The equation and the catch
Maximum sprint velocity is stride length times stride frequency, so any real gain in top speed has to arrive through one of those two numbers. The catch is that both are set by what happens in the fraction of a second your foot spends on the ground, so they trade against each other when you force one. On a force treadmill, 33 runners with top speeds spanning 6.2 to 11.1 metres per second were compared at their own limits, and the fastest applied ground forces around a quarter greater than the slowest, while the time taken to swing the leg through to the next step did not differ between them. So the runner who looks quick-footed is really the runner striking the ground harder, and shortening your stride on purpose to buy frequency tends to cost you length instead of buying speed.
6.2–11.1 m/s
Top speeds tested
33 runners at their own maximum on a force treadmill
8.4 m/s
Club senior backs
Average top speed in a 300-player amateur rugby cohort
20–40 m
Where top speed arrives
When club rugby players reached max velocity in a 50 m sprint
How to train each lever
| Lever | What actually moves it | Tools |
|---|---|---|
| Stride length | Cue a harder strike into the ground, not a longer reach | Heavy lifting, plyometrics, sled and hill sprints |
| Stride frequency | Rose most clearly after assisted overspeed work in a pool of 21 training studies, though not conclusively more than plain sprinting | Assisted or downhill sprints, fast skipping drills |
In club cohorts timed through gates, players reached top speed somewhere between 20 and 40 metres into a long sprint, and which end of that window they hit varied with age and position. So if your training never includes runs of 30 metres or more at full effort, your top speed never actually gets rehearsed. Flying sprints handle that: build up over about 20 metres, hold maximal speed for the next stretch, and take a full walking recovery so every effort stays honest. Keep the volume small, and treat the session as skill work for hitting the ground harder rather than as conditioning.