Why Fuel?

During any physical activity, your muscles use carbohydrates and fat for fuel (It also uses lactate in a small amount, but to keep things simple, we will first only focus on the aforementioned two sources of energy). Generally, the higher your exertion level, the more sugars you burn and the more important it becomes to fuel your efforts in order to aid your muscle glycogen stores in providing energy to your muscle fibers and to aid your liver in keeping your blood glucose levels stable.

Science has found that the consumption of Sports fuel during physical activity can lead to

1. Improved performance and enjoyment, helping to make those goals more attainable.

2. Less muscle damage and fatigue afterwards, allowing you to do what you love the next day with a lower risk of burnout.

Prof. Tim Noakes published his “Central Governor” theory a while back. And I believe it is the current best theory, along with physical muscle damage, to explain fatigue. It mentions that the brain is the main controller of the body and that the unconscious mind, which is connected to many physiological receptors, takes over from your conscious will when you risk damage to the brain through your actions.

A further explanation of this statement is the fact that the brain has no energy stored in itself and relies fully on blood glucose for energy (The brain of a person on a well-formulated ketogenic diet, however, can adapt to rely heavily on ketones after a long adaptation period, mitigating its need for glucose). Brain cells begin to die after as little as one minute without energy, so when the brain's sensors sense that your exercise is causing your blood glucose concentration to drop below a certain level, it initiates feelings of muscle pain and fatigue, forcing you to lower your intensity so that your working muscles use less blood glucose hereby preserving the glucose in your blood for use by the brain so that it can stay happy and healthy.

This means that fueling is probably important for different reasons than what has been believed for a very long time. It was believed that it was important only to supplement your muscle glycogen levels (carbohydrates stored in your muscles, which usually run out after about 60 to 90 minutes of exercise). But the muscles of a relatively fit person are very adaptive and will just burn a higher percentage of fat as their glycogen stores become emptier (even at high intensities). Thus, the real importance of fueling is to supplement your blood glucose pool when your muscles start to take up glucose from the blood (which happens at very high intensities or when your muscle glycogen is depleted and you remain exercising at a high intensity) to satisfy its need for energy thereby lowering your blood glucose to critical levels which may be harmful to the brain. But luckily, your brain stops you from letting that happen, but unfortunately, it does so by forcing you to slow down.

Simply put. When you fuel your main goal is to maintain a proper blood glucose level to keep your brain happy and nourished, so that it can stay strong and determined, and allow you to push your limits. In a nutshell, you can only go as fast as your unconscious brain allows you to go.