For the heavy training types.


energy systems (or pathways) are confusing.

There are three systems:

1) Immediate anaerobic – produces energy for 0-10 seconds and relies on stored body chemicals, notably creatine phosphate to fuel it. If a full recovery is provided between repetitions then these chemicals will quickly replenish themselves allowing for the system to provide more immediate energy. There’s no reliance on oxygen to provide energy. This system fuels for example, a 40m sprint, a tennis serve or javelin throw.

2) Short-term anaerobic – produces energy for 10-90 seconds. Like the previous system it relies primarily on stored body chemicals as the prime fuel source, however as the 90 second mark approaches more oxygen is brought into aid the quest to sustain the high exercise intensity. However, no amount of oxygen consumption will provide enough energy to sustain this system. It’s rather like lighting a fuse to a stick of dynamite. The fuse consumes itself, burning more oxygen as it does and then blows the dynamite up. If you were to start running as fast as you could, you too would ‘blow up’. You’d stop when you burned your fuse (your body’s relevant energy chemicals) and would not be able to use anymore oxygen. This is the type of energy required for a 400m run or a tennis rally.

3) Aerobic – produces energy potentially for hours and relies on oxygen to fuel a chemical reaction in muscles to keep them contracting. If it were not for factors such as a reduction in fuel stores in the body (notably carbohydrate) and over-heating the body could theoretically continue exercising aerobically indefinitely. This is the type of energy required for a marathon.

Now, in reality all sports and activities rely on some mix of the energy systems. One of the easiest ways to contextualise this is again to consider sports events. The 100m is virtually exclusively immediate anaerobic, whilst the marathon is virtually exclusively aerobic. Field and racket sports and martial arts tend to rely on the short-term anaerobic system and the aerobic system. Recovery between points/rounds/plays provides the time for the former system to (attempt to) replenish itself and lower intensity work is fuelled by aerobic energy.

The aerobic system is in fact needed by all power and speed sports performers to some extent, as it provides a base of fitness for the anaerobic systems to be built on. Consider a tennis player; they could be on court for three hours plus. They will need good aerobic power to recover between points. However, this does not mean that they will need to do lots of long steady-state aerobic runs – their training should still primarily be anaerobic.

Lactic acid
Lactic acid is produced during high intensity exercise, when the body goes into upper end short-term anaerobic territory. The most obvious example is the 400m runner who will be running at 90% effort and will severely tax his or her short-term anaerobic system. However, a similar state of affairs can happen when making a sprint for home during a 10k race or during a hill climb during a long distance cycle race (this shows the interdependency of the energy systems). Now, the slightly confusing part, lactate is another body chemical. It is present in the body at all times and is used to generate energy, notably in muscles. At low exercise intensities, the rate of lactate clearance meets the rate of lactate production. However, as energy levels increase lactate production can outstrip lactate production. When this happens a different chemical reaction takes place in the muscles and lactic acid is produced. This is believed to irritate nerve endings, creating those ‘familiar’ muscular burning sensations. Once intense exercise is ceased lactic acid converts back to lactate and elevated levels of lactate return to base levels.

You can’t prevent the build-up of lactic acid. However, you can improve your lactic tolerance and increase the point when its build up become debilitating. This is achieved by performing short-term anaerobic interval training workouts (and providing a base of aerobic fitness). The fitter you get the harder you can push yourself. In fact it’s argued that mentally learning how to cope with the build up of lactic is crucial.

Guess who has being studying lately. :-)