The National Football League Combine: performance differences between drafted and nondrafted players entering the 2004 and 2005 drafts

The purpose of this study was to examine performance differences between drafted and nondrafted athletes (N = 321) during the 2004 and 2005 National Football League (NFL) Combines. We categorized players into one of 3 groups: Skill, Big skill, and Linemen. Skill players (SP) consisted of wide receivers, cornerbacks, free safeties, strong safeties, and running backs. Big skill players (BSP) included fullbacks, linebackers, tight ends, and defensive ends. Linemen (LM) consisted of centers, offensive guards, offensive tackles, and defensive tackles. We analyzed player height and mass, as well as performance on the following combine drills: 40-yard dash, 225-lb bench press test, vertical jump, broad jump, pro-agility shuttle, and the 3-cone drill. Student t-tests compared performance on each of these measures between drafted and nondrafted players. Statistical significance was found between drafted and nondrafted SP for the 40-yard dash (P < 0.001), vertical jump (P = 0.003), pro-agility shuttle (P < 0.001), and 3-cone drill (P < 0.001). Drafted and nondrafted BSP performed differently on the 40-yard dash (P = 0.002) and 3-cone drill (P = 0.005). Finally, drafted LM performed significantly better than nondrafted LM on the 40-yard dash (P = 0.016), 225-lb bench press (P = 0.003), and 3-cone drill (P = 0.005). Certified strength and conditioning specialists will be able to utilize the significant findings to help better prepare athletes as they ready themselves for the NFL Combine.     

Body size and composition of National Football League players

The purpose of this study was to present a profile of body size and composition of National Football League (NFL) players prior to the start of the regular season. Fifty-three members of the Indianapolis Colts professional football team were measured for height, body mass, and percentage body fat using the BOD POD air-displacement plethysmography system during summer camp of the 2003 football season. These data were categorized by position for comparison with previous studies of NFL football players. The relationships observed were as follows (= represents nonsignificant; > represents p < or = 0.05): Height: Offensive Line = Defensive Line = Quarterbacks/Kickers/Punters = Tight Ends > Linebackers > Running Backs = Wide Receivers = Defensive Backs. Body Mass: Offensive Line = Defensive Line > Tight Ends = Linebackers > Running Backs = Quarterbacks/ Kickers/Punters > Wide Receivers = Defensive Backs. Percentage Body Fat: Offensive Line > Defensive Line > Quarterbacks/ Kickers/Punters = Linebackers = Tight Ends > Running Backs = Wide Receivers = Defensive Backs. Comparisons to teams in the 1970s indicate that body mass has increased only for offensive and defensive linemen; however, height and body fat among player positions have not dramatically changed. Furthermore, the body mass index is not an accurate measure or representation of body fat or obesity in NFL players. These data provide a basic template for size profiles and differences among various positions and allow comparisons with other studies for changes in the NFL over the past 3 decades.     

Positional physical characteristics of players drafted into the National Football League

To investigate the positional physical requirements necessary to be drafted into the National Football League (NFL), data from the annual NFL combine over the years 2005-2009 were examined. Only those players invited to the combine and subsequently drafted in the same year (n = 1,136) were included in the study. Data from 8 combine physical performance tests were examined for 15 positions. Combine measures evaluated for the center, cornerback, defensive end, defensive tackle, free safety, fullback, inside linebacker, offensive guard, offensive tackle, outside linebacker, quarterback, running back, strong safety, tight end, and wide receiver positions were the 9.1-, 18.3-, and 36.6-m sprints, the vertical and broad jumps, the 18.3-m shuttle run, the 3-cone drill, and the 102.1-kg bench press for maximum repetitions and, from this, a predicted measure of 1 repetition maximum. A 1-way analysis of variance detected differences in all 9 performance measures (p < 0.01). Post hoc independent t-tests indicated that over most tests many positions exhibited outcomes significantly different from most other positions. Generally, lineman positions performed inferiorly in sprint, jump and change-of-direction ability measures and superiorly in the upper body strength measures. Conversely, defensive back positions were the worst performers in the upper body strength test, and wide receivers and defensive backs were the best performers in all other measures. In general, offensive and defensive positions that commonly compete directly against one another display similar physical characteristics. Any advantages (statistically significant and not) between positions in direct competition were consistently in favor of defensive positions. The results of the present research present position-specific profiles for each of 15 positions. Coaches and practitioners will be able to use the findings of this research to better prepare athletes for entry into the NFL.     

Relationships between the flexed-arm hang and select measures of muscular fitness

The flexed-arm hang (FAH) has been used to assess arm and shoulder girdle strength for 35 years despite little evidence to support its use. The purpose of this study was to determine what muscular fitness component, if any, was related to the FAH. The traditional overgrip chin-above-bar test and 5 different variations were compared with absolute strength (1 repetition maximum [1RM] lat pull down), relative strength (1RM.mass(-1)), and muscle endurance (repetitions to failure at 70% of the 1RM). Sixty college-age women volunteered for the study. Relationships were examined using Pearson Product Moment Correlation. No significant relationship was found between any of the FAH variations and absolute strength or muscle endurance; however, all FAH variations correlated significantly with relative strength (1RM.mass(-1)). The strongest relationship was with the undergrip FAH timed to 90 degrees of elbow extension (r = 0.72). Investigators concluded that the FAH is a test of weight-relative muscular strength and appears unrelated to absolute strength or muscle endurance.     

Relationships between stretch-shortening cycle performance and maximum muscle strength

This study aimed to examine the relationships between muscle power output using the stretch-shortening cycle (SSC) and maximum strength, as measured by the 1 RM (1 repetition maximum) test and the isokinetic dynamometer under elbow flexion. Sixteen trained, young adult males pulled a constant load of 40% MVC (maximum voluntary elbow flexion contraction) by ballistic elbow flexion under the following two preliminary conditions: 1) the static relaxed muscle state (SR condition) and 2) using the SSC (SSC condition). Muscle power was determined from the product of the pulling velocity and load mass by a power measurement instrument with a rotary encoder. The 1 RM bench press (1RM BP) and isokinetic maximum strength under elbow flexion with the Cybex-325 were measured as indicators of dynamic maximum strength. 1) The early power output exerted under the SSC condition showed a significant and high correlation with the 1 RM BP (r = 0.83), but only moderate correlation with the isokinetic muscle strength (r = 0.50-0.67). 2) The contribution of the 1 RM BP to the early muscle contraction velocity exerted under the SSC condition was large. These results suggested that muscle power exerted using the SSC shows a stronger relationship with maximum muscle strength measured by a 1 RM test rather than isokinetic maximum strength.     

Sprinting patterns of National Rugby League competition

The purpose of this study was to investigate the sprinting demands of National Rugby League (NRL) competition and characterize the sprinting patterns of different rugby league playing positions. Thirty-seven elite rugby league players (mean ± SE age: 23.6 ± 0.5 years) underwent global positioning satellite analysis during 104 NRL appearances. The majority (67.5%) of sprint efforts were across distances of <20 m. The most common sprint distance for hit-up forwards was 6-10 m (46.3%). Outside backs had a greater proportion (33.7%) of sprint efforts over distances of ≥21 m. The proportion of sprint efforts over 40 m or greater for hit-up forwards, wide running forwards, adjustables, and outside backs was 5.0, 7.4, 5.0, and 9.7%, respectively. Of the sprints performed, approximately 48.0% involved contact, approximately 58.0% were preceded by forward locomotion (forward walking, jogging, or striding), whereas over 24.0% occurred from a standing start. Hit-up forwards more commonly sprinted from a standing start, or after lateral movement, whereas forward striding activities more commonly preceded sprint efforts for the adjustables and outside backs. The majority of sprint efforts were performed without the ball (78.7 vs. 21.3%). Most sprint efforts (67.5%) were followed by a long recovery (i.e., ≥5 minutes). Outside backs had the greatest proportion (76.1%) of long duration recovery periods and the smallest proportion (1.8%) of short duration recovery periods (i.e., <60 seconds) between sprints. The results of this study demonstrate differences among rugby league playing positions for the nature of sprint efforts and the typical distances covered during these efforts. Furthermore, the activities preceding and the recovery periods after sprint efforts were different among playing positions. These findings suggest that rugby league sprint training should be tailored to meet the individual demands of specific playing positions.     

Relationships between and among selected measures of sweet-taste preference and dietary intake

The extent to which the sensory properties of foods influencedietary practices remains poorly characterized. Hedonic attributesappear to exert the predominant role among sensory factors.Therefore a parametric study to ascertain the relationshipsbetween measures of sweet-taste preferences and selected relevantdietary measures was undertaken. Twenty-five healthy, normalweight adults kept 7-day diet records and provided hedonic responsesto (i) lists of foods on questionnaires, (ii) prepared coffeeand oatmeal samples on category and visual analog scales, and(iii) water and coffee via an adjustment task. Ratings wereobtained under conditions where samples were swallowed versusexpectorated and viewed as ‘normal foods’ versus‘test samples’. Correlations were then sought betweendietary variables and both individual and aggregate profilesof preference measures. Either analytic approach revealed significantassociations with estimates of preferred tastes of the diet,but only taste profiles comprised of several taste preferencemeasures together were significantly related to nutrient intake(i.e. carbohydrate and alcohol calories). This observation,as well as findings obtained from the different testing proceduresand contexts, are considered from a methodologic perspective(i.e. what are the optimal conditions for examining diet–tasterelationships).     

Relationships between National Wetlands Inventory maps and hydrophytic vegetation in Florida

This paper reports a preliminary investigation about National Wetlands Inventory (NWI) maps to see how they might be used in conjunction with other sources of information to provide offsite wetlands regulatory delineation. A geographic information system was used to overlay and compare NWI maps with ground-based tree species composition data from the US Department of Agriculture Forest Service Forest Inventory and Analysis program (FIA). Ninety plots located in the Apalachicola National Forest in northern Florida were used. The NWI mapped 42 of the 90 plots as wetlands. FIA data was used to calculate Prevalence Index (PI) scores. Twenty-four additional plots had PI < 3.0 and thus had hydrophytic vegetation. These plots may also have been wetlands by the Cowardin definition. The hypothesis that wetland identification did not differ between natural-origin versus planted forests was evaluated. NWI classified 61% of natural stands with PI <3.0 as wetlands, whereas 38% of planted stands with PI < 3.0 were mapped as wetlands. There were statistically significant differences (P < 0.05) in the relationships between hydrophytic vegetation and wetland status for plantations and natural-origin stands. FIA data was used to compare the actual frequency of species found in wetlands with the frequency ranges assigned for the NWI Regional Indicators. The observed frequency of occurrence in NWI-mapped wetlands agreed with the Regional Indicator frequency range for 6 of the 18 species. Most species not in agreement were reasonably close to their assigned frequency range, but some differed substantially. While this was a pilot-scale study, we believe that this technique can ultimately yield valuable new information on the tree characteristics of NWI wetlands, especially at larger spatial scales, such as states or regions.     

Relationship between hockey skating speed and selected performance measures

The objective of this study was to determine the relationship between specific performance measures and hockey skating speed. Thirty competitive secondary school and junior hockey players were timed for skating speed. Off-ice measures included a 40-yd (36.9-m) sprint, concentric squat jump, drop jump, 1 repetition maximum leg press, flexibility, and balance ratio (wobble board test). Pearson product moment correlations were used to quantify the relationships between the variables. Electromyographic (EMG) activity of the dominant vastus lateralis and biceps femoris was monitored in 12 of the players while skating, stopping, turning, and performing a change-of-direction drill. Significant correlations (p < 0.005) were found between skating performance and the sprint and balance tests. Further analysis demonstrated significant correlations between balance and players under the age of 19 years (r = -0.65) but not those over 19 years old (r = -0.28). The significant correlations with balance suggested that stability may be associated with skating speed in younger players. The low correlations with drop jumps suggested that short contact time stretch-shortening activities (i.e., low amplitude plyometrics) may not be an important factor. Electromyographic activities illustrated the very high activation levels associated with maximum skating speed.     

Relationship between football playing ability and selected performance measures

The relationships between football playing ability (FPA) and selected anthropometric and performance measures were determined among NCAA Division I-A football players (N = 40). Football playing ability (determined by the average of coaches' rankings) was significantly correlated with vertical jump (VJ) in all groups (offense, defense, and position groups of wide receiver-defensive back, offensive linemen-defensive linemen, and running back-tight end-linebacker). Eleven of 50 correlations (groups by variables), or 22%, were important for FPA. Five of the 11 relationships were related to VJ. Forward stepwise regression equations for each group explained over half of the criterion variable, FPA, as indicated by the R(2) values for each model. Vertical jump was the prime predictor variable in the equations for all groups. The findings of this study are discussed in relation to the specificity hypothesis. Strength and conditioning programs that facilitate the capacity for football players to develop forceful and rapid concentric action through plantar flexion of the ankle, as well as extension of the knee and hip, may be highly profitable.     

Activity cycles of National Rugby League and National Youth Competition matches

Examination of ball-in-play periods (i.e., match activity cycles) is a method used to provide insight into the physical demands of team sport competition. However, to date, no study has investigated the ball-in-play time of rugby league matches. This study investigated the activity cycles (i.e., ball-in-play periods) of elite National Rugby League (NRL) and National Youth Competition (NYC) matches. Video recordings of 393 NRL matches and 388 NYC matches were coded for activity and recovery cycles. Time when the ball was continuously in play was considered activity, whereas any stoppages during the match (e.g., for scrums, penalties, line drop-outs, tries, and video referee decisions) were considered recovery. The total time the ball was in play for NRL and NYC matches was approximately 55 minutes and 50 minutes, respectively. In comparison with NYC matches, NRL matches had longer average activity cycles (81.2 ± 16.1 vs. 72.0 ± 14.7 seconds, effect size [ES] = 0.60). The average longest activity cycle was also higher (ES = 0.48) in NRL (318.3 ± 65.4 seconds) than in NYC (288.9 ± 57.5 seconds) matches. The longest activity cycle from any match was 667 and 701 seconds for NRL and NYC matches, respectively. The NRL matches had a smaller proportion of short duration (<45 seconds) activity cycles and a greater proportion of longer duration (>91-600 seconds) activity cycles. In conclusion, meaningful differences in activity cycles were observed between NRL and NYC matches, with NRL competition demonstrating longer ball-in-play periods, a smaller proportion of short duration activity cycles, and a larger proportion of longer duration activity cycles. These findings suggest that the ability to perform prolonged high-intensity exercise, coupled with the capacity to recover during brief stoppages in play, is a critical requirement of professional rugby league match play.     

Relationships between four measures of genetic distance and breeding behavior in spring wheat

We estimated the genetic distances among 10 spring wheat genotypes based on pedigree data, morphological traits and AFLP markers, used individually and combined with morphological traits, to find the best predictors of general- and specific-combining abilities among parental genotypes. Ten wheat parents were crossed in a diallel form, disregarding reciprocal hybrids, totaling 45 combinations. The F(1) hybrids, F(2) populations and parents were evaluated in the field in 2007. The experimental plots consisted of 20 plants for F(1) hybrids and 40 plants for parental and F(2) populations. All methods (pedigree data, AFLP markers and morphological traits, used individually and combined) were found to be useful for the assessment of genetic diversity. The significant coefficient correlations ranged from low (0.45) to moderate (0.67) between the distance measures and hybrid performance. There was significant agreement between the distance measures based on AFLP markers vs morphological traits + AFLP markers (r = 0.47) and between pedigree data vs morphological traits + AFLP markers (r = 0.43). The pedigree distance was positively associated with traits 100-kernel weight and grain yield per plant in F(1) (correlations of 0.67 and 0.62, respectively) and F(2) (correlations of 0.62 and 0.59, respectively) generations. These correlation values indicate that the genetic distance, based on pedigree data, could replace diallel crosses for the selection of parents with higher combining ability and with moderate reliability.     

The extended relationship between child cardiovascular risks and academic performance measures

Objective: To examine the relationship between children's overweight status and other cardiovascular risk fitness factors and academic performance among fifth‐grade students. Research Methods and Procedures: Using a sample of 968 fifth‐grade students (50.7% boys; mean age = 10.6 years), children's cardiovascular risks (BMI, blood pressure, acanthosis nigricans) and fitness measures were compared with their mean group performance scores across four subscales (mathematics, reading/language arts, science, and social studies) of a statewide standardized academic performance test. Results: Of this sample, 39% were either at risk for being overweight or were already overweight; slightly over one half were of normal weight. Initial findings revealed a significant relationship between children's weight category and their reading/language arts, mathematics, and science test scores even after controlling for a proxy of socioeconomic status. When additional cardiovascular risk and fitness measures were included in the model, however, children's BMI status had no association. Instead, a composite fitness index, children's blood pressure, sex, and proxy of socioeconomic status were significantly associated with children's academic test scores. Discussion: This study expanded our understanding of the connection between children's overweight risks and academic performance by examining the impact of other cardiovascular risk factors such as high blood pressure and measures of fitness. These findings support the development and implementation of childhood cardiovascular risk surveillance programs that evaluate not only children's overweight risks but also their fitness, risk for type 2 diabetes, and/or high blood pressure by showing a relationship between some of these risks and children's academic test performance.     

Relationships between skeletal muscle characteristics and aerobic performance in sedentary and active subjects

Forty-eight sedentary and 39 quite active or well-trained men participated in this study. Muscle biopsy samples were taken from the vastus lateralis for the determination of fiber type composition (I, IIa, IIb), fiber type area, and assay of the following enzymes: malate dehydrogenase (MDH), 3-hydroxyacyl CoA dehydrogenase (HADH) and oxoglutarate dehydrogenase (OGDH). Maximal oxygen uptake (VO2max) was determined with a progressive cycle ergometer test, while endurance performance or maximal aerobic capacity (MAC) was defined as the total work output during a 90-min cycle ergometer test. Correlation analysis revealed no evidence of association between fiber type composition and VO2max kg-1 or MAC kg-1 in sedentary subjects, while active men exhibited significant correlation between % type I (r = 0.52), % type IIb (r = 0.31) and VO2max kg-1. Enzyme activities were not significantly correlated with MAC kg-1 and VO2max kg-1 in sedentary men while active men exhibited significant correlation for the three enzymes (0.37 less than or equal to r less than or equal to 0.51) with VO2max kg-1. These results show that the contribution of muscle fiber type and enzyme activities to aerobic performance may be inflated from a statistical point of view by the training status heterogeneity of subjects. They also suggest that variation in these muscle characteristics does not account for the individual differences in aerobic performance of subjects who have never trained before. Therefore, the assessment of muscle characteristics is not as useful as originally thought for the detection of individuals with a high potential for endurance performance among untrained subjects.     

北京百花山自然保护区地面生苔藓植物与生态环境的关系

运用典范对应分析法,定量分析了北京百花山自然保护区37个森林植被样地中33种主要地面生苔藓植物与生态环境之间的关系,结果表明：该区森林植被样地与环境因子的关系呈现多元化特点：相同植被聚为一组、环境因子相似的植被聚为一组、植被相同环境因子不同归为不同组和生境特殊的植被自成一组。得出该区多数地面生苔藓植物的分布与乔木郁闭度的相关性最大且与人为干扰程度密切相关,少数种类与草本层盖度和灌木盖度呈正相关。此外凋落物盖度、海拔、苔藓植物的生长基质也直接影响苔藓植物的分布。     

Relationships between metabolic rate, muscle electromyograms and swim performance of adult chinook salmon

Oxygen consumption rates of adult spring chinook salmon Oncorhynchus tshawytscha increased with swim speed and, depending on temperature and fish mass, ranged from 609 mg O₂ h^?1 at 30 cm s^?1 (c. 0·5 BL s^?1) to 3347 mg O₂ h^?1 at 170 cm s^?1 (c. 2·3 BL s^?1). Corrected for fish mass, these values ranged from 122 to 670 mg O₂ kg^?1 h^?1, and were similar to other Oncorhynchus species. At all temperatures (8, 12·5 and 17° C), maximum oxygen consumption values levelled off and slightly declined with increasing swim speed >170 cm s^?1, and a third‐order polynomial regression model fitted the data best. The upper critical swim speed (U_crit) of fish tested at two laboratories averaged 155 cm s^?1 (2·1 BL s^?1), but U_crit of fish tested at the Pacific Northwest National Laboratory were significantly higher (mean 165 cm s^?1) than those from fish tested at the Columbia River Research Laboratory (mean 140 cm s^?1). Swim trials using fish that had electromyogram (EMG) transmitters implanted in them suggested that at a swim speed of c. 135 cm s^?1, red muscle EMG pulse rates slowed and white muscle EMG pulse rates increased. Although there was significant variation between individual fish, this swim speed was c. 80% of the U_crit for the fish used in the EMG trials (mean U_crit 168·2 cm s^?1). Bioenergetic modelling of the upstream migration of adult chinook salmon should consider incorporating an anaerobic fraction of the energy budget when swim speeds are ≥80% of the U_crit.