What is Fartlek training ? Write in brief.

Fartlek training method is used for developing endurance.The word 
'fartlek'is a swedish word means 'speed play'.this training method lays emphasis on both the aerobic and anaerobic systems.In this method ,speed is not preplanned so it is left upto the individual.Self discipline plays a vital role in fartlek training method.The rate of heart beat ranges between 140 to 180 per minutes.Such examples are-warmup, jogging or slow running.
Advantages
1.It keep the heart rate up allowing an athelet to get good cardiovascular endurance.
2.It is good for aerobic and anaerobic fitness.
3.It is not rigid but flexible in nature.
4.In this training method no equipment is required.
Disadvantages
1.It is difficult to see how hard the trainee is making efforts.
2.Sometimes the athelete is likely to drop efforts.
3.It may cause accidents because it is not pre planned.