What every athlete or fitness enthusiast will need to address at one time or another is what their fueling needs are. Rather it be to increase performance, reach particular weight goals or avoid bonking at their next race, it is something that will need some consideration in order to make your workouts the most beneficial they can be. What makes this task difficult is the amount of information one is confronted with when they begin their search for answers. The answers can come from a workout buddy, the guy behind the counter at a nutrition store, articles, sports-related media sources or by experimentation.
What most athletes don’t appreciate is the depth of the science behind it, nor understand that the study of performance nutrition is young and evolving as its importance becomes more relevant. There is also an increase in recreational runners, weekend warriors, endurance athletes and fitness gurus that are looking to reach new goals. So, the good news is that there is a hunger for nutritional education along with many products and ways to achieve it. The bad news is that there is a lot of confusion out there along with the omission of a simple fact-our bodies all function differently, different types of exercise require different fuel needs and there is no “magic” formula that will work because the body is constantly adapting to stressors or compensating in its own way to maintain homeostasis (internal stability) that can be somewhat unpredictable.
So, the first thing that one must do is try to define what kind of athlete are you? How often do you exercise and at what intensity? What is your fitness level in regards to body fat percentage, body type, weight and cardiac health? What are some hormonal or biological factors that can affect your energy cycles, such as diabetes, thyroid or genetic history? What is your age and how long have you been active?
Secondly, one must have a general understanding of the energy cycles we go through when exercising. Here are a couple of diagrams that can help explain which ones we use. Remember that we will cycle through these the longer we are active or if intensity of activity is moderate to high, such as in endurance sports, HIIT sessions or interval sets. The cycle is only as good as what the body has stored, can access and is available for digestion or metabolized which is influenced by so many factors, including gastric function, enzymes and blood flow.
The three energy cycles are the phosphagen system, glycolysis and the aerobic system. All energy for activity come from converting ATP (adenosinetriphosphate) to ADP (adenosine diphosphate), AMP (adenosine mono-phosphate) and inorganic phosphate. This is a water-requiring process (another reason hydration is important). Our muscles don’t store much ATP, so we must constantly resynthesize it through a circular type of mechanism. Which system is turned on to produce ATP is dependent on how quickly they need it and how much. The phosphagen system is the fastest pathway, but can only provide enough ATP for about 10 seconds. This can be intensely fast or power moves. The glycolysis system is the second quickest way to synthesize ATP and is the superior energy system for intense activity lasting from 30 seconds to 2 minutes. This is where carbohydrates (blood glucose or stored muscle glycogen in the form of glucose) is broken down to produce two molecules of ATP. So, very little is produced, but you get that energy quickly. This process will have two potential outcomes-conversion into lactate (when demand for oxygen is greater than supply available-anaerobic exercise) or when there’s enough oxygen available to meet the muscle’s needs (aerobic exercise) then it is used to create more ATP. When oxygen is lacking, due to acidosis, inhibition of certain enzyme reactions and inhibited release of calcium interferes with electrical activity in muscles that can affect their ability to contract, produce force and the intensity will decrease. The last system and the most important, yet complex is the aerobic. It is the slowest, but the produces the most ATP. It uses blood, glucose (sugar), glycogen and fat to resynthesize ATP in the muscles cells. Carbohydrates, glucose and glycogen are metabolized using the Krebs cycle, ultimately producing water and ATP. This process produces 36 molecules of ATP for every molecule of glucose broken down, 18 times more than the other systems. Fat is the major fuel needed for this system and is the largest store of energy in the body (about 70,000 calories of fat are available during lower-intensity aerobic exercise). The breakdown of these fatty acids yields more ATP than other systems, for example, the fatty acid called palmitate produces over 125 molecules of ATP. This is why it seems easier to go long and slow.
So, how can we make sense of all this information in regards to personalizing our fuel needs? Let’s breakdown this down to those first questions we asked. If you are a recreational athlete or one that exercises to maintain health, to lose weight and typically works out 3-5 days per week at 60 minutes or less without significant interval or intense training, then for the most part, your body has what it needs for those workouts as long as you have hydrated well (drinking 2-4 cups of water 3-4 hours before and 1-2 cups an hour before). You should have eaten 3-4 hours before, consuming 300-600 calories of mostly healthy carbohydrates (2-3g/body weight), moderate in protein and low in fat for that pre-exercise meal. If you partake in higher intensity workouts, power moves (body building) or interval/speed drills, then you may need to refuel in carbohydrates (30-60gms/120-240 calories) every 45-60 minutes to replenish stores. This can be achieved through beverages or easily digested foods. You may also have to drink 6-12 oz of water if carbohydrates are consumed in solids.
Now for those endurance athletes that have workouts lasting longer than 90 minutes. Again, depending on the make-up of those workouts (speed drills, fluctuating heart rate zone requirements or long and steady) will affect what you will need. This is where practice is going to be key. If you are going long and steady, you are going to be conserving oxygen which is going to help in the production of ATP and can decrease your need for glucose or carbohydrate replenishment because you should access fat stores. You will still need to consume some water to help with the conversion process, but this is dependent on factors such as sweat rate or training adaptions. The key is finding out what is in your gas tanks, but being prepared if it begins running low and know the signs. High performing athletes have trained their bodies to run primarily on carbohydrate and glycogen stores within their muscles and liver. They tend to race slightly deficient on the fluid side, but their bodies have adapted to this stressor and compensates. They have low body fat percentages, but how fine-tuned how their aerobic system functions with hours and hours of training per day in an aerobic state. They also know that they have to make sure that their daily intake is high in carbohydrates to allow for breakdown, storage and accessibility. So, most of their daily calories are high in carbohydrates, moderate in protein for muscle repair and low in fat (because we already store so much more in the cellular sense than we ever thought).
The most important thing any person can do to see gains in their goals, rather they be performance or general health related is to realize that every BODY is different. We have different ratios of slow and fast twitch muscle cells that dictate if we are genetically built for sprints or longer runs and affects how we use our energy systems or cycles. If we have a family history of diabetes or display signs of metabolic syndrome, then we must be more diligent in how much glucose we consume due to our bodies containing higher blood levels and can be more sensitive to insulin release, if we have surges in glucose consumption. Hormones affect these cycles, liver health and body fat distribution can affect how efficiently the cycles run. Emotions can influence how glucose is used (the more nervous we are at a race, the more we are burning due to increased adrenaline and cortisol). External factors such as heat, cold or clothing will effect production (will be more focused on cooling or heat production and less on sending blood to working muscles). Lastly, gastrointestinal systems are different in how we absorb, breakdown and ultimately get those nutrients out to blood vessels that transport nutrients to working muscles. Also, if we are not partaking in nutrient dense foods, then we could be deficient on enzymes and key vitamins or minerals that act as catalysts or carriers for all this cycling of energy “cells.”
So, the key in finding out what your fueling needs are is to practice during your training sessions. Take note on how you feel, perform and post-workout recovery needs. You would be amazed at how much the body can do, compensate for weaknesses or when lacking the proper nutrients. It will get what it needs, one way or another, but it comes at a cost. The best thing you can do is eat a variety of whole foods that are nutritious so that you can keep storage units full, readily accessible and replenish what you have taken away. Ultimately, the body will shut you down, if you cannot compromise with it. This can come in the form of a bonk at a race, stalled weight loss, decreased performance, injury or lacking motivation as a mental survival tool to tell you that enough is enough. Listen closely to your body, it’s the only body we got and can do amazing things!