The ideal training surfaces are in between hard, unforgiving concrete and soft, cushy sand. These two opposites do offer a good contrast, however, for understanding the principles involved in harder and softer running surfaces. For example, it helps you understand why, in general, you'll run faster on something hard like concrete, and that foot-to-surface contact time is longer on softer surfaces. Let's go over the range of different surfaces:
Concrete. Probably the hardest surface to run on, concrete is also usually the most convenient for runners in urban areas. One advantage to concrete is that it's typically very even, unlike many of nature's soft surfaces.
Asphalt. Made from crude oil tar and mixed with sand or gravel, asphalt is slightly softer than concrete (which is cement with water, sand and gravel). Although they recommend it over concrete, running experts don't really consider asphalt a "soft surface."
Gravel. Many parks and running trails in suburban areas are made of crushed gravel, which experts consider a soft surface that's ideal for triathlon run training. It's a good middle-of-the-road choice.
Track. Often made from rubberized and synthetic material, tracks vary in hardness. However, they usually offer a moderately soft surface on which to run.
Treadmill. Having a treadmill inside will protect you from the elements and offer decent shock absorption.
Dirt. Running on plain dirt paths will offer some shock absorption, but it can get muddy or uneven during bad weather.
Grass. Grass adds a little more cushion than dirt, but can also hide rocks and uneven patches that you could trip on.
Wood chips. Many experts cite trails made of wood chips or sawdust as their favorite surface to train on. They absorb shock very well and, unlike dirt and grass that can get muddy, these trails stay pretty sturdy after rain.
Damp sand. If you're looking for a good workout on the beach, most experts recommend staying near the shore where the sand is flatter and more compact.
Soft sand. Because it's so uneven and will absorb most of your running energy, soft sand is generally considered too difficult to train on.
So what difference will it make what surface you run on or how shock-absorbent it is? Next, we'll discuss the many advantages of soft surface training.