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

The coil-globule transition of confined polymers

We study long polymer chains in a poor solvent, confined to the space between two parallel hard walls. The walls are energetically neutral and pose only a geometric constraint which changes the properties of the coil-globule (or "$\theta$-") transition. We find that the $\theta$ temperature increases monotonically with the width $D$ between the walls, in contrast to recent claims in the literature. Put in a wider context, the problem can be seen as a dimensional cross over in a tricritical point of a $\phi^4$ model. We roughly verify the main scaling properties expected for such a phenomenon, but we find also somewhat unexpected very long transients before the asymptotic scaling regions are reached. In particular, instead of the expected scaling $R\sim N^{4/7}$ exactly at the ($D$-dependent) theta point we found that $R$ increases less fast than $N^{1/2}$, even for extremely long chains.Comment: 5 pages, 6 figure

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

Risk of injuries in Paralympic track and field differs by impairment and event discipline A prospective cohort study at the London 2012 Paralympic Games

Background: The incidence rates (IRs) and factors associated with injuries in the sport of Paralympic athletics (track and field) have not been comprehensively and prospectively studied. Purpose: To determine injury IRs, characteristics of injuries, and associated factors in the sport of athletics at the London 2012 Paralympic Games. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 977 athletes competing in the sport of athletics were followed over a total 10-day competition period of the Paralympic Games. Daily injury data were obtained via 2 databases: (1) a custom-built, web-based injury and illness surveillance system (WEB-IISS), maintained by team medical personnel; and (2) the organizing committee database, maintained by medical providers in the medical stations operated by the London Organising Committee of the Olympic and Paralympic Games. Athlete impairment and event discipline were obtained via the International Paralympic Committee athlete database. IRs (injuries per 1000 athlete-days) by impairment, event discipline, sex, and age were examined. Results: The overall IR was 22.1 injuries per 1000 athlete-days (95% CI, 19.5-24.7). In track disciplines, ambulant athletes with cerebral palsy experienced a lower incidence of injuries (IR, 10.2; 95% CI, 4.2-16.2) when compared with ambulant athletes from other impairment categories. Athletes in seated throwing experienced a higher incidence of injuries (IR, 23.7; 95% CI, 17.5-30.0) when compared with athletes in wheelchair racing (IR, 10.6; 95% CI, 5.5-15.6). In both track and field disciplines, the majority of injuries did not result in time loss from competition or training. Ambulant athletes experienced the greatest proportion of injuries to the thigh (16.4% of all injuries; IR, 4.0), observed predominantly in track athletes. Wheelchair or seated athletes experienced the greatest proportion of injuries to the shoulder/clavicle (19.3% of all injuries; IR, 3.4), observed predominantly in field athletes. Conclusion: This is the first prospective cohort study examining injury IRs and associated factors in the sport of athletics at the Paralympic Games. Injury patterns were specific to the event discipline and athlete impairment. The majority of injuries occurred to the thigh (ambulant athletes) or shoulder/clavicle (wheelchair or seated athletes) and did not result in time loss. </jats:sec

Host resistance to rat cytomegalovirus (RCMV) and immune function in adult PVG rats fed herring from the contaminated Baltic Sea

The immunotoxic potential of many classes of environmental contaminants has been well established in laboratory studies, with much attention being focussed on aryl hydrocarbon (Ah)-receptor binding polychlorinated biphenyl (PCB), polychlorinated dibenzo-p-dioxin (PCDD), and polychlorinated dibenzofuran (PCDF) congeners. In a semi-field study, we previously showed that harbour seals (Phoca vitulina) fed herring from the contaminated Baltic Sea had lower natural killer cell activity, T-lymphocyte functionality and delayed-type hypersensitivity responses than seals fed herring from the relatively uncontaminated Atlantic Ocean. While ethical and practical constraints preclude in-depth studies in seals, specific reagents and a wider array of immune function tests allow such studies in laboratory rats. We therefore carried out a feeding study in rats aimed at extending our observations of contaminant-induced immunosuppression in harbour seals. The same two herring batches used in the seal study were freeze-dried, supplemented and fed. to female adult PVG rats for a period of 4 1/4 months. Daily contaminant intakes of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalents (TEQ) were estimated to be 0.3 ng/kg body weight and 1.6 ng/kg in the Atlantic and Baltic groups, respectively. At the end of the feeding experiment, no contaminant-related changes in spleen CD4+/CD8+cellularity, natural killer cell activity, or mitogen-induced proliferative responses of thymus or spleen cells could be detected. However, total thymocyte numbers and thymus CD4+/CD8+ratios were reduced in the Baltic group. A novel model was established to assess the specific T-cell response to rat cytomegalovirus (RCMV). When applied to the feeding study, no differences between the Atlantic and Baltic groups in the RCMV-induced proliferative T-lymphocyte responses could be detected, but virus titres in salivary glands of infected rats of the Baltic Sea group were higher. These elevated RCMV titres and changes in thymus cellularity suggest that the dietary exposure to low levels of contaminants may have been immunotoxic at a level which our immune function test could not otherwise detect. While the herring diet per se appeared to have an effect on several immune function parameters, lower plasma thyroid hormone levels in the Baltic Sea group of rats confirmed that exposure to the environmental mixture of contaminants led to adverse PHAH-related health effects

Cerebellar Cathodal Transcranial Direct Stimulation and Performance on a Verb Generation Task: A Replication Study

The role of the cerebellum in cognitive processing is increasingly recognized but still poorly understood. A recent study in this field applied cerebellar Transcranial Direct Current Stimulation (c-tDCS) to the right cerebellum to investigate the role of prefrontal-cerebellar loops in language aspects of cognition. Results showed that the improvement in participants' verbal response times on a verb generation task was facilitated immediately after cathodal c-tDCS, compared to anodal or sham c-tDCS. The primary aim of the present study is to replicate these findings and additionally to investigate possible longer term effects. A crossover within-subject design was used, comparing cathodal and sham c-tDCS. The experiment consisted of two visits with an interval of one week. Our results show no direct contribution of cathodal c-tDCS over the cerebellum to language task performance. However, one week later, the group receiving cathodal c-tDCS in the first visit show less improvement and increased variability in their verbal response times during the second visit, compared to the group receiving sham c-tDCS in the first visit. These findings suggest a potential negative effect of c-tDCS and warrant further investigation into long term effects of c-tDCS before undertaking clinical studies with poststroke patients with aphasia

Genome-wide analysis of macrosatellite repeat copy number variation in worldwide populations: Evidence for differences and commonalities in size distributions and size restrictions

Background: Macrosatellite repeats (MSRs), usually spanning hundreds of kilobases of genomic DNA, comprise a significant proportion of the human genome. Because of their highly polymorphic nature, MSRs represent an extreme example of copy number variation, but their structure and function is largely understudied. Here, we describe a detailed study of six autosomal and two X chromosomal MSRs among 270 HapMap individuals from Central Europe, Asia and Africa. Copy number variation, stability and genetic heterogeneity of the autosomal macrosatellite repeats RS447 (chromosome 4p), MSR5p (5p), FLJ40296 (13q), RNU2 (17q) and D4Z4 (4q and 10q) and X chromosomal DXZ4 and CT47 were investigated. Results: Repeat array size distribution analysis shows that all of these MSRs are highly polymorphic with the most genetic variation among Africans and the least among Asians. A mitotic mutation rate of 0.4-2.2% was observed, exceeding meiotic mutation rates and possibly explaining the large size variability found for these MSRs. By means of a novel Bayesian approach, statistical support for a distinct multimodal rather than a uniform allele size distribution was detected in seven out of eight MSRs, with evidence for equidistant intervals between the modes. Conclusions: The multimodal distributions with evidence for equidistant intervals, in combination with the observation of MSR-specific constraints on minimum array size, suggest that MSRs are limited in their configurations and that deviations thereof may cause disease, as is the case for facioscapulohumeral muscular dystrophy. However, at present we cannot exclude that there are mechanistic constraints for MSRs that are not directly disease-related. This study represents the first comprehensive study of MSRs in different human populations by applying novel statistical methods and identifies commonalities and differences in their organization and function in the human genome

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