Energy Requirements for a 100m Sprint

The 100-meter sprint requires intense, all-out effort for a very short time. The world's best sprinters finish the event in under 10 seconds. Because a sprinter's muscles need energy as quickly as possible, most of it comes from their stores of two immediately accessible high-energy compounds. To replenish those compounds, a sprinter's muscles must also use other, slower energy systems.

Adenosine Triphosphate

Ultimately, the energy our cells need comes from the foods we eat. Cells break down carbohydrates and fats to provide energy, then store that energy in the form of adenosine triphosphate (ATP). ATP is often termed the cell's energy currency. When cells need energy, they break off a phosphate ion from ATP, yielding a compound called adenosine diphosphate. That reaction releases energy, which can be harnessed to perform work such as contracting muscles.

Energy During Sprinting

Because the breakdown of stored ATP releases energy almost instantaneously, it is the primary energy source as a sprinter explodes out of the blocks. However, muscles only store enough ATP for two to three seconds of maximal power output. To rapidly replenish ATP, muscle cells break down another high-energy compound called creatine phosphate (CP). This is called the ATP-CP or phosphagen energy system, sometimes referred to as the alactic anaerobic system because it does not require oxygen.

Other Energy Sources

Muscle cells only store enough ATP and CP for about 10 seconds of maximal power output. As a sprinter nears the finish line, another energy system, termed anaerobic glycolysis or the lactic acid system, comes into play. Muscle cells metabolize carbohydrates, releasing energy to re-synthesize ATP and CP while yielding a product called lactate. This process produces energy very quickly, although not quite as quickly as the ATP-CP system. That's why even world-class sprinters slow down in the final seconds of a 100-meter race.

Replenishing Energy

After a sprint, muscle cells must replenish their stores of ATP and CP. Complete restoration can take two to eight minutes. The energy to re-synthesize ATP and CP comes from the lactic acid system as well as from a third system, the aerobic energy system, which uses oxygen to restore ATP and CP. This process partly accounts for excess post-exercise oxygen consumption, or EPOC, and explains why sprinters breathe heavily after a race despite relying almost entirely on anaerobic metabolism during the event.