Players perform repeated short bursts of vigorous activity (work periods) interspersed with relief intervals, which include movements such as slow jogging, walking, and passive defence. Most intense work periods in netball are less than five seconds. In fact, the average sprint times of skilled netball players during a game have been shown to be less than 1.5 seconds (Steele and Chad, 1992).
The predominant energy source required for short bursts of intense effort lasting less than 10 seconds is provided from the breakdown of high-energy phosphates, adenosine triphosphate (ATP) and creatine phosphate (CP). These substances, stored in muscles, provide a rapidly available energy source without need for oxygen to provide fuel. High-energy phosphates are the predominant fuel source used in netball to enable players to perform characteristic explosive sprints, jumps, and leaps intermittently throughout a match. .
The ATP-CP energy system, however, cannot support all - out efforts longer than 5 to 10 seconds. Fortunately for netball players, ATP-CP stores depleted after maximal efforts are rapidly replenished during relief intervals, with half the energy source available for use 30 seconds following an intense effort. Although netball predominantly involves short bursts of movement, energy made available to replenish ATP and CP stores comes from aerobic metabolism of foodstuffs. Furthermore, the duration of a match (usually one hour) taxes the aerobic energy system to provide fuel for endurance.
Various forms of time-motion analyses have monitored the physiological requirements of netball match play and studies, which have recorded heart rates and blood, lactate levels during competition matches. Information gained from such analyses has provided a valuable basis upon which training programs specific to netball can be developed. .
Apart from energy systems, additional physical demands are required to enhance netball performance.