This paper presents a novel way of using real-time heart rate information to control a physically interactive biathlon (skiing and shooting) computer game. Instead of interfacing the game to an exercise bike or other equipment with speed output, the skiing speed is directly proportional to heart rate. You can freely choose the form of physical exercise, which makes it easier for people with different skill levels and backgrounds to play together. The system can be used with any exercise machine or form. To make playing meaningful instead of simply exercising as hard as you can, a high heart rate impedes the shooting part of the game by making the sight less steady. This balancing mechanism lets the player try out different tactics, varying from very slow skiing and sharp shooting to fast skiing and random shooting. The game has been evaluated in a user study with eight participants. The results show that heart rate interaction is fun and usable interaction method.