Paarlauf is a very good way to work the lactate shuttle energy system within the body.
Basically, when we work anaerobically (not using oxygen) a by-product is produced, commonly known as lactic acid to athletes.
Part of this is lactate, which is an energy source which can be utilised when running at a less intensive level. Therefore, if
the athlete in a paarlauf, who is not on the harder run, runs at about 60-80% of the speed of the intensive reps they use this energy
system effectively recycling waste energy products from the harder reps.
This is very useful and is being more commonly used by athletes now that in previous years. A good session could therefore be
500m for the athlete running hard, with a 300m recovery between each. 10 repetitions of this (maybe in two sets of 5 with a 5minute gap
would constitute a very good paarlauf session for an 800/1500m runner. This model can be adapted for different distances.