Behaviour Is the Mechanism: Why Performance Change Requires Behaviour Change

Applied Behavioural Sports Science Series

One of the most persistent challenges in high-performance sport is the gap between what an athlete knows and what an athlete consistently does. Despite an increasingly sophisticated ecosystem of monitoring systems (training load, relative power, body composition, readiness scores, etc.) we still encounter the same behavioural inconsistencies. Such as, athletes who understand what needs to change but fail to enact the behaviours that bring about that change.

We can tell an athlete with remarkable precision:
“Reduce 2–3% body fat.”
“Recover more effectively.”

Yet the central truth at the intersection of complex systems theory, behavioural science, Ariely’s research on irrationality, Kahneman’s dual-process psychology, and Thaler and Sunstein’s work on choice architecture remains:

Performance only changes when behaviour changes. All other information (testing, monitoring, education) is context, not mechanism.

It is this truth that makes behavioural design frameworks essential. Wendel’s Designing for Behavior Change argues that if behaviour is the goal, the environment must be constructed to produce the behaviour, not only instruct it. In this sense, behavioural design becomes the practical extension of complex systems thinking in athlete preparation.

Athletes Are Not Rational Actors: Lessons from Kahneman and Ariely

Sport can often assumes that athletes behave rationally. That once provided with precise information (your body fat is too high, your aerobic capacity too low) an athlete will adjust their behaviour in a rational way. However, both Kahneman and Ariely demonstrate why this assumption is flawed.

Kahneman’s work shows that day-to-day behaviours are governed by ‘System 1’ which are automatic, habitual, emotional, effort-minimising.

Ariely takes this further, demonstrating that humans are predictably irrational. We reliably make suboptimal choices even when we possess full knowledge of what the optimal action would be. These irrationalities follow patterns:

• we overvalue immediate rewards (present bias)

• we underestimate the cost of future effort

• we default to the easiest available option

• we respond disproportionately to friction

• we anchor on irrelevant cues

• we choose what is visible, convenient, or socially validated

Therefore, an athlete who knows they should reduce late-night snacking or push harder in gym sessions is not failing because they lack discipline. They are behaving exactly as behavioural science predicts humans behave when tired, stressed, emotionally depleted, or surrounded by cues that trigger convenience over intention.

As a result:

Strategies that rely on rational explanation (‘System 2’) will always fail when the behaviour in question is driven by automatic, emotional, or convenience-based processes (System 1).

This is why education-heavy approaches fail. Why meetings rarely lead to sustained behaviour change and why athletes nod with complete sincerity yet revert to familiar patterns within 24 hours.

Ariely’s work, perhaps more than any other, makes the case for why behavioural design must become central to performance environments.

Athletes as Complex Adaptive Systems: Why Linear Solutions Don’t Work

My PhD research positions athletes and their preparation environments as complex adaptive systems:

• behaviours are emergent

• relationships are nonlinear

• internal states fluctuate

• small changes can produce large outcomes

• environmental constraints shape degrees of freedom

In a complex system, behavioural output cannot be changed through linear instruction or isolated interventions. It must be altered through constraint manipulation, environment shaping, and the design of interactions.

This aligns directly with Wendel’s behavioural diagnosis process, which begins by asking “What system of constraints is currently producing the behaviour we see?” This is where the second major thread of behavioural science emerges.

Nudge Theory: The Power of Choice Architecture

Thaler and Sunstein’s Nudge introduces the idea that humans make decisions within environments, and these environments (physical, social, structural) shape choices.

In other words:

The environment is not neutral. It is an active force that influences behaviour with or without our awareness.

Nudges are small design features that alter behaviour without restricting choice. They are powerful because they leverage the automaticity of ‘System 1’ rather than fighting against it.

Applied to sport, nudges could include:

• placing recovery modalities along the exit path so athletes naturally pass them

• locating high-protein foods (or carbohydrates) at the front of the buffet

• using simple visual prompts for hydration or sleep routines

Research shows similar effects described in complex systems theory, such as small adjustments in choice architecture producing disproportionately large behavioural changes.

In brief:

• Ariely explains why athletes make irrational choices.

• Kahneman explains which cognitive system drives those choices.

• Thaler & Sunstein explain how environments shape those choices.

• Wendel explains how to design environments that produce better choices.

• Complex systems theory explains why those choices produce emergent patterns.

These lenses converge to form a unified behavioural model of athlete preparation. One I intend to coin ‘Applied Behavioural Sports Science’.

Why Knowledge Alone Does Not Shift Behaviour

Every practitioner knows an athlete who understands exactly what they need to do, yet fails to act consistently. Behavioural science explains why this happens:

• System 1 is fast and automatic.

• System 2 is slow and rarely available under fatigue.

• Humans are predictably irrational.

• The environment influences behaviour more than intention.

• Small frictions drastically reduce compliance.

• Habits stabilize around convenience, not optimality.

Therefore, this is a system design problem not an athlete problem.

Wendel’s behavioural diagnosis highlights common points of failure:

• insufficient motivation

• excessive friction

• absence of cues

• conflicting identities

• unsupportive social norms

• competing priorities

Complex systems theory adds that these forces interact to stabilise a behavioural attractor which is a pattern of behaviour that persists because it is consistent with the system’s constraints.

This means, If you want to change athlete behaviour, don’t try to change the athlete, change the system.

Behaviour Is the Mechanism of Adaptation

All physiological outcomes (body composition, strength, aerobic capacity) depend on repeated behaviours:

• consistent protein intake

• training intent

• progression adherence

• sleep routines

• hydration

• proper recovery execution

The outcomes are physical; however, the mechanism is behavioural.

Ariely would say: People do not naturally do the right thing, even when they know what the right thing is.

Kahneman would say: The behaviour must suit the architecture of the mind.

Thaler & Sunstein would say: Design the environment so the right choice is the easy choice.

Wendel would say: The behaviour is the intervention.

Complex systems theory would say: Alter the constraints; the system will reorganise.

This convergence is the foundation of Applied Behavioural Sports Science.

Integrating Behavioural Design into High-Performance Sport

High-performance sport must transition:

• from education to behavioural design

• from information to environment shaping

• from instruction to constraints manipulation

• from athlete blame to system renovation

• from output measurement to input architecture

Our monitoring systems are only as effective as the behaviours they inspire. Behavioural design shows us how to create environments where elite behaviours become the natural, automatic, predictable outcome by default and not the exception.

The following blog posts will explain how.