fartlek

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Slow/Easy = Speed 5-8
Medium = speed 8-12
Fast/hard = speed 12-15
sprint = speed 15+ 

Warm up - 5 minutes @ medium

main 1
30 seconds @ fast/hard
90 second (recovery) @ slow/easy
 
repeat 5 times

MAIN 2
3 minutes @ medium
4 minutes (RECOVERY) @ SLOW/EASY
 
REPEAT 3 TIMES

MAIN 3
30 SECONDS @ FAST/HARD
90 SECOND (RECOVERY) @ SLOW/EASY
 
REPEAT 3 TIMES