For big gains, step away from solid ground: sand may be the best workout surface, say researchers in Italy.

They had soccer players sprint on sand, grass and artificial turf and discovered that 
the sand surface led to greater power output 
and the biggest kilojoule burn. It also had less impact on the players’ joints. “On sand, your foot slips and sinks,” says study author Dr Paolo Gaudino. “This forces your lower-leg muscles to do more work.”

To find out just how hard exercising on sand is, try doing 60 seconds of 
burpees the next time you hit the beach.