Does surface explains the speed difference? (Read 716 times)

Since last week I'm adding a (slightly) longer run to my scheme. Last week I ran 5K, my speed was only 13 min/mile. route: towpath along the canal -> asphalt. Today I ran during my sons' judo practice, on the 'Finnish track' at the local sports center, surface -> wood chips. Today I ran 5.7K in the same timespam, so my speed was 11:50 min/mile. My heartrate was in the same, rather low, range, so I think it must be the surface that explains the difference in speed? So: Is a rather hard surface (asphalt, concrete...) always 'slower' than a soft one (dirt, grass, Finnish track?

Generally, asphalt would be "faster"; you would get more spring out of it than the wood chips, I would think. As to the differences in time, I wouldn't worry about it too much. There are so many factors that can go into it: your current energy levels, how much glycogen your body had available at the time, your perceived state (how do you think you felt), time of day, temperature, the overall difficulty of the course, etc etc ad nauseum. Don't take too much stock in fluctuations.

Oh, I agree the softness of the track definitely reduced the overall impact of the running, so that might be a factor to a greater or lesser degree.

So: Is a rather hard surface (asphalt, concrete...) always 'slower' than a soft one (dirt, grass, Finnish track?

If I remember Mr. Pangborn and 11th grade physics at all (and, well, I don't ... but let's pretend), it should be exactly the opposite. Scout7 got it right, as is his habit. And why do they call what nun's wear a "habit?" Anyone know? If it gets worn out, do they call it a "bad habit?" Sorry. Mind wandered. Where was I? I mean, besides procrastinating at work and writing silly posts and wishing I wasn't tapering. Oh. Mr. Pangborn. Right. According to him (and he had a really cute daughter - so I respect him), running on a softer surface would absorb energy that would otherwise be propelling you forward; with a harder surface, the energy would be working for you. It's like this: what hits a golf ball farther - a steel golf club, or a piece of soft wood? Or a nice big cone of cotton candy? Mmm. Cotton candy. Mr. Pangborn would say the steel, every time. But I wouldn't trust him. He gave me a D, I think. Plus, when we built rockets for a class project, and mine blew up, he gave me another D (okay, a D-plus) ... because it blew up. But here's the thing: it was SUPPOSED to blow up. And I told him so ahead of time. So my rocket functioned perfectly (hmmm, note to self: reword that sentence). The point? The point is that physics is probably all wrong, and Mr. Pangborn was kind of a weenie. Of course, you could test your theory. Go run in the soft sand of the beach and see how fast you go.

And do you know the difference between a European and an American? For a European 150km is 'far, far away'. For an American 150 years is 'long, long ago'.

Actually, most of us Yanks would be way, way too busy figuring out what the heck a "kilometer" is to get to the 150 year part. The only Americans likely to know what 10 kilometers means ... are runners.

It's all about conservation of energy in the physics sense. Your legs act like springs, and thus have a spring constant. On compression (when you land), some of the kinetic energy (the downward motion) is converted to potential energy. It is released on the push off as kinetic energy. When you land on soft surfaces like the beach, these surfaces absorb some of the energy on the push off (Newton's Third Law of Motion). The lost energy is used to push the sand apart. On hard surfaces like asphalt, there is less give. The asphalt pushes back on you so there's less energy lost. One exception to the soft/hard surface rule is the rubberized track because most of the energy is returned to you as the rubber beneath you decompresses.