Ground Contact Time: Joseph Coyne on Speed Training

Based on Episode 74 of the Just Fly Performance Podcast, a conversation between host Joel Smith and performance coach and sport scientist Joseph Coyne.

Ground contact time is the number Joseph Coyne organizes speed and power training around, and it reorders a lot of weight-room priorities. Coyne, who has prepared world-class sprinters and long jumpers for the Chinese Athletics Association alongside coach Randy Huntington, points out that sprinting at top speed lives in a window of roughly 80 to 100 milliseconds on the ground, while a jump takeoff sits near 120 to 140. His argument is that once you know the contact time your event demands, you stop training for a generic score and start training to produce the most displacement inside that exact window. This conversation walks through how he uses contact time, how he manipulates the force-velocity curve at the point an athlete competes, how he tests jumps, and how he keeps fragile elite hamstrings healthy.

Key Takeaways

• Ground contact time is the organizing metric. Max-velocity sprinting is about 80 to 100 milliseconds on the ground; jump-mat contacts run near 120, and a long-jump board sits around 120 to 140.
• Chase maximal displacement at a set contact time, not a raw reactive strength index. A tiny hop with a very short contact can flatter the RSI while missing what the event needs.
• Train the force-velocity curve where you compete. Once an athlete is generally strong, add assisted and resisted work slightly faster and slower than competition speed to shift the curve at that exact point.
• Strength has a ceiling; power training does not. Once an athlete is strong enough, keep the power the same while shedding load, because you compete with a fixed body mass.
• Above 10 meters per second, hamstrings are fragile. Protect them with eccentric strength and fascicle length, using low Nordic volumes rather than grinding hundreds of reps.

What ground contact time is, and why it beats a raw RSI

Coyne’s starting point is that every event has a signature time on the ground, and training should respect it. He rattles the numbers off from memory.

Sprinting is about 80 to 100 milliseconds at maximum velocity. On the jump mats you’re probably going to get about 120 milliseconds, and off the board it’s about 120 or 140. So you look at those contact times for your athletes and try to maximize displacement at those contact times.

That framing is also why he has cooled on the reactive strength index as a headline metric. RSI is flight time divided by contact time, so an athlete can chase a big number by barely leaving the ground, which tells you little about a jump or a sprint step.

Instead of an RSI, you should look at contact times and maximal displacement at certain contact times, which is essentially like an RSI. But you can have a really low displacement, a really low jump, with a great contact time, and I find the typical flight time divided by contact time a little bit biased.

He wants the coaching cue reversed: fix the time on the ground, then ask for the most displacement inside it. Systems that let you set a target contact time, he notes, double as a teaching tool, because they force an athlete to feel how much they can load and extend against the ground in the time the event allows.

From a coaching consideration, it has to be maximal displacement at set contact times.

Train the force-velocity curve where you actually compete

Early in his career Coyne thought of the force-velocity curve as something you raise evenly and shift to the right. Working with elite athletes changed that. Once an athlete has a base, he targets the precise slice of the curve that matches their event.

Once you’ve done that with any beginning athlete, you have to bump the force-velocity curve at the position you compete at. So if you’re a sprinter, you do sprinting a little bit faster than you can sprint, sprinting that’s assisted, sprinting that’s resisted and slower, sprinting lighter than body weight, sprinting heavier than body weight, to get those changes right at that specific junction of the curve.

The tools are deliberately small: a weighted vest, an empty barbell held on the back or overhead, ankle weights, wrist weights, each one nudging the force or the velocity side right around competition speed. He still starts a raw beginner by building general strength, sometimes up to a back squat near 170 to 180 percent of body weight, but he warns against living in the weight room chasing a magic lift while neglecting the sprinting itself.

Once your strength is strong enough, that’s it. You have diminishing returns from that point on.

Jump testing that actually transfers

Coyne rebuilt the Samozino and Morin force-velocity profiling method in a spreadsheet so he could change the projection angle, because a bilateral vertical jump assumes a 90-degree takeoff that does not describe his athletes. A sprinter leaving the blocks projects near 40 degrees; a long jumper closer to 25. He also stopped relying on a single test, running a small battery instead.

We’d look at maybe four or five different jumps, including a body-weight countermovement jump, a dip jump off the takeoff leg, and a 10-second repeater jump, and create effect sizes or z-scores against the best person in the group. That tells you what each athlete needs to focus on.

The point of scoring against the best athlete in the squad is direction, not ranking: a springy athlete who lags on the takeoff-leg dip jump gets more of that, while a stiff athlete who lags on the repeater jump trains the elastic quality. In the weight room he leans on a few honest markers rather than a long testing menu, including a 20-centimeter dynamic step-up loaded to roughly three times body weight, squat-jump velocities and heights off a body-weight load, and pneumatic power near 70 watts per kilogram.

Strength versus power, and training at peak-power weight

Coyne keeps the weekly structure blunt: a max-strength day where the goal is to lift as heavy as possible, and a power day where the goal is to move as fast as possible, both monitored with velocity so nothing drifts slow. He often pairs a heavy lift with a slower jump on strength days and a drop jump on power days, keeping the fast contact under about 120 milliseconds. His most transferable idea borrows straight from the track: find an athlete’s peak power, then chase that same power at lighter and lighter loads.

You don’t get to run down the track or take off in a long jump with a barbell on your back. Your mass is fixed, so you have to improve the acceleration and velocity components to increase power. You find the peak power at their peak-power weight, then create that same power at lighter and lighter weights.

Whether to complex or contrast a heavy lift with a fast movement is a practical call, not a rule. Near a competition he strips the contrast work out, because the athlete is already getting plenty of jumping in technical training and he does not want to overload it.

Protecting hamstrings above 10 meters per second

At the elite end, Coyne says durability outranks any weight-room number, because the fastest athletes live on the edge of hamstring injury.

If you’re running above 10 meters per second, your hamstrings are predisposed to being fragile just at those speeds. Your biggest job is stopping them from getting injured.

He frames the risk with the “quadrant of doom” from researchers David Opar and Anthony Shield: short fascicle length paired with low eccentric strength is the danger zone, while long fascicles and high eccentric strength protect an athlete. That drives his exercise choice toward eccentric work that lengthens fascicles, using a K-Box for eccentric hip-extension loading and a careful Nordic progression that starts with isometric holds and manual eccentric curls before full Nordics. Crucially, he keeps the volume low.

Research shows 100 reps per week versus eight reps per week gives about similar changes in eccentric strength and fascicle length. So I go with the low-volume approach, and I might even start with two sets of two.

Over-speed, resisted work, and making the test the training

On the 1080 Sprint, much of it under Randy Huntington’s direction, Coyne quantifies over-speed rather than guessing at it with bands. He starts an athlete around 10 percent faster than they can run, then holds that speed while reducing the towing force so the body adapts to moving that fast on its own. Resisted work follows the same peak-power logic he uses in the gym, and he even hands a coaching-first version to team-sport athletes.

You put on as much weight as it takes to make them look good when they accelerate, get them to remember that, and then slowly start taking weight off while asking them to keep what looked really good.

Underneath all of it is a habit he wants coaches to adopt: stop treating testing as a separate event. He would rather the daily training carry the measurement, so the numbers reflect real training states instead of one hopeful day every few weeks.

It’s almost worthless doing tests once every six weeks. You want to embed everything you do into your training, record it, and monitor it over time.

Frequently asked questions

What is ground contact time?
Ground contact time is how long a foot stays on the ground during a stride or a jump takeoff. Coyne uses it as the organizing number for training: max-velocity sprinting is roughly 80 to 100 milliseconds, a jump-mat contact is near 120, and a long-jump board sits around 120 to 140. Knowing the window your event demands lets you train to produce force inside it rather than chasing a generic score.

Is the reactive strength index still useful?
Coyne finds a raw RSI biased, because flight time divided by contact time can reward barely leaving the ground. He prefers to fix a target contact time and then ask for maximal displacement inside it, which keeps the test tied to what the sprint step or jump actually needs.

How do you train the force-velocity curve for a specific event?
After building a general base, Coyne adds work slightly faster and slower than competition speed right at the point the athlete competes: assisted and resisted sprints, lighter and heavier than body weight, plus small loads like weighted vests, ankle weights, and empty barbells, to shift the curve exactly where it matters.

How do you protect elite sprinters’ hamstrings?
Because hamstrings grow fragile above about 10 meters per second, Coyne builds eccentric strength and fascicle length using K-Box eccentrics and a graded Nordic progression, and he keeps the volume low, citing research that eight reps a week produces changes similar to 100.

What weight-room markers does Coyne track for sprinters and jumpers?
He watches a handful of honest numbers: a 20-centimeter dynamic step-up loaded to about three times body weight, squat-jump velocities and heights against a body-weight load, and pneumatic power near 70 watts per kilogram, and he embeds those checks in daily training rather than isolated test days.

About the authors

Joseph Coyne is a performance coach, exercise physiologist, and sport scientist from the Gold Coast, Australia. At the time of this episode he was the physical preparation coach for the Chinese Athletics Association’s jump and sprint section, handling speed and power for their best sprinters and long jumpers alongside coach Randy Huntington, after serving as a performance manager at the Chinese Olympic Committee’s National Sports Training Center in Beijing. He has also run a sports injury and performance clinic in Queensland, Australia, and writes on special strength, jump testing, and speed development for SimpliFaster.

Joel Smith is the host of the Just Fly Performance Podcast and the founder of Just Fly Sports, a former collegiate strength and track and field coach focused on speed, power, and athletic development. Listen to the full episode with Joseph Coyne on Just Fly Sports.