Amongst endurance athletes, there are many words and phrases that are commonplace but to outsiders, may seem like a foreign language – Fartlek is likely high on this list. However, of all the words, none are more fear-inducing than the dreaded ‘bonk.’ There is a good reason why bonking is also referred to as, “hitting the wall!”
Quick physiology refresher… bonking is the result of running out of glycogen (stored glucose – i.e., blood sugar).
Therefore, endurance athletes do everything in their power to avoid the bonk from carbohydrate loading to the complete opposite – glycogen depletion training (GDT). The theory behind GDT is that by training at very low glycogen levels (and likely hitting the wall), an individual will train their body to be more efficient at burning fat than carbohydrates (i.e., glycogen).
INFLAMMATION AND GENETICS
A 2015 study by Nieman et al., found that low glycogen levels are correlated with increased levels of inflammation, which acts as a stressor on the body. Additionally, Nieman states that while there are things that individuals can do to lessen the inflammation response, such as interval training, at the end of the day, how someone is able to preserve glycogen stores as compared to another is largely based on genetics. In other words, two athletes of equal ‘fitness’ could perform the same GDT workouts and have two very different responses.
In summary, due to the increased chance of inflammation that GDT likely causes, and the fact that individuals have varied responses to low glycogen, it is advised to focus on a well-rounded training program that incorporates interval-based workouts and proper nutrition to minimize the chance of bonking – both in training and in competition.