The most effective running technique is...
Humans may be born to run but fitness experts differ on exactly how to embark on what has been called the most natural cardiovascular workout.
Some chase one ideal form, others work with the body's individual flow, but all praise the soft landing.
For Dr Nicholas Romanov, Miami-based sports scientist, two-time Olympic coach and creator of the Pose Method, running is a teachable skill requiring clean, precise movements.
''There's a universal, archetypal running form,'' said Romanov, whose forthcoming book ''The Running Revolution'' lays out the forward body tilt, forefoot landing and short, frequent steps that characterise the Pose form.
His method purports to exploit gravity rather than muscular strength to drive the running body forward faster, farther and injury-free.
Romanov said to assume a precise running pose, fall into gravity and pull back into the pose to re-establish a natural process that was perverted by poor coaching and harmful shoes.
''It's not my standard, its nature's standard,'' said Romanov, who describes running as controlled falling.
''Pain is the penalty for violating nature. When you're going against gravity, it all crashes (down).''
Dr Heather K. Vincent, a fellow of the American College of Sports Medicine (ACSM) supports the forward lean, lifted knees and rapid foot turnover encouraged by the Pose Method, but remains wary of its one-size-fits-all form.
''We try to encourage control, strength. I'm not sure you can fit a running style to all bodies,'' said Vincent, director of University of Florida Sports Performance Centre.
Vincent added that most runners' steps are too long.
She recommends a running cadence of 180 steps per minute, using a metronome if needed.
''It feels more like shuffling at first,'' said Vincent, who trains clients in jump-rope jumping and jogging to foster the forward lean, knee lift and proper shoulder-hip-ankle alignment.
Her recent report for the American College of Sports Medicine recommended zero-drop running shoes, which allow forefoot and heel to be the same distance from the ground because they foster safer running mechanics, shorter stride and forefoot landing.
''I don't believe everyone should be forefoot landing but everyone should land softly,'' she said.
Connecticut-based running coach Tom Holland believes if you want to be a really good runner, you run.
''Bodies are smart machines that go to the path of least resistance,'' said Holland, author of ''The Marathon Method.''
Holland thinks most injuries result from doing too much too soon, not from heel striking and he believes in landing lightly.
''Imagine you're sneaking up on someone and you'll naturally go to a shorter, faster stride,'' he said. ''You can't overstrike and run softly.''