This study examined the short-term training effects of two volumes of a dynamic warm up performed 4 days per week over a 3 1/2-week period. A total of 25 Division III wrestlers volunteered for the study. Three participants either dropped out or were unable to attend post-testing, resulting in 22 total participants completing the study. Groups were divided into control, low volume, and high volume groups. All participants completed pre and poststudy performance tests including the standing long jump, proagility, start-stop-cut, and 30- meter sprint. The low and high volume training groups each performed the same dynamic warm up prior to each pre-season captain's practice. The control group did not participate in an organized warm up. The low volume group performed one set of each warm up exercise, and the high volume group performing two sets of each warm up exercise. Data analysis indicated significant increases in performance for the standing long jump (p = .011) and start-stop-cut (p = .000) measures among the entire sample population. However, there was no significant difference between the groups in these measures. No significant results were found either for the sample as a whole or between groups for the proagility and 30-meter measures. The increased performance of all groups, including the control group, fails to provide evidence for the effectiveness of training with either warm up volume. Further research is needed to address limitations of this study to determine effectiveness of various warm up volumes.

Suchomel, TJ, Bailey, CA, Sole, CJ, Grazer, JL, and Beckham, GK. Using reactive strength index-modified as an explosive performance measurement tool in Division I athletes. J Strength Cond Res 29(4): 899-904, 2015 - The purposes of this study included examining the reliability of reactive strength index-modified (RSImod), the relationships between RSImod and force-time variables, and the differences in RSImod between male and female collegiate athletes. One hundred six Division I collegiate athletes performed unloaded and loaded countermovement jumps (CMJs). Intraclass correlation coefficients and typical error expressed as a coefficient of variation were used to establish the relative and absolute reliability of RSImod, respectively. Pearson zero-order product-moment correlation coefficients were used to examine the relationships between RSImod and rate of force development, peak force (PF), and peak power (PP) during unloaded and loaded jumping conditions. Finally, independent samples t-tests were used to examine the sex differences in RSImod between male and female athletes. Intraclass correlation coefficient values for RSImod ranged from 0.96 to 0.98, and typical error values ranged from 7.5 to 9.3% during all jumping conditions. Statistically significant correlations existed between RSImod and all force-time variables examined for male and female athletes during both jumping conditions (p ≤ 0.05). Statistically significant differences in RSImod existed between male and female athletes during both unloaded and loaded CMJs (p < 0.001). Reactive strength index-modified seems to be a reliable performance measurement in male and female athletes. Reactive strength index-modified may be described and used as a measure of explosiveness. Stronger relationships between RSImod, PF, and PP existed in female athletes as compared with that in male athletes; however, further evidence investigating these relationships is needed before conclusive statements can be made. Male athletes produced greater RSImod values as compared with that produced by female athletes.

The purpose of this study was to examine the differences in reactive strength index-modified (RSImod), jump height (JH), and time to takeoff (TTT) between 6 U.S. collegiate sport teams. One hundred six male and female Division I collegiate athletes performed unloaded (<1 kg) and loaded (20 kg) countermovement jumps as part of an ongoing athlete monitoring program. Reactive strength index-modified, JH, and TTT values for each team were compared using 1-way analysis of variance. Statistically significant differences in RSImod (p < 0.001), JH (p < 0.001), and TTT (p 0.003) existed between teams during the unloaded jumping condition. Similarly, statistically significant differences in RSImod (p < 0.001), JH (p < 0.001), and TTT (p 0.028) existed between teams during the loaded jumping condition. Men's soccer and baseball produced the greatest RSImod values during both the unloaded and loaded jumping conditions followed by women's volleyball, men's tennis, women's soccer, and women's tennis. The greatest JH during unloaded and loaded jumping conditions was produced by men's baseball followed by men's soccer, women's volleyball, men's tennis, women's soccer, and women's tennis. Men's soccer produced shorter TTT compared with men's baseball (12.7%) and women's soccer (13.3%) during the unloaded and loaded jumping conditions, respectively. Collegiate sport teams exhibit varying reactive strength characteristics during unloaded and loaded jumping conditions. Understanding the differences in RSImod between sports may help direct the creation of training and monitoring programs more effectively for various sports.

Bakgrund: Förkortad hamstringmuskulatur är vanligt bland fysiskt aktiva. Inadekvat hamstringmuskellängd och ökad styvhet i hamstringsmuskulatur är möjliga orsaker till skador i hamstring. Den senaste tiden har det blivit allt vanligare med användning av foamroller till syfte att behandla dessa förkortningar och styvhet.  Syfte: Syftet med denna studie är undersöka om användning av foamroller har någon direkt påverkan på töjbarheten och smärttolerans i hamstringsmuskulatur efter ett behandlingstillfälle. Metod: En experimentell studie utfördes där tio friska fysiskt aktiva män (ålder 25,4 ± 3 år, längd 183 ± 9,5 cm, vikt 78,5 ± 7,2 kg) med självrapporterad nedsatt rörlighet baksida lår rekryterades och genomgick två kortare behandlingar (3 x 30 sekunder), med foamroller och statisk stretch på deras dominanta ben (det ben dom sparkar boll med), vid två separata tillfällen. Mätningar av passiv rörlighet i knäled, styvhet i hamstringmuskulatur och smärttolerans på biceps femoris mest ömmande punkt utfördes före och direkt efter varje testtillfälle. Data sammanställdes och analyserades i IBM SPSS för skillnader före och efter gällande förändringar på rörlighet, styvhet och smärttolerans. Resultat: Små skillnader kunde observeras mellan behandlingarna.  Vid statisk stretch noterades en viss skillnad i styvhet på -0,76 Nm. I båda behandlingarna noterades en ytterst liten ökning i rörlighet på hamstringsmuskulaturen med större förändring i statisk stretch, +0,1 grader.  Smärttröskeln var lägre efter båda behandlingar, -125,5 kPa efter foamroller respektive -99,3 kPa efter statisk stretch. Dock visade inte resultatet på någon statistiskt signifikant skillnad i påverkan av passiv ledrörlighet, uppmät styvhet i hamstring eller smärttröskel.   Konklussion: Studien var liten och undersökte endast korttidseffekter, men resultatet talar för att det inte finns någon reell påverkan på biceps femoris styvhet eller smärttolerans med användning av foamroller. / Nej

No description available.

Controlled deformation. Under with conditions can the iron deformation process be affected? This work is focused on expanding steel profiles. Using various tests, I will confront the visual results with the technical possibilities of the material. Attempting to find a boundary that is still permissible in terms of maximum steel loading just before the material starts to fail. The resulting installation should show the enormous forces needed to distort the material, where the viewer will be directly confront with the process.

京都大学 / 0048 / 新制・課程博士 / 博士(人間健康科学) / 甲第18200号 / 人健博第17号 / 新制||人健||2(附属図書館) / 31058 / 京都大学大学院医学研究科人間健康科学系専攻 / (主査)教授 黒木 裕士, 教授 三谷 章, 教授 杉本 直三 / 学位規則第4条第1項該当 / Doctor of Human Health Sciences / Kyoto University / DFAM

No description available.

No description available.

Stretch activation (FSA) is the delayed increase in fiber specific tension (force per cross-sectional area) following a rapid stretch and can improve muscle performance during repetitive cyclical contractions. Historically considered minimal in skeletal muscle, our recent work showed the ratio ofstretch- to calcium-activated specific tension (FSA/F0) increased from 10 to 40% with greater inorganic phosphate (Pi) levels in soleus muscle fibers (Straight et al., 2019). Given Pi increases with muscle fatigue, we hypothesize that FSA helps maintain force generation during fatigue. To test this, FSA, induced by a stretch of 0.5% fiber length, was examined during Active (pCa 4.5 (pCa = -log([Ca2+]), pH 7.0, Pi 5 mM), High Ca2+ Fatigue (pCa 4.5, pH 6.2, Pi 30 mM) and Low Ca2+ Fatigue (pCa 5.1, pH 6.2, Pi 30 mM) in fibers expressing myosin heavy chain (MHC) I, IIA, IIX and IIB isoforms from soleus and extensor digitorum longus muscles of C57BL/6NJ mice. F0 of all MHC isoforms decreased from Active to High Ca2+ Fatigue to Low Ca2+ Fatigue, as expected. In MHC IIX and IIB fibers, FSA occurred under all conditions and FSA/F0 increased from Active (17-20%) to High Ca2+ Fatigue (32-35%) to Low Ca2+ Fatigue (42-44%). In MHC IIA fibers, FSA/F0 increased similarly to MHC IIX and IIB fibers from Active (14%) to High Ca2+ Fatigue (32%) but stayed elevated under Low Ca2+ Fatigue (35%). For MHC I fibers, no discernable FSA was apparent in either High – or Low Ca2+ Fatigue, leaving an FSA/F0 value in Active only ( 4%). These results show that FSA is a significant modulator of specific tension production under fatiguing conditions in fast-contracting muscle fibers. This mechanism could play an important physiological role during cyclical contractions, when the antagonistic muscle rapidly stretches the agonist muscle, by reducing the effect of fatigue on specific tension production.