The most significant disadvantage of fartlek training is that, compared to other running workouts, it is easier for athletes to skip the hard portions and more difficult for coaches to monitor progress from workout to workout, according to Teach PE and The University of Sheffield. Fartlek training is used to build running speed and endurance, according The University of Sheffield.
Fartlek training is an exercise routine where periods of hard exercise are mixed with periods of easy exercise. Teach PE cites the example of a running workout where athletes sprint for ten seconds (hard), fast walk for twenty seconds (easy) and then jog for one minute (easy).
Teach PE also notes that there are advantages to fartlek training. It is good preparation for sports that require pace changes, and it is also easily adaptable to individual levels of fitness. The University of Sheffield notes that fartlek training provides a great introduction to higher-intensity workouts. It is also helpful in preparation for a variety of sporting events and team games. Fartlek training also uses all of the body's energy systems, which prepares athletes for changes in exercise intensity during competition. Fartlek training also benefits athletes by improving oxygen capacity, lactate threshold and exercise economy.