Most programs list “speed work” as a single line item. Book it for Tuesday, run some sprints, move on. The mechanics underneath that single word describe at least three separate physical qualities, each with its own force demands, its own timeline for adaptation, and its own place in a training year.
Three Different Sprints
Acceleration runs from a standing or rolling start out to roughly 10 to 20 meters. It’s dominated by horizontal force production. Ground contact time is relatively long, often above 200 milliseconds. The athlete drives the ground away at a shallow angle to overcome inertia. Rabita and colleagues (2015) measured world-class sprinters. The fastest accelerators weren’t simply the strongest athletes overall. They directed the most force horizontally, not just the most force in total.
Max velocity, reached beyond 30 meters for most field-sport athletes, looks mechanically different. Ground contact time drops to roughly 80 to 100 milliseconds. The body sits more upright, and force needs applying almost entirely vertically, in far less time, to hold top speed. Morin and colleagues (2015) identified the hamstrings as the primary driver of this late-swing, early-stance force production. That’s distinct from the quad-and-hip-dominant pattern seen in acceleration.
Change of direction and agility form a third quality entirely. Nimphius and colleagues (2018) reviewed the evidence on linear sprint speed against COD performance. The correlation between them was weak. Straight-line speed predicts surprisingly little about an athlete’s ability to decelerate and redirect. COD performance depends heavily on eccentric braking strength and reactive strength, qualities linear sprinting doesn’t train directly.
Measuring Which Quality Needs Work
Samozino and colleagues (2016) developed a method for extracting an individual force-velocity profile from a single timed sprint. It needs nothing more exotic than radar, GPS, or a set of timing gates. The output is three numbers. F0 is the athlete’s theoretical maximum horizontal force at zero velocity. V0 is their theoretical maximum velocity at zero force. Pmax is the peak power where force and velocity combine most effectively.
Plotting these against a population-average profile shows where an athlete sits. Some carry a force deficit: velocity capability outpaces the ability to apply force into the ground. They respond best to heavy resisted sprints, sled pushes, or strength work with a horizontal emphasis. Others carry a velocity deficit: they can produce force but can’t apply it quickly. They respond better to overspeed methods, plyometrics, and unloaded max-velocity sprinting. Morin and Samozino (2016) argue this profile, not a generic sprint time, should guide which method gets prioritized.
Why the Training Methods Don’t Belong in the Same Phase
Acceleration and force-deficit correction pair naturally with a max-strength training block. Heavy sled work and resisted sprints share enough mechanical overlap with strength training to program together efficiently, and both develop over similar timeframes.
Max velocity work asks for something a max-strength phase doesn’t provide: low residual fatigue and high technical intent. Running near top speed under heavy accumulated fatigue produces poor mechanics. It adds injury risk without building the quality it’s meant to build. That’s why max-velocity emphasis tends to sit better in a conversion or pre-competition phase, once general strength is established and volume has come down.
Change of direction and reactive strength need their own progression. Build it around eccentric strength and depth-jump intensity, managed independently of the linear-speed work. Lumping COD drills into a generic “speed day” ignores that the neuromuscular demand, and the adaptation timeline, matches neither acceleration nor max velocity training.
The Planning Mistake This Creates
Treating speed as one quality with one weekly session compresses three distinct adaptations into a single block. An athlete can improve acceleration all preseason and still underperform at max velocity in competition. The two were never trained as separate targets with separate progressions.
A program map that only shows “speed” as a single row hides this problem. Breaking speed into acceleration, max velocity, and change of direction, each sequenced against the phase it fits, is a small planning change with a real effect on which quality improves, and when.
Related reading: Deload weeks: why less load can build more strength and Concurrent training and the interference effect.
References
Rabita G, Dorel S, Slawinski J, et al. Sprint mechanics in world-class athletes: a new insight into the limits of human locomotion. Scand J Med Sci Sports. 2015;25(5):583-594. DOI: 10.1111/sms.12389. PMID: 25640466
Morin JB, Gimenez P, Edouard P, et al. Sprint acceleration mechanics: the major role of hamstrings in horizontal force production. Front Physiol. 2015;6:404. DOI: 10.3389/fphys.2015.00404. PMID: 26733873
Nimphius S, Callaghan SJ, Bezodis NE, Lockie RG. Change of direction and agility tests: challenging our current measures of performance. Strength Cond J. 2018;40(1):26-38. DOI: 10.1519/SSC.0000000000000309
Samozino P, Rabita G, Dorel S, et al. A simple method for measuring power, force, velocity properties, and mechanical effectiveness in sprint running. Scand J Med Sci Sports. 2016;26(6):648-658. DOI: 10.1111/sms.12490. PMID: 26043810
Morin JB, Samozino P. Interpreting power-force-velocity profiles for individualized and specific training. Int J Sports Physiol Perform. 2016;11(2):267-272. DOI: 10.1123/ijspp.2015-0638. PMID: 26694658
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