Speed comes down to how much force you can push into the ground and how quickly you can do it. That simple formula, repeated over dozens of steps, is what separates a fast person from an average one. But behind that formula sits a web of factors: your muscle fiber composition, your nervous system’s wiring, the stiffness of your tendons, and the specific way your body is trained to coordinate all of it. The fastest human speed ever recorded was about 27.5 miles per hour, hit by Usain Bolt midway through his world-record 100 meters in 2009. Here’s what it takes to get anywhere close.
Muscle Fiber Type and Genetics
Your muscles contain two broad categories of fibers: slow-twitch fibers, which are built for endurance, and fast-twitch fibers, which contract powerfully and rapidly but fatigue quickly. Fast people tend to have a higher proportion of fast-twitch fibers, and that ratio is largely set by genetics.
The most studied gene in this area is ACTN3, which provides instructions for a protein called alpha-actinin-3 found predominantly in fast-twitch fibers. People who carry two copies of the “R” version of this gene (the 577RR genotype) tend to have a higher proportion of fast-twitch fibers and are overrepresented among elite sprinters and power athletes. People with two copies of the alternate version (577XX) produce a nonfunctional version of the protein, which shifts the balance toward slow-twitch fibers. That genotype shows up more often in endurance athletes like long-distance runners and cyclists. You can’t change your genotype, which is one reason raw speed potential varies so much between individuals even before training enters the picture.
Your Nervous System Matters More Than You Think
Having fast-twitch muscle fibers is only useful if your brain can activate them quickly enough. The rate at which your muscles ramp up force, known as rate of force development, turns out to depend more on neural signaling than on the muscle itself. Research comparing voluntary contractions to electrically stimulated ones found that force produced in the first 40 milliseconds of a rapid effort was about 60% lower when the person initiated it voluntarily. The limiting factor wasn’t the muscle’s capacity; it was how fast the nervous system could switch it on.
Specifically, the ability to produce force rapidly depends on how quickly motor neurons begin firing and how high their discharge rate climbs in the first 50 to 75 milliseconds of a contraction. This is why two people with similar muscle mass can have very different acceleration. The faster person’s nervous system recruits more motor units, and recruits them sooner, during each ground contact. Training with explosive movements can improve this neural drive over time, which partly explains why sprinters get faster even without gaining muscle.
Ground Contact Time and Stride Mechanics
Speed is the product of two things: how long your strides are and how frequently you take them. At lower speeds, getting faster mostly means lengthening your stride. But as you approach top speed, stride length plateaus and further gains come from increasing stride frequency, turning your legs over faster.
One of the clearest differences between fast and average runners is ground contact time, the duration each foot spends on the ground per step. Elite sprinters average about 0.08 seconds of ground contact per step. Sub-elite sprinters spend closer to 0.14 seconds. That gap of just six hundredths of a second per step means the elite sprinter applies force faster, recovers elastic energy more efficiently, and repositions their legs sooner for the next stride. Over a 100-meter race involving roughly 45 steps, those fractions add up to the difference between world-class and merely good.
Shorter ground contact doesn’t mean less force. It means delivering the same or greater force in a smaller window. That requires both the neural speed to activate muscles instantly and the structural stiffness in your tendons and joints to bounce off the ground like a rigid spring rather than sinking into it.
Tendons as Springs
Your Achilles tendon plays a critical role in how efficiently you return energy with every step. During the stance phase of running, the tendon stretches as it absorbs impact, then snaps back to help propel you forward. This elastic recoil means your calf muscles don’t have to do all the work themselves; the tendon acts as a biological spring, storing and releasing energy.
Tendon stiffness matters here. A stiffer tendon can store energy and release it faster, which suits the demands of sprinting where ground contact is extremely brief. However, balance is important. Research on runners who increased their Achilles tendon stiffness through training found that while the tendon stretched the same amount during each step, the recoil (the snap-back that returns energy) was reduced by about 30%. This suggests that there’s an optimal range of tendon stiffness for speed, and going past it can actually reduce the elastic benefit. The fastest sprinters tend to have tendons that are stiff enough to handle enormous forces without being so rigid that they lose their spring-like quality.
Your Body’s Fuel System Has a Timer
Sprinting at maximum effort runs on a different energy system than jogging or distance running. Your muscles store a small amount of ready-to-use energy that can fuel about 1 to 2 seconds of all-out work. A secondary reserve, the phosphocreatine system, extends that window but is largely depleted within about 10 seconds of sprinting. After that, the body leans heavily on anaerobic glycolysis, which produces energy faster than aerobic metabolism but generates metabolic byproducts that cause the burning sensation and force slowdown you feel in a long sprint.
This is why even the fastest humans slow down in the final 20 meters of a 100-meter dash. The energy systems that power top-end speed simply can’t sustain it beyond a few seconds. Faster sprinters don’t necessarily have larger fuel stores. They’re better at delivering force during the brief window those stores are available and at minimizing their speed loss as those stores fade.
When Speed Peaks
Elite sprinters tend to reach peak performance around age 25 to 26 for men and 26 to 27 for women in the 100 meters. For longer sprints like the 400 meters, peak age shifts slightly later, to about 25.6 for men and 27.5 for women. This reflects the time it takes for the nervous system, muscle architecture, and technical skill to fully mature and align. Speed declines after this window are gradual at first, driven by small losses in fast-twitch fiber size, tendon elasticity, and neural firing rate that accumulate over years.
Training That Actually Builds Speed
Since speed depends on force production, ground contact efficiency, and neural activation, the most effective training targets all three. Plyometric exercises, movements involving rapid stretching and contracting of muscles like jump squats, depth jumps, and bounding drills, train your muscles and tendons to store and release energy faster. Over time, they reduce ground contact time by improving how quickly your body can reverse direction from absorbing impact to pushing off.
Sprint training itself is irreplaceable because it teaches the nervous system to coordinate the exact pattern of muscle activation that running demands. Short sprints of 10 to 40 meters at maximum effort train acceleration, while longer sprints of 60 to 150 meters develop top-speed mechanics and the ability to maintain form under fatigue. Heavy resistance training, particularly exercises like squats and deadlifts, builds the raw force capacity that the nervous system can then learn to express more quickly.
The key distinction is that speed training must be done at or near maximum intensity. Moderate-effort running improves endurance but does little for top-end speed because it doesn’t challenge the fast-twitch fibers or the neural pathways responsible for explosive movement. You have to practice being fast to get faster.