Consider the chaos: creating ecological validity in the Return to Sport process

By Dr Matt Taberner @MattTaberner & Dr Daniel Cohen @danielcohen1971

From the spectators who view from afar, to the backroom staff who work on the front-line, the beauty of sport is its unpredictability. Whether it is football played on the lush pitches of the English Premier League (EPL) or basketball on the gleaming courts of the National Basketball Association (NBA), movement in sport is spontaneous, reactive and non-linear. Movement in team sports is chaotic and highly variable, often initiated by the interaction between players, transition between phases of play and the direction/speed of the ball. As characteristics of movement in competition, it would seem logical and appropriate to progressively incorporate these qualitative aspects within a sports-specific reconditioning approach following injury.

We recently proposed the ‘control-chaos continuum’ as an adaptable framework for on-pitch rehabilitation in elite football, incorporating progressively greater perceptual and neurocognitive challenges.[1] The concepts from which the framework was constructed also have the potential for application across other team sports including rugby, Australian rules football, basketball and American football.[2] The question however remains: how can practitioners gradually replicate the team training environment and the conditions of ‘chaos’ in rehabilitation while respecting the principle of specificity?

Consider the context to create chaos

Despite conflicting evidence over the precise definition of the concept, ecological validity is a vital consideration for practitioners underpinning training prescription to replicate the physiological, neurocognitive, technical, tactical and psychological demands integral to their sport.[3,4] The planning and monitoring process used for a healthy athlete should also be applied in rehabilitation, taking into account that training is being prescribed in the presence of an injury (Figure 1). Within this context, ecological validity can be described as the extent to which rehabilitation represents the sport-specific and club-specific structure and training environment that an athlete will be exposed to upon return to sport (RTS). The early phases of rehabilitation may comprise of general training, limiting movement variability by applying task and environmental constraints upon the athlete to shape the environment to the required outcomes.[5,6,1] These early phases of the continuum may be described as having two layers of control, high control over running speeds during the return to linear running and control over directional change load alongside progression of running speeds and integration of technical skills.[1] Physical qualities important to the sport are targeted within the constraints of the injury, building a foundation towards RTS load targets. Importantly, improving athlete confidence is one of the main objectives of the controlled phases which shows that progress is being made in the athlete’s RTS journey before the practitioner can begin applying the ‘art’.[7]

Figure 1.  Model for incorporating ecological validity in the Return to Sport (RTS) process. Progressive sports-specific rehabilitation centered around the athlete incorporating aspects related to the club and coaching environment (training methodology – periodisation structure – game model). Within session i.e. drill design and content should progressively incorporate appropriate physiological, technical, tactical, neurocognitive, and psychological elements to prepare the athlete for RTS. Monitoring process should incorporate aspects used in the team setting – external load (locomotor/mechanical derived measures), internal load (hear-rate derived measures), subjective (rate of perceived exertion derived measures) and response (strength & power diagnostics, pain, joint effusion) to inform progression and RTS decision-making.

What about the game?

The transition to later phases of the continuum, allows the practitioner to express their creative ability and game understanding as they incorporate ‘chaos’ in an athlete-centered approach.[8] Rehabilitation now moves from a base of general training towards increasing levels of specificity. From a planning perspective, a sport-specific periodisation structure progresses to a club-specific structure and the unique load demands inherent to the game model of the coach leading the preparation of players for competition.[9] Session structure should progressively mimic the composition of team training on acquisition days, targeting the physical qualities important to athlete’s sport and position.[10,11,12] However, it must be recognised that there is substantial inter-individual variability in physical outputs and qualities among athletes in the same position, which may reflect the game model used.[13,14,15] Multiple acquisition blocks within a micro cycle enable RTS load targets to be achieved, exposing the athlete to increments in volume, intensity and stimuli that reflect the demands of the athlete’s position, sport and injury-specific considerations.[1] At a session content level, i.e. drill design, should incorporate stimuli requiring appropriate neurocognitive challenges, spatial awareness and technical skill content related to the game model that mimic the demands of competition (Figure 2).[16,17,18] Video analysis may provide further insight on the contextual requirements placed upon the player in both training and competition. This provides a powerful tool for the practitioner to gain a true understanding of the environment and stimuli required, alongside pre-injury data.[19,20] The training of physical qualities while progressively integrating these contextual elements together increase the load capacity of the athlete, with the goal of reducing reinjury risk upon RTS.[21,22]

Figure 2. Application of the coaches’ game model in a rehabilitation context. Progressively structure the weekly micro cycle towards the club-specific model in preparation for Return to Sport. Drill design and session content should incorporate elements related to the position of the athlete, key game moments (attacking, defending, transitions between moments), the athlete’s capabilities (physical qualities to be trained) and technical/tactical elements guided by the coaching staff.


High chaos, represents the last phase of the continnum, incorporating worse-case scenario drills and position-specific conditioning reflecting the intensity of competition. Dependent upon the severity of injury and associated length of absence from training, the consensus of the shared decision-making team may recommend a return to partial training. This may involve the athlete in the team warm-up and modified within certain training drills such as a ‘floating player’ within small-sided games. Exposing the player to elements of ‘player traffic’ through partial team re-integration or the integration of additional players/support staff is a vital component of ecological validity in rehabilitation, challenging an athlete’s level of awareness of other athletes and allowing assessment of their response to a situation requiring high level decision-making.[23] The transition to a club-specific training structure may incorporate a taper within the micro cycle prior to return to full team training once RTS load targets have been achieved. Again, this would reflect the existing club training structure, allowing the practitioner to address variables such as number of consecutive training days, training duration and associated load markers of volume using technology such as global positioning systems. Importantly, consideration should also be given to the phase of the season or periods of fixture congestion when determining the plan for the returning athlete, i.e. for a gradual introduction to competition minutes in the case of a long-term absentee. When making plans for a return to competition, expertise from the interdisclinary team is best heard in a shared decision-making approach.[24]

Having highlighted these perspectives, the question arises as to whether traditional rehabilitation approaches provide an ecologically invalid stimulus,[4] potentially creating a false dawn that the athlete is ready to cope with demands of training/competition. To challenge athletes beyond traditional models, incorporate greater ecological validity within your rehabilitation; consider the context (quantitative and qualitative), consider the stimuli and the response – bring the chaos and expose the athlete to the true demands of their sport.


The ACPSEM blog series for BJSM is co-ordinated by Dr Helen McElroy @helenmcelroy

Taberner, M1@MattTaberner 

  1. School of Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK

Dr Matt Taberner is a sports scientist and S&C coach with over 12 years’ experience working within the English Premier League. Matt holds a BSc in Sports Science, MSc in Sports Nutrition, F.A. Fitness Trainers Award, NSCA CSCS, and RSCC*D credentials and has just successfully defended his Professional Doctorate thesis at Liverpool John Moore’s University titled ‘Constructing a framework for Return to Sport in Elite Football’.

Cohen, DD2,3 @danielcohen1971

  1. Masira Research Institute, University of Santander (UDES), Bucaramanga, Colombia
  2. Mindeportes (Colombian Ministry of Sport)

Dr Daniel Cohen is a sports scientist with over 15 years of experience of research and support to elite football teams and in the NBA and the NFL in the use of force platforms in the evaluation of healthy and injured players. Daniel has a BSc in Exercise Science, MSc in Nutrition and Physical Activity and a PhD in the area of strength and power testing.

Competing Interests:



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