Last Wednesday, October 6th, Bruno Tassignon has successfully defended his PhD Thesis. Functional performance tests and return-to-sport decision-making: Focusing on translational research with special interest in fatigue and the brain. Another successful collaboration between our group and the MFYS Laboratory of Prof. Romain Meeussen. Although the defence has already taken place, we do like to share the content of Bruno’s thesis as it holds some key practical implications.
The full thesis (in pdf) can be downloaded here.
Summary
Regular physical activity has beneficial health effects, but simultaneously a considerable risk of incurring a musculoskeletal injury exists. These injuries have substantial repercussions both in the short-term and long-term. Clinicians attempt to mitigate the injury risk by trying to identify people at risk and providing preventative strategies. Injury risk screenings encompass functional performance tests to map impairments that could lead to a future injury. Functional performance tests are measures of the physical capacity of an individual involving multi-joint movements or postures. The flaws of the current functional performance tests show a clear need to research the clinimetric properties of current functional performance tests and develop and validate new functional performance tests.
When an individual gets injured, the clinician's goal will be to improve the patient’s quality of life, let the individual successfully return-to-sport, mitigate re-injury risk, and prevent long-term sequelae. Functional performance tests are also deemed essential within the return to the sport decision-making process. Yet, these are generally the same functional performance tests that are used for injury risk screening. Hence, they have identical flaws. Furthermore, the return-to-sports world consensus statement indicated that “return-to-sport decisions should always use information gathered from a battery of tests mimicking the reactive elements and the decision-making steps athletes use in real sport situations.” Nevertheless, the current functional performance tests do not approach the actual sport context. A similar call for the development and validation of new functional performance tests emerges in the return-to-sport domain. This is important since a clear choice was made, preferring an objective criteria-based return-to-sport approach. However, information is lacking on scientifically sound return-to-sport criteria following common sports injuries. Therefore, research and consensus are needed on return-to-sport criteria for highly prevalent sports injuries.
To bridge the gap between research and clinical practice, sports medicine showed increased interest in the complexity sciences’ paradigm. Correspondingly, the application and interpretation of functional performance tests are affected by this. Functional performance tests are thus only one piece of the puzzle when compiling an injury risk profile, monitoring rehabilitation progress, or making a return-to-sport decision. This also allows for functional performance testing in different contexts with parameters closely related to the sport (e.g. fatigue). Yet when it comes to fatigue research, all too often, clinicians have to extrapolate fundamental research findings and make elaborated assumptions in clinical practice. Meaning that the inclusion of various measuring instruments (e.g. psychological, physiological, social, biomechanical) could prove interesting. Nevertheless, the functional performance test domain lacks research on the application of relevant contextual factors. For instance, how different types of fatigue affect functional test performance and alter underlying physiological and psychological mechanisms.
The overall purpose of this dissertation was to contribute to clinical decision-making and functional performance testing across the sports injury spectrum. The three specific objectives encompassed: (1) establishing return-to-sport criteria following lateral ankle sprains, (2) mapping the reliability characteristics of the reactive balance test, (3) exploring electrophysiological brain changes induced by various types of fatigue when participants performed the Y-balance test and reactive balance test.
The systematic review (Chapter 2) showed that currently, no scientifically sound return-to-sport criteria following lateral ankle sprain injury could be determined. This was because not one original research study was performed on this topic. Therefore, we provided an overview of the relevant retrieved questionnaires, clinical assessment measures, functional and sport-specific performance tests within ankle sprain populations. Based upon this empirical research, return-to-sport variables were proposed. This chapter also encompasses rationales and considerations for return-to-sport decision-making following lateral ankle sprain injury. For instance, we advocate for implementing complex systems theory into the return-to-sport decision-making and the utilisation of the return-to-sport continuum.
In Chapter 3, the reliability study is the first to assess test-retest, intra- and inter-rater reliability of the reactive balance test within a recreationally trained population. Excellent intra- and inter-rater reliability for both outcomes (i.e. visuomotor response time and accuracy) were found. When choosing, let the same rater evaluate the outcome measures of the reactive balance test since the values show marginally better results for intra-rater reliability than inter-rater reliability. However, test-retest reliability showed good reliability for visuomotor response time and moderate reliability for accuracy. These results indicate that the reactive balance test is suited for performing analyses over time at the group level.
In the subsequent phase of the project (Chapter 4 & 5), the aim was to contribute to the lack of application of contextual factors and the need for translational research. This research vacuum was addressed by inducing different types of fatigue in healthy individuals performing the Y-balance test and the reactive balance test while simultaneously exploring (electro)physiological changes at the brain level.
The third study (Chapter 4) was designed to evaluate the impact of mental fatigue on electrophysiological brain measurements during the Y-balance test and reactive balance test performance. Even though mental fatigue was successfully induced, it did not affect Y-balance test performance. However, an increase in prefrontal cortex theta activity was observed when performing the Y-balance test in a mentally fatigued state. This means mental fatigue was successfully induced, suggesting a lower availability of attentional resources and poorer decision-making. Regarding reactive balance test performance, only accuracy was compromised due to mental fatigue. No changes in visuomotor reaction time and electrophysiological brain outcome measures were found following the mental fatigue intervention.
In Chapter 5, the results showed that acute physical fatigue impairs the accuracy of the reactive balance test. In contrast, the Y-balance test performance and visuomotor response time of the reactive balance test remained unaffected. Nevertheless, the underlying changes at the peripheral and central physiological levels completely differed from the previous study. During the execution of both tests, acute physical fatigue induced alterations in electrophysiological brain outcome measures in line with previous Wingate literature. Higher α power in the prefrontal cortex, motor cortex and posterior parietal cortex, and higher β power in the prefrontal and posterior parietal cortex were observed during the execution of the Y-balance test in a fatigued state. Following acute physical fatigue, α and β power increments were found in the posterior parietal cortex and the prefrontal cortex during the execution of the reactive balance test, respectively.
In summary, the research findings of this dissertation show that:
no scientifically sound return-to-sport criteria following lateral ankle sprain injury are currently available;
The reactive balance test has acceptable reliability characteristics and therefore is suited for performing analyses over time at the group level.
mental and acute physical fatigue do not impact YBT performance, even when underlying physiological and psychological changes are present;
the reactive balance test is capable of detecting fatigue changes at the group level culminating in decreased accuracy. When mentally fatigued, no changes at the electrophysiological brain level were measured. In a physically fatigued state, the electrophysiological findings were partially in line with previous Wingate literature.
The first area for future research is the development of objective return-to-sport criteria following common sports injuries. Also, a high need exists for more collaboration within the sports injury domain with practitioners, experts in other domains, between research institutes, etc. Research involving neurocognitive functional performance tests could offer innovative ways to assess patients and participants within injury prevention, rehabilitation and return-to-sport decision-making contexts. An additional research avenue might be to apply relevant contextual factors to bring functional performance testing closer to the relevant sport context. It is necessary to acknowledge that fundamental and translational research is still very much needed and still has an important role in the sports injury domain. For instance, the brain is gradually claiming the centre of attention in ligament injury research caused by sports participation. These insights open up perspectives for fundamental, translational and practical research and could change how we screen, test, rehabilitate and train these individuals.
Work published in this thesis
Tassignon B, Verschueren J, De Pauw K, Roelands B, Van Cutsem J, Verhagen E, et al. Mental fatigue impairs clinician‐friendly balance test performance and brain activity. Translational Sports Medicine. 2020;3(6):616-25.
Tassignon B, Verschueren J, De Wachter J, Maricot A, De Pauw K, Verhagen E, et al. Test-retest, intra- and inter-rater reliability of the reactive balance test in healthy recreational athletes. Physical Therapy in Sport. 2020;46:47-53.
Tassignon B, Verschueren J, Delahunt E, Smith M, Vicenzino B, Verhagen E, et al. Criteria-Based Return-to-sport Decision-Making Following Lateral Ankle Sprain Injury: a Systematic Review and Narrative Synthesis. Sports Med. 2019;49(4):601-19.
Tassignon B, Verschueren J, De Pauw K, Verhagen E, Meeusen R. Acute fatigue alters brain activity and impairs reactive balance test performance. Translational Sports Medicine. 2021;4(4):488-99.