The physical demands of surfing have been revealed in 2 studies involving professional surfers. In one study surfers were fitted with tiny, state-of-the-art waterproof heart rate monitors and GPS units that were worn for the duration of 3 heats at 2 different surf competitions. The researchers set out to establish how strenuous and how long the surfers spent in each one of the various activities that surfing comprises of, such as paddling to the waves, waiting about in the water for waves, and riding the waves. The average speeds of rides were more than 25 mph.
They found that only 8% of the time that the surfers were in the water was actually spent riding a wave. Surfers spent 54% of their total time in the water paddling to the waves. The remainder of each session was used keeping position while waiting for waves or in quick, intense periods of paddling to get a wave. Their heart rates soared to 190 plus beats/minute throughout the competitions and hardly ever dropped below 120 beats/ minute. They also covered a considerable area while paddling, with an average of over half a mile throughout every heat, or approximately a mile and a half for each competition.
The results clearly indicate that surfing is a substantial workout demanding high-level aerobic endurance, considering how long they spent paddling and that the heart rate remains over 120 beats /minute no less than 80 % of the time.
In another study in a lab surfers lay on a bench and simulated ocean paddling by turning paddles attached to a flywheel. Although all of the surfers were strong, the surfers that could generate the maximum wattage when paddling happened to be the highest-ranked surfers in the group, suggesting that their muscle strength allowed them to get back to the waves quicker after each ride and consequently get more waves.