfunction. Another group of researchers asked sub-elite athletes to wear a continuous glucose monitor and found instances where elites were experiencing hyperglycemia like pre-diabetics. This phenomenon of reduced glucose uptake in athletes is not limited to healthy subjects, it exists in elite and sub-elite groups. Whether this hyperglycemia is linked to excessive training was not discussed, but this research explains the arrival of continuous glucose monitoring in our sport (Supersapiens, a company that offers a glucose monitor, is an Ironman sponsor).
The moral of this story is that low- and moderate-intensity work is the backbone of a great triathlon training program. There is simply no replacing the largest portfolio of low- to moderate-intensity training you can build with small doses of higher intensity.
If your goal is healthy body weight and good cardiovascular fitness, low- and moderateintensity training is the highest rate of return with lowest risk of training error. Be patient with yourself, and you will realize the benefit of this work with time. Like building a good investment portfolio, consistency pays off over time.
Melanie McQuaid is a three-time Xterra world champion who lives, trains and coaches in Victoria, B.C.