Final answer:
The glycolytic system, which uses glycogen to produce ATP without oxygen, is best for sustained speed over 60-90 seconds, such as activities like a 400 m run.
Step-by-step explanation:
Energy Systems for Sustained Speed
For sustained speed over periods of 60-90 seconds, such as in events like the 400 m run, the energy system that is most effective is the glycolytic system. This system uses glycogen as an energy source to produce ATP anaerobically, meaning without the presence of oxygen. The glycolytic system can supply energy rapidly and is efficient for activities that last slightly beyond a minute but typically under two minutes. This duration aligns well with the window of 60-90 seconds mentioned in the question.
The glycolytic system, also known as anaerobic glycolysis, involves around 12 chemical reactions to break down glycogen into glucose, which is then converted to ATP and lactic acid as a by-product. This biochemical process allows for a fast supply of energy although it is not as quick as the phosphagen system used for very short, intense efforts like weightlifting but much faster than aerobic respiration used in endurance events like marathons. Therefore, for events requiring sustained speed and lasting from one to around one and a half minutes, the glycolytic system is the most appropriate energy system.