I’ve heard runners talking about concrete being harder to run on opposed to a softer blacktop surface. Is this true and why?
If you go hit blacktop with a hammer and concrete with a hammper both are very hard surfaces. A runners strike is not as hard as a hammer stike…or is it?
In theory, the blacktop (being tar based) is going to be softer than concrete (a very rigid material). In practice, though, it’s so near the same as to mot make much of a difference. If you’re worried about the hardness of the surface you’re running on, go with dirt or gravel trails.
It’s one of those things, like moment of inertia with wheels, where there is, in theory, an actual effect.
The problem lies in the fact that the effect is so vanishingly small in relation to everything else going on that nobody can actually feel the effect.
I recall reading a survey article a few years ago in which some epidemiological types pulled together long-term studies of running injuries. They found that running surface had no correlation to injury rate – including running on trails versus asphalt and concrete.
I have always felt that the asphalt versus concrete thing was complete BS. However, I am sure that somebody will post some sort of anecdote about how all their injuries went away when they switched from concrete to asphalt, or vice versa. As always, anecdotes tell us basically nothing.
I’m sure I remember reading in runners world an article rating different surfaces and it stated that concrete was 10 times harder than black top. For what its worth.
i’ve noticed a difference, i’ve had pain on concrete and not on blacktop, with the same shoes.
with the shoes i’ve got now - saucony omnis - I never have pain so it doesn’t matter. but I think there is a difference.
in drag racing, the first 1/3 to 1/4, sometimes half, of the track , is concrete instead of asphalt.
this is because the 7000 horsepower motors would tear the crap out of asphalt on launch.
the more concrete before the transition to asphalt, the faster the track.
so it’s definately harder.
it probably depends how heavy you are whether you notice.
my motor is significantly less than 7000hp, so I’m probably safe running on either surface.
Definitely a big difference in my experience (with appropriate ST carve outs for lack of study size, sample rate blah blah blah). Based in the UK all of my road running is on tarmac/blacktop and that’s my benchmark. The only times I’ve run on concrete is when doing sessions on an old aerodrome and on a couple of visits to New York the first of which was to do last year’s marathon. Every time I’ve definitely noticed that fatigue sets in faster and harder on concrete than I would expect and I’m happy to put this down to getting less back from the road with every step and having to compensate by expending more energy with every stride. I admit the differences are miniscule but you take a lot of steps in a mararthon and I just feel that it adds up - concrete to tarmac is one step on the road which nds in the still firm bu undoubtedly beneficial surface they put on athletics tracks.
One other observation is that I remember an article about the time of the last Olympics saying there was a decision to be made as to how firm to make the track as a miniscule change could be seen as favouring sprinters over long distance guys or vice versa. 100m guys can’t take more than 30 odd strides in a race and if it matters to them it’d definitelty matter on an IM.
From a post by Rick Denney years ago on rec.sport.triathlon. By the way, he’s an engineer:
Well, there’s asphalt and there’s asphalt. The nice thing about
asphalt is that it can be mixed to different hardnesses. Asphalt is
also thermoplastic, and gets softer in hot weather. Most asphalts in
residential areas are softer, because it’s cheaper. And the asphalt on
run/bike trails is softer still. Some running tracks are paved with
asphalt so soft that vehicles can’t drive on them without leaving
visible ruts.
When asphalt pavements are laid, they are quite soft–soft enough to
leave footprints. Then, they are rolled to increase their density and
hardness by reducing the voids in the material. But at their hardest,
asphalts are nowhere near as hard as portland-cement concrete.
Asphalt is a plastic, and, like most plastics, is not very elastic,
especially at high frequencies and transient impacts. That means that
it absorbs energy rather than giving it back. It relaxes back into
shape slowly. Portland-cement concrete, on the other hand, is brittle
and elastic, even at high frequencies, and springs back on impact.
Because of its hardness, it springs back quickly–while your foot is
still heading toward the ground.
Note for pedants: Asphalt is also concrete. The term “concrete” refers
to the mixture of some sort of cement and rock aggregate. In asphaltic
pavements, the cement is asphalt, and in what we normally call
concrete pavements, the cement is portland cement. Portland cement is
hard. PC pavements will normally not form ruts with any amount of
use unless the pavement breaks down. Asphaltic pavements form ruts
routinely.
A car causes noticeable deflection in the asphaltic pavements used in
residential streets and bike trails, especially when they are
relatively new. The deflection relaxes back for the most part, and you
don’t notice. A car typically weighs 3600 pounds, and sits on four
wheels. Let’s say the heaviest wheel carries 700 pounds. At 35 psi,
the contact patch will be 20 square inches.
Go with me.
A normal person’s foot is three inches at it widest and 10 inches
long. (Not my foot, heh, heh.) If the average width is 2 inches, then
the contact patch is 20 square inches. But you land on the heel or the
midfoot, and the contact patch at landing is probably more like 4-6
square inches. A runner strikes the ground with dynamic momentum,
however, and the point of impact (guessing wildly) is maybe twice the
body weight. That’s, say, 300 pounds. Assuming a 6-square-inch contact
patch, that comes to about 50 psi. More than a car. Surprised?
Based on the above, I’d bet that asphaltic pavements absorb
high-frequency transient impacts noticeably better than concrete. But
it’s not even on the same planet as what your shoe does. I’d assume
that asphalt takes just a bit of the edge off the impact. Whether that
makes any difference or not I don’t know.
Rick “Seems to in my case” Denney
I buy this theory. I think that it feels softer to run on, and concrete is harder but faster. It makes sense, asphalt is essentially dense rubber with rock in it. I weigh 190 lbs and am moving forward at about 8-9 mph and also falling down at 9.8 ft/s squared. My physics is out of date, but my guess is that I’m striking my “contact patch” with alot more than 300 lbs.
From another standpoint … I’ve fallen off of my bike, skateboards, rollerblades and other things on both concrete and asphalt … concrete it is way, way harder and hurts way, WAY more. Plus, having a finer “tooth” to it it makes a much finer roadrash that makes a much cleaner scar. Much like a band saw vs. a chainsaw.
Running on golf courses dominates…short grass and very soft!
I notice the difference when running long distances. Once I ran 10 miles or so on the concrete boardwalk at Virginia Beach and woke up the next day extremely sore.
Dave in VA
It’s just that boardwalk … my girlfriend and I did things down there and were also sore the next day.
The reason I asked is most of the time I can’t tell the difference between the two surfaces. However, most blacktop running paths or roads where I live are sloped for water drainage so running on them is difficult. However, there is a brand new concrete river path that is mostly concrete and flat (no sloping) so running is great.
I just wondered if I would feel the difference between both surfaces…and so far I can’t.
Happy training folks.