Originally made from wood, shells are now almost always made from a composite material (usually a double skin of carbon-fibre reinforced plastic with a sandwich of honeycomb material) for strength and weight advantages. FISA rules specify minimum weights for each class of boat so that no individual team will gain a great advantage from the use of expensive materials or technology.
Rowing is one of the few non-weight bearing sports that exercises all the major muscle groups, including quads, biceps, triceps, lats, glutes and abdominal muscles. The sport also improves cardiovascular endurance and muscular strength. High-performance rowers tend to be tall and muscular: although extra weight does increase the drag on the boat, the larger athletes' increased power tends to be more significant. The increased power is achieved through increased length of leverage on the oar through longer limbs of the athlete. In multi-person boats (2,4, or 8), the lightest person typically rows in the bow seat at the front of the boat.