As a coach (if interested in a coach click here) and avid runner, people always ask me about training methods and training surfaces. Today, after frequent conversations on the subject in the past few months, I would like to discuss training surfaces in general. First off there is no one right surface and likewise no one wrong surface. There are various opinions on surface in general and accepted ideas, some with academic data to back them up, others with less empirical observations. That said, I’m not going to link the bevy of articles to support what I’m about to type, but the reading is out there if you want scientific data; still, one of the best parts about coaching is getting a large sample size to support or refute claims.
So on to the fun:
Road: Typically the least forgiving surface, but a necessary evil in the modern world. Road is fast and fairly flat and even. Your feet do not have to develop advanced proprioception to run on the road, except for ramps and the occasional imperfection aside, the surface is predictable and hazards can been seen well ahead of time. Repeated road running can beat the legs down—they can have the lethargic approach, the exhausted feel as the force generated by running is deflected back into your body. Professional coaches often avoid road running unless their athletes are training for marathon length races and they limit it even then. Common injuries include overuse injuries, sore legs, shin splints, joint pain depending on your running style and form.
Grass: Grass, whether a manicured field, or a green oasis next to a sidewalk is soft. Much more forgiving on the body, the impact of running is absorbed by the surface instead of being deflected back. Your feet are much more alive here; proprioception is needed because each and every footfall is unique. Thus your balance muscles grow, but your feet and core work much harder compared to road. In addition to the extra work, the need to focus on landing patterns can slow you down here or there. We love to use grass for strides post run (always barefoot) and for any speed workout we can. If you are into minimalism or neutral shoes, grass is for you. The more time on grass running fast, the stronger the legs are. Common injuries include ankle rolls, overuse injuries, muscle soreness from repeated use of balance muscles.That said, running around a soccer field or a park creates a set of manicured trails for your use. Use for anything you can do on a track. 400's, 1000's, even mile repeats, especially if training for cross country.
Trails: A subset of grass, trail running also gives a highly productive surface, one that results in diminished impact on the body. Adding to the challenge comes the normal trail elements: mud, sand, and roots/rocks. The first two only force you to work harder, resulting in a stronger runner without the beat down of roads. Mud and sand (beach running as well) simulate hill running as they force you to dig in to generate force and momentum. This digging mimics running up and incline and will thus stress your muscles, building strength. Roots and rocks can create painful falls, but like with grass, focused running on trails will not only work on your balance muscles and core, but it will also increase proprioception and thus, over time, you will have more stable footing. I recommend using trails often, as in as often as you can, for some or all of your runs. Long runs can and should be done on trails to increase the overall training benefit.
Track: We use a rubberized track for training. If using asphalt, then consult the road section above while accounting for added force placed on your turn leg. Timber tracks are somewhere between grass and trail as well. That said, rubber tracks are very soft surfaces compared to the road (they do vary in both quality and hardness), they run fast and tend to push you along. Generating speed on this surface is easy, keeping it as well, it doesn’t deaden the legs right away, but your turn leg often suffers from the stress of constant turning. Typically, the turn leg is called on to generate a lot of the power and can fall into a condition of being over worked. Many track runners complain about having hip pain on their outside leg as well. We tend to avoid the track unless we are doing a track workout in track season, a couple days a week. Even then, we try to switch directions to vary the impact of the stress.
Treadmill: You're inside, on a low impact surface. Typically treadmills have a slight decline, and thus you seem to run faster because downhill running is faster. You are also not moving the air, a fact which makes the running a bit easier, but may cause increased perspiration. Your full running muscle matrix is not engaged, but the workout is still solid. Running at the same speed setting can be difficult though, for off of the machine, you tend to change speeds throughout your run, even if trying to hit an 8 minute mile, while on a treadmill you set the machine and go. Pay attention and be careful not to fall asleep on them.