The stopwatch may say two athletes are fast. The curve reveals whether both can remain fast while changing the direction of their run.
In football, the shortest line between two points is not always the best solution. The attacker bends the run around the defensive line to stay onside, keeps the ball in view, and accelerates into space. The defender tracks an opponent without turning every adjustment into braking and a new acceleration.
These actions do not behave like a linear sprint with a slight bend. Nor are they the same as a 90-degree cut. The trajectory is continuous, the trunk leans inward, and each leg takes on a different role so the centre of mass can continue accelerating around the curve.
If competition demands curvilinear speed, the programme needs to preserve linear sprinting while also assessing and training the specific ability to run on a curve.
The number that changes the question
In 901 sprint actions observed over ten matches of a Premier League team, 86% were performed with some degree of curvature. The sample came from a single team and does not authorize turning the percentage into a universal rule for every player, position or championship.
But the result dismantles a common simplification: preparing football speed using only straight starts and perfectly sagittal accelerations does not reproduce the variety of match movements. In the same study, 66% of sprints began from a rolling acceleration, 62% involved trunk rotation, and almost half ended in a duel or interaction with the ball.
901 actions · 10 matches · one Premier League team · 2017–2018 season
Curved sprinting and cutting change the trajectory in different ways
In curved sprinting, direction changes across several cyclical foot contacts. The athlete leans inward and tries to preserve tangential speed while producing the lateral force needed to follow the arc.
In a cutting change of direction, one dominant plant redirects the body. The athlete usually needs to reduce speed before contact, absorb force, and reaccelerate in another direction. The cost, timing, and mechanical organisation are different.
Continuous trajectory
Curved Sprint
The trajectory changes gradually. No single lateral plant concentrates the entire redirection.
- Cyclic steps
- Medial trunk lean
- Aim to preserve speed
Concentrated redirection
90° cut
The change is concentrated in a cutting contact, usually after preparing to reduce speed.
- Dominant lateral plant
- Braking and reorientation
- Objective: exit in a new direction
That distinction appears in the data. In 33 players, performance in the curved sprint and 90-degree cut test showed moderate correlations, between r = 0.33 and 0.41. This represents approximately 11% to 17% of shared variance, depending on the comparison — little to treat the two tasks as synonymous.
The same study found opposite dominance directions between curve and cut in about 70% of athletes. That doesn't mean 70% had a problem. It means that the fastest side in one task did not need to be the fastest side in the other, consistent with the distinct requirements of each leg.
| Test | What the athlete does | What the result reports | What it does not show on its own |
|---|---|---|---|
| TestLinear sprint | ActionAccelerate or run straight. | InformsSpeed and acceleration in the sagittal plane. | Does not showAbility to sustain speed while running around a curve. |
| TestCurved Sprint | ActionIt gradually changes the direction in cyclical steps. | InformsCurvilinear speed, preferred direction, and response to radius. | Does not showAbility to brake and exit a hard cut. |
| Test90° cut | ActionDecelerates, plants laterally, and reaccelerates. | InformsPerformance in a pre-planned change of direction. | Does not showFull reactive agility or curvilinear velocity. |
Interpretation depends on protocol, distance of entry, speed, angle and context. Tests with the same name can measure different tasks.
On a curve, the legs stop doing the same job
In a straight line, both legs tend to fulfill more similar roles. On the curve, one is on the inner side of the arc and the other on the outer side. A study with only nine players — therefore a small biomechanical base — showed that the inner leg was more affected when the task went from straight to curve, especially by increasing contact time.
Electromyography also showed different patterns: in the protocol studied, the biceps femoris and gluteus medius were more active in the outside leg, while the semitendinosus and adductors were more active in the inside leg. The finding helps explain the mechanism, but it does not provide a universal strength-training prescription or prove that isolating those muscles will improve sprinting.
General strength builds capacity. The trajectory teaches the athlete to use this ability in the curve.
Another study, with 84 players between U15 and U20, observed that the relationship between linear and curvilinear sprint decreased with age. The side considered “good” improved between categories, while the “weak” side did not follow the same rhythm; the asymmetry was higher in the U20.
This is a cross-sectional association, not longitudinal footage of each athlete maturing. Even so, the pattern supports a useful hypothesis: as position, experience, and game habits specialise movement, running on a curve may become a skill that is progressively less explained by linear speed.
The penalty arc becomes a 17-metre laboratory
The test proposed by Fílter and colleagues uses a marking already found on every regulation pitch: the penalty arc. The athlete sprints 17 metres along the line, once in each direction. Timing gates can mark the start and finish; standardised video positioning is also a practical alternative.
Essential protocol
In 40 experienced players, the protocol showed good reliability between sessions. Linear velocity explained approximately 35% of the curved sprint variation. This confirms a common base of speed, but leaves most of the difference associated with factors that the straight test does not capture.
The test should serve to monitor performance, not to manufacture diagnosis. A time asymmetry may reflect tactical role, frequency of exposure, motor preference, radius adopted or measurement error. Without prospective association with injury and without minimal error clearly incorporated into the decision, “different side” is not synonymous with “problem side”.
What the training evidence supports
In 2025, a randomized trial involving 19 U16 players was published. Over six weeks, one group completed 11 linear sprint sessions and the other completed curvilinear sprint sessions, with equivalent volume.
The two groups improved different measures of linear sprint and direction change. The decisive difference was specific: only the group that trained in curve significantly improved the curved sprint on both sides, and comparisons between groups favored curve training in this task.
In 2026, another trial with 18 youth players compared narrow- and wide-radius curves over 12 sessions in six weeks. Both groups improved several measures, with no statistically significant difference between radius conditions. This suggests that different curves may be useful, but the study is small, did not include a group without curved-sprint training, and does not prove that radius is irrelevant in every situation.
| Study | Design | Main finding | Key limitation |
|---|---|---|---|
| StudyFílter et al. · 2020 | Design40 players; test of 17 m. | FindingGood reliability and only 35% of variance explained by linear sprint. | LimitValidates the test, not a training programme. |
| StudySolleiro-Duran et al. · 2025 | Design19 U16; randomized; 6 weeks. | FindingSpecific adaptations; only the curved-sprint group improved curved-sprint performance in both directions. | LimitA small sample of male players from a single age group. |
| StudySolleiro-Duran et al. · 2026 | Design18 youth players; two radii; 6 weeks. | FindingBoth radii produced improvements; there was no difference between groups. | LimitNo control group and low power for small differences. |
Proportionate conclusion: experimental evidence supports some specificity from curved-sprint training in youth players. There is still no universal dose or enough evidence to select a single ‘ideal’ radius.
How to integrate the curve without losing speed
The mistake would be to replace all straight running with cone drills. Linear speed remains a fundamental quality and showed an important relationship with multidirectional tasks. The best programme combines qualities and distributes the stimulus according to the player, position, phase of the calendar, and actual exposure.
- Preserve a linear sprint base.Acceleration, maximal speed, and the ability to produce horizontal force remain relevant to running fast along any trajectory.
- Practise curves in both directions.Start with predictable trajectories and high technical quality; progress to different radii and speeds without turning every repetition into fatigue.
- Separate testing from training.The 17-metre arc standardises the assessment. In training, the trajectory can vary to reflect the running channel, position, opponent, and tactical intent.
- Add perceptual demands after stabilising the skill.Rolling starts, orientation to the ball, reading the defender, and moving at the right moment bring the task closer to the game.
- Use strength as support, not as a substitute.Unilateral strength training and trunk, ankle, foot, and hip control can expand the athlete’s options; transfer must be consolidated by sprinting on a curve.
- Monitor trend, not an isolated number.Time, consistency, side, radius, entry speed, and the athlete’s response tell a better story when tracked over time.
The greater the player’s specialisation and the more curvilinear the competitive role, the less confidence we should place in a single linear test to represent all of that player’s speed.
Five errors that reduce the utility of the curve
- Calling any cone circuit a curved sprint. If there is clear braking and a cutting plant, the task has changed.
- Measure only the preferred side. A bilateral comparison helps describe the athlete, provided it is not automatically converted into a risk indicator.
- Always training the same radius. The game features open, closed curves and transitions between them.
- Adding resistance without controlling the vector. A sled, cable, or weighted vest alters the mechanics; evidence on resisted curved-sprint setups is still insufficient.
- Eliminate linear sprint. Specificity does not mean exclusivity. Curved sprinting broadens the programme; it does not erase its foundations.
The speed that finds the way
The curved sprint leaves a bigger lesson than the test itself. Performance does not live in isolated capacities; it emerges when strength, coordination, perception and context need to resolve a real trajectory.
An athlete can be very fast in a straight line and still lose time when they need to lean, organise the legs asymmetrically, keep the ball in view, and attack space without being taken out of the play.
The straight line measures how fast the athlete runs. The curve reveals if the speed knows where to go.
Frequently asked questions
Is curved sprinting a change of direction?
It changes the direction of travel, but it does not behave like a traditional cut. Redirection is gradual and distributed across several foot contacts, with less braking concentrated in a single contact.
Can the penalty arc be used as a test?
Yes. The published protocol uses 17 metres of the arc in both directions, with standardised timing. Timing gates are the most direct option; video can be useful when camera position and frame identification are controlled.
Does asymmetry on the curve mean a greater risk of injury?
This cannot be concluded from the available studies. The asymmetry describes a difference in performance between sides; the interpretation requires measurement error, history, function and evolution of the athlete.
Should you train only curved sprints?
No. The body of evidence supports integrating linear and curved-sprint training. They share a speed foundation but produce partly specific adaptations.