It is not only better for a rower to be muscular, it is essential. However, the type of muscle development ideal for a rower focuses on strength and endurance rather than bulk. Rowing demands tremendous muscular endurance and peak power for sprints. As the Sports Fitness Advisor website states, rowing is "one of the most physically strenuous of all sports."
Elite rowers tend to be muscular, fit and tall because of the physics of the sport. Tall rowers have longer limbs, which act as levers to move the boat through the water with maximum efficiency. Strong rowers move the boat through the water faster because of their additional power. Most top male rowers are more than 6 feet tall and weight about 210 lb. The top female rowers are around 6 feet tall and weigh about 170 lb. As the BBC Sport website says, almost all of the rower's weight is muscle, since any extra weight reduces the speed of the boat.
If you have the basic body type for rowing, adding muscle and endurance power can make you a champion. A program in Australia to recruit teenagers with rowing potential singled out Megan Fox, who had never rowed a boat, for her textbook build for rowing. In the 1996 Olympic Games, after nine years of training, Fox won the gold medal.
The type of muscular strength you want for rowing emphasizes peak power, peak muscular endurance. To develop strength and endurance, Sports Fitness Advisor recommends sport-specific weight training, including seated rows, hip sled work and single-arm rows. These exercises give you muscles capable of providing peak power for sprinting early in the race to establish position, for the long glide of the middle section of the race and then another all-out sprint to the wire. The Wellness MA website contains a complete strength training workout routine for rowers, including weight training exercises for your legs, arms, chest, abs and low back.
If you don't have the ideal size for rowing, you can compete in lightweight rowing, open to men up to 160 lb. and women up to 140 lb. There are world championships for lightweight rowers, both male and female, and some colleges and rowing clubs have lightweight teams. In fact, FISA, the governing body of rowing, encourages lightweight racing as a way to promote rowing in countries and regions with populations of smaller statured people, such as Latin America and Asia. However, the strength and endurance demands are the same lightweight racing as you they are in open, or heavyweight, rowing. So you still have to hit the weight room for sport-specific workouts to build the strong and lean muscles you'll need for rowing