SAFD: So I have thoughts about fueling. Essentially, I feel that people completely overdo and over-think the entire subject. You don’t need to supplement normal eating for 5ks or 10ks or 10-milers. There should be a reason why you are consuming extra salt and sugar. If you’re driving a car that has enough gas to go 400 miles, do you refill the gas tank after driving 5 miles?
(1) Unless you are sweating for more than 3 hours, you don’t need to supplement with electrolytes. Electrolytes are salts such as sodium, chloride, potassium, calcium, and magnesium. Electrolytes are necessary to direct fluid to the inside and outside of your cells, leading to optimal hydration. We lose most of our electrolytes through urination, not sweating. A normal diet will contain enough sodium for exercise under a marathon distance. If you finish a race still hydrated, then there’s no need to eat more salt.
(2) Gels, chews, etc. It’s all just sugar. Our bodies need ATP as a substrate for muscle contraction. Within cells, energy is provided by the “metabolic fuels” such as carbohydrates, lipids (fat), and proteins. Simple carbs are easily converted into ATP, while fat takes longer and requires more energy to create ATP (which is the basis for Adkins and other low-carb diets). People hit “the wall” when their glycogen stores are depleted and the body switches to the fat stores for energy. Some training plans even have fasting runs to get the body used to running with no glycogen stores.
Most of the supplements rely on sugars such as glucose and fructose for energy. Our bodies can only absorb about 60 grams per hour of glucose, which is quickly absorbed through the small intestine. Adding fructose allows the body to consume more carbs, since it has to be processed through the liver first before it becomes cellularly available. Both fructose and glucose are stored in the liver as glycogen, and if you eat 2-3 hours before a race, then your body can run for around 120-160 minutes without any additional fuel. Again, if your glycogen stores aren’t depleted, and your muscles have adequate ATP to contract, then eating extra sugar during a run under 120 minutes does nothing. Adding to that, if you’re running at a slower pace, your body will rely more on its fat stores for energy than carbs, which are primarily consumed at zone 4-5 efforts.
