19 Jul 2016
BURN FAT, RACE FAST!
There’s no denying that carbohydrates are king when it comes to high-intensity cycling. Climbing Alpe d’Huez leaves your heart beating to the max, and the only way you can get enough energy to working muscles fast enough is by breaking down this essential macronutrient. However, a gramme of carbohydrate only delivers four calories of energy. That compares to fat, which is over double that at nine calories per gramme. If only you could utilise more fat for cycling than carbs…
There’s an increasing school of thought that if the body is starved of carbohydrate, it’s forced to break down more fats for energy. For endurance athletes like cyclists this is the Holy Grail. Why? Well, your body stores around 1,800 carbohydrate calories in a form called glycogen in the liver and muscle cells before releasing it into the bloodstream in the form of glucose. It’s then broken down in cell powerhouses called mitochondria, one of the results being energy.
The problem is, cycling a sportive can burn up to 800 calories an hour, leaving a shortfall if you rely on carbohydrates, which could result in bonking. However, that’s where fat comes in. Even a fit cyclist stores up to 100,000 calories of fat in muscle fibres and fat cells. So by training with low glycogen levels, your body has no choice but to use fat stores.
To delve a touch deeper into the science, the main adaptation to fasted endurance sessions is enhanced mitochondrial volume in your muscles. That means all the enzymes and sites of aerobic metabolism are unregulated to a greater extent. The phenomenon is known as mitochondrial biogenesis, and as a result of these changes, you become more efficient at using fat for fuel at a given exercise intensity, which means you conserve glycogen for the harder parts of the race.
The key word is ‘intensity’. How hard you train is affected by muscle and liver glycogen levels. If they’re low, so too will blood glucose levels, which’ll make the session feel too tough and could ultimately lead to illness. That’s why it’s appropriate to pencil in fasted efforts during sessions that aren’t too intense.