USING UNDERWATER 3D KINEMATICS TO IMPROVE THE PARALYMPIC SWIMMING CLASSIFICATION SYSTEM

Swimming is a fundamental sport at the Olympic and Paralympic games, with the Paralympic classification system being the key difference between these games. To improve the accuracy of the classification system this case study investigated differences in the underwater hand kinematics of the affected and unaffected limb of an elite Para swimmer with hemiplegic cerebral palsy. In this case study, hemiplegic cerebral palsy caused impairments in strength, motor coordination and range of motion that affected hand speeds and trajectory paths during the underwater stroke phases. This work illustrates the benefit of using objective impairment and sport-specific measurements to gain insights into the impact that health conditions have on performance to guide Para swimming classification. This biomechanical analysis lays the foundations for the future improvement in international Para classification system

Improving the objectivity of the current World Para Swimming motor coordination test for swimmers with hypertonia, ataxia and athetosis using measures of movement smoothness, rhythm and accuracy

The current protocol for classifying Para swimmers with hypertonia, ataxia and athetosis involves a physical assessment where the individual’s ability to coordinate their limbs is scored by subjective clinical judgment. The lack of objective measurement renders the current test unsuitable for evidence-based classification. This study evaluated a revised version of the Para swimming assessment for motor coordination, incorporating practical, objective measures of movement smoothness, rhythm error and accuracy. Nineteen Para athletes with hypertonia and 19 non-disabled participants performed 30 s trials of bilateral alternating shoulder flexion-extension at 30 bpm and 120 bpm. Accelerometry was used to quantify movement smoothness; rhythm error and accuracy were obtained from video. Para athletes presented significantly less smooth movement and higher rhythm error than the non-disabled participants (p < 0.05). Random forest algorithm successfully classified 89% of participants with hypertonia during out-of-bag predictions. The most important predictors in classifying participants were movement smoothness at both movement speeds, and rhythm error at 120 bpm. Our results suggest objective measures of movement smoothness and rhythm error included in the current motor coordination test protocols can be used to infer impairment in Para swimmers with hypertonia. Further research is merited to establish the relationship of these measures with swimming performance

Maximal fully-tethered swim performance in Para swimmers with physical impairment

The assessment of swimming propulsion should be a cornerstone of Paralympic swimming classification. However, current methods do not objectively account for this component. This study evaluated the swimming propulsion of swimmers with and without physical impairment using a 30 s maximal fully-tethered freestyle swim test. Methods: Tethered forces were recorded during maximal fully-tethered swimming in eighty competitive swimmers with (n = 70) and without (n = 10) physical impairment. The relationships between absolute and normalised tether forces and maximal freestyle swim speed were established using general additive models. Results: Para swimmers with physical impairment had lower absolute and normalised tether forces than able-bodied swimmers, and there were moderate positive correlations found between tether forces and sport class (τ = .52 to .55, p < .001). There was a nonlinear relationship between tether force measures and maximal freestyle swim speed in the participant cohort (adj. R2 = .78 to .80, p < .001). Para swimmers with limb deficiency showed stronger relationships between tether force measures and maximal freestyle swim speed (adj. R2 = .78 to .82, p < .001) than for Para swimmers with hypertonia (adj. R2 = .54 to .73, p < .001) and impaired muscle power (adj. R2 = .61 to .70, p < .001). Conclusions: Physical impairments impact on Para swimmers’ tether forces during maximal fully-tethered freestyle swimming, explaining a significant proportion of their activity limitation. It is recommended that maximal fully-tethered swimming be included in Paralympic swimming classification as an objective assessment of swimming propulsion

The impact of limb deficiency impairment on Para swimming performance

Swimmers with limb deficiency are a core population within Para Swimming, accordingly this study examined the contribution of limb segments to race performance in these swimmers. Data were obtained for 174 male Para swimmers with limb deficiency. Ensemble partial least squares regression showed accurate predictions when using relative limb segment lengths to estimate Para swimmers’ personal best race performances. The contribution of limb segments to performance in swim events was estimated using these regression models. The analysis found swim stroke and event distance to influence the contributions of limb segments to performance. For freestyle swim events, these changes were primarily due to the increased importance of the hand, and decreased importance of the foot and shank, as the distance of the event increased. When comparing swim strokes, higher importance of the thigh and shank in the 100 m breaststroke compared with other swim strokes confirms the separate SB class. Varied contributions of the hand, upper arm and foot suggest that freestyle could also be separated from backstroke and butterfly events to promote fairer classification. This study shows that swim stroke and event distance influence the activity limitation of Para swimmers with limb deficiency suggesting classification should account for these factors

Froude Efficiency and Velocity Fluctuation in Forearm-Amputee Front Crawl: Implications for Para Swimming Classification

Purpose: The impact of physical impairment on Froude efficiency and intra-cyclic velocity fluctuation in Para swimmers is not well documented. Identification of differences in these variables between disabled and non-disabled swimmers could help develop a more objective system for assigning Para swimmers to classes for competition. This study quantifies Froude efficiency and intra-cyclic velocity fluctuation in unilateral forearm-amputee front crawl swimmers, and evaluates associations between these variables and performance. Methods: Ten unilateral forearm-amputee swimmers completed front crawl trials at 50 m and 400 m pace; three-dimensional video analysis provided mass centre, wrist and stump velocities. Intra-cyclic velocity fluctuation was calculated as: 1) maximum - minimum mass centre velocity, expressed as % of mean velocity, and 2) coefficient of variation in mass centre velocity. Froude efficiency was the ratio between mean swimming velocity and wrist plus stump velocity during each segment’s respective: 1) underwater phase, and 2) propulsive underwater phase. Results: Forearm-amputees’ intra-cyclic velocity fluctuation (400 m: 22 ± 7%; 50 m: 18 ± 5%) was similar to published values for non-disabled swimmers, whilst Froude efficiencies were lower. Froude efficiency was higher at 400 m (0.37 ± 0.04) than 50 m pace (0.35 ± 0.05; p < .05) and higher for the unaffected limb (400 m: 0.52 ± 0.03; 50 m: 0.54 ± 0.04) than the residual limb (400 m: 0.38 ± 0.03; 50 m 0.38 ± 0.02; p < .05). Neither intra-cyclic velocity fluctuation nor Froude efficiency were associated with swimming performance. Conclusions: Froude efficiency may be a valuable measure of activity limitation in swimmers with an upper limb deficiency and a useful metric for comparing swimmers with different types and severity of physical impairment

Active drag as a criterion for evidence-based classification in Para swimming

Paralympic classification should provide athletes with an equitable starting point for competition by minimizing the impact their impairment has on the outcome of the event. As swimming is an event conducted in water, the ability to overcome drag (active and passive) is an important performance determinant. It is plausible that the ability to do this is affected by the type and severity of the physical impairment, but the current World Para Swimming classification system does not objectively account for this component. The aim of this study was to quantify active and passive drag in Para swimmers and evaluate the strength of association between these measures and type of physical impairment, swimming performance, and sport class. Methods Seventy-two highly trained Para swimmers from sport classes S1 to S10 and 14 highly trained nondisabled swimmers were towed by a motorized winch while the towing force was recorded. Passive drag was measured with the arms held by the side; active drag was determined during freestyle swimming using an assisted towing method. Results Active and passive drag were higher in Para swimmers with central motor and neuromuscular impairments than for nondisabled swimmers and were associated with severity of swim-specific impairment (sport class) and maximal freestyle performance in these swimmers (r = −0.40 to −0.50, P ≤ 0.02). Para swimmers with anthropometric impairments showed similar active and passive drag to nondisabled swimmers, and between swimmers from different sport classes. Conclusions Para swimmers with central motor and neuromuscular impairments are predisposed to high active drag during freestyle swimming that impacts on their performance. It is recommended that drag measures be considered in revised classification for these swimmers, but not for those with anthropometric impairments

The impact of an assistive pole, seat configuration and strength in Paralympic seated throwing

Purpose: To quantify the influence of the assistive pole, seat configuration, and upper-body and trunk strength on seated-throwing performance in athletes with a spinal-cord injury (SCI). Methods: Ten Paralympic athletes competing in wheelchair rugby, basketball, or athletics (seated throws) participated in 2 randomized sessions: seated throwing and strength tests. Participants threw a club from a custom-built throwing chair, with and without a pole. 3D kinematic data were collected (150 Hz) for both conditions using standardized and self-selected seat configurations. Dominant and nondominant grip strength were measured using a dynamometer, and upper-body and trunk strength were measured using isometric contractions against a load cell. Results: Seated throwing with an assistive pole resulted in significantly higher hand speed at release than throwing without a pole (pole = 6.0 ± 1.5 m/s, no pole = 5.3 ± 1.5 m/s; P = .02). There was no significant difference in hand speed at release between standardized and self-selected seating configurations during seated throwing with or without an assistive pole. Grip strength (r = .59–.77), push/pull synergy (r = .81–.84), and trunk-flexion (r = .50–.58) strength measures showed large and significant correlations with hand speed at release during seated throwing with and without an assistive pole. Conclusions: This study has demonstrated the importance of the pole for SCI athletes in seated throwing and defined the relationship between strength and seated-throwing performance, allowing us to better understand the activity of seated throws and provide measures for assessing strength that may be valid for evidence-based classification

Classifying motor coordination impairment in Para swimmers with brain injury

© 2018 Sports Medicine Australia Objectives: The International Paralympic Committee has mandated that International Sport Federations develop sport-specific classification systems that are evidence-based. This study examined the predictive and convergent validity of instrumented tapping tasks to classify motor coordination impairments in Para swimming. Design: Cross-sectional. Methods: Thirty non-disabled participants and twenty-one Para swimmers with brain injury completed several instrumented tapping tasks as an assessment of upper and lower limb motor coordination. Para swimmers also completed a maximal freestyle swim to obtain a performance measure. The predictive and convergent validity of instrumented tapping tasks was examined by establishing differences in test measures between participants with and without brain injury and defining the strength of association between test measures and maximal freestyle swim speed in Para swimmers, respectively. Results: Random forest successfully classified 96% of participants with and without brain injury using test measures derived from instrumented tapping tasks. Most test measures had moderate to high correlations (r = 0.54 to 0.72; p < 0.01) with maximal freestyle swim speed and collectively explained up to 72% of the variance in maximal freestyle swim performance in Para swimmers with brain injury. Conclusions: The results of this study evidence the predictive and convergent validity of instrumented tapping tasks to classify motor coordination impairments in Para swimmers with brain injury. These tests can be included in revised Para swimming classification to improve the objectivity and transparency in determining athlete eligibility and sport class for these Para athletes

A Phase 1 Human Immunodeficiency Virus Vaccine Trial for Cross-Profiling the Kinetics of Serum and Mucosal Antibody Responses to CN54gp140 Modulated by Two Homologous Prime-Boost Vaccine Regimens

A key aspect to finding an efficacious human immunodeficiency virus (HIV) vaccine is the optimization of vaccine schedules that can mediate the efficient maturation of protective immune responses. In the present study, we investigated the effect of alternate booster regimens on the immune responses to a candidate HIV-1 clade C CN54gp140 envelope protein, which was coadministered with the TLR4-agonist glucopyranosyl lipid A-aqueous formulation. Twelve study participants received a common three-dose intramuscular priming series followed by a final booster at either 6 or 12 months. The two homologous prime-boost regimens were well tolerated and induced CN54gp140-specific responses that were observed in both the systemic and mucosal compartments. Levels of vaccine-induced IgG-subclass antibodies correlated significantly with Fc gamma R engagement, and both vaccine regimens were associated with strikingly similar patterns in antibody titer and Fc gamma R-binding profiles. In both groups, identical changes in the antigen (Ag)-specific IgG-subclass fingerprint, leading to a decrease in IgG1 and an increase in IgG4 levels, were modulated by booster injections. Here, the dissection of immune profiles further supports the notion that prime-boost strategies are essential for the induction of diverse Ag-specific HIV-1 responses. The results reported here clearly demonstrate that identical responses were effectively and safely induced by both vaccine regimens, indicating that an accelerated 6-month regimen could be employed for the rapid induction of immune responses against CN54gp140 with no apparent impact on the overall quality of the induced immune response. (This study has been registered at http://ClinicalTrials.gov under registration no.NCT01966900.