Cardio

[anythingtobenormal]

What are the best forms or cardio to do without machines or equipment?
Running obviously but if I was to start running myself what distance should I start at,5k?
Or till failure?

 

[cooIguy]

14 incline treadmill 6 speed

 

[cooIguy]

i just read about 12/3/30 method it also might work