The following is an example of Fartlek training:
A. Warm-up, sprint 100 m, rest, slowly walk back (repeat 5 times), cool down
B. Warm up, run 20 sec, rest 10 sec (repeat 8 times) cool down
C. Warm-up, swim-sprint 50 m, slow 100 m (x 5 further each time), cool down
D. 45 minute step aerobics class