Energy for physical effort

The energy of a body activity is produced by three different sources.

Two sources are anaerobic (they do not use oxygen) contrary to the third which is aerobic (it is the most important).

Each source is defined by a capacity (total amount of potential energy) and a power (amount of energy usable by unity of time). Compared to a tank with a tap, the capacity correspond to the tank volume and the power to the tap flow.

Working concurrently, these sources have a specific working time corresponding to three different types of effort.

Alactic anaerobic source (for less than 30 s of effort)

This source is mainly used for "explosive" sport (weightlifting, jumping, throwing, 100 m running, 50 m swimming). The capacity is from 23 to 36 kJ (*). The maximal power is from 4 to 12 kW (*), it is immediately available and can't generally be maintained more than 8 s. The recovery time after a maximal effort is 6 to 8 min.

Functioning of the alactic anaerobic source

Lactic anaerobic source (for less than 3 min of effort)

This source is mainly used for "short" sports (gymnastic, 200 to 1000 m running, 100 to 300 m swimming). The capacity is from 95 to 120 kJ (*). The maximal power is from 3 to 8 kW (*), it is progressively available and can't generally be maintained more than 1 min. The recovery time after a maximal effort is 1 to 2 h.

Functioning of the lactic anaerobic source

Aerobic source (for more than 3 min of effort)

This source is mainly used for "long" sports. The capacity is almost unlimited. The maximal power is from 1 to 2 kW (*), it is very progressively available and can't generally be maintained more than 7 min. The recovery time after a maximal effort is 24 to 48 h.

This is the main source because it allows regenerating the previous ones. Everyone should improve it (sportsman or not). As the aerobic capacity (total amount of energy open to oxidative way) is not measurable, endurance is analysed instead as the decrease of the power during time.

The aerobic power corresponds to the aptitude to consume the oxygen of the air : capture, transport, utilization. Capture is depending on the respiratory system efficiency. Transport is depending on the red corpuscles density and cardiac flow in the cardiovascular system. Utilization is depending on the oxidative efficiency of cells (number and sizes of mitochondria) in the muscular structure.

The aerobic endurance corresponds to the aptitude to consume as long as possible great quantities of oxygen. It depends on capillary density into muscular structure and reserves of glucid and water.

Functioning of the aerobic source

Relative importance of energy sources

N.B. The three sources are not independent. They works concurrently, at different degrees, which creates an illusion of a serial processing. For each source, the surface between curve and time axis represents the capacity.

(*) The lowest value is for a sedentary adult, the highest for a high level sportsman.