There are more than one type Jammers in gyms .Pretty much standard off season training equipment for football players. And most other sports training. Use it for strength to cardio or anywhere in the middle.
Variety of positions from two hand, one hand, push/pulls, twist, one leg, two legs, splits, etc. Excellent piece of equipment for all around training, fro the Pro to the average guy who just wants to get in shape. Good luck.