An investigation of elbow loading in one-handed tennis backhand groundstrokes using computer simulation

A 3D subject-specific computer simulation model of a ball-racket system linked to an upper-limb and torso was developed to investigate factors which may result in adverse loading at the elbow during one-handed backhand groundstrokes. Rigid hand, forearm, upper-arm and torso segments were driven by joint angle time histories obtained from backhand performances. Wobbling mass segments were incorporated to represent soft tissue motion. The upper-limb model was attached to a forward dynamics model of the racket-ball system using spring-dampers at the thenar and hypothenar eminences of the hand. The racket frame was represented using two rigid bodies with two torsional spring-dampers to allow motion in and out of the racket plane. The stringbed was represented by nine point masses connected using elastic springs. A point mass representation of the tennis ball allowed normal and oblique impacts at the nine locations on the stringbed. Inertia parameters for the elite tennis player and the rackets and visco-elastic parameters for the rackets and ball were determined from independent experimental tests. Visco-elastic parameters for the hand and wobbling masses were determined within the matching process of six backhand trials. Excellent agreement between performance and matching simulations was obtained with a mean RMS difference of 1.3% based on racket kinematics, outbound ball velocity and time of ball contact. Simulation results suggest that the inertia and stiffness parameters of the racket frame and the stringbed tension have a relatively small influence on elbow loading within current design ranges. In contrast, the off-centre ball impact simulations resulted in an 11% increase in peak internal elbow joint force, a 22% increase in peak pronation-supination net torque and a 19% increase in peak elbow-flexion extension net torque around the elbow joint. This research suggests that racket frame vibration is an unlikely mechanism for tennis elbow and that an accumulation of peak loads from off-centre hits is a more likely cause.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Subject-specific computer simulation model for determining elbow loading in one-handed tennis backhand groundstrokes.

A subject-specific angle-driven computer model of a tennis player, combined with a forward dynamics, equipment-specific computer model of tennis ball–racket impacts, was developed to determine the effect of ball–racket impacts on loading at the elbow for one-handed backhand groundstrokes. Matching subject-specific computer simulations of a typical topspin/slice one-handed backhand groundstroke performed by an elite tennis player were done with root mean square differences between performance and matching simulations of < 0.5°over a 50 ms period starting from ball impact. Simulation results suggest that for similar ball–racket impact conditions, the difference in elbow loading for a topspin and slice one-handed backhand groundstroke is relatively small. In this study, the relatively small differences in elbow loading may be due to comparable angle–time histories at the wrist and elbow joints with the major kinematic differences occurring at the shoulder. Using a subject-specific angle-driven computer model combined with a forward dynamics, equipment-specific computer model of tennis ball–racket impacts allows peak internal loading, net impulse, and shock due to ball–racket impact to be calculated which would not otherwise be possible without impractical invasive techniques. This study provides a basis for further investigation of the factors that may increase elbow loading during tennis strokes

A COMPARISON OF QATARI AND CHINESE CADET TABLE TENNIS PLAYERS: ANALYSIS OF ASIAN CHAMPIONSHIP TEAM COMPETITION

Video analysis was performed during the Asian Cadet Table Tennis Championships to determine playing style and patterns of top and lower ranked nations. China and Qatar were chosen for analysis based on their performance during the tournament (1st/2nd playoff and 7th/8th playoff respectively). Notational analysis techniques were implemented to analyze 3 matches for each nation. Significant (

Development of the Infant Gut Microbiome Predicts Temperament Across the First Year of Life

Perturbations to the gut microbiome are implicated in altered neurodevelopmental trajectories that may shape life span risk for emotion dysregulation and affective disorders. However, the sensitive periods during which the microbiome may influence neurodevelopment remain understudied. We investigated relationships between gut microbiome composition across infancy and temperament at 12 months of age. In 67 infants, we examined if gut microbiome composition assessed at 1–3 weeks, 2, 6, and 12 months of age was associated with temperament at age 12 months. Stool samples were sequenced using the 16S Illumina MiSeq platform. Temperament was assessed using the Infant Behavior Questionnaire-Revised (IBQ-R). Beta diversity at age 1–3 weeks was associated with surgency/extraversion at age 12 months. Bifidobacterium and Lachnospiraceae abundance at 1–3 weeks of age was positively associated with surgency/extraversion at age 12 months. Klebsiella abundance at 1–3 weeks was negatively associated with surgency/extraversion at 12 months. Concurrent composition was associated with negative affectivity at 12 months, including a positive association with Ruminococcus-1 and a negative association with Lactobacillus. Our findings support a relationship between gut microbiome composition and infant temperament. While exploratory due to the small sample size, these results point to early and late infancy as sensitive periods during which the gut microbiome may exert effects on neurodevelopment

KINEMATIC DIFFERENCES BETWEEN ‘ONE-FOOTED’ AND ‘TWO-FOOTED’ YOUNG SOCCER PLAYERS KICKING WITH THE NON-PREFERRED LEG

The purpose of this study was to examine kinematic differences between ‘one-footed’ and ‘two-footed’ players when kicking with the non-preferred leg at a target and with maximal effort. Eighteen highly-trained young soccer players were categorised as one-footed (n=9) and two-footed (n=9) based on results of a kicking test. Motion analysis data showed that two-footed players run-up straighter and have less pelvic rotation at ball-foot impact than one-footed players and the differences are likely to be meaningful (ES differences of 0.89 and 0.99 respectively). Run-up angle and pelvic rotation angle are significantly correlated (P < 0.1). The study found that two-footed players are significantly smaller in stature than one-footed players (P < 0.1). Practical implications for soccer coaches arose from the study

Contact with Caregivers is Associated with Composition of the Infant Gastrointestinal Microbiome in the First 6 Months of Life

Objectives Little is known about how physical contact at birth and early caregiving environments influence the colonization of the infant gastrointestinal microbiome. We investigated how infant contact with caregivers at birth and within the first 2 weeks of life relates to the composition of the gastrointestinal microbiome in a sample of U.S. infants (n = 60). Methods Skin-to-skin and physical contact with caregivers at birth and early caregiving environments were surveyed at 2 weeks postpartum. Stool samples were collected from infants at 2 weeks, 2, 6, and 12 months of age and underwent 16S rRNA sequencing as a proxy for the gastrointestinal microbiome. Associations between early caregiving environments and alpha and beta diversity, and differential abundance of bacteria at the genus level were assessed using PERMANOVA, and negative binomial mixed models in DEseq2. Results Time in physical contact with caregivers explained 10% of variation in beta diversity at 2 weeks\u27 age. The number of caregivers in the first few weeks of life explained 9% of variation in beta diversity at 2 weeks and the number of individuals in physical contact at birth explained 11% of variation in beta diversity at 6 months. Skin-to-skin contact on the day of birth was positively associated with the abundance of eight genera. Infants held for by more individuals had greater abundance of eight genera. Discussion Results reveal a potential mechanism (skin-to-skin and physical contact) by which caregivers influence the infant gastrointestinal microbiome. Our findings contribute to work exploring the social transmission of microbes

Maternal ABO Phenotype as a Predictive Factor for Pregnancy Complications Related to Prematurity

Objective: The ABO blood types are associated with cancers, cardiovascular disease, and Type 2 diabetes in adult males and females. Associations of ABO blood type and adverse pregnancy outcomes have not been extensively studied. The purpose of this study was to investigate the relationship with ABO blood groups and risk of adverse pregnancy outcomes contributing to premature birth.Study design: Data on ABO phenotypes and pregnancy outcomes were collected from the medical records of 1,462 premature infants (22-34 weeks). Adverse pregnancy outcomes that were studied in relation to maternal blood type included gestational hypertension (GHTN), preeclampsia (PREE), chorioamnionitis (CA), preterm premature rupture of membranes (PPROM), and intrauterine growth restriction (IUGR)Results: 1,462 charts of mothers with premature infants (22-34 weeks) were studied measuring the relative risk by using standardized statistical software (SPSS).Our study group had 46 mothers with GHTN, 405 with PREE, 282 with CA, 504 with PPROM, and 94 with IUGR. A+ Caucasian mothers had a 28% increased risk of developing preeclampsia (RR= 1.28 (1.09-1.52); 95% CI= .003). B mothers are ata 46% decreased risk of developing chorioamnionitis versus all other blood groups (RR= 0.54, 95% CI= 0.36-0.81; P= .003). Conversely, O+ Caucasian mothers were 2.53 times more likely to develop chorioamnionitis compared to all other blood types (RR=2.53, 95% CI= 1.09-5.88; P= .031).Conclusions: Maternal ABO phenotype significantly influences the incidence of preeclampsia and chorioamnionitis. Pregnancy is a unique antigen-antibody phenomenon with the fetus serving as an antigen to the mother. We postulate that blood group antigen expression at the endothelial level may influence maternal disease states

An Initial In Vitro Investigation into the Potential Therapeutic Use of SupT1 Cells to Prevent AIDS in HIV-Seropositive Individuals

HIV infection usually leads to a progressive decline in number and functionality of CD4+ T lymphocytes, resulting in AIDS development. In this study, I investigated the strategy of using inoculated SupT1 cells to move infection from HIV-1 X4 strains toward the inoculated cells, which should theoretically prevent infection and depletion of normal CD4+ T cells, preventing the development of AIDS-related pathologies. Interestingly, the persistent in vitro replication in SupT1 cells renders the virus less cytopathic and more sensitive to antibody-mediated neutralization, suggesting that replication of the virus in the inoculated SupT1 cells may have a vaccination effect in the long run. In order to mimic the scenario of a therapy in which SupT1 cells are inoculated in an HIV-seropositive patient, I used infected SupT1/PBMC cocultures and a series of control experiments. Infections were done with equal amounts of the wild type HIV-1 LAI virus. The SupT1 CD4+CD8+ T cell population was distinguished from the PBMC CD4+CD8− T cell population by FACS analysis. The results of this study show that the virus-mediated killing of primary CD4+ T cells in the SupT1/PBMC cocultures was significantly delayed, suggesting that the preferential infection of SupT1 cells can induce the virus to spare primary CD4+ T cells from infection and depletion. The preferential infection of SupT1 cells can be explained by the higher viral tropism for the SupT1 cell line. In conclusion, this study demonstrates that it's possible in an in vitro system to use SupT1 cells to prevent HIV infection of primary CD4+ T cells, suggesting that further exploration of the SupT1 cell line as a cell-based therapy against HIV-1 may prove worthwhile

Statewide Molecular Epidemiology of Mycobacterium tuberculosis Transmission in a Moderate- to Low-Incidence State: Are Contact Investigations Enough?

To assess the circumstances of recent transmission of tuberculosis (TB) (progression to active disease <2 years after infection), we obtained DNA fingerprints for 1,172 (99%) of 1,179 Mycobacterium tuberculosis isolates collected from Maryland TB patients from 1996 to 2000. We also reviewed medical records and interviewed patients with genetically matching M. tuberculosis strains to identify epidemiologic links (cluster investigation). Traditional settings for transmission were defined as households or close relatives and friends; all other settings were considered nontraditional. Of 436 clustered patients, 114 had recently acquired TB. Cluster investigations were significantly more likely than contact investigations to identify patients who recently acquired TB in nontraditional settings (33/42 vs. 23/72, respectively; p<0.001). Transmission from a foreign-born person to a U.S.-born person was rare and occurred mainly in public settings. The time from symptom onset to diagnosis was twice as long for transmitters as for nontransmitters (16.8 vs. 8.5 weeks, respectively; p<0.01). Molecular epidemiologic studies showed that eliminating diagnostic delays can prevent TB transmission in nontraditional settings, which elude contact investigations