Dizziness, a sudden, all-consuming loss of energy, a desire to get off the bike, sit down and have a nap – bonking is a cyclist’s nightmare.
We spoke to nutrition scientist, athlete and pioneer of Osmo Nutrition – Dr Stacy Sims – to find out exactly what’s going on when you bonk, how to avoid it, and what to do if you do bonk when cycling.
There are two kinds of ‘bonking’, but most don’t know this. “One type of bonking is from a drop in blood volume (loss of body water) and is perceived as flat, dead legs, a drop in power with an elevated heart rate. Most people think this is a need for calories, but in fact, they are behind the 8-ball in hydration.”
If you find yourself struggling with this, the outlook isn’t great for the rest of your ride, Dr Sims explained: “This takes hours to come back from- no, guzzling water doesn’t help (water will just sit in the stomach), and typical sports drinks can exacerbate the dehydration.”
“The only real way to mitigate this kind of bonking is to avoid it by drinking a low carbohydrate-electrolyte drink throughout your ride (don’t go for “liquid calories”- eg calories in the bottle- this is more fueling and does not address hydration needs).”
However, there is a way to limit the effects: “If you haven’t been able to avoid this, to get home, drink water with a dash of salt (1/16th tsp in 20oz water) to pull fluid into the body- but remember, it takes hours to recover from body water losses.”