Nutrition for Exercise

This lecture was kind of interesting as it explained the nutrient requirements for endurance athletes. (If you're a bodybuilder, some of this stuff might still apply, but maybe not. I don't know. Go ask an actual dietitian if you want proper advice.)

The first few slides were about energy balance, so you might want to review that if you live under a rock and have never heard of it before.

Effects of exercise on energy intake

Does exercise make you eat more? And if so, is exercise really worth it? The answers are yes and yes. In the short-term, exercise does cause a small increase in energy intake, but this is offset by the energy expenditure during exercise, so exercise is worth it. Furthermore, people who exercise regularly have been found to be better at regulating their appetite. Exercise also increases basal metabolic rate and decreases R-value, which means that more fat is burned. (A low R-value means that more fat is burned, whereas a high R-value means that more carbohydrates are burned.)

Athlete nutrition

In this post, we'll be focusing more on endurance athletes, though the requirements will probably change for bodybuilders and other types of athletes. Endurance athletes tend to have a much larger overall energy intake than us plebs, and a larger percentage of their daily energy intake is made up of carbohydrates (around 70% as compared to the usual 50-55%). This is because, as stated here, muscle glycogen is the limiting factor in how long we can exercise for.

Now for a couple of notes about protein, as protein is a nutrient of interest for many aspiring to get buff. Our general requirements are 0.8g/kg of body mass, but this can increase to 1.6g/kg in certain athletes (e.g. bodybuilders). Many athletes do consume protein powders, but if you already have adequate protein intake, protein powders provide little benefit. Furthermore, excessive protein may increase the risk of osteoporosis, colonic cancers and impaired kidney function in the long-term. However, it has been suggested that consuming a protein and a high GI snack immediately after a workout might increase the production of naturally-occurring anabolic hormones, increasing dem gainzzzzzzzzzzz. :D :D :D

For the rest of this section, I'm going to write about nutrient needs for an endurance athlete participating in a lengthy competition (>1hr). Some of this may also be applicable to shorter events. However, as I said above, if you want to know what's necessary for your specific needs, you should speak to a professional.

Pre-workout

As mentioned here, many endurance athletes participate in "carb loading" during the few days leading up to a competition. "Carb loading" involves consuming a lot of carbohydrates (10-12g/kg) while reducing your training load. If done correctly, the result is nearly doubled levels of carbohydrates.

Roughly 3-4 hours before a competition, a pre-competition meal may be consumed. This pre-competition meal is high in carbohydrates while low in fat and protein. Plenty of fluid is also consumed. Depending on the person, a liquid meal may be consumed (especially if they have a tendency to throw up during events).

Roughly 30-60 minutes before a competition, a pre-competition snack may be consumed. This snack tends to be in liquid form to prevent nausea. The foods consumed for this snack are low to medium GI foods in order to prevent rebound hypoglycaemia. In rebound hypoglycaemia, a large spike in insulin causes glucose levels to decrease rapidly, which is usually pretty great, but not if you're about to start exercising and consuming carbohydrates.

During the event

Yes, food is consumed during the event (at least in events longer than an hour). Generally athletes aim for around 30-60g/hr of carbohydrates, as well as 400-800mL/hr (100-200mL/15min) of fluid. Combining carbohydrates with fluid can be beneficial, but the percentage of carbohydrates should remain within 6-8% for optimal absorption. Cold and flavoured fluids containing electrolytes are desirable as these qualities encourage athletes to drink more and stay hydrated. Moderate to high GI carbohydrates are preferable as they result in faster release of glucose into the bloodstream.

Recovery

Post-exercise, high GI foods are consumed to accelerate glycogen replenishment. This may be followed up with low- or mid-GI foods. Plenty of fluid is also consumed, with an aim to consume 1.5x the amount of fluid lost.

Nutritional aids

There are many nutritional aids that people use but for the purposes of this post I will only focus on three: caffeine, beetroot juice and the mouth-rinsing technique.

Caffeine

Caffeine, as you probably know, improves arousal, reaction time, and so on. Caffeine increases free fatty acid metabolism, which may help preserve muscle glycogen. However, caffeine can also result in dehydration, restlessness, and so on. Also, for competition purposes, a really concentrated form of caffeine needs to be given, such as caffeine tablets.

Beetroot juice

Beetroot juice is rich in nitrates, which can increase vasodilation and muscle blood flow.

Mouth-rinsing

There is some evidence to suggest that simply rinsing the mouth with carbohydrates without actually swallowing them can stimulate carbohydrate receptors in the oral cavity, which results in the activation of performance-enhancing signalling pathways.