Deceleration Load: Why It Deserves to Be Treated as Its Own Variable
- Jo Clubb
- 1 day ago
- 5 min read
This article explores deceleration as a movement demand and the implications for performance and injury risk in team sport athletes.
For many years, load monitoring in team sports focused almost exclusively on total running distance and high-speed running. More recently, acceleration metrics have received greater attention. Yet for a long time, deceleration was largely overlooked, often dismissed as simply “slowing down”.
But what if deceleration is not just a secondary movement outcome, but one of the most decisive and mechanically demanding loads we expose athletes to?
As part of my athlete testing series in collaboration with VALD, I wanted to focus on deceleration, but felt it warranted a deeper dive than some of my other topics. So in this article, Part 1, I explore the mechanical load that underpins a deceleration and why it deserves to be treated as its own variable, rather than as the mirror image of acceleration. In Part 2 (coming soon), I will explore how we can assess and track deceleration.
Why Deceleration Is Not Just the Opposite of Acceleration
In many monitoring systems, acceleration and deceleration metrics are paired together. The assumption is often that however we interpret acceleration data, we can simply apply the same logic in reverse for deceleration.
Mechanically, however, this assumption does not hold. Acceleration and deceleration place fundamentally different demands on the neuromuscular system. Treating them as a mirror image risks underestimating both the load athletes experience and the implications for fatigue, injury risk, and performance. I've previously explored this discussion on the topic of defining acceleration, and deceleration efforts elsewhere on the blog.
Frequency and Intensity: Decelerations Occur More Often, and at Higher Extremes
Across a wide range of team sports, athletes are exposed to decelerations more frequently than accelerations, particularly at higher intensities. A systematic review in Sports Medicine led by Damian Harper has shown that, with the exception of American football, decelerations occur more often than accelerations across multiple team sports (Harper et al., 2019).
In addition, athletes typically reach higher absolute maximum values when decelerating than when accelerating, such as – 5.7 to 6.3 m/s/s and 4.4 to 4.7 m/s/s respectively during matches in La Liga 2 (Oliva-Lorenzo et al., 2020).
Deceleration Carries a Much Higher Mechanical Cost
Beyond frequency and intensity, the mechanical cost of deceleration is substantially greater than many other locomotor actions. Research examining soccer match play has shown that mean effort per metre is approximately 28% higher during acceleration compared to other match activities, and yet as much as 65% higher during deceleration (Dalen et al., 2016).
This reflects the very high braking forces that must be generated and absorbed in a short time window when athletes slow down from high speeds. As illustrated in the Science of Muli-directional Sport figure below, the ground reaction force (GRF) generated during decelerating from high speed can be ~2.7 times greater than initial acceleration and
~1.3 times greater than maximal velocity sprinting.
Muscle Action: Why Braking Is So Costly
From a muscular perspective, acceleration and deceleration rely on different contraction modes.
Acceleration is predominantly concentrically driven
Deceleration involves high-intensity eccentric and quasi-isometric muscle actions
These contraction modes are capable of generating substantially higher muscular tension than concentric actions alone. As a result, braking is not only different to acceleration, but often more demanding for the musculoskeletal system. This helps explain why deceleration carries a disproportionate fatigue cost relative to the distance or time involved.
The high braking forces involved in deceleration mean that repeated exposure can contribute to a cycle of neuromuscular fatigue, reduced coordination and increased tissue stress, subsequently increasing injury risk.
Crucially, these forces occur very early in ground contact. Looking back at the figure from the Science of Multidirectional Speed team from earlier, we can see that the high-impact loads in deceleration occur within the first 10–40% of stance and must be attenuated very quickly. This is particularly relevant when considering many injury mechanisms, including ACL injuries, occur within the first 50 milliseconds of foot contact.
If deceleration is not monitored distinctly and appropriately, practitioners may be missing a key driver of injury risk, particularly during periods of increased load or return-to-performance progressions.
Performance Matters Too: Deceleration and Winning
Deceleration is not only relevant from an injury-risk perspective. It also plays a crucial role in performance.
Analyses of match play in elite football have shown that deceleration is one of the most common individual movements preceding goals (Martínez-Hernández et al., 2022). This is probably not surprising if we consider that effective deceleration potentially enables:
Higher approach speeds
Faster repositioning
More effective offensive and defensive actions
In many team sports, key moments occur in highly congested, rapidly changing environments during split seconds. The ability to decelerate efficiently can be the difference between arriving first, arriving late, or not arriving at all.
What Determines Deceleration Ability?
Deceleration capacity is not determined by strength alone. The Braking Performance Framework, again led by Damian Harper, highlights a combination of neuromuscular and biomechanical factors that underpin horizontal deceleration ability. These include strength qualities, coordination, and the ability to control and attenuate force under high braking demands.
At this stage, it is important to recognise the complexity of the task, without yet diving into measurement approaches, which I'll come onto in Part 2.
Key Takeaways
Deceleration is not the mirror image of acceleration
It occurs more frequently and often at higher intensities
It carries a substantially higher mechanical and fatigue cost
It is relevant to both injury risk and performance outcomes
For these reasons, deceleration deserves explicit attention within load monitoring and athlete testing systems, rather than being treated as a secondary or derivative metric.
Understanding why deceleration matters is only the first step. The next challenge is deciding how we assess and monitor deceleration capacity in applied settings, given the limitations of current tools.
That question is the focus of Part 2 of this series, where we will explore what existing metrics can and cannot tell us, and how to make better decisions despite imperfect data.
FAQs
Is deceleration more important than acceleration?
Not necessarily more important, but it is often under-represented despite its high mechanical and fatigue cost. Deceleration capacity also links with both performance and injury risk in sport.
Can GPS deceleration counts measure deceleration capacity?
Deceleration counts describe exposure, not capacity. This distinction is explored in detail in Part 2.
Why is deceleration relevant to ACL injuries?
High braking forces occur very early in ground contact, within timeframes (such as the first 50 milliseconds of contact) relevant to many non-contact injury mechanisms.
Stay tuned for more insights on athlete testing in our series sponsored by VALD Performance, particularly Part 2 on Decelerations. Subscribe to our blog to stay updated!
This article is support by VALD Performance. For more information, about their technology, visit their website.