# is running speed only a (body weight) / (leg strength) ratio?

I want to be able to run fast. Sub (7.5-min / mile) at a marathon distance. I am trying to figure out why I can't run that pace for even 1-mile. I am not interested in endurance yet. Building endurance at a slow pace is not the way I want to train.

Are any of the following bullet points wrong?

• the only variables that influence speed are (1)cadence (2) stride length.
• cadence has a very low upper bound. (170 strides / min) seems as high as possible.
• a stride causes you to be propelled forward, and lifted upward. And, this "lifting upward" side-effect is the real limiting factor.

Therefore, a runner who wants to go as fast as possible need only work on minimizing the ratio of (body weight) / (leg strength), right? Gravity is slowing me down. Is there anything other variable that could possibly make me run fast?

(I already eat an good diet. And, I can't believe hydration matters for runs of just 3 miles).

• Would you consider training a variable? Aug 23, 2014 at 20:14
• I was told that you can't just grind your way to running 7.5-min/mile for a marathon. Progressing from 10-min/mile, to 9.5-min/mile, to 9-min/mile, etc. seems logical, but does not work (or so I was told). You would top-out at like 9.5-min/miles. Training lets that pace become easier to do, but you never get any faster. Aug 24, 2014 at 2:06
• If you want to run sub 7:30 for a marathon, it takes miles and miles. There are no shortcuts. As I've said often on here, "Run. Run lots. Mostly slow, sometimes fast." There are no shortcuts. Most runners go too fast for their slow paces, and too slow for their fast paces. Did I mention there are no shortcuts?
– JohnP
Aug 24, 2014 at 2:57

1. "the only variables that influence speed are (1)cadence (2) stride length." Yes these two variables define your speed. But how to achieve high cadence of a longer time is a complex issue.

2. "cadence has a very low upper bound. (170 strides / min) seems as high as possible." Wrong. Many recommend 180, so 170 isn't considered a very high cadence.

3. "a stride causes you to be propelled forward, and lifted upward. And, this "lifting upward" side-effect is the real limiting factor." I don't think so. While it probably eats up a serious part of the energy, I don't think it is the limiting factor (see below)

Your conclusion is more or less right, if we are taking very short distances. Very short. Like ... kicking. And even in that case there are different factors to consider. There are different kind of muscle cell (look up fast twitch for example); Your tendons store energy from the impact on the ground and release it for the next step, so how good that works has an effect as well. These are just two examples.

If you just want to run fast, congratulation, you are probably done. I'm sure you can run 100m in below 7.5min/mile.

If you want to run longer, you'll have to train endurance. But you don't want that, so there is nothing to add to this answer...

• 180 is certainly not the upper limit of cadence. In a 10000m race the pros will range between 180 and 200, going up to 215 for the last round if they were previously running at low cadence (which is everything below 190). Sep 1, 2014 at 16:18