Concussed athletes may have persistent walking impairments, study suggests

"On average, a professional rugby union player is more likely than not to sustain a concussion after 25 matches" and "Sports-related concussion [SRC] increases the risk of subsequent injury by about 50 per cent in elite male football players".

These are the titles of two articles published in 2018 and 2014, respectively, confirming the importance of SRC to researchers, the media and the public.

In a significant development, a recent international study, whose lead author is University College Dublin PhD student Fionn Büttner, reports that individuals with SRC have impaired walking characteristics that persist beyond standard clinical recovery timelines.

What is SRC? In 2016, an international conference on concussion in sport, defined SRC as a traumatic brain injury induced by biomechanical forces, that may be caused by a direct blow to the head, face, neck or elsewhere on the body with an impulsive force transmitted to the head: "SRC typically results in the rapid onset of short-lived impairment of neurological function that resolves spontaneously."

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Büttner, of UCD’s School of Public Health, Physiotherapy, and Sports Science, is investigating the clinical recovery of amateur athletes who present to hospital emergency departments following SRC. Büttner told The Irish Times that this international collaboration aimed to determine whether individuals with an SRC would exhibit persistent walking and balance impairments compared to non-concussed individuals during a dual-task assessment: “A dual-task assessment evaluates an individual’s ability to perform two tasks simultaneously; for example a cognitive task – such as spelling a five-letter word backwards – and a physical task such as walking. In this study, we analysed original data from 26 studies. Theories propose that an individual’s performance on either one, or both, tasks can be affected during a dual-task assessment.

“This is thought to occur following SRC due to a limited capacity to distribute attention across two simultaneous tasks. We anticipated that concussed individuals would exhibit walking impairments (eg, slower walking speed or greater instability) during dual-task assessments due to a concussion-associated attentional deficit.”

‘Walked more slowly’

Büttner’s team’s results indicated that recently concussed individuals “walked more slowly and with greater side-to-side instability compared to non-concussed individuals when evaluated using a dual-task assessment up to two months following SRC”. Importantly, when a single-task walking assessment was performed, these impairments weren’t identified in concussed individuals up to two months following SRC.

Might one infer from these findings that concussed athletes deemed ready for competition, based on traditionally used single-task assessments, might be insufficiently recovered?

Büttner emphasises that their findings need to be interpreted carefully: “Concussion recovery is complex from both a clinical and physiological perspective, and our study is only one of many ongoing studies in SRC aiming to provide clarity on concussion-related impairments that athletes may exhibit following injury and throughout recovery.” Their findings, says Büttner, need to be interpreted primarily in the context of two features of their study: patient-centred outcomes and the risk of bias.

Patient-centred outcomes are meaningful to patients and matter in how they live their lives. Examples of patient-centred outcomes, Büttner explains, that may occur following return-to-play after SRC include recurrent SRC, subsequent lower extremity musculoskeletal injury, or impaired health-related quality of life: “Our study analysed only laboratory-oriented outcomes, such as walking speed, without any follow-up period to identify whether individuals with dual-task impairments experience worse patient-centred outcomes following SRC.”

As for the risk of bias, Büttner comments: “A high risk of bias in the research studies included in our larger study can reduce the strength of our findings and weaken the inferences that can be made from the results of each study. Consequently, the difference in dual-task performance observed in our study between concussed and non-concussed individuals should be interpreted cautiously.”

What future role might dual-task testing play in relation to competitive athletes with SRC?

Sensorimotor impairments

Büttner speculates that dual-task assessments may identify subtle, yet persistent, sensorimotor impairments that manifest only in settings where the athlete performs two or more demanding (cognitive and motor) tasks concurrently, such as in a sporting environment: “It’s been proposed that dual-task impairments may be related to subsequent lower extremity, musculoskeletal injury risk following SRC. This could inform future return-to-play decision-making and impairment-specific rehabilitation strategies if future research can’t disprove this hypothesis,” he says. “However, further research is needed to investigate this relationship between dual-task impairments following SRC and subsequent lower extremity, musculoskeletal injury risk.”

Is Büttner satisfied with current measures to determine whether rugby players are fit to return to competition?

“World Rugby have been world-leading in developing player welfare policies to optimise the assessment and management of professional and amateur rugby players with suspected SRC. Further original research and evidence syntheses, such as our study, will enable the identification of other clinical assessments that may augment return-to-play decision-making.”

Büttner cites the Concussion in Sport graduated return-to-play (GRTP) protocol, which is supported by World Rugby: “This provides a structured, stepwise, return-to-play template for increasing exercise intensity, volume, and specificity to return an athlete to competition following SRC. Return-to-play decision-making is multi-factorial and related to physical, psychological, and social factors, and subtle nuances are permitted in the GRTP protocol in that ‘Players who are confirmed with a concussion should follow their union’s GRTP protocols’. In our opinion, the current use of best-available evidence and clinical assessment strategies in rugby union, combined with a pragmatic clinical assessment, render current measures that inform return-to-play decision-making acceptable.”

The valuable work undertaken by Büttner’s team adds to the evidence base aimed at safeguarding those whose sports place them at risk of SRC.