Deceleration Demands Part 2: Testing Physical Capacities
- Jo Clubb
- 5 hours ago
- 7 min read
This article in our deceleration mini-series explores the options and challenges of testing deceleration capacity.
In Part 1 of this series, we established that deceleration is not simply the mirror image of acceleration. It carries unique mechanical demands, which in turn influence the fatigue cost and injury risks associated with decelerating actions in team sports. The logical next step, then, is to ask how we can test deceleration capacity in applied, field-based settings.
It is important to distinguish this from monitoring deceleration load. Monitoring helps us understand an athlete’s exposure to deceleration demands over time, whereas testing is concerned with assessing an athlete’s capacity to perform and tolerate those demands. Monitoring deceleration load will therefore, be covered in my next video, Part 3 in this mini-series on deceleration.
In this article, the focus is solely on how we can assess an athlete’s ability to decelerate.
What Do We Mean by Deceleration Capacity?
Deceleration capacity reflects how effectively an athlete can reduce their momentum under high braking demands. However, deceleration capacity is not a single, isolated quality.
As discussed in Part 1, the Braking Performance Framework, led by Damien Harper and colleagues, has highlighted that horizontal deceleration ability is underpinned by a combination of:
neuromuscular qualities, such as strength and force production
biomechanical and technical factors, including posture, limb positioning, and braking strategy
inter- and intra-limb coordination, which mediates how these qualities are expressed
This complexity immediately presents challenges when we attempt to assess deceleration in the field.
Key Challenges in Deceleration Testing
Ultimately, when testing deceleration, we are attempting to quantify the time taken to reduce velocity between two different points.
Unlike maximal acceleration or sprint testing, where athletes begin from a stationary start, deceleration testing requires athletes to first build up speed before they are required to brake. As a result, the performance outcome we observe is influenced by the velocity reached prior to deceleration. This is a fundamental issue that underpins many of the challenges associated with deceleration testing.
Dependence on Approach Velocity
Deceleration scores are strongly dependent on the velocity an athlete reaches before braking. Two athletes may demonstrate similar stopping times, yet arrive at the braking zone at very different speeds.
This complicates interpretation and makes between-athlete comparisons problematic. For this reason, deceleration testing data is often most informative when used for within-athlete comparisons over time, rather than ranking athletes against one another.
The Role of Momentum
Momentum is the product of mass and velocity. Athletes with greater body mass must therefore work harder to decelerate themselves from the same speed as lighter athletes.
This further complicates comparisons between individuals and reinforces the need to interpret deceleration testing data with appropriate context.
Pre-Planned vs Reactive Deceleration
Another important consideration is whether a test involves pre-planned or reactive deceleration. This distinction is similar to the difference between testing change of direction (pre-planned) and agility (reactive), as we discussed in the post on speed testing. Introducing a reactive component increases variability and adds a cognitive demand to the task.
Neither approach is inherently right or wrong, but practitioners should be intentional in their choice and remain aware of the protocol used when interpreting both their own data and findings reported in the literature.
Athletes with greater body mass must therefore work harder to decelerate themselves from the same speed as lighter athletes.
Common Approaches to Testing Deceleration Capacity
There are several practical field-based approaches that can be used to assess deceleration capacity. Each provides different information and carries specific strengths and limitations.
Change of Direction Tests (e.g. the 505 Test)
One common way to assess deceleration is through sharp change of direction tasks, including the 505 test (discussed further below).
By incorporating a sharp change of direction, the test forces the athlete to decelerate rapidly and reduce their velocity to zero before re-accelerating. Similar logic applies to tasks such as back-pedalling, which constrain the athlete to stop and reverse their movement.
While highly practical and widely used, these tests embed deceleration within a broader change of direction task. As a result, performance is influenced not only by braking capacity, but also by turning technique and re-acceleration ability.
Sprint-to-Stop and Prescribed Braking Distance Tests
Another approach is to ask athletes to accelerate to a sprint before decelerating to a stop at a pre-set distance. Timing gates, such as VALD’s SmartSpeed system, can be positioned at multiple points throughout these tasks to capture split times and quantify how long it takes an athlete to reduce velocity across the braking phase.
In some variations, athletes are required to begin decelerating at a marked point, such as the ADA test below, which helps to constrain braking onset and improve repeatability. These tests allow practitioners to examine braking performance more directly, particularly when compared longitudinally within the same athlete.
The Acceleration–Deceleration Ability (ADA) Test
A newer assessment gaining traction with the increased attention on deceleration is the Acceleration–Deceleration Ability (ADA) test (Harper et al., 2020).
In this test, athletes accelerate maximally over a fixed distance, typically 20 metres, before being instructed to decelerate as quickly as possible and back-pedal to the original line (or alternatively, just come to a standstill). The back-pedal serves as a constraint to ensure athletes fully reduce their velocity to zero.
The ADA test provides an integrated performance outcome, reflecting both acceleration and braking ability. With timing games, such as VALD's SmartSpeed, we should be able to separate the acceleration and deceleration portions of the test.
Using the 505 Test to Calculate Deceleration Deficit
While we traditionally think of the 505 test as an assessment of change of direction, it of course has an underpinning factor of deceleration capacity. Furthermore, we can combine an athlete's time in this test with a linear speed test to derive additional insight through the calculation of a deceleration deficit.
This approach involves subtracting an athlete’s linear 15-metre sprint time from their 15-metre approach time within the 505 test. The resulting value helps contextualise how much braking demand is introduced when a turn is added.
Deceleration deficit can be useful for identifying athletes whose change of direction performance may be limited by their braking ability, rather than their linear speed, as explored further in this publication by Rich Clarke and colleagues (2022). Rich uses z-scores to normalise the athletes' scores in both a deceleration deficit (DD) and change of direction deficit (CODD) to see the bias within their abilities for both dominant and non-dominant sides.
However, it is important to remember that even with this calculation, deceleration is still being assessed within a predominantly linear plane. In many team sports, curvilinear sprinting and deceleration may occur more frequently, adding another layer of complexity. Assessing curvilinear sprinting and decelerration has recently been explored in more detail by Lucas Galmiche and Dr Morgan Williams from VALD, in this article.
Proxy Measures of Deceleration Capacity
In some cases, practitioners may not have the opportunity to perform dedicated on-field deceleration testing. In these situations, it may be useful to consider proxy measures.
Research has shown associations between horizontal deceleration ability and drop jump performance, particularly reactive strength index (RSI) (Harper et al., 2021) This relationship is intuitive, as both tasks involve rapid force attenuation and high eccentric demands.
Athletes with greater RSI have been shown to demonstrate superior horizontal deceleration ability, with underlying contributions from both jump height and ground contact time. In addition, of the drop jump kinetic variables examined, concentric mean force had the largest associations with horizontal deceleration ability.
While proxy measures should not replace direct deceleration testing where possible, they may provide useful context, particularly when interpreted alongside other physical performance data.
Athletes with greater RSI have been shown to demonstrate superior horizontal deceleration ability
Summary and Practical Takeaways
Testing deceleration capacity in applied settings is inherently complex. Deceleration ability is strongly influenced by:
the velocity reached prior to braking
the athlete’s momentum, driven by both speed and body mass
the technical and coordinative demands of braking
the structure of the test itself
Field-based tests such as the ADA test, sprint-to-stop tasks, and the 505 test provide accessible ways to assess deceleration performance, but each comes with strengths and limitations.
The most meaningful insights are likely to emerge when deceleration testing data is interpreted within athletes over time, and combined with information from other physical performance tests to build a more complete athlete profile.
In the next article and video, the focus will shift from testing to monitoring deceleration load, exploring how we count decelerations in training and competition, and the challenges associated with doing so.
Frequently Asked Questions (FAQs)
What is deceleration capacity in sport?
Deceleration capacity refers to an athlete’s ability to rapidly reduce momentum under high braking demands. It reflects a combination of neuromuscular strength, movement mechanics, coordination, and the ability to tolerate high eccentric and quasi-isometric loading, rather than a single physical quality.
What is the best test for deceleration capacity?
There is no single “best” test. Sprint-to-stop tasks, the Acceleration–Deceleration Ability (ADA) test, and change of direction tests such as the 505 all provide different information. Test selection should be driven by the specific question being asked, as well as the context such as the population being tested and the technology availabile.
Can other tests act as proxy measures for deceleration capacity?
Yes. Research has shown associations between horizontal deceleration ability and drop jump performance, particularly Reactive Strength Index (RSI) and concentric force. If direct deceleration testing is not feasible, drop jump metrics may provide a useful proxy, especially when interpreted alongside other physical performance data.
Stay tuned for more insights on athlete testing in our series sponsored by VALD Performance. Subscribe to our blog to stay updated!
This article is support by VALD Performance. For more information, about their technology, visit their website.