Kinetic and Kinematic Properties of D-I Male Sprinters

The purpose of the study was to explore and determine kinetic and kinematic variables that related to D-I male sprinters maximal running velocity performance. The current study was separated into 3 individual chapters: 1.) Kinematic analysis magnitude of acceleration for braking and propulsion phases during foot contact phase at maximal speed sprinting; 2.) Using kinetic isometric mid-thigh pull variables to predict D-I male sprinters’ 60m performance; 3.) Relationship of whole and lower body angular momentum cancellation during terminal swing phase to sprint performance. Methods: for sprint measurement all the athletes were participated 2 trials of 100% effort running through 60 meters. The sprint time was measured by an electronic timing gate system. The electronic timing gate system was placed at every 10 meter intervals from the start line for 60 m. Six cameras were placed between 50 m and 60 m for kinematic data collection and analysis. Volume captured by the cameras is 7.5 m long, 1.2 m wide, and 1.95 m high. Reflective markers were attached on the body landmarks based on Vicon Nexus full body plugin model. The strength assessments were performed in a customized power rack, and kinetic values were collected via a dual force plate setup (2 separate 91 cm x 45.5 cm force plates, Roughdeck HP, Rice Lake, WI). The position for each isometric pull was established before each trial using goniometry, with each bar height corresponding to a 125±5º knee angle and a near-vertical trunk position. Results: current study partially support previous assumption that fast sprinters can minimize braking phase during foot contact phase when they are running maximal velocity. However, those minimizing effects did not impact maximal running velocity performance. Second, the study showed that fast sprinters can produce greater force during a short period of time than slower sprinters. Moreover, a certain trend of statistical significance was observed from the third study that angular momentum cancellation between lower bodies at frontal plane may be related to maximal running velocity performance. Discussion: the current study confirmed that fast sprinters can produce greater force in a short period time. However, the current study did not show statistical significance of angular momenta cancellation and sprint performance. Only a level of trend was observed. Thus, further study should examine sprinters with different training background, especially elite level sprinters is definitely needed

The Validity of Using One Force Platform To Quantify Whole-Body Forces, Velocities, and Power During a Plyometric Push-Up

Background: Previous studies have typically measured velocity and power parameters during the push-up, either using one or two force platforms. The purpose of the study was to compare the force, velocity, and power parameters between the one-force-platform method and the two-force-platform method during plyometric push-ups. Methods: Thirty-four physically active young adults participated in the study to perform the plyometric push-up. For the two-force-platform calculation method, the forces applied to the feet and hands were both measured. For the one-force-platform calculation method, the forces applied to the feet were assumed to be constant, while the forces applied to hands were measured by one force platform. Whole-body linear velocities were calculated based on the impulse and momentum theorem. Whole-body power was calculated as the product of the whole-body forces and velocities. Results: The one-force-platform method overestimated the whole-body velocities and power compared with the two-force-platform method (1.39 ± 0.37 m/s vs. 0.90 ± 0.23 m/s, Cohen’s d = 1.59, p \u3c 0.05; 1.63 ± 0.47 W/body weight vs. 1.03 ± 0.29 W/body weight, Cohen’s d = 1.49, p \u3c 0.05). These differences were caused by the decreased forces applied to the feet compared to the initial value throughout most of the push-up phase. Large to perfect correlations (r = 0.55 – 0.99) were found for most variables between the two-force-platform and one-force-platform methods. Previous findings of push-up velocities and power using the two-force-platform and one-force-platform methods should be compared with caution. While the two-force-platform method is recommended, linear regression equations may be used to predict velocities and power parameters obtained from one force platform. Conclusions: For those professionals who need to accurately quantify kinetic variables during the plyometric push-up, the two-force-platform method should be considered

USING KINETIC ISOMETRIC MID-THIGH PULL VARIABLES TO PREDICT D-I MALE SPRINTERS’ 60M PERFORMANCE

The purpose of the study was to determine the relationship of isometric mid-thigh pull kinetic variables including: peak force (PF), instantaneous force at 50, 90, 200 and 250 milliseconds (F@50, 90, 200 and 250 ms) rate of force development (RFD@ 50, 90, 200 and 250 ms) and impulse at 50, 90, 200, and 250 ms (IP @ 50, 90, 200 and 250 ms) to college male sprinters’ 60 m running performance. Eleven NCAA Division I male sprinters participated in the study that included two testing sessions. The first session included sprint testing and the second session included isometric mid-thigh pull strength assessment. The results from current study indicated that explosive force production variables (F@ 50 ms, RFD @ 50 and 90 ms, IP @ 90 and 200 ms) showed strong correlations with 60 m running time and maximal running velocity; while the MPF was not related to sprint variables

Principal Component Regression Analysis of Nutrition Factors and Physical Activities with Diabetes

The associations of nutrition factors and physical activities with adult diabetes are inconsistent; while most of these factors are inter correlated. The aims of this study are to overcome the disturbance of the multicollinearity of the risk factors and examine the associations of these factors with diabetes using the principal component analysis (PCA) and regression analysis with principal component scores (PCS). Totally, 659 adults with diabetes and 2827 non-diabetic were selected from the 2012 Health Information National Trends Survey (HINTS 4, Cycle 2). PCA was utilized to deal with multicollinearity of the risk factors. Weighted univariate and multiple logistic regression analyses were used to estimate the associations of potential factors and PCS with diabetes. The odds ratios (ORs) with 95% confidence intervals (CIs) were estimated. The first 3 PCs for nutrition factors and physical activities could explain 70% variances. The first principal component (PC1) is a measure of nutrition factors (fruit and vegetables consumption), PC2 is a measure for physical activities (moderate exercise and strength training), and PC3 is about calorie information use and soda use. Weighted multiple logistic regression showed that African Americans, middle aged adults (45-64 years), elderly (65+), never married, and with lower education were associated with increased odds of diabetes. After adjusting for others factors, the PC1 showed marginal association with diabetes (OR=0.84, 95% CI=0.70-1.01); while PC2 and PC3 revealed significant associations with diabetes (OR=0.73, 95% CI=0.61-0.86 and OR=0.85, 95% CI=0.74-0.99, respectively). In conclusion, PCA can be used to reduce the indicators in complex survey data. The first 3 PCs of nutrition factors and physical activities were associated with diabetes. Promotion of health food and physical activities should be encouraged to help decrease the prevalence of diabetes

Generalized Linear Mixed Model Analysis of Urban-Rural Differences in Social and Behavioral Factors for Colorectal Cancer Screening

Objective: Screening for colorectal cancer (CRC) can reduce disease incidence, morbidity, and mortality. However, few studies have investigated the urban-rural differences in social and behavioral factors influencing CRC screening. The objective of the study was to investigate the potential factors across urban-rural groups on the usage of CRC screening. Methods: A total of 38,505 adults (aged ≥40 years) were selected from the 2009 California Health Interview Survey (CHIS) data - the latest CHIS data on CRC screening. The weighted generalized linear mixed-model (WGLIMM) was used to deal with this hierarchical structure data. Weighted simple and multiple mixed logistic regression analyses in SAS ver. 9.4 were used to obtain the odds ratios (ORs) and their 95% confidence intervals (CIs). Results: The overall prevalence of CRC screening was 48.1% while the prevalence in four residence groups - urban, second city, suburban, and town/rural, were 45.8%, 46.9%, 53.7% and 50.1%, respectively. The results of WGLIMM analysis showed that there was residence effect (p\u3c0.0001) and residence groups had significant interactions with gender, age group, education level, and employment status (p\u3c0.05). Multiple logistic regression analysis revealed that age, race, marital status, education level, employment stats, binge drinking, and smoking status were associated with CRC screening (p\u3c0.05). Stratified by residence regions, age and poverty level showed associations with CRC screening in all four residence groups. Education level was positively associated with CRC screening in second city and suburban. Infrequent binge drinking was associated with CRC screening in urban and suburban; while current smoking was a protective factor in urban and town/rural groups. Conclusions: Mixed models are useful to deal with the clustered survey data. Social factors and behavioral factors (binge drinking and smoking) were associated with CRC screening and the associations were affected by living areas such as urban and rural regions

The TLR9 ligand, CpG-ODN, Induces Protection Against Cerebral Ischemia/Reperfusion Injury via Activation of pi3k/Akt Signaling.

Toll-like receptors (TLRs) have been shown to be involved in cerebral ischemia/reperfusion (I/R) injury. TLR9 is located in intracellular compartments and recognizes CpG-DNA. This study examined the effect of CpG-ODN on cerebral I/R injury. C57BL/6 mice were treated with CpG-ODN by i.p. injection 1 hour before the mice were subjected to cerebral ischemia (60 minutes) followed by reperfusion (24 hours). Scrambled-ODN served as control-ODN. Untreated mice, subjected to cerebral I/R, served as I/R control. The effect of inhibitory CpG-ODN (iCpG-ODN) on cerebral I/R injury was also examined. In addition, we examined the therapeutic effect of CpG-ODN on cerebral I/R injury by administration of CpG-ODN 15 minutes after cerebral ischemia. CpG-ODN administration significantly decreased cerebral I/R-induced infarct volume by 69.7% (6.4±1.80% vs 21.0±2.85%, P\u3c0.05), improved neurological scores, and increased survival rate, when compared with the untreated I/R group. Therapeutic administration of CpG-ODN also significantly reduced infarct volume by 44.7% (12.6±2.03% vs 22.8±2.54%, P\u3c0.05) compared with untreated I/R mice. Neither control-ODN, nor iCpG-ODN altered I/R-induced cerebral injury or neurological deficits. Nissl staining showed that CpG-ODN treatment preserved neuronal morphology in the ischemic hippocampus. Immunoblot showed that CpG-ODN administration increased Bcl-2 levels by 41% and attenuated I/R-increased levels of Bax and caspase-3 activity in ischemic brain tissues. Importantly, CpG-ODN treatment induced Akt and GSK-3β phosphorylation in brain tissue and cultured microglial cells. PI3K inhibition with LY294002 abolished CpG-ODN-induced protection. CpG-ODN significantly reduces cerebral I/R injury via a PI3K/Akt-dependent mechanism. Our data also indicate that CpG-ODN may be useful in the therapy of cerebral I/R injury

Predicting Countermovement Jump Heights By Time Domain, Frequency Domain, and Machine Learning Algorithms

© 2017 IEEE. In this paper, we introduce an experiment evaluating performance of football players in countermovement jumps (CMJs). Three methods including time domain, frequency domain, and machine learning algorithms are proposed for performance evaluation. Correlation coefficients and p-values are given for time domain and frequency domain methods, and prediction errors are given for different machine learning algorithms

Analyses of Countermovement Jump Performance in Time and Frequency Domains

This study aimed to analyze counter-movement jump (CMJ) performance in time and frequency domains. Fortyfour Division I American football players participated in the study. Kinetic variables were collected from both dominant and non-dominant legs using two force plates. Normalized peak power, normalized net impulse, and normalized peak force significantly correlated with jump height (r =.960, r =.998, r =.725, respectively with p \u3c.05). The mean frequency component was significantly correlated with CMJ performance (r =.355 with p \u3c.05). The reliability of the frequency variables was higher than the time domain variables. Frequency domain variables showed weaker correlations with jump height compared with time domain variables. Frequency domain analysis provides frequency components, which represent the rate of energy transmission from the eccentric phase to the end of the push-off phase. Frequency component information may provide additional information for the analyses of CMJ performance for athletes

Effect of External Loading on Force and Power Production During Plyometric Push-Ups

One common exercise to train upper-body strength and power is the push-up. Training at the loads that would produce the greatest power is an effective way to increase peak power. The purpose of the current study was to quantify the changes in peak force, peak power, and peak velocity among a modified plyometric push-up and plyometric push-ups with or without external loading in physically active young adults. Eighteen male and 17 female participants completed 4 push-ups: (a) modified plyometric push-up on the knees, (b) plyometric push-up without external loading, (c) plyometric push-up with an external load of 5% of body weight, and (d) plyometric push-up with an external load of 10% of body weight. Two force platforms were set up to collect vertical ground reaction forces at the hands and feet. The modified plyometric push-up demonstrated the lowest force, power, and velocity (5.4≥ Cohen\u27s dz ≥1.2). Peak force and force at peak velocity increased (3.8≥ Cohen\u27s dz ≥0.3) and peak velocity and velocity at peak power decreased (1.4≥ Cohen\u27s dz ≥0.8) for the push-up without external loading compared with the 2 push-ups with external loading. No significant differences were observed for peak power among the push-ups with or without external loading (0.4≥ Cohen\u27s dz ≥0.1). Although peak power is similar with or without external loading, push-ups without external loading may be more beneficial for a quick movement, and push-ups with external loading may be more beneficial for a greater force production

Aortic Stiffness Increases During Prolonged Sitting Independent of Intermittent Standing Or Prior Exercise

Introduction: Adverse vascular responses can occur during prolonged sitting, including stiffening of the aortic artery which may contribute to cardiovascular disease. Few studies have investigated the impact of intermittent standing and/or prior exercise as strategies to attenuate these potentially deleterious vascular changes. Purpose: To investigate central vascular health responses during prolonged sitting, with and without intermittent standing and/or prior exercise. Methods: Fifteen males aged 18 to 31 years were recruited. Subjects completed a control condition [Sitting Only (SO)], and three randomized strategy conditions [Sitting Plus Standing (SSt), Exercise Plus Sitting (ES), Exercise Plus Sitting Plus Standing (ESSt)]. For all conditions, measurements of carotid–femoral pulse wave velocity (cfPWV) were taken at pre- and post-intervention, and brachial and central blood pressure (BP) at pre-, 1-h, 2-h, and 3-h intervention. Results: cfPWV significantly increased from pre- to post-intervention for all conditions (all p ≤ 0.043), as did brachial mean arterial pressure (MAP) and diastolic BP, and central MAP and diastolic BP for the control condition (all p ≤ 0.022). Brachial and central systolic BP were significantly higher during SO compared to ESSt at 1 h, and compared to ES for central systolic BP (all p ≤ 0.036). Conclusions: Strategies of intermittent standing and/or prior exercise may not prevent aortic stiffening during sitting but may attenuate BP elevations in the brachial and aortic arteries. Future research should investigate causal mechanistic links between sitting and aortic stiffening, and other attenuation strategies