The muscles that make you run faster are primarily in your hips and the back of your legs. Your glutes, hamstrings, hip flexors, and calves do the heaviest work during sprinting, but your core and even your upper body play supporting roles that affect how efficiently you transfer force into the ground. Understanding which muscles matter most, and what they actually do at high speed, can help you focus your training where it counts.
Glutes: The Engine for Horizontal Force
Your gluteus maximus is the largest muscle in your body, and its primary job during sprinting is to drive your leg backward against the ground. This backward push is what creates horizontal ground reaction force, which is the force that actually propels you forward. The glutes are highly activated during both the time your foot is on the ground and while your leg swings behind you, making them essential throughout the entire stride cycle.
Interestingly, the relationship between glute size and sprint speed is more nuanced than you might expect. A study of sprint runners published in PLoS One found that overall gluteus maximus volume did not significantly correlate with sprint velocity. The researchers suggested this may be because different regions of the glute serve different functions, so raw size alone doesn’t capture what matters. What likely matters more is how forcefully and quickly you can activate the muscle, not just how big it is. This is why explosive exercises like hip thrusts, sprints, and heavy deadlifts tend to improve speed more than simply building mass.
Hamstrings: Speed’s Most Demanding Muscle
Your hamstrings do double duty during sprinting, and the second job is what makes them so vulnerable to injury. During the push-off phase, they work alongside your glutes to extend your hip and drive you forward. But their more demanding role happens during the late swing phase, when your leg is whipping forward and the knee is extending rapidly in front of you.
At that moment, the hamstrings act as a brake. They lengthen under enormous tension to decelerate your lower leg before your foot strikes the ground. The forces involved are staggering: research in Sports Medicine describes hamstring loads during this phase reaching as high as ten times your body weight, which actually exceeds the muscle’s maximum force-producing capacity in a stationary position. The hamstrings manage this by absorbing and storing elastic energy as they stretch, functioning more like a spring than a simple contracting muscle.
This braking role is critical for two reasons. It controls your stride so your foot lands in the right position, and it prepares your leg to immediately generate force on ground contact. Weak or poorly conditioned hamstrings can’t handle these loads, which is why hamstring strains are the most common injury in sprinting. Nordic curls and other eccentric exercises that train the muscle while it lengthens are particularly effective for building the type of hamstring strength that translates to speed.
Hip Flexors: The Overlooked Speed Muscle
The psoas major, your deepest hip flexor, is one of the strongest predictors of sprint performance. Its job is to pull your thigh forward and upward during the recovery phase of your stride. The faster you can bring your leg through, the faster your stride rate, and stride rate is one of only two variables that determine your speed (the other being stride length).
A study in the Journal of Physiological Anthropology found a striking correlation between psoas muscle volume and curve sprinting speed (r = −0.859), making it one of the strongest muscle-to-performance relationships in sprint research. Sprinters with larger psoas muscles consistently ran faster. This makes sense biomechanically: the psoas is the largest hip flexor, and a more powerful hip flexor can snap the knee up and forward more quickly, setting up the next ground contact sooner.
Most people underestimate how much hip flexor strength matters for speed. If you feel like your legs are “heavy” at top speed or you struggle to bring your knees up quickly, weak hip flexors are a likely bottleneck. Resisted knee drives, hanging leg raises, and sled marches all target this area.
Calves: Your Ground Contact Spring
The soleus and gastrocnemius, the two main calf muscles, control your ankle joint and the Achilles tendon, which together act as a stiff spring during each foot strike. When your foot hits the ground at speed, the Achilles tendon absorbs and returns elastic energy, and your calf muscles regulate how stiff that spring is.
Research published in the Journal of Applied Physiology measured Achilles tendon forces during running and found they reached over 4,600 newtons at higher speeds, roughly six times body weight for an average runner. As speed increased, electrical activity in both calf muscles rose significantly (10% in the gastrocnemius and 14% in the soleus), meaning they work harder to maintain ankle stiffness at faster paces. A stiffer ankle means less energy is lost at ground contact and more of your force goes into forward propulsion.
The practical takeaway: calf strength and stiffness matter for speed, especially the ability to produce force quickly. Plyometric exercises like pogo hops, single-leg calf raises, and depth jumps train this reactive stiffness more effectively than slow, heavy calf raises alone.
Quadriceps: Shock Absorbers and Knee Drive
Your quadriceps play a somewhat different role than the muscles above. During the early stance phase, as your foot strikes the ground and your knee bends slightly to absorb impact, the quads contract eccentrically, meaning they lengthen under load to control the bend and prevent your leg from collapsing. This is especially demanding during acceleration, when ground contact forces are highest.
The quads also contribute to knee extension during the drive phase, working alongside the hip flexors to swing the leg forward. They’re not the primary producer of horizontal force, but without adequate quad strength, you lose the structural integrity needed to transfer power from your hips through to the ground.
Core Muscles: Preventing Energy Leaks
Every time you take a stride, your pelvis rotates in all three planes of motion. Your trunk has to counter-rotate to keep you facing forward and to maintain balance. The deep core muscles, particularly the transversus abdominis and multifidus, control these rotations.
MRI research published in BMJ Open Sport and Exercise Medicine showed that the transversus abdominis serves two simultaneous roles during running: it stabilizes the spine and it helps manage breathing. When your right leg swings forward, the pelvis rotates left, and the core muscles on the right side eccentrically control that rotation while also facilitating the trunk’s counter-rotation. This happens with every single stride.
A weak core allows excessive pelvic rotation and trunk wobble, which bleeds energy that should be going into forward motion. You won’t notice it as a specific weakness; it shows up as a general loss of efficiency, especially when you’re fatigued. Planks and crunches have limited carryover here. Rotational and anti-rotation exercises like Pallof presses, cable chops, and single-leg movements train the core in ways that actually mimic the demands of running.
Upper Body: Balance at High Speed
Your arms and shoulders don’t generate forward propulsion directly, but they play a meaningful role in balance and force production. Arm swing serves two main purposes during sprinting: it counterbalances the rotational momentum created by your legs, and during the acceleration phase, it helps increase both stride rate and ground reaction forces.
At top speed, the forward and backward motions of the arms cancel each other out in terms of horizontal momentum, so their contribution shifts almost entirely to balance and trunk stabilization. The shoulder muscles maintain arm position, and the lats help drive the arms backward in sync with the opposite leg. Coaches and researchers consistently identify arm drive as a stabilizing mechanism that allows the lower body to operate at maximum output without the torso spinning out of control.
Muscle Fiber Type and Speed Potential
Beyond which muscles you train, the type of fibers those muscles contain influences your speed ceiling. Muscle fibers come in two broad categories: slow-twitch (Type I) fibers that resist fatigue but contract slowly, and fast-twitch (Type II) fibers that produce rapid, powerful contractions.
Elite sprinters carry a high percentage of fast-twitch fibers. Analysis of a champion sprinter’s quadriceps revealed that 24% of fibers were the fastest type (Type IIx), 34% were the moderately fast type (Type IIa), and 29% were slow-twitch. That’s a roughly 70/30 fast-to-slow ratio. The general sprinter population typically shows around 15% of the fastest fiber type, with fewer than 6% at the single-fiber level, making this particular athlete an outlier.
Fiber type is largely genetic, but training can shift fibers along the spectrum. Heavy, explosive resistance training and sprint work encourage your existing fibers to behave more like fast-twitch fibers, improving their ability to produce force quickly. Endurance training pushes fibers in the opposite direction. If speed is your goal, your training should emphasize short, maximal efforts over long, slow work.