The Iron Man 3 workout: Tips from Robert Downey Jr.'s personal trainer
We use Alpha Strong bags because the handles of the bags are well made and well placed on the bag. Using the handles that are closest to the middle of the bag squat down and grab the handles.
"Power throws are a full body exercise encompassing your full body. Be sure to keep your abs engaged (tight). The first notion from here is to press up with the legs moving from a squat position (use your legs, not your lower back) to a position where the bag is hanging at your waist and your legs are extended.
Now flip the bag up to rest on your chest (like you would on a clean and jerk). Finally push the bag in a throwing motion releasing the bag. Quickly get to the bag and repeat this 8-12 times, doing 3-4 sets.
Tip when throwing: If you throw with an upward motion you work more shoulders while an outward motion works more chest."