VO2 max and energy sources

Updated: Jul 8

Your body uses differences sources of energy (macronutrients - carbohydrates, proteins and fat) that goes through very complicated processes to cause muscle contractions. To give you an idea, take a look at this (simplified) diagram.

We will discuss the use of different energy sources at different stages of training, looking into VO2 max.

VO2max is the maximum amount of oxygen that your lungs can utilised during exercise.

When training, an athlete can use percentage VO2max as an indication of how hard they are training.

At 40% VO2max , you are using 40% of the amount of oxygen that you are capable of using. At 100% VO2max you are using everything that you can. BUT, you can only sustain a certain force at 100% for less than 5 seconds. Using 40% VO2max will allow you to sustain a specific pace or force for a longer period.

The duration and intensity of the exercise that you are engaging in, determines the % that you would want to maintain.

*Men contain a higher amount of haemoglobin in their blood than females, allowing them to carry approximately 15% more oxygen in their blood when it leaves the lungs. Thus, men have a higher VO2max.

At different percentages of VO2max your body uses different energy sources, following different pathways. This science makes it possible to develop nutrition strategies that can be very specific to type and duration of an event.

We look at 5 different stages of % VO2max

  • Supermaximal (100% VO2max)

  • Supermaximal (<100% VO2max)

  • Maximal (~85% VO2max)

  • Submaximal (60 - 80% VO2max)

  • Submaximal (40 - 60% VO2max)

Example of strategies:

  1. Supermaximal: An athlete who participates in weight lifting requires small bouts of energy, when performing a single rep (repetition). The force that the muscle must generate requires a lot of energy. The pathway used for the release of energy for muscle contractions is via the ATP/PCr pathway. This pathway uses Creatine to recycle ADP molecules and phosphorylate it into ATP (energy loaded molecules). Knowing this, allows us to develop a strategy where Creatine levels in the body is increased to optimise performance by increasing the rate of ATP production. ENERGY SUBSTANCES: CREATINE

  2. Supermaximal: A sprinter competing in an event lasting between 6 and 60 seconds (200m race), performs at almost 100% VO2max , while ensuring that they can maintain their pace for the duration of the event. The main substrates for energy and muscle contractions are ATP/PCr and glycogen, following anaerobic pathways. This athlete should not only maintain high levels of creatine in the body, but should also have glycogen stores available. ENERGY SUBSTANCES: CREATINE AND GLYCOGEN (CARBOHYDRATES)

  3. Maximal: Middle distance runners perform at above 85% VO2max and mainly uses 3 pathways for energy production. An athlete participating in a 1500m event can follow the following strategy: regulate and maintain creatine levels, dietary glucose in the blood and glycogen stores in the muscle and liver. This will allow the body to utilise energy from three different pathways. ENERGY SUBSTANCES: CARBOHYDRATES AS GLUCOSE AND GLYCOGEN

  4. Submaximal (>5 mins - 5 hours ): When participating in endurance events at a VO2max of 60 - 85%, your body follows 5 pathways for energy production and used different substrates. To ensure optimal performance, an athlete needs to have enough of all the different substrates to produce a maximum amount of energy and avoid fatigue. There are 5 pathways to produce energy (discussed below). ENERGY SUBSTANCES: CARBOHYDRATES, FAT AND PROTEIN

  5. Submaximal (>5 hours): VO2max of 40 - 60%. Follows the same five energy pathways, but the levels must be elevated throughout the event to avoid energy depletion. ENERGY SUBSTANCES: CARBOHYDRATES, FAT AND PROTEIN


  • ATP/PCr (substrate - creatine)

  • Intramuscular triglycerides IMTG (substrate - fat)

  • Glycogenolysis (glycogen from muscle and liver)

  • Glycolysis (Blood glucose)

  • Amino acid (enters TCA)

Nutritional strategies can help with preparation for an event and optimal performance during the event.

Sports and Exercise Nutrition, First Edition. Lanham-New, SA. Stear, SJ, Shirreffs, SM. Collins, AL. 2011.

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