Just Dune It. Make hill workouts tougher by doing them on sand.

Percy Cerutty, coach of Australia's 1960 Olympic 1500-meter winner Herb Elliott, favored sand-dune workouts for their ability to build speed, strength, and endurance. At Cerutty's seaside base, Elliott would sprint up a dune as many as 50 times in a row. The result: He retired never having lost a mile or 1500-meter race.

Dune training has become a rite of passage, from the coast of Wales (where Steve Ovett, the record-setting British miler, trained) to the shores of Lake Michigan (where American 5K record holder Molly Huddle tested herself as a college student). Here's what you need to know to try it.

The Benefits

Running on loose, dry sand takes 20 to 60 percent more energy than running on grass. Plus, soft sand absorbs some of the energy from your foot strike instead of pushing you forward, and forces you to activate more lower-leg muscles to stay upright. The result is levels of lactate, a marker of anaerobic fatigue, that spike two or three times higher than on firm surfaces. one study found athletes improved VO2 max by 10 percent after eight weeks of sand workouts twice a week, compared with just six percent for those doing the same workouts on grass.

Loose sand's other perk is its low impact forces, which produce less muscle damage and subsequent soreness. Physiology aside, the best reason to hit the dunes might be as a mental toughness workout, Huddle says: It's impossible not to make your legs burn.

The Workouts

Cerutty used three key dune circuits for workouts. The shortest was a steep climb just 25 meters long, but at a 60-degree incline. To replicate this, try 10 reps of a hill that takes about 15 seconds to climb; walk or jog down for recovery, taking enough time that you're ready to sprint hard again on the next rep. The midlength circuit was about 400 meters long, finishing at the top of a steep hill. For this kind of workout, start with six reps, and take at least 2:00 recovery. Finally, the longest circuit was a rolling loop of just over a mile up and down the dunes. Start with three reps and take 3:00 recovery.

If you have regular access to dunes, include a sand hill workout once a week during base training. If you're making a special trip to run on dunes, pick a medium-length incline that takes 45 to 90 seconds to climb, to strike a balance between strength and endurance. See how many reps you can do (then take a few days to recover).

The Caveats

It's hard to maintain good form when your feet keep sliding backward. For a more powerful stride, push hard off your back foot (even though it's slipping) rather than reaching forward with your front. The soft surface may put extra strain on your Achilles tendon, so avoid sand workouts if you have a history of Achilles problems, and stop if you feel calf pain.

The other big issue is whether to wear shoes, and there's no right answer. If you leave them on, wear tall socks to keep sand out. If you take them off, your foot and ankle muscles will work extra hard, so keep the first few workouts short.

When running on dunes, stick to preexisting paths and respect local rules about access.

Alex Hutchinson is a former physicist and national-class runner, and a National Magazine Award-winning science journalist.