Im new here, so go easy on me if the question is a bit bland or improperly written. I just decided to post this question since I haven’t been able to find adequate answers to this question anywhere else on the internet, and I need this information to set a baseline for a sci-fi story I am working on to create a scale to measure the level of superhuman or non-superhuman speed a character possesses. I’m just wondering how fast the most physically powerful human could move in a single step, like side-stepping or any sort of similar burst of movement meant for either closing the gap on an opponent or dodging an attack directed at them in combat. I already know the typical peak human sprint speed is at around 20 mph, but sprint speed is not what I want to know as stated previously.
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$\begingroup$ Why is the Sprint speed not what you want? It's a reasonable upper limit. $\endgroup$– L.Dutch ♦Commented Nov 5, 2019 at 4:20
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$\begingroup$ Has your person got blocks as they do in the sprint, or maybe something else to spring off - if not then grip could be an issue to get the center of mass moving. $\endgroup$– Escaped dental patient.Commented Nov 5, 2019 at 4:23
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$\begingroup$ Because a human can’t accelerate up to top speed in a single fluid movement and sprinting isn’t really used for anything other than fleeing. In combat, sprinting isn’t going to apply the best. In combat it’s more about agility than sprinting as fast. I also already know how fast a human can sprint. Also no, they don’t have any blocks, as I’m talking more fighting maneuvers such as side-to-side shuffles or sidesteps. $\endgroup$– user70198Commented Nov 5, 2019 at 4:25
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1$\begingroup$ Just remember that a step is nothing more than falling, followed by extending the leg (one leg in this case) to translate the downward vector of falling into a lateral vector of motion. The physical limit will be determined by how quickly a human leg can extend, without loosing traction on the ground. There are a lot of physics involved. $\endgroup$– Vogon PoetCommented Nov 5, 2019 at 4:41
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$\begingroup$ Side stepping is slower than a forward movement - we're designed to move forward far more easily than moving sideways. But it sounds like what you might be asking is how fastest motion capable of a human - is that it? $\endgroup$– HalfthawedCommented Nov 5, 2019 at 4:41
2 Answers
The speed a human can move is determined almost entirely by how rapidly the muscles can contract. The theoretical maximum speed for a human runner is 40 mph:
The new work shows that running speed limits are set by the contractile speed limits of the muscle fibers themselves, with fiber contractile speeds setting the limit on how quickly the runner's limb can apply force to the running surface.
When asking about how fast a human could move in a single step, you should specify if this is the first step, an accelerating step, or a peak speed stride. I will calculate the first step.
If you eliminate friction concerns, the limits for a human accelerating would likely be based on bone strength. If you applied enough force to your leg - about 1,300 lbs-force (5783 Newton’s) in one step - the best human leg would break. This means a persons weight will limit how fast they can accelerate in any one step. So consider your ideal human athlete mass, and calculate the force to break their legs, that will be the human limit for accelerating in one step.
For example, a 60 kg (132 lb) sprinter will apply 1,300 lbf by accelerating 96.4 m/s2 (using $a = \frac{F}{m}$). Now to find the speed after one stride, we need to calculate how long the stride takes, starting with the average 96 inch man’s stride: $$t = \sqrt \frac{2s}{a} = \sqrt \frac{2 \times 96 in}{96.4 m/s^2} = 0.176327 s$$
Next we calculate how much speed he has gained in that short time:
$$96.4 m/s^2 \times 0.176327 s = 17 m/s \text{ or } 38 mph$$
This is what is theoretically possible for a 130lb man’s single step before breaking his leg.
So next we look at the muscle fibers, if they can physically contract fast enough to launch a human this quickly. Again, referring to the article in the Journal of Applied Physiology:
"Our simple projections indicate that muscle contractile speeds that would allow for maximal or near-maximal forces would permit running speeds of 35 to 40 miles per hour and conceivably faster," Bundle said.
So a human with perfectly tuned muscles could theoretically accelerate to 38mph in a single step. However, the world’s fastest man alive, Usain Bolt, has sprinted at a top speed of 28mph. It’s good to reason that any “normal” human accelerating to more than 28 mph in one step is probably superhuman, while anyone reaching greater than 38 mph in one step is guaranteed to be superhuman.
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$\begingroup$ 28mph - is an "averaged" maximum speed. Human deccelarates and reaccelerates each step wile running. So maximim peak speed (including vertical part) should be about 30-35 mph. $\endgroup$– ksbesCommented Nov 5, 2019 at 7:34
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$\begingroup$ Where did you find a 60kg male sprinter? For reference, Bolt is 94kg. $\endgroup$ Commented Nov 5, 2019 at 8:25
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1$\begingroup$ Yeah I started intuitively working on a woman sprinter thinking they would be quicker = lighter, then saw the muscle mass played a bigger part. Bolt would have a much slower theoretical acceleration due to bone breaking limit. I still think a smaller person will have a better “one step” maximum, sprinters need more muscle mass for endurance. An average male sprinter is 75-80 kg. $\endgroup$ Commented Nov 5, 2019 at 12:58
If sprint speeds is not what you are looking for, but rather short bursts of movement with little to no acceleration to start with, you might want to look into some famous martial artists, like Bruce Lee's famous one inch punch (more info here).
I don't think anyone really measures how fast / far someone can jump sans momentum, but you could look into similar exercises applied to kicking for example, which could help give a general idea of a "peak" human's muscular tension.
