The effect of water-based plyometric training on vertical stiffness and athletic performance

© 2018 Sporri et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Since higher vertical stiffness is related to superior athletic performance, training has traditionally been aimed at augmenting this variable to enhance neuromuscular output. However, research has linked elevated stiffness with increased injury risk, therefore, this study examined the effect of a novel training intervention on vertical stiffness and athletic performance. Vertical stiffness, jump performance and athletic performance were assessed in two randomly allocated groups, prior to, and following, an eight-week period. One group was exposed to a training intervention involving aqua-based plyometrics (n = 11) over the 8 weeks while the other acted as a control group (n = 9). The training intervention involved hopping, jumping and bounding in water at a depth of 1.2m whilst control participants performed their normal training. There were no significant changes in vertical stiffness in either group. Countermovement jump height and peak power significantly increased within the aqua plyometric group (p < 0.05). Athletic performance markers improved in the aqua plyometric group as measured using an agility and a 5-bound test exhibiting superior values at the post-test (p < 0.05). The results suggest that an aqua plyometric training program can enhance athletic performance without elevating stiffness. The increase in athletic performance is likely due to a reduction in ground reaction forces created by the buoyancy of the water, causing a shorter amortization phase and a more rapid application of concentric force. The findings from this study can inform exercise professionals and medical staff regarding the ability to enhance neuromuscular performance without elevating vertical stiffness. This has implications for improving athletic performance while concurrently minimising injury risk

Biceps femoris long head morphology in youth competitive alpine skiers is associated with age, biological maturation and traumatic lower extremity injuries

Lower extremity injuries are common in competitive alpine skiers, and the knee and lower leg are often affected. The hamstring muscles, especially the biceps femoris long head (BFlh), can stabilize the knee and the hip and may counteract various adverse loading patterns during typical mechanisms leading to severe lower extremity injuries. The aim of the present study was to describe BFlh morphology in youth competitive alpine skiers in relation to sex, age and biological maturation and to investigate its association with the occurrence of traumatic lower extremity injuries in the upcoming season. 95 youth skiers underwent anthropometric measurements, maturity offset estimations and ultrasound assessment, followed by 12-months prospective injury surveillance. Unpaired t tests showed that the two sexes did not differ in BFlh morphology, including fascicle length (Lf), pennation angle (PA), muscle thickness (MT) and average anatomical cross-sectional area (ACSAavg). In contrast, U16 skiers had longer fascicles than U15 skiers (9.5 ± 1.3 cm vs 8.9 ± 1.3 cm, p < 0.05). Linear regression analyses revealed that maturity offset was associated with Lf (R2 = 0.129, p < 0.001), MT (R2 = 0.244, p < 0.001) and ACSAavg (R2 = 0.065, p = 0.007). No association was found between maturity offset and PA (p = 0.524). According to a binary logistic regression analysis, ACSAavg was significantly associated with the occurrence of traumatic lower extremity injuries (Chi-square = 4.627, p = 0.031, RNagelkerke2 = 0.064, Cohen f = 0.07). The present study showed that BFlh morphology is age- and biological maturation-dependent and that BFlh ACSAavg can be considered a relevant modifiable variable associated with lower extremity injuries in youth competitive alpine skiers

Using distinct molecular signatures of human monocytes and dendritic cells to predict adjuvant activity and pyrogenicity of TLR agonists

We present a systematic study that defines molecular profiles of adjuvanticity and pyrogenicity induced by agonists of human Toll-like receptor molecules in vitro. Using P3CSK4, Lipid A and Poly I:C as model adjuvants we show that all three molecules enhance the expansion of IFNγ+/CD4+ T cells from their naïve precursors following priming with allogeneic DC in vitro. In contrast, co-culture of naive CD4+ T cells with allogeneic monocytes and TLR2/TLR4 agonists only resulted in enhanced T cell proliferation. Distinct APC molecular signatures in response to each TLR agonist underline the dual effect observed on T cell responses. Using protein and gene expression assays, we show that TNF-α and CXCL10 represent DC-restricted molecular signatures of TLR2/TLR4 and TLR3 activation, respectively, in sharp contrast to IL-6 produced by monocytes upon stimulation with P3CSK4 and Lipid A. Furthermore, although all TLR agonists are able to up-regulate proIL-1β specific gene in both cell types, only monocyte activation with Lipid A results in detectable IL-1β release. These molecular profiles, provide a simple screen to select new immune enhancers of human Th1 responses suitable for clinical application

Identification of CD4+ T Cell Epitopes in C. burnetii Antigens Targeted by Antibody Responses

Coxiella burnetii is an obligate intracellular Gram-negative bacterium that causes acute Q fever and chronic infections in humans. A killed, whole cell vaccine is efficacious, but vaccination can result in severe local or systemic adverse reactions. Although T cell responses are considered pivotal for vaccine derived protective immunity, the epitope targets of CD4+ T cell responses in C. burnetii vaccination have not been elucidated. Since mapping CD4+ epitopes in a genome with over 2,000 ORFs is resource intensive, we focused on 7 antigens that were known to be targeted by antibody responses. 117 candidate peptides were selected from these antigens based on bioinformatics predictions of binding to the murine MHC class II molecule H-2 IAb. We screened these peptides for recognition by IFN-γ producing CD4+ T cell in phase I C. burnetii whole cell vaccine (PI-WCV) vaccinated C57BL/6 mice and identified 8 distinct epitopes from four different proteins. The identified epitope targets account for 8% of the total vaccination induced IFN-γ producing CD4+ T cells. Given that less than 0.4% of the antigens contained in C. burnetii were screened, this suggests that prioritizing antigens targeted by antibody responses is an efficient strategy to identify at least a subset of CD4+ targets in large pathogens. Finally, we examined the nature of linkage between CD4+ T cell and antibody responses in PI-WCV vaccinated mice. We found a surprisingly non-uniform pattern in the help provided by epitope specific CD4+ T cells for antibody production, which can be specific for the epitope source antigen as well as non-specific. This suggests that a complete map of CD4+ response targets in PI-WCV vaccinated mice will likely include antigens against which no antibody responses are made

Differential Effect of TLR2 and TLR4 on the Immune Response after Immunization with a Vaccine against Neisseria meningitidis or Bordetella pertussis

Neisseria meningitidis and Bordetella pertussis are Gram-negative bacterial pathogens that can cause serious diseases in humans. N. meningitidis outer membrane vesicle (OMV) vaccines and whole cell pertussis vaccines have been successfully used in humans to control infections with these pathogens. The mechanisms behind their effectiveness are poorly defined. Here we investigated the role of Toll-like receptor (TLR) 2 and TLR4 in the induction of immune responses in mice after immunization with these vaccines. Innate and adaptive immune responses were compared between wild type mice and mice deficient in TLR2, TLR4, or TRIF. TRIF-deficient and TLR4-deficient mice showed impaired immunity after immunization. In contrast, immune responses were not lower in TLR2−/− mice but tended even to be higher after immunization. Together our data demonstrate that TLR4 activation contributes to the immunogenicity of the N. meningitidis OMV vaccine and the whole cell pertussis vaccine, but that TLR2 activation is not required

Mechanisms of NK Cell-Macrophage Bacillus anthracis Crosstalk: A Balance between Stimulation by Spores and Differential Disruption by Toxins

NK cells are important immune effectors for preventing microbial invasion and dissemination, through natural cytotoxicity and cytokine secretion. Bacillus anthracis spores can efficiently drive IFN-γ production by NK cells. The present study provides insights into the mechanisms of cytokine and cellular signaling that underlie the process of NK-cell activation by B. anthracis and the bacterial strategies to subvert and evade this response. Infection with non-toxigenic encapsulated B. anthracis induced recruitment of NK cells and macrophages into the mouse draining lymph node. Production of edema (ET) or lethal (LT) toxin during infection impaired this cellular recruitment. NK cell depletion led to accelerated systemic bacterial dissemination. IFN-γ production by NK cells in response to B. anthracis spores was: i) contact-dependent through RAE-1-NKG2D interaction with macrophages; ii) IL-12, IL-18, and IL-15-dependent, where IL-12 played a key role and regulated both NK cell and macrophage activation; and iii) required IL-18 for only an initial short time window. B. anthracis toxins subverted both NK cell essential functions. ET and LT disrupted IFN-γ production through different mechanisms. LT acted both on macrophages and NK cells, whereas ET mainly affected macrophages and did not alter NK cell capacity of IFN-γ secretion. In contrast, ET and LT inhibited the natural cytotoxicity function of NK cells, both in vitro and in vivo. The subverting action of ET thus led to dissociation in NK cell function and blocked natural cytotoxicity without affecting IFN-γ secretion. The high efficiency of this process stresses the impact that this toxin may exert in anthrax pathogenesis, and highlights a potential usefulness for controlling excessive cytotoxic responses in immunopathological diseases. Our findings therefore exemplify the delicate balance between bacterial stimulation and evasion strategies. This highlights the potential implication of the crosstalk between host innate defences and B. anthracis in initial anthrax control mechanisms

Generation in vivo of peptide-specific cytotoxic T cells and presence of regulatory T cells during vaccination with hTERT (class I and II) peptide-pulsed DCs

Optimal techniques for DC generation for immunotherapy in cancer are yet to be established. Study aims were to evaluate: (i) DC activation/maturation milieu (TNF-α +/- IFN-α) and its effects on CD8+ hTERT-specific T cell responses to class I epitopes (p540 or p865), (ii) CD8+ hTERT-specific T cell responses elicited by vaccination with class I alone or both class I and II epitope (p766 and p672)-pulsed DCs, prepared without IFN-α, (iii) association between circulating T regulatory cells (Tregs) and clinical responses

Vertical stiffness : relationship with soft-tissue injuries in Australian footballers and investigation of a novel modification technique

University of Technology Sydney. Faculty of Health.NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. The hardcopy may be available for consultation at the UTS Library.NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. ----- Injuries are of widespread concern to professional sporting organisations, sport and recreation groups and individual athletes. In particular, injuries have a profoundly negative effect on many aspects of human physiology and implications range from long-term health issues to financial ramifications in elite team sport. Injuries in running-based team sports, including the Australian Football League, have been scrutinised in the past 20 years, with previous research examining certain risk factors associated with injuries, however, many are considered as non-modifiable. Injury prevention strategies are required to identify, modify and minimise the impact of modifiable and intrinsic risk factors. One such modifiable risk factor that has recently received attention due to its reported links to soft-tissue non-contact injuries is vertical stiffness. The aim of this project was to conduct a series of studies investigating the role of stiffness in injuries in Australian footballers, and to examine a novel method of modifying this neuromechanical variable. Study one determined the acute seasonal changes of stiffness in Australian footballers and examined the relationship with non-contact, in-season, soft-tissue injuries. No significant differences were recorded for bilateral vertical stiffness between the injured and non-injured groups throughout the season. When assessing vertical stiffness asymmetry, the injured group displayed a significantly higher value than the non-injured group at the end of the pre-season. This information can be used by medical and conditioning staff as an injury prevention method and player screening protocol. Furthermore, given these results, intervention strategies to modify stiffness require investigation. The role of stiffness in athletic performance has been documented, and to date, it appears that a stiffer muscle-tendon complex is advantageous to athletic performance, however, stiffness that is too high or too low may be linked to an elevated risk of soft-tissue injury. Whilst training interventions to increase stiffness have been investigated, few have focused on reducing stiffness in the lower-body. Hence, study two examined the efficacy of a novel training intervention, aqua plyometrics, to reduce stiffness without negatively affecting athletic performance. There were no significant changes to stiffness recorded, however, athletic abilities and jump performance significantly increased. Improvements to athletic performance in the absence of changes to stiffness will be of particular interest to exercise practitioners, conditioning coaches and medical staff for assessing, monitoring and managing stiffness in Australian football players and other team sport athletes

Assessment of 5 Hz and 10 Hz GPS units for measuring athlete movement demands

This study aimed to assess the validity and inter-unit reliability of 5 Hz and 10 Hz global positioning system (GPS) units and determine the differences between these units as measures of team sport athlete movement demands. A team sport simulation circuit was completed by eight trained male participants to examine the following movement demands: total distance covered (TD), peak speed and the distance covered, time spent and number of efforts performed at different speed zones. Additionally, repeated high intensity efforts, player load and exertion index were investigated. The analysis using paired samples t-test and percentage typical error of measurement (%TEM) revealed that 10 Hz GPS units provided a valid and reliable measure of TD (p>0.05, %TEM=1.3). The 5 Hz units also displayed reliable measures of TD (%TEM=1.2). It was apparent that as the speed of movement increased, the level of GPS error increased for both 5 Hz and 10 Hz units (%TEM: 0- 14%). The updates in GPS firmware and increased sampling rates have further improved the validity and inter-unit reliability of GPS. Consequently, practitioners can more confidently rely on the data obtained from current GPS units during training and matches, however, caution is required when measuring high speed movements