Which is superior in improving the performance of short-distance sprints starting in a lateral direction, forward- or false-step technique?

When athletes in ball game sports start sprinting in the forward direction from a parallel stance, they commonly use the forward- and false-step techniques. Previous studies focusing on the performance of short-distance sprints starting in the forward direction have demonstrated that the false-step technique is superior to the forward-step technique. Although athletes start sprinting in various directions based on relevant visual cues, such as movements of the ball or the opponent players, the effectiveness of each technique for starting a sprint in the other direction is still unclear. This study aims to clarify the effectiveness of each technique in improving the performance of the short-distance sprint starting in the lateral direction. In this study, 20 athletes started 5-m sprints in the right direction from the parallel stance using either of these two techniques. Kinematic and kinetic analyses were performed from movement initiation to the flight phase after the second step in the sprinting direction. The average and terminal sprint velocities throughout this range were larger in the forward-step technique (p = 0.039 and 0.003), indicating its superiority in traveling and accelerating performance. The change of sprint velocity in the initial phase until the contact of the first step in the sprinting direction was smaller in the false-step technique (p < 0.001), although this phase included "false step." These results indicate that the forward-step technique is superior in sprints starting in the lateral direction, and the advantage results from greater acceleration in the initial phase immediately after movement initiation. These findings imply the sprint-directional dependence of the relative superiority of these techniques, providing an impetus for athletes and coaches to consider and establish the effective training and coaching methods of short-distance sprints.

Step techniques for backward and sideward sprint starts used by high-level male soccer players.

From standing in a parallel stance, two common techniques for sprint starts are forward and false steps. In the forward step technique, athletes take a first step in the sprinting direction; in the false step technique, the first step is in the opposite direction to the sprinting direction. Although the false step technique, including a redundant step, has generally been considered as an inferior technique, athletes habitually use it to start sprinting in a forward direction. The present study aimed to clarify which step technique is habitually used by high-level male soccer players when they start sprinting in a backward or a sideward direction. From a stationary standing position, 15 male soccer players were instructed to sprint backward and rightward three times each, and the step techniques used to start sprinting were recorded. In the backward sprint start trials, 2 trials were done using the forward step technique and 43 using the false step technique. In the rightward sprint start trials, 27 trials were done using the forward step technique and 18 using the false step technique. While the false step technique was used significantly more than the forward step technique in the backward sprint start trials (p < 0.001), no significant difference was found between the use of either technique in the rightward sprint start trials (p = 0.18). The results demonstrate that high-level male soccer players habitually use the false step technique in a backward sprint start and use both techniques with similar frequencies in a sideward sprint start.

Compressive mechanical stress enhances susceptibility to interleukin-1 by increasing interleukin-1 receptor expression in 3D-cultured ATDC5 cells.

BACKGROUND: Mechanical overload applied on the articular cartilage may play an important role in the pathogenesis of osteoarthritis. However, the mechanism of chondrocyte mechanotransduction is not fully understood. The purpose of this study was to assess the effects of compressive mechanical stress on interleukin-1 receptor (IL-1R) and matrix-degrading enzyme expression by three-dimensional (3D) cultured ATDC5 cells. In addition, the implications of transient receptor potential vanilloid 4 (TRPV4) channel regulation in promoting effects of compressive mechanical loading were elucidated. METHODS: ATDC5 cells were cultured in alginate beads with the growth medium containing insulin-transferrin-selenium and BMP-2 for 6 days. The cultured cell pellet was seeded in collagen scaffolds to produce 3D-cultured constructs. Cyclic compressive loading was applied on the 3D-cultured constructs at 0.5 Hz for 3 h. The mRNA expressions of a disintegrin and metalloproteinases with thrombospondin motifs 4 (ADAMTS4) and IL-1R were determined with or without compressive loading, and effects of TRPV4 agonist/antagonist on mRNA expressions were examined. Immunoreactivities of reactive oxygen species (ROS), TRPV4 and IL-1R were assessed in 3D-cultured ATDC5 cells. RESULTS: In 3D-cultured ATDC5 cells, ROS was induced by cyclic compressive loading stress. The mRNA expression levels of ADAMTS4 and IL-1R were increased by cyclic compressive loading, which was mostly prevented by pyrollidine dithiocarbamate. Small amounts of IL-1ß upregulated ADAMTS4 and IL-1R mRNA expressions only when combined with compressive loading. TRPV4 agonist suppressed ADAMTS4 and IL-1R mRNA levels induced by the compressive loading, whereas TRPV4 antagonist enhanced these levels. Immunoreactivities to TRPV4 and IL-1R significantly increased in constructs with cyclic compressive loading. CONCLUSION: Cyclic compressive loading induced mRNA expressions of ADAMTS4 and IL-1R through reactive oxygen species. TRPV4 regulated these mRNA expressions, but excessive compressive loading may impair TRPV4 regulation. These findings suggested that TRPV4 regulates the expression level of IL-1R and subsequent IL-1 signaling induced by cyclic compressive loading and participates in cartilage homeostasis.

Overexpression of Interleukin-1α Suppresses Liver Metastasis of Lymphoma: Implications for Antitumor Effects of CD8+ T-cells.

Interleukin (IL)-1 plays a key role in carcinogenesis, tumor progression, and metastasis. Although IL-1 may enhance the expansion of CD8+ T-cells, the pathological contribution of IL-1-activated CD8+ T-cells to tumor metastasis remains unclear. This study used a liver metastasis model of the EL4 T-cell lymphoma cells transplanted into human IL (hIL)-1α conditional transgenic (hIL-1α cTg) mice. Overproduction of hIL-1α suppressed both macroscopic and histological liver metastasis of EL4 T-cell lymphoma. The hIL-1α-induced inflammatory state increased the number of CD8+ T-cells both within and around metastatic tumors. Moreover, larger numbers of CD8+ T-cells showed greater infiltration of liver blood vessels in hIL-1α cTg mice than in control wild-type mice. Terminal deoxynucleotidyl transferase dUTP nick-end labeling staining of liver tissue from hIL-1α cTg mice indicated increased apoptosis of cells in the tumor. Localization of apoptosis cells resembled that of CD8+ T-cells. In addition, cytotoxicity assay showed that CD8+ T-cell counts from tumor-bearing hIL-1α cTg mice correlated with cytotoxicity against EL4. In summary, IL-1α suppresses lymphoma metastasis, and IL-1α-activated CD8+ T-cells may play important roles in inhibiting both tumor metastasis and metastatic tumor growth.

Phospholipid polymer electrodeposited on titanium inhibits platelet adhesion.

To develop metallic materials with thromboresistance, a block-type copolymer (PMbA) was immobilized onto a titanium surface with electrodeposition. The polymer was composed of a poly(2-(methacryloyloxy)ethyl phosphorylcholine (MPC)) segment and a poly(2-aminoethylmethacrylate) segment, which was designed to electronically adsorb to the surface oxide layer on the titanium surface. We confirmed that the polymer was synthesized as expected by nuclear magnetic resonance and gel permeation chromatography. In a 0.26 mmol L(-1) PMbA solution adjusted to pH 11, -3.0 V (vs. an Ag/AgCl electrode) was applied to a titanium substrate for 300 s. The immobilization of PMbA on the titanium was confirmed with X-ray photoelectron spectroscopy and an atomic force microscope. The water contact angle and amount of adsorbed protein on the PMbA-modified surface were decreased. Thrombus formation was not observed all over the surface even when the surface was contacted with human blood without an anticoagulant. Therefore, PMbA covered the surface with even density and poly(MPC) segments in PMbA inhibited platelet adsorption. Electrodeposition with PMbA improves the blood compatibility of a titanium substrate in a simple process.