HIIT workouts

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hi has anyone seen the workouts on the youtube channel "fitness blender"
they have a 1000 calorie workout, but also more sensible ones

here are some links

1000 calories workout - http://www.youtube.com/watch?v=I5COzZlxaI4

cardio workout - http://www.youtube.com/watch?v=fcN37TxBE_s

belly fat loss - http://www.youtube.com/watch?v=RRDtQ7Zmp6c

be interested in your thoughts