Scoping review of dual-task interference in individuals with intellectual disability.

Dual-task paradigms can provide insights on the structures and mechanisms underlying information processing and hold diagnostic, prognostic, and rehabilitative value for populations with cognitive deficits such as in individuals with intellectual disability (ID). In this paradigm, two tasks are performed separately (single-task context) and concurrently (dual-task context). The change in performance from single- to dual-task context represents dual-task interference. Findings from dual-task studies have been largely inconsistent on whether individuals with ID present with dual-task-specific deficits. The current review aimed to map the published literature on dual-task methods and pattern of dual-task interference in individuals with ID. A scoping review based on Arksey and O'Malley's five-stage methodological framework was performed. Seventeen electronic databases and registries were searched to identify relevant studies, including gray literature. Charted data from included studies were analyzed quantitatively and qualitatively. PRISMA guidelines informed the reporting of this review. Twenty-two studies involving 1,102 participants (656 with ID and 446 without ID) met the review's inclusion criteria. Participants in the included studies were heterogeneous in sex, age (range 3-59 years), etiology and ID severity. Included studies characterized their ID-sample in different ways, most commonly using intelligence quotient (IQ) scores. Other measures of intellectual function (e.g., mental age, ID severity, verbal and/or visuospatial ability scores) were also used, either solely or in combination with IQ. Methods of dual-task testing varied across studies, particularly in relation to dual-task combinations, equation of single-task performance between groups, measurement and reporting of dual-task performance for each single-task, and task priority instructions. Thematic content of the included studies were: (1) structural interference to dual-tasking; (2) etiology-based differences in dual-tasking; (3) gait and balance dual-task performance; (4) testing executive function using dual-task paradigms; and (5) training effect on dual-task performance. Although the evidence consistently supported the intact dual-tasking ability of individuals with ID, the pattern of dual-task interference was inconsistent. Likewise, the evidence was inconclusive regarding dual-task deficit specific to individuals with ID because of heterogeneity in dual-task study designs among included studies.

Athletes with intellectual disability: The effects of cognitive deficits and sports practice on bipedal standing balance.

BACKGROUND: Athletes with intellectual disability represent a unique population who experiences the contrasting effects of cognitive deficits and benefits of sports on balance. This study investigated the combined impact of intellectual disability and sport practice on balance. METHOD: Center-of-pressure excursion in bipedal stance of 2 disability (with and without intellectual disability) × 2 sport practice (athlete and novice) participant groups was measured in several balance conditions. RESULTS: Sport practice exerted no significant effect on any of the center-of-pressure measures used. In contrast, intellectual disability's effects on balance, which were most apparent in challenging balance conditions, were significant (p < .05) and had large effect sizes (ηp 2 > 0.13). CONCLUSION: The negative effects of cognitive deficits on the balance of young adults with intellectual disability underscore the need for effective interventions. Although findings did not support sports' balance-remediating potential, the value of sport participation for individuals with intellectual disability cannot be fully dismissed just yet.

The Underlying Mechanisms of Sports Injuries in Paralympic Goalball: A Mixed-Method Study.

OBJECTIVE: Data from the Paralympic Games indicate a fluctuating injury incidence in the Paralympic sport goalball, but the mechanisms behind have not been explored. The aims of this study are to (1) quantitatively analyze goalball injuries reported in the London 2012 and Rio 2016 Paralympic Games, (2) qualitatively explain the differences between both games, and (3) qualitatively assess general injury mechanisms and prevention opportunities of injuries in Goalball. DESIGN: This is a mixed-method study. Injury incidence rates were analyzed from data collected during the 2012 and 2016 Paralympic Games. Then, semistructured interviews of games participants qualitatively explored injury mechanisms and prevention opportunities. RESULTS: A reduction of injuries occurred from 2012 (incidence rate, 19.5; 95% confidence interval, 12.5-26.5) to 2016 (incidence rate: 5.6; 95% confidence interval, 1.7-9.5). In both games, acute traumatic injuries were most common. Female athletes reported higher rate of injuries compared with males ( P = 0.05). Qualitative data revealed that causes of injuries were collisions, overuse, and poor physical conditioning. The differences between the two games were explained by equipment, environment, and preparations. CONCLUSIONS: The result from this study indicates that injuries in goalball are multifactorial. Ultimately, the mixed-method data from this study can help the sports context develop prevention measures.

Physical activity, fear avoidance beliefs and level of disability in a multi-ethnic female population with chronic low back pain in Suriname: A population-based study.

BACKGROUND: Chronic low back pain (CLBP) is an important cause for reduced daily physical activity (PA) and loss of quality of life, especially in women. In Suriname, a middle-income country in South America, the relationship between PA and CLBP is still unknown. AIMS: To assess the level of PA in women with CLBP of different ethnicity, and to identify whether fear avoidance beliefs (FAB), disability, co-occurring musculoskeletal pain sites and various sociodemographic and lifestyle factors were associated with self-reported PA. METHODS: A cross-sectional community-based house-to-house survey was conducted between April 2016 and July 2017. The survey followed the Community Oriented Program for Control of Rheumatic Diseases methodology. Selection criteria were being female of Asian-Surinamese, African-Surinamese or of Mixed ethnicity and aged 18 or older, living in an urban area, and reporting CLBP. Data was collected on PA, FAB, disability, co-occurring musculoskeletal pain sites, CLBP intensity and sociodemographic and lifestyle factors. RESULTS: Urban adult women with current CLBP (N = 210) were selected. Nearly 57% of the population met the WHO recommendation on PA, with work-related PA as the largest contributor to total self-reported PA. Most women showed low FAB scores (FABQ-Work ≤34 (96.2%) and FABQ-PA ≤14 (57.6%)) and low disability levels (Oswestry Disability Index ≤20 (62.4%)). An inverse association between total PA and FABQ-Work (OR = 0.132, CI: 0.023; 0.750) was found. In contrast, total PA had a significant, positive association with disability (OR = 2.154, CI: 1.044; 4.447) and workload (OR = 2.224, CI: 1.561; 3.167). All other variables showed no association with total PA. CONCLUSION: This was the first study in Suriname reporting that 43.3% of urban adult women with CLBP were physically inactive. Total self-reported PA is influenced by FABQ-Work, average to heavy workload and moderate to severe disability. In this study, PA-Work was the major contributor to total PA. Therefore, future longitudinal studies should evaluate different types and aspects of PA in relation to CLBP management.

Cognitive-motor multitasking in athletes with and without intellectual impairment.

PURPOSE: We investigated cognitive-motor multitasking in 29 top athletes with intellectual impairment (II) recruited during the European Championship Games organized by Virtus (World Intellectual Impairment Sports) and 29 control (CT) athletes matched for age, sex, sports practiced, and lifetime accumulated practice hours. METHODS: Participants performed a cognitive task that required recognizing previously displayed visual objects among distractors. The motor task required maintaining a stable upright posture balancing on a rocking board placed atop a force plate which assessed center-of-pressure (COP) movement. Both tasks were performed separately (with participants seated for the cognitive single task) and concurrently under dual-task conditions, wherein participants memorized objects while balancing. We analyzed recognition accuracy, COP path length, and sample entropy of the COP trajectory as a measure for automaticity of postural control. RESULTS: As expected, CT-athletes outperformed II-athletes in the cognitive task but the two groups have comparable performance in the postural task under single- and dual-task conditions. When multitasking, CT-athletes switched to more automatic postural control and maintained their postural sway at single-task levels. II-athletes prioritized balance thereby successfully keeping COP excursion comparable to single-task conditions. However, this came with pronounced costs for memory performance, which was unaffected by multitasking in CT-athletes. CONCLUSION: The adaptive capacity observed in control athletes was not at the disposal of II-athletes who revealed pronounced sensitivities to multitasking interference. This sensitivity obviously was not compensated for by either athletic competence or potential transfer of athletic skill to domain-general cognitive functions.

Low back pain prevalence, beliefs and treatment-seeking behaviour in multi-ethnic Suriname.

OBJECTIVES: The aims were to determine, for the first time, the prevalence of low back pain (LBP) in urban and rural communities and to assess back beliefs and treatment-seeking behaviour in Suriname, a multi-ethnic country in the Caribbean community. METHODS: A cross-sectional community-based survey using the Community Oriented Program for the Control of Rheumatic Diseases methodology was performed between April 2016 and July 2017. Information was collected on LBP prevalence and LBP-related treatment seeking, beliefs about LBP [Back Beliefs Questionnaire (BBQ)], level of disability (Oswestry Disability Index) and the risk of developing persistent disabling pain (Start Back Screening Tool). RESULTS: A total of 541 out of 2902 individuals reported current acute or chronic LBP. It was more prevalent in urban (20.2%) than in rural (13.7%) communities, especially in females and older adults (>55 years of age). Individuals from rural areas [median BBQ = 18.00 (14.00-22.00)] had significantly more negative beliefs than the urban population [median BBQ = 25.00 (19.00-31.00); P < 0.001]. Maroons displayed more negative beliefs than Creole (P = 0.040), Hindustani (P < 0.001), Javanese (P < 0.001) and mixed ethnicity (P < 0.001) groups. At least 75% of the LBP population sought care, especially from a western health-care practitioner. Seeking treatment and having a higher risk of developing persistent disabling pain was significantly associated with more disability (P < 0.001). Age ≥45 years (P < 0.001), Indigenous ethnicity (P < 0.05) and functional disability (P < 0.001) were factors influencing treatment seeking. CONCLUSION: Low back pain is a prevalent health problem in the Surinamese urban community, especially in older adults and among females. Most individuals experiencing LBP visited a western health-care practitioner and had more negative beliefs compared with other communities.

Steering Does Affect Biophysical Responses in Asynchronous, but Not Synchronous Submaximal Handcycle Ergometry in Able-Bodied Men.

Real-life daily handcycling requires combined propulsion and steering to control the front wheel. Today, the handcycle cranks are mostly mounted synchronously unlike the early handcycle generations. Alternatively, arm cycle ergometers do not require steering and the cranks are mostly positioned asynchronously. The current study aims to evaluate the effects of combining propulsion and steering requirements on synchronous and asynchronous submaximal handcycle ergometry. We hypothesize that asynchronous handcycling with steering results in the mechanically least efficient condition, due to compensation for unwanted rotations that are not seen in synchronous handcycling, regardless of steering. Sixteen able-bodied male novices volunteered in this lab-based experiment. The set-up consisted of a handcycle ergometer with 3D force sensors at each crank that also allows "natural" steering. Four submaximal steady-state (60 rpm, ~35 W) exercise conditions were presented in a counterbalanced order: synchronous with a fixed steering axis, synchronous with steering, asynchronous with a fixed axis and asynchronous with steering. All participants practiced 3 × 4 mins with 30 mins rest in between every condition. Finally, they did handcycle for 4 mins in each of the four conditions, interspaced with 10 mins rest, while metabolic outcomes, kinetics and kinematics of the ergometer were recorded. The additional steering component did not influence velocity, torque and power production during synchronous handcycling and therefore resulted in an equal metabolically efficient handcycling configuration compared to the fixed condition. Contrarily, asynchronous handcycling with steering requirements showed a reduced mechanical efficiency, as velocity around the steering axis increased and torque and power production were less effective. Based on the torque production around the crank and steering axes, neuromuscular compensation strategies seem necessary to prevent steering movements in the asynchronous mode. To practice or test real-life daily synchronous handcycling, a synchronous crank set-up of the ergometer is advised, as exercise performance in terms of mechanical efficiency, metabolic strain, and torque production is independent of steering requirements in that mode. Asynchronous handcycling or arm ergometry demands a different handcycle technique in terms of torque production and results in higher metabolic responses than synchronous handcycling, making it unsuitable for testing.

Fairness, technology and the ethics of Paralympic sport classification.

Fairness in sport is a widely shared meritocratic norm. Its application is usually restricted to equality of opportunity to compete for victory. Paralympic sports lay down a further challenge in that equality of opportunity must be shaped by considerations of fairness, evidenced by the development of discrete competition categories to construct fair and meaningful contests. In this article, we extend these philosophical ideas to consider how Fair Equality of Opportunity might operate in the context of Paralympic sports classification. We articulate three conceptions of fairness relevant to these sports: (i) background fairness; (ii) procedural fairness; and (iii) stakes fairness. We critically review the International Paralympic Committee's Policy on Sport Equipment in relation to the first two conceptions and argue that greater clarification, theorization and rule modification is required if physical prowess, as opposed to equipment technology, is to be assured as the dominant determinant of Paralympic athletic success.

Challenges and opportunities in wheelchair basketball classification- A Delphi study.

The International Paralympic Committee (IPC) mandates Paralympic Sports to develop evidence-based classification systems that allocate athletes into 'classes' according to the impact of their impairment on sport-specific performance. In wheelchair-basketball, a panel of classifiers assesses athlete's performance through observation. One key barrier to evidence-based classification is the absence of defined eligible impairments, including clear guidelines on how to assess them and their impact on wheelchair basketball performance. This study aims to reach expert consensus on issues specific to wheelchair basketball that can benefit from evidence-based classification. It offers recommendations for refining the classification manual, thus improving adherence to the IPC classification code. A three-round Delphi study was conducted with 29 experts in wheelchair basketball. The experts agreed with the new definition for the aim of wheelchair basketball classification, which is in line with the IPC code. Cases identified as having the highest risk for disagreement between classifiers included classifying players with upper limb deficiency or with impaired coordination. The panel failed to agree on changing the classification procedures and on defining the eligible impairment list. This study identifies issues specific to wheelchair basketball classification to be addressed in future research. Additional discussions need to take place to promote further resolution.

Conceptual model of sport-specific classification for para-athletes with intellectual impairment.

The present paper describes the conceptual basis of evidence-based classification of para-athletes with intellectual impairment (II). An extensive description of the theoretical and conceptual foundation of the system as currently conceived is provided, as are examples of its applications in the three sports included in the Paralympic programme for II-athletes in 2020 (i.e., athletics, swimming and table tennis). Evidence-based classification for II-athletes is driven by two central questions: i. How can intellectual impairment be substantiated in a valid and reliable way, and ii. Does intellectual impairment limit optimal sport proficiency? Evolution of the system and current best practice for addressing these questions are described, and suggestions for future research and development are provided. Challenges of understanding and assessing a complex (multifaceted and intersectional) impairment in the context of sport also are considered.

Objective Measurement of Ball-Handling Proficiency in Wheelchair Sports: A Systematic Review.

Background: In Paralympic sports, classification of athletes based on the impact of impairments on the ability to perform is needed, to prevent a one-sided and predictable outcome of the competition in which the least impaired athlete has the best chance to win. Classification is developing from expert opinion based to evidence based. In wheelchair court sports, there is evidence to support the impact of impairment on wheeled mobility, but not on ball handling. To assess the impact of impairment on the ability to perform ball-handling activities, standardised tests for ball handling are needed. Purpose: To assess if reliable and valid standardised tests for the measurement of ball-handling proficiency in a wheelchair or able-bodied court sports exist; to assist in the development of Evidence-Based Classification (EBC) in wheelchair court sports according to the guidelines of the International Paralympic Committee (IPC). Methods: The review was conducted according to the Meta-Analysis of Observational Studies in Epidemiology (MOOSE) statement. Search terms used were "wheelchair," "ball," "ball sports," "test," and "performance." Databases searched were Medline, Embase, PubMed, and Sport Discus. Study quality was assessed using the Strengthening the Reporting of Observational Studies in Epidemiology checklist. Results: Twenty-two articles were included. Foundational Movement Skills in ball-handling proficiency were assessed. Tests for throwing maximal distance showed sufficient reliability and validity. Precision in throwing showed low-to-moderate reliability and conflicting results in validity. Throwing techniques differed between studies. Dribbling the ball showed high reliability, but conflicting results in validity. Conclusions: Tests for throwing maximal distance, throwing precision, and dribbling the ball can be used in standardised tests for activity limitation in wheelchair court sports. However, tests need to be adapted and standardised and then reassessed for reliability and validity in athletes with and without arm impairment.

Perspectives on research conducted at the Paralympic Games.

BACKGROUND AND PURPOSE: In 1994, the International Paralympic Committee (IPC) established the IPC Sport Science Committee in an effort to bring Paralympic Movement relevant research questions to the academic world. In 1996, the IPC Sport Science Committee put an application system in place, allowing scholars to conduct research at the Paralympic Games. The aim of this perspective paper is to overview the main outcomes of the fifty-six research projects conducted from Atlanta 1996 until PyeongChang 2018 during Paralympic Games' time; and to discuss the state-of-the-art of the IPC Research Strategic Goals. METHODS: Research projects conducted at the Paralympic Games from Atlanta 1996 to PyeongChang 2018 were clustered according to the IPC Research Strategic Goals (publications retrieved through the following procedure: analyzing the IPC Medical & Scientific Department project file; systematic search of Pubmed and SportDiscus with "Name Principal Investigator" and "Paralympic" as search terms; email to principal investigator if no outcome retrieved). RESULTS: Games-time projects targeted Paralympic research strategic goals, such as athletes' health, athletes' performance, evidence-based classification, participation, Paralympic legacy, and education. CONCLUSION: Some of the projects proved high relevance and became standard Games' operations; however, generally, projects operate in isolation and could benefit from collaboration with expert-stakeholders (e.g., athletes, coaches, governing International Sport Federations, relevant IPC departments, network of academic scholars). Sport science research in the Paralympic Movement should move fast and collaborative to catch up on evolution.IMPLICATIONS FOR REHABILITATIONFrom a health perspective, fine-tuning of the patient/athlete-equipment interface to optimize function/performance is a challenge for the rehabilitation specialist/coach.The musculoskeletal balance of the shoulder joints is a lifelong concern for permanent wheelchair users, especially those involved in dynamic wheelchair sports.Education about autonomic dysreflexia and boosting in patients/athletes with spinal cord injury is an integral part of the rehabilitation process.Rehabilitation experts have an ideal educational profile to contribute to evidence-based classification, as a para-sports classifier, or as a researcher.

Reliability of center of pressure excursion as a measure of postural control in bipedal stance of individuals with intellectual disability: A pilot study.

The high prevalence of postural instability in individuals with intellectual disability (ID) warrants the need for reliable and practical postural control assessments. Stabilometry is a postural control assessment that has been widely used for clinical populations. However, the scant systematic knowledge about the reliability of stabilometric protocols for adults with ID renders results questionable and limits its value for clinicians and researchers. The study's purpose was to develop a stabilometric protocol for adults with and without ID based on optimal combinations of shortest necessary trial durations and the least number of trial repetitions that guarantee sufficient reliability. Participants performed six trials of bipedal standing in 2 vision (eyes open vs eyes closed) x 2 surface (solid vs compliant) conditions on a force platform. Several parameters were calculated from the first 10-, 20-, and 30-s interval of every center-of-pressure (COP) trial data. For different trial durations, we identified the number of trials that yielded acceptable relative (intraclass correlation coefficient ≥ 0.70) and absolute (standard error of measurement < 20%) reliability using the Spearman-Brown prophecy formula. To determine the optimal combination of trial duration and number of repetition for each COP parameter, we implemented a two-step process: 1) identify the largest number of repetition for each of the three trial durations and then 2) select the trial duration with the lowest number of repetition. For both ID- and non-ID groups, we observed a trend whereby shorter trial durations required more repetitions and vice versa. The phase plane and ellipse area were the most and least reliable center-of-pressure parameter, respectively. To achieve acceptable reliability, four 30-s trials of each experimental condition appeared to be optimal for testing participants with and without ID alike. The results of this research can inform stabilometric test protocols of future postural control studies of adults with ID.

Effect of Sildenafil Citrate on Exercise Capacity in Athletes With Spinal Cord Injury.

PURPOSE: Ingestion of sildenafil citrate has performance-enhancing effects at high altitudes above 3800 m in able-bodied individuals. It is unknown whether it can improve the performance of athletes with spinal cord injury (SCI) at moderate altitudes (<2200 m), relevant to Paralympic competitions. As most men with SCI suffer from erectile dysfunction of neurologic origin and use sildenafil on a regular basis, it seems important to study the impact of sildenafil on exercise capacity. The outcome of this study is also relevant to the antidoping community. METHODS: Twenty-seven healthy male wheelchair athletes with a motor-complete SCI participated in this prospective double-blind, randomized, placebo-controlled study. The participants performed arm cranking exercise to exhaustion at sea level and moderate altitude (2200 m) after ingestion of 50 mg sildenafil citrate or a placebo. Peak power output, peak oxygen uptake, peak heart rate, rating of perceived exertion, oxygen saturation, and lactate concentrations at exhaustion were measured. RESULTS: Friedman analysis showed that peak power output at sea level was significantly higher (P = .004) under placebo treatment (median [minimum; maximum]: 120 W [35; 170]) compared with sildenafil (115 W [40; 165]). Blood oxygen saturation under sildenafil treatment at sea level (98% [81; 100]) was significantly higher (P = .006) compared with sildenafil treatment at moderate altitude (94% [85; 100]). All other parameters revealed no impact of sildenafil or altitude. CONCLUSIONS: In this study, the ingestion of sildenafil citrate in athletes with SCI demonstrated no positive effects on peak arm-cranking-exercise capacity compared with placebo either at sea level or at moderate altitude.

Fitts' Law is Applicable to Trunk Coordination Measurements in a Sitting Position.

Trunk coordination is essential for many activities of daily living in wheelchair users. This study investigated whether Fitts' law is applicable to trunk movements in a sitting position. Fourteen healthy adults performed two series of 24 tasks of trunk flexion-extension movements in a sitting position. The results showed significant linear relationships between average group movement time (MT) and index of difficulty (ID) over all tasks (r2 = 0.92) and within target distances (0.94 < r2 < 1.00). Target distance affected intercept and slope (P < 0.001). Hence, Fitts' law is applicable to the studied trunk movements in a sitting position, indicating these trunk movements tasks could serve as a basis for qualitative trunk coordination tests. Transferability of these conclusions to wheelchair users, and optimal test design should be further investigated.

Does a cycling program combined with education and followed by coaching promote physical activity in subacute stroke patients? A randomized controlled trial.

BACKGROUND: To investigate the effects of a three month active cycling program followed by coaching on physical activity in subacute stroke patients. METHODS: Patients (n = 59; mean age =65.4 ± 10.3) aged ≤80 years with first stroke and able to cycle at 50 revolutions/minute enrolled 3-10 weeks post stroke. Patients were randomly allocated to three month active cycling group (n = 33) or to a control group (n = 26), 3 x 30 minutes training/week. Afterwards, the active cycling group was randomized into a coaching (n = 15) versus non-coaching group (n = 16) for nine months. Physical activity was measured by objective and self-reported measures, which were taken before/after the active cycling program and during six and 12 months, except the Baecke-questionnaire, which was used at baseline and 12 months. RESULTS: A significant difference was found in Baecke/sport (95% confidence interval: 0.06, 2.24; p = 0.039) between the active cycling group and the control group, in patients with severe motor function deficits at baseline. Patients in the control group performed significant less sports at 12 months (mean Baecke/sportbaseline =3.07 ± 1.21, mean Baecke/sport12months = 1.43 ± 0.98; p = 0.01). Furthermore, all groups showed significant changes over time in all measures at three months (except: Physical Activity Scale for Individuals with Physical Disabilities, diary/Mets*minutes-moderate) and 12 month and additionally in a subgroup with severe motor function deficits (except diary Mets*minutes-sedentary). CONCLUSION: When active cycling combined with education is used in subacute patients with severe motor function deficits, more sport participation might be observed after one year. No other significant group differences were found over time. In all groups, however, patients showed significant improvement over time in physical activity measures. Future work is needed to explore the most effective coaching approach after an aerobic training program. Implications for Rehabilitation The active cycling program combined with education is applicable in subacute stroke patients as it required little stand-by assistance due to chip cards, the intensity was gradually built and the involvement of caregivers in the educational sessions. This training approach also revealed applicable in severely impaired stroke patients and might facilitate sport participation on the long-term. This randomized controlled study aims to quantify physical activity after stroke by using a combination of objective and self-report measures, which revealed detailed information about different aspects of physical activity levels. There is a need for coaching approaches that facilitate aerobic exercise after ending a supervised program. A coaching approach needs to guide patients in adopting aerobic exercise as a part of a lifestyle change and needs to be less time consuming.

Balance Perturbations as a Measurement Tool for Trunk Impairment in Cross-Country Sit Skiing.

In cross-country sit-skiing, the trunk plays a crucial role in propulsion generation and balance maintenance. Trunk stability is evaluated by automatic responses to unpredictable perturbations; however, electromyography is challenging. The aim of this study was to identify a measure to group sit-skiers according to their ability to control the trunk. Seated in their competitive sit-ski, 10 male and 5 female Paralympic sit-skiers received 6 forward and 6 backward unpredictable perturbations in random order. k-means clustered trunk position at rest, delay to invert the trunk motion, and trunk range of motion significantly into 2 groups. In conclusion, unpredictable perturbations might quantify trunk impairment and may become an important tool in the development of an evidence-based classification system for cross-country sit-skiers.

Cluster analysis of novel isometric strength measures produces a valid and evidence-based classification structure for wheelchair track racing.

BACKGROUND: The Para athletics wheelchair-racing classification system employs best practice to ensure that classes comprise athletes whose impairments cause a comparable degree of activity limitation. However, decision-making is largely subjective and scientific evidence which reduces this subjectivity is required. AIM: To evaluate whether isometric strength tests were valid for the purposes of classifying wheelchair racers and whether cluster analysis of the strength measures produced a valid classification structure. METHODS: Thirty-two international level, male wheelchair racers from classes T51-54 completed six isometric strength tests evaluating elbow extensors, shoulder flexors, trunk flexors and forearm pronators and two wheelchair performance tests-Top-Speed (0-15 m) and Top-Speed (absolute). Strength tests significantly correlated with wheelchair performance were included in a cluster analysis and the validity of the resulting clusters was assessed. RESULTS: All six strength tests correlated with performance (r=0.54-0.88). Cluster analysis yielded four clusters with reasonable overall structure (mean silhouette coefficient=0.58) and large intercluster strength differences. Six athletes (19%) were allocated to clusters that did not align with their current class. While the mean wheelchair racing performance of the resulting clusters was unequivocally hierarchical, the mean performance of current classes was not, with no difference between current classes T53 and T54. CONCLUSIONS: Cluster analysis of isometric strength tests produced classes comprising athletes who experienced a similar degree of activity limitation. The strength tests reported can provide the basis for a new, more transparent, less subjective wheelchair racing classification system, pending replication of these findings in a larger, representative sample. This paper also provides guidance for development of evidence-based systems in other Para sports.