There is no sound basis for declaring a 30-minute beach walk more effective than what most people do in a gym. The study reported that walking on sand cost 2.1 to 2.7 times more metabolic energy at the same speed. It also found that running on sand cost about 1.6 times more than running on the hard surface. The hour-at-the-gym comparison does not holdA 30-minute sand walk can be a demanding aerobic session. If the outcome were calories used during the session, sand walking might perform well.