How much does lower body strength impact Paralympic running performance?

Evaluating the Validity of Tests to Predict Sprint and Change of Direction Speed in Para-Athletes With Brain Impairments

Maximum running speed is a performance determinant in para-athletics and cerebral palsy football. Sixty international para-athletes with brain impairments completed five activity-limitation tests (standing broad jump, four bounds for distance, split jumps, 10-m speed skip, and running in place) and two criterion tests (40-m sprint and modified agility test). The same three tests (standing broad jump, four bounds for distance, and 10-m speed skip) that correlated with running performance in nondisabled runners (.67 < r < -.82; p < .05; 75% of variance) also correlated in para-athletes with brain impairments (.41 < r < -.62; p < .01; 55% of variance). Standing broad jump, four bounds for distance, split jumps, and running in place also correlated with change-of-direction speed (.43 < r < -.63; p < .01; 58% of variance). Results indicate that methods of classification for para-athletics with nondisabled runners are also valid with para-athletes with brain impairments, and new sport-specific relationships were found for assessing the performance of rapid and short sprints toward different directions, specific of a team para-sport like cerebral palsy football.

Running capacity in children with bilateral cerebral palsy: What are the biomechanical and neuromotor differences between runners and walkers?

BACKGROUND

Running is a high-level locomotor activity requiring more from joints, muscles and a more complex interaction of the neuromuscular system than walking. High-level locomotor activity has the potential to shed light on motor function deficits that lower-level activity does not reveal. Therefore, the study aimed to compare biomechanical and neuromotor function between a group of children with bilateral cerebral palsy who are able and unable to run.

METHODS

Retrospectively, children with bilateral cerebral palsy aged between 6 and 18 years who completed a clinical gait analysis between 2006 and 2019 were included. Participants were categorized as walkers or runners based on the presence of a double floating phase. Spasticity, selectivity, muscle weakness, and passive range of motion of the lower limbs were measured and dichotomized as «normal» or «abnormal» based on reference values. Functional tasks reflecting balance (standing on one leg) and power (single leg and two-legged jumps) were realized and evaluated as failure or success.

FINDINGS

75 children with bilateral cerebral palsy (53 runners/22 walkers) were included. Children classified as runners were stronger (hip flexors, p = 0.006; hip abductors, p = 0.022; knee flexors, p = 0.001; dorsiflexors, p = 0.014), had greater selectivity (hip flexors, p = 0.011; dorsiflexors, p = 0.001; plantiflexors, p = 0.043) and lower spasticity at the knee extensors (p = 0.045). No differences were observed in the passive range of motion between the two groups. Children classified as runners performed better at all tasks of balance and power (p < 0.05).

INTERPRETATION

Flexors muscles strength and selectivity and knee extensor spasticity are key points for running ability in children with bilateral cerebral palsy.

Assessment of muscle strength in para-athletes: A systematic review of observational studies

Accurate and reliable evaluation of muscle strength in para-athletes is essential for monitoring the effectiveness of strength training and/or rehabilitation programmes, and sport classification. Our aim is to synthesise evidence related to assessing muscle strength in para-athletes. Four databases were searched from January 1990 to July 2021 for observational studies focusing on strength assessment. Independent screening, data extraction, and quality assessment were performed in duplicate. A total of 1764 potential studies were identified. Thirty met the inclusion criteria and were included in the review. The mean age of participants was 30.7 years (standard deviation [SD]: 2.4). The majority were men (88%) participating in wheelchair sports, including basketball, rugby, and tennis (23/30: 76%). Overall quality varied, with more than half of the studies failing to identify strategies for dealing with confounding variables. Despite manual muscle testing being a standard component of para-sport classification systems, evidence examining strength characteristics in para-athletes is derived primarily from isometric and isokinetic testing. In studies that included comparative strength data, findings were mixed. Some studies found strength values were similar to or lower than able-bodied athletic controls. However, an important observation was that others reported higher shoulder strength in para-athletes taking part in wheelchair sports than both able-bodied and disabled non-athletes. Studies need to develop accessible, standardised strength testing methods that account for training influence and establish normative strength values in para-athletes. There is also a need for additional studies that include female para-athletes and para-athletes with greater functional impairments.

Association between upper-limb isometric strength and handcycling performance in elite athletes

This study investigated the association among isometric upper-limb strength of handcyclists and sport-specific performance outcomes. At two international events, 62 athletes were tested on upper-limb strength, measured with an isometric-strength setup and with Manual Muscle Test (MMT). Horizontal force (Fz), effectiveness, rate of development, variability, and asymmetries were calculated for upper-limb pull and push. Performance measures were mean (POmean) and peak (POpeak) 20-s sprint power output and average time-trial velocity (TTvelocity). Regression models were conducted to investigate which pull and push strength variables associated strongest with performance measures. Additional regression analyses were conducted with an MMT sum score as predictor. Push and pull Fz showed the strongest associations with all outcomes. Combined push and pull Fz explained (p < .001) 80-81% of variance of POmean and POpeak. For TTvelocity, only push Fz was included in the model explaining 29% of the variance (p < .001). MMT models revealed weaker associations with sprint PO (R2 = .38-.40, p < .001) and TTvelocity (R2 = .18, p = 0.001). The findings confirmed the relevance of upper-limb strength on handcycling performance and the significance of ratio-scaled strength measures. Isometric strength outcomes are adequate sport-specific indicators of impairment in handcycling classification, but future research should corroborate this notion and its potential to discriminate between sports classes.

To What Degree Does Limb Spasticity Affect Motor Performance in Para-Footballers With Cerebral Palsy?

Spasticity is considered a contributor to hypertonia, frequently presented in people with cerebral palsy (CP), affecting muscle function and motor activities. In CP football, the classification system determines that this impairment is eligible for competitive para-sports due to the impact on activity limitation and sports performance. However, the relationship between this feature (i.e., spastic hypertonia) and performance determinants has not been explored yet. This study aimed to assess the association of clinical spasticity measurements with the performance of sport-specific tests used for classification purposes. Sixty-nine international footballers with CP voluntarily participated in this study. The Australian Spasticity Assessment Scale was used to measure spasticity in lower limbs muscle groups and activity limitation tests were conducted considering dynamic balance, coordination, vertical and horizontal jumps, acceleration, and change of direction ability. Low-to-moderate negative significant associations were found between the hip spasticity and measures of dynamic balance and dominant unipedal horizontal jump capacity. Additionally, moderate associations were reported between the knee spasticity and the non-dominant unipedal horizontal jump capacity and the change of direction actions with the ball. The ankle spasticity score reported small to moderate associations with the change of direction assessment without the ball and bipedal and dominant unipedal horizontal jump capability. Finally, the total spasticity score only presented a significant association with horizontal jump performance. This is a novel study that provides evidence of the associations between an eligible neural impairment and relevant specific measures of activity limitation tests. These results suggest that the amount of spasticity according to each evaluated joint muscle group of the lower limbs presents a low-to-moderate significant relationship with determined measures of dynamic balance, coordination, horizontal jump, acceleration, and change of direction ability with and without the ball in international-level CP footballers. Further studies are necessary to elucidate the real contribution of neural and non-neural impairments related to hypertonia on fundamental sport-specific motor skills of para-footballers with CP.

Development of evidence-based classification for para surfers with physical impairments: A narrative review

The sport of competitive para surfing is growing internationally without established classification procedures. A classification structure is essential for equitable sport competition and worldwide sport progression. This narrative review summarizes the existing knowledge on Paralympic classification and surfing biomechanics. Its primary purpose is to describe the development of an evidence-based para surfing classification structure that follows the International Paralympic Committee (IPC) Classification Code. Two databases-PubMed and Google Scholar-were searched for three themes: "Paralympic classification", "performance determining factors in surfing", and "impact of impairments on surf performance". The IPC Classification Code and IPC regulations were obtained from the IPC website and official publications. Seventy-six relevant articles were utilized to guide the design of this preliminary para surfing classification structure. A conceptual framework on athlete characteristics, adaptive sport characteristics, and use of equipment is presented to build the essential knowledge base for continual growth of para surfing. This classification structure and conceptual framework will support para surfing sport expansion and help pave the way for its inclusion in the Paralympic Games.

The relation between sprint power and road time trial performance in elite para-cyclists

OBJECTIVES

Whilst cycling performance has been studied extensively, very little is known about the performance of para-cyclists. This study assessed the relation between sprint power and road time trial performance in elite para-cyclists, and whether this relation differed based on impairment type and type of bike used.

DESIGN

Cross-sectional.

METHODS

During international para-cycling events, 168 athletes (88 bicycles, 17 tricycles, 56 recumbent handbikes and 7 kneeling handbikes) performed 20-s sport-specific sprint tests (mean power output (POmean) W), and their road time trial performance (average speed (km/h)) was taken from the official results. Multilevel regression models to assess the relation of sprint with time trial performance were composed for i. leg-cyclists: bicycle and tricycle and ii. arm-cyclists: recumbent- and kneeling handbike, adjusted for identified confounders. Furthermore, impairment type (categorized as i) muscle power/range of motion, ii) limb deficiency/leg length difference, and iii) coordination) and bike type were tested as effect modifiers.

RESULTS

POmean ranged from 303 ± 12 W for recumbent handcyclists to 482 ± 156 W for bicyclists. POmean was significantly related to time trial performance, for both leg-cyclists (β = 0.010, SE = 0.003, p < 0.01) and arm-cyclists (β = 0.029; SE = 0.005, p < 0.01), and impairment type and bike type were not found to be effect modifiers.

CONCLUSIONS

Sprint power was related to road time trial performance in all para-cyclists, with no differences found in this relation based on impairment type nor bike type. For those competing on a bicycle, tricycle, recumbent- or kneeling handbike, sprint tests might therefore be useful to predict or monitor time trial performance.

Using Decision Trees to Support Classifiers' Decision-Making about Activity Limitation of Cerebral Palsy Footballers

This study aimed (1) to determine the appropriateness of using decision trees as a classification tool for determining the allocation of sport classes of para-footballers with "moderate vs. mild" cerebral palsy (CP) profiles of spastic diplegia/hemiplegia and ataxia/athetosis based on observational outcomes by international classifiers, and (2) to identify what key observational features were relevant to discriminating among different impairment levels. A sample of 16 experienced international classifiers from five world regions participated in this study, observing activity limitation of a final sample of 21 international CP footballers when performing 16 gross-motor and sports-specific tests for balance (n = 3), coordination (n = 5), running, accelerations and decelerations (n = 3), jumping (n = 4), and change of direction ability (n = 1). For the overall sample (336 observations), the model included eight decision nodes and 24 branches with 17 leaves, including side-step, side-stepping, and triple hop as the tests with the best sensitivity (precision = 67.0%). For those with spastic diplegia (64 observations: Two nodes, six branches with five leaves), the range of motion in the side-step test and the balance in the tandem walk tests correctly classified 89.1% of the observations. In those with athetosis and ataxia (96 observations), the model included five nodes, 15 branches, and 11 leaves (176 observations, precision = 86.5%). For those with spastic hemiplegia, a model containing two nodes, six branches, and five leaves had 90.9% accuracy, including observational features of balance in the side-step test and symmetry in the side-stepping test. The observational tool used in this study, based on the impact of specific impairment measurements of hypertonia, athetosis, and ataxia, can be used to determine which assessments are more appropriate for discriminating between functional profiles in para-footballers with CP.

Is impaired coordination related to match physical load in footballers with cerebral palsy of different sport classes?

Impaired coordination is a characteristic feature in cerebral palsy (CP) football players. This study aimed to determine the relationships of three coordination tests with match physical load during competition of para-footballers from different sport classes. Records from 259 para-footballers from 25 national teams were obtained in four international competitions held in 2018 and 2019. The three coordination tests were conducted prior to competition (i.e., rapid heel-toe, side-stepping, and split jumps), and physical match load was recorded by GPS devices during the real game: i.e., maximum/mean, total distance, distance covered at different speed zones, number of accelerations/decelerations at different intensities, and player load. FT1 and FT3 players have the lowest and highest performance in all the coordination tests, respectively, but inconclusive between-groups differences were obtained (p=0.022‒0.238). Split jumps and side-stepping tests are associated with the performance of moderate and high accelerations during competition (r = -0.20‒0.71; p<0.01). Significant correlations (r = 0.36‒0.71; p<0.01) were obtained between all the coordination measures. Coordination tests better discriminate those with more severe impairments and some evidence for the validity of the new CP football sport classes is provided. Further research is necessary to identify the portion of the variance in sports performance that coordination explains.

Cluster analysis of impairment measures to inform an evidence-based classification structure in RaceRunning, a new World Para Athletics event for athletes with hypertonia, ataxia or athetosis

RaceRunning enables athletes with limited or no walking ability to propel themselves independently using a three-wheeled frame that has a saddle, handle bars and a chest plate. For RaceRunning to be included as a para athletics event, an evidence-based classification system is required. This study assessed the impact of trunk control and lower limb impairment measures on RaceRunning performance and evaluated whether cluster analysis of these impairment measures produces a valid classification structure for RaceRunning. The Trunk Control Measurement Scale (TCMS), Selective Control Assessment of the Lower Extremity (SCALE), the Australian Spasticity Assessment Scale (ASAS), and knee extension were recorded for 26 RaceRunning athletes. Thirteen male and 13 female athletes aged 24 (SD = 7) years participated. All impairment measures were significantly correlated with performance (rho = 0.55-0.74). Using ASAS, SCALE, TCMS and knee extension as cluster variables in a two-step cluster analysis resulted in two clusters of athletes. Race speed and the impairment measures were significantly different between the clusters (p < 0.001). The findings of this study provide evidence for the utility of the selected impairment measures in an evidence-based classification system for RaceRunning athletes.

Biomechanics of starting, sprinting and submaximal running in athletes with brain impairment: A systematic review

OBJECTIVES

Para athletes with brain impairment are affected by hypertonia, ataxia and athetosis, which adversely affect starting, sprinting and submaximal running. The aim was to identify and synthesise evidence from studies that have compared the biomechanics of runners with brain impairments (RBI) and non-disabled runners (NDR).

DESIGN

Systematic review.

METHODS

Five journal databases were systematically searched from inception to March 2020. Included studies compared the biomechanics of RBI (aged>14 years) and NDR performing either block-starts, sprinting, or submaximal running.

RESULTS

Eight studies were included, analysing a total of 100 RBI (78M:22F; 18-38 years) diagnosed with either cerebral palsy (n=44) or traumatic brain injury (n=56). Studies analysed block-starts (n=3), overground sprinting (n=3) and submaximal running (n=2), and submaximal treadmill running (n=1). Horizontal velocity during starts, sprinting and self-selected submaximal speeds were lower in RBI. During sprinting and submaximal running, compared with NDR, RBI had shorter stride length, step length, and flight time, increased ground-contact time, increased cadence, and reduced ankle and hip range of motion. In submaximal running, RBI had decreased ankle-power generation at toe-off.

CONCLUSIONS

There is limited research and small sample sizes in this area. However, preliminary evidence suggests that RBI had lower sprint speeds and biomechanical characteristics typical of submaximal running speeds in NDR, including increased ground-contact times and reduced stride length, step length, and flight times. Meaningful interpretation of biomechanical findings in RBI is impeded by impairment variability (type, severity and distribution), and methods which permit valid, reliable impairment stratification in larger samples are required.

An Observational Tool to Assess Activity Limitation in Ambulatory People with Cerebral Palsy When Performing Motor Skills

Ratios of physical activity and sports participation in people with cerebral palsy (CP) are still low compared with people without a disability. For an adequate and useful practice, physical activity professionals should understand how different types of CP profiles constrain the performance of motor skills that are required during sports practice. This study aims to develop an observation-based assessment tool to evaluate activity limitations in individuals with a moderate level of CP when performing skills requiring jumping, sprinting, change of direction, coordination, and balance. Nineteen observers with different backgrounds from five world regions were recruited for this study, with accredited experience classifying/observing para-athletes with CP. All observers watched videos of 20 international para-athletes with different CP profiles (bilateral spasticity, athetosis/ataxia, unilateral spasticity; all Gross Motor Function Classification System level I) performing 16 motor tasks, and their observations were recorded throughout an ad-hoc data collection instrument. A total of 6080 units of qualitative information were recorded for data analysis. An observation-based tool with qualitative descriptors is derived from data analyses, describing how coordination and balance affected mainly in those with dyskinesia/ataxia, range of movement in those with diplegia, and asymmetries in those with hemiplegia. This tool would help sports practitioners and physical educators to better understand how different CP profiles constrain the performance of motor skills.

Evaluation of the bilateral function in para-athletes with spastic hemiplegia: A model-based clustering approach

OBJECTIVES

Spastic hemiplegia is one of the most common forms of cerebral palsy, in which one side of the body is affected to a greater extent than the other one. Hemiplegia severity (i.e. moderate vs mild forms) is currently used in some Para sports for classification purposes. This study evaluates the sensitivity of several tests of stability (e.g. one-legged stance test), dynamic balance (side-step test), coordination (rapid heel-toe placements), range of movement (backward stepping lunge), and lower limb power (the triple hop distance and the isometric peak force of the knee extensors) to discriminate between the impaired and unimpaired lower extremities' function in para-athletes with spastic hemiplegia.

METHODS

A sample of 87 international para-athletes with cerebral palsy took part in the study, and their bilateral performance was measured for the abovementioned tests. The tests' sensitivity to discriminate between impaired vs unimpaired legs was assessed using Boruta's method.

RESULTS

The triple hop distance, the magnitude of the mean velocity in the one-legged stance test and the time to perform the rapid heel-toe placement test are the most sensitive variables when performing random forest classifiers. In addition, the study confirms two optimal clusters by Gaussian finite mixture models to represent the athletes' performance.

CONCLUSIONS

Reference scores for the clusters are provided, demonstrating that coordination, balance, and power of the lower limbs are relevant variables for classifying para-athletes with spastic hemiplegia.

Vertical and Horizontal Jump Capacity in International Cerebral Palsy Football Players

PURPOSE

To evaluate the reliability and validity of vertical and horizontal jump tests in football players with cerebral palsy (FPCP) and to analyze the jump performance differences between current International Federation for Cerebral Palsy Football functional classes (ie, FT5-FT8).

METHODS

A total of 132 international parafootballers (25.8 [6.7] y; 70.0 [9.1] kg; 175.7 [7.3] cm; 22.8 [2.8] kg·m^-2; and 10.7 [7.5] y training experience) participated in the study. The participants were classified according to the International Federation for Cerebral Palsy Football classification rules, and a group of 39 players without cerebral palsy was included in the study as a control group. Football players' vertical and horizontal jump performance was assessed.

RESULTS

All the tests showed good to excellent relative intrasession reliability scores, both in FPCP and in the control group (intraclass correlation = .78-.97, SEM < 10.5%). Significant between-groups differences (P < .001) were obtained in the countermovement jump, standing broad jump, 4 bounds for distance, and triple hop for distance dominant leg and nondominant leg. The control group performed higher/farther jumps with regard to all the FPCP classes, obtaining significant differences and moderate to large effect sizes (ESs) (.85 < ES < 5.54, P < .01). Players in FT8 class (less severe impairments) had significantly higher scores in all the jump tests than players in the lower classes (ES = moderate to large, P < .01).

CONCLUSIONS

The vertical and horizontal jump tests performed in this study could be applied to the classification procedures and protocols for FPCP.

The influence of lower limb impairments on RaceRunning performance in athletes with hypertonia, ataxia or athetosis

OBJECTIVES

RaceRunning enables athletes with limited or no walking ability to propel themselves independently using a three-wheeled running bike that has a saddle and a chest plate for support but no pedals. For RaceRunning to be included as a Para athletics event, an evidence-based classification system is required. Therefore, the aim of this study was to assess the association between a range of impairment measures and RaceRunning performance.

METHODS

The following impairment measures were recorded: lower limb muscle strength assessed using Manual Muscle Testing (MMT), selective voluntary motor control assessed using the Selective Control Assessment of the Lower Extremity (SCALE), spasticity recorded using both the Australian Spasticity Assessment Score (ASAS) and Modified Ashworth Scale (MAS), passive range of motion (ROM) of the lower extremities and the maximum static step length achieved on a stationary bike (MSSL). Associations between impairment measures and 100-meter race speed were assessed using Spearman's correlation coefficients.

RESULTS

Sixteen male and fifteen female athletes (27 with cerebral palsy), aged 23 (SD = 7) years, Gross Motor Function Classification System levels ranging from II to V, participated. The MSSL averaged over both legs and the ASAS, MAS, SCALE, and MMT summed over all joints and both legs, significantly correlated with 100 m race performance (rho: 0.40-0.54). Passive knee extension was the only ROM measure that was significantly associated with race speed (rho = 0.48).

CONCLUSION

These results suggest that lower limb spasticity, isometric leg strength, selective voluntary motor control and passive knee extension impact performance in RaceRunning athletes. This supports the potential use of these measures in a future evidence-based classification system.

Neuromuscular features in sprinters with cerebral palsy: case studies based on paralympic classification

Despite the evolution of runner performance in athletes with cerebral palsy (CP), little is known about neuromuscular parameters of sprinters from different classes, especially related to power output, muscular imbalances and asymmetry indexes in lower limbs. The aim of this study was to assess muscle power, muscular imbalance and asymmetry in sprinters with CP. Four male sprinters with CP (age, 18 to 27 years; body mass, 58.5 to 72.8 kg; height, 161.5 to 174 cm) classified as T38, T37, T36, T35 according to International Paralympic Committee functional classification, performed vertical counter movement jump and squat jump on force plate and isokinetic torque evaluations in both limbs. The concentric peak torque (PT) was measured at 60°/sec, 120°/sec and 180°/sec and PT eccentric at 60°/sec and 120°/sec. The asymmetry indexes, conventional and functional ratios were assessed. the results showed that athletes with more severe impairments (T35 and T36) showed worse performance to muscle power, more muscular imbalance and higher asymmetry in PT between limbs (> 10%). The exception was T37 athlete, who presented the better performance for all variables. it is concluded that CP athletes with more severe impairments showed lower jumping performance and torque production of knee extensors and flexors, they showed greater asymmetries between limbs. Finally, considering the results of T37 athlete, it seems that the athletic training for a longer period can reverse part of the neuromuscular impairments caused by CP.

How does the ball influence the performance of change of direction and sprint tests in para-footballers with brain impairments? Implications for evidence-based classification in CP-Football

The aims of this study were: i) to analyze the reliability and validity of three tests that require sprinting (10 m, 25 m, 40 m), accelerations/decelerations (Stop and Go Test) and change of direction (Illinois Agility Test), with and without ball, in para-footballers with neurological impairments, and ii) to compare the performance in the tests when ball dribbling is required and to explore the practical implications for evidence-based classification in cerebral palsy (CP)-Football. Eighty-two international para-footballers (25.2 ± 6.8 years; 68.7 ± 8.3 kg; 175.3 ± 7.4 cm; 22.5 ± 2.7 kg·m-2), classified according to the International Federation of Cerebral Palsy Football (IFCPF) Classification Rules (classes FT5-FT8), participated in the study. A group of 31 players without CP was also included in the study as a control group. The para-footballers showed good reliability scores in all tests, with and without ball (ICC = 0.53-0.95, SEM = 2.5-9.8%). Nevertheless, the inclusion of the ball influenced testing reproducibility. The low or moderate relationships shown among sprint, acceleration/deceleration and change of direction tests with and without ball also evidenced that they measure different capabilities. Significant differences and large effect sizes (0.53 < ηp2 < 0.97; p < 0.05) were found when para-footballers performed the tests with and without dribbling the ball. Players with moderate neurological impairments (i.e. FT5, FT6, and FT7) had higher coefficients of variation in the trial requiring ball dribbling. For all the tests, we also obtained between-group (FT5-FT8) statistical and large practical differences (ηp2 = 0.35-0.62, large; p < 0.01). The proposed sprint, acceleration/deceleration and change of direction tests with and without ball may be applicable for classification purposes, that is, evaluation of activity limitation from neurological impairments, or decision-making between current CP-Football classes.