High Sprint Research Articles

Muscle morphological changes and enhanced sprint running performance: A 1-year observational study of well-trained sprinters.

Numerous cross-sectional studies have attempted to identify the muscle morphology required to achieve high sprint velocity. Our longitudinal study addressed an unanswered question of cross-sectional studies: whether hypertrophy of the individual trunk and thigh muscles induced by daily training (e.g., sprint, jump, and resistance training) is linked to an improvement in sprint performance within well-trained sprinters. Twenty-three collegiate male sprinters (100-m best time of 11.36±0.44s) completed their daily training for 1year without our intervention. Before and after the observation period, the sprint velocities at 0-100m, 0-10m, and 50-60m intervals were measured using timing gates. The volumes of 14 trunk and thigh muscles were measured using magnetic resonance imaging. Muscle volumes were normalized to the participants' body mass at each time point. Sprint velocities increased at the 0-100m (p<0.001), 0-10m (p=0.019), and 50-60m (p=0.018) intervals after the observation period. The relative volumes of the tensor fasciae latae, sartorius, biceps femoris long head, biceps femoris short head, semitendinosus, and iliacus were increased (all p<0.050). Among the hypertrophied muscles, only the change in the relative volume of the semitendinosus was positively correlated with the change in sprint velocity at the 50-60m interval (p=0.018 and ρ=0.591). These findings suggest that semitendinosus hypertrophy seems to be associated with sprint performance improvement within well-trained sprinters during the maximal velocity phase.

Influence of the External Workload on Calf Muscle Strain Injuries in Professional Football Players: A Pilot Study.

The influence of external workload variables on the development of calf muscle strainsin football players has not been previously explored. Overloaded players would have an increased risk of calf muscle strain injury. Prospective observational study. Level 4. A total of 41 professional football players from 1 team were monitored for 2 consecutive seasons. Total distance covered (TD), and distances covered at high-intensity running, high sprint running, low (LACC) and high (HACC) acceleration, low (LDEC) and high (HDEC) deceleration, and at high metabolic load distance (HMLD) were monitored with GPS units. Accumulated players' external workload in the week before injury was compared with the weekly mean value of the 6 weeks before injury occurred for each player. Ten players (24.3%) suffered 16 calf muscle strain injuries (3.1 injuries per 1000 hours of match play; 0.5 injuries per 1000 hours of training exposure). Players with a calf muscle injury were older (p = 0.03), with higher body weight (p = 0.01) and height (p = 0.03). Injured players displayed substantially higher total training volume (p < 0.01), TD (p < 0.01), LACC (p < 0.01), LDEC (p < 0.01), HACC (p < 0.01), HDEC (p < 0.01), and HMLD (p = 0.03) in the week before injury, in comparison with the mean values of these variables in the 6 weeks before injury. A week with a higher-than-habitual external workload might increase the risk of calf muscle strain injury in professional football players. Calf muscle injuries were preceded by a week with unusually high workloads associated with accelerating and decelerating distances and higher training volumes. Monitoring external workload indicators may be helpful in determine players with a higher risk of calf muscle strain injury due to excessive workload during training/competition.

Running-specific prosthesis' performance characterization by dynamic finite element approach.

Composite running-specific prostheses (RSP) are widely used by athletes with lower limb amputations to simulate the spring-like behavior of biological legs. However, the effect of these devices on the biomechanics of athletes with transtibial amputations remains uncertain. To address this issue, this study proposes a time-dependent finite element model that uses angles and dynamic loads during ground contact to evaluate RSP performance parameters such as stiffness and energy efficiency. The study also examines the impact of running speed and RSP geometry on performance. The in-silico characterization approach used in this study takes into account both the intrinsic characteristics of the RSP and the athlete's biomechanics to identify the influence of fundamental geometric variables of the RSP on performance. The model is verified by comparing its results with experimental data. The study found that as running speed increases, RSP stiffness, vertical ground reaction force (vGRF), and contact time decrease. The force-displacement profiles of RSP are nonlinear, but a linear function can be used to accurately represent their behavior at high sprinting speeds. Using higher RSP reduces energy efficiency and vGRF due to their lower stiffness. J-curve RSP result in higher stiffness, vGRF, and strain energy, while C-curve RSP are associated with longer contact times and higher energy efficiency.

Passive and active muscle elasticity of medial gastrocnemius is related to performance in sprinters.

Limited information is available on the association between muscle material properties and sprint performance. We aimed to identify whether and how the elasticity of passive and active muscle of the medial gastrocnemius (MG) is related to sprint performance. MG shear wave speed was measured under passive and active (20%, 50%, 80% of maximal voluntary contraction [MVC]) conditions, with ultrasound shear wave elastography, in 18 male sprinters. Passive and active ankle joint stiffness was assessed by applying a short-range fast stretch during 0%, 20%, 50%, and 80% MVC of plantar flexion. Additionally, rate of torque development (RTD) during explosive plantar flexion was measured. Passive and active MG shear wave speed was negatively correlated with 100-m race time. Passive MG shear wave speed was positively correlated with RTD, and RTD was negatively correlated with 100-m race time. MG shear wave speed at 50% and 80% MVC showed a positive correlation with ankle joint stiffness at the corresponding contraction level, and ankle joint stiffness at 50% and 80% MVC showed negative correlations with 100-m race time. These correlations were significant even after controlling for MVC torque. Our findings indicate that passive and active muscle elasticity of plantar flexor is important to achieve superior sprint performance. Specifically, high elasticity of passive MG could be related to superior sprint performance through high explosive torque production. In contrast, high elasticity of active MG at moderate-to-high intensity is likely related to high sprint performance through high ankle joint stiffness.

Muscle size of individual hip extensors in sprint runners: Its relation to spatiotemporal variables and sprint velocity during maximal velocity sprinting

Hip extensor muscle size is related to sprint running performance. However, the mechanisms underlying this relationship remain unclear. To gain insights into this issue, the present study examined the relationships between the individual hip extensor sizes, spatiotemporal variables (step frequency and length, and their determinants), and sprint velocity during maximal velocity sprinting. Magnetic resonance images of the hip and right thigh were obtained from 26 male sprinters to determine the volumes of the gluteus maximus, individual hamstrings and adductors, and gracilis. Muscle volumes were normalized to their respective body mass and recorded as relative muscle volumes. The sprinters performed a 100-m sprint with their maximal effort. Their sprint motions were recorded using cameras to calculate the mean sprint velocity and the spatiotemporal variables at 50–60 m interval. The sprint velocity was significantly correlated with the relative volume of the semitendinosus (r = 0.497, P = 0.010), but not with the volumes of the other examined muscles. The relative volume of semitendinosus significantly correlated with the stance distance (r = 0.414, P = 0.036) and the stance distance adjusted by the stance time (r = 0.490, P = 0.011). Moreover, there were significant correlations between the stance distance and step length (r = 0.592, P = 0.001), and between the step length and sprint velocity (r = 0.509, P = 0.008). These results suggest that the semitendinosus contributes to attaining long stance distance and thereby high sprint velocity during maximal velocity sprinting.

Relationship among Change of Direction Performance, Muscular Power and Sprint Speed in Female and Male Elite Soccer Players

We aimed to identify useful parameters to develop an effective fitness training strategy for senior female soccer players. Hence, we examined the change of direction performance (CODp), sprint speed, muscular power, and anthropometric data among female soccer players, and compared the findings with those from similar tests applied in male soccer players. Thirty-three female and forty male soccer players from the top Japanese league were examined. The differences between elite vs. sub-elite players and playing position were assessed, and simple correlation coefficients between motor performance and anthropomorphic parameters were analyzed. As a result, elite male and female players had better CODp and muscular power than sub-elite players. Elite male players had higher sprint speed than sub-elite players (p<0.01), regardless of position. However, in female players, the sprint speed was dependent on position. A large difference in the effect size for sprint speed was observed between female forwards (FW) and midfielders (MF) (d=0.85) and defenders (DF) (d=1.00) (FW

Physiological characteristics and acute fatigue associated with position-specific speed endurance soccer drills: production vs maintenance training

ABSTRACT Objective: The study aimed to compare the physiological characteristics and acute fatigue associated with position-specific speed endurance production (SEP) and maintenance (SEM) soccer drills. Methods: Twenty male soccer players performed a position specific drill consisting of 8 exercise bouts each lasting ~30 s interspersed by 150 s (SEP) and 60 s (SEM) of passive recovery. A selection of players (n = 10) completed neuromuscular assessments pre and post drill. Results: Players covered greater high speed (12%), very high speed (49%) and sprint (218%) running distances in SEP (P < 0.05, ES: 0.51–0.80). SEP resulted in greater peak (7%) and average (10%) running speeds (P < 0.01, ES: 0.70–0.93). Mean and peak heart rate responses were greater in SEM (4–10%, P < 0.01, ES: 0.97–1.84) whilst blood lactate concentrations were higher following SEP (6%, P < 0.05, ES: 0.42). Reductions in vertical countermovement jump height were more pronounced immediately after SEP (2%, P < 0.05, ES: 0.36) but 24 h post SEM (4%, P < 0.05, ES: 0.52). Horizontal countermovement jump performance was reduced immediately post SEP and SEM (3–5%, P < 0.01, ES: 0.22–0.38) and 24 h post SEM (4%, ES: 0.32). Conclusion: The data demonstrate that position-specific SEP and SEM drills overload different physiological indices and induce small impairments in some neuromuscular measures.

Prior workload has moderate effects on high-intensity match performance in elite-level professional football players when controlling for situational and contextual variables

ABSTRACT This investigation examined the effect of prior workload on high-intensity football match performance. Player load variables were recorded using a global positioning system and converted into composite variables: rolling season accumulated load (AL), exponentially weighted moving average acute, chronic and acute:chronic workload ratio (A:C). Match-play high-intensity performance-per-minute: accelerations (ACC), sprints, high-speed running (HSR) and high metabolic load (HMLd) distances; and situational and contextual variables were recorded for all games. Partial least squares modelling, and backward stepwise selection determined the most parsimonious model for each performance variable. Quadratic relationships of small to moderate effect sizes were identified for sprint AL and sprint performance, HSR AL and HSR performance, acute HMLd and HMLd performance, acute sprint load and ACC performance and A:C sprint load and ACC performance. Match performance was typically greatest between the mean and +1SD. High chronic HMLd, and combined acceleration and deceleration (ACC+DEC) load exerted small beneficial effects on HMLd and HSR performance, whereas high acute load exerted trivial to moderate negative effects. High sprint A:C exerted a small beneficial effect on sprint performance and playing position exerted small effects on HSR and HMLd performance. Prior workload has trivial to moderate effects on high-intensity match performance in professional players.

Anthropometric Clusters of Competitive Cyclists and Their Sprint and Endurance Performance.

Do athletes specialize toward sports disciplines that are well aligned with their anthropometry? Novel machine-learning algorithms now enable scientists to cluster athletes based on their individual anthropometry while integrating multiple anthropometric dimensions, which may provide new perspectives on anthropometry-dependent sports specialization. We aimed to identify clusters of competitive cyclists based on their individual anthropometry using multiple anthropometric measures, and to evaluate whether athletes with a similar anthropometry also competed in the same cycling discipline. Additionally, we assessed differences in sprint and endurance performance between the anthropometric clusters. Twenty-four nationally and internationally competitive male cyclists were included from sprint, pursuit, and road disciplines. Anthropometry was measured and k-means clustering was performed to divide cyclists into three anthropometric subgroups. Sprint performance (Wingate 1-s peak power, squat-jump mean power) and endurance performance (mean power during a 15 km time trial, O2peak) were obtained. K-means clustering assigned sprinters to a mesomorphic cluster (endo-, meso-, and ectomorphy were 2.8, 5.0, and 2.4; n = 6). Pursuit and road cyclists were distributed over a short meso-ectomorphic cluster (1.6, 3.8, and 3.9; n = 9) and tall meso-ectomorphic cluster (1.5, 3.6, and 4.0; n = 9), the former consisting of significantly lighter, shorter, and smaller cyclists (p < 0.05). The mesomorphic cluster demonstrated higher sprint performance (p < 0.05), whereas the meso-ectomorphic clusters established higher endurance performance (p < 0.001). Overall, endurance performance was associated with lean ectomorph cyclists with small girths and small frontal area (p < 0.05), and sprint performance related to cyclists with larger skinfolds, larger girths, and low frontal area per body mass (p < 0.05). Clustering optimization revealed a mesomorphic cluster of sprinters with high sprint performance and short and tall meso-ectomorphic clusters of pursuit and road cyclists with high endurance performance. Anthropometry-dependent specialization was partially confirmed, as the clustering algorithm distinguished short and tall endurance-type cyclists (matching the anthropometry of all-terrain and flat-terrain road cyclists) rather than pursuit and road cyclists. Machine-learning algorithms therefore provide new insights in how athletes match their sports discipline with their individual anthropometry.

PO-120 Research on the fluctuation of Reticulocyte during different altitude training patterns in swimming athletes

Objective To explore the fluctuation of reticulocyte during different altitude training in swimming athletes and their difference between altitude training focused on special aerobic capacity and altitude training focused on high load and sprint, to provide the theory basis for further analyze the altitude training improve the physiological function and athletic performance.&#x0D; Methods Twenty female swimming athletes participated in altitude training for four weeks, which could be divided into two patterns, special aerobic capacity group(G1, n=9) and intensity and sprint group(G2, n=11). Fasting venous blood samples were drawn for each week were determined using Beckman Coulter LH780 automated hematology analyzer, including Reticulocyte related parameters such as Reticulocyte percentage (Ret%), Reticulocyte count (Ret#) and immature Reticulocyte fraction (IRF) and also erythrocyte related parameters.&#x0D; Results (1) In G1, Ret%, Ret# and MRV showed continuous decline and represented minimum level in 4th week. While IRF increased during 2nd and 3rd, and then decreased in 4th week. (2) In G2, Ret%, Ret# and MRV were relatively steady during 1st and 2nd week. Ret% and Ret# gave an increased in 3rd week, and then decreased in 4th week, while MRV decreased in 3rd week and increased in 4th week. IRF significantly decreased in latter period compared to earlier period. (3) There were no significant changes for RBC, HCT and HGB in both G1 and G2. MCV, MCH, MCHC and RDW showed improved in later stages compared to their in earlier stages for all in G1, while MCV increased and then decreased, MCH and MCHC continued decline, and RDW kept at sustaining higher levels in G2.&#x0D; Conclusions (1) Reticulocytes were not in accordance with the trend of erythrocyte during different altitude training. Compared to erythrocyte, the behavior of Reticulocyte could reflect erythropoiesis, and IRF could more sensitively detect the change of bone marrow stimulation in particular.&#x0D; (2) The variability of Reticulocytes during altitude training was influenced by hypoxia, training and especially their interactive effects. In aspect of training type, it was crucial for considering the fluctuation of training load and athletes’ adaptation during different patterns. &#x0D;

Muscle morphology of the vastus lateralis is strongly related to ergometer performance, sprint capacity and endurance capacity in Olympic rowers

ABSTRACTRowers need to combine high sprint and endurance capacities. Muscle morphology largely explains muscle power generating capacity, however, little is known on how muscle morphology relates to rowing performance measures. The aim was to determine how muscle morphology of the vastus lateralis relates to rowing ergometer performance, sprint and endurance capacity of Olympic rowers. Eighteen rowers (12♂, 6♀, who competed at 2016 Olympics) performed an incremental rowing test to obtain maximal oxygen consumption, reflecting endurance capacity. Sprint capacity was assessed by Wingate cycling peak power. M. vastus lateralis morphology (volume, physiological cross-sectional area, fascicle length and pennation angle) was derived from 3-dimensional ultrasound imaging. Thirteen rowers (7♂, 6♀) completed a 2000-m rowing ergometer time trial. Muscle volume largely explained variance in 2000-m rowing performance (R2 = 0.85), maximal oxygen consumption (R2 = 0.65), and Wingate peak power (R2 = 0.82). When normalized for differences in body size, maximal oxygen consumption and Wingate peak power were negatively related in males (r = −0.94). Fascicle length, not physiological cross-sectional area, attributed to normalized peak power. In conclusion, vastus lateralis volume largely explains variance in rowing ergometer performance, sprint and endurance capacity. For a high normalized sprint capacity, athletes may benefit from long fascicles rather than a large physiological cross-sectional area.

The fast and the curious: locomotor performance and exploratory behaviour in eastern chipmunks

Although locomotor performance and behaviour are closely linked to survival in many wild animals, our understanding of the potentially important co-adaptations between locomotor performance and behaviour is still limited. Our objective was to quantify the among-individual correlation (rind) and within-individual correlation (re) between locomotor performance and personality traits in wild eastern chipmunks (Tamias striatus). We repeatedly measured sprint speed, docility, and exploration behaviour and found that all traits were significantly repeatable. Sprint speed was not correlated with docility and time spent in the centre of the open field. However, sprint speed was significantly and negatively correlated with distance moved in the open field at both the among-individual (rind = − 0.59) and the within-individual (re = − 0.54) levels. Thus, individuals with high locomotor performance are less explorative in a novel environment, which is somewhat counter-intuitive and opposite to the predictions generated by the pace-of-life syndrome and the “phenotypic compensation” hypotheses. Our results suggest that sprint speed and exploratory behaviour are co-specialised traits as they can reinforce each other’s effects in reducing predation risk. In refuging species such as chipmunks (i.e. individuals have to leave a refuge to forage), low exploration levels may reduce exposure to predators and high sprint speed may further reduce the probability of capture given an encounter with a predator. Thus, looking at how locomotor performance and behaviour interact and contribute to fitness is key to understanding the multivariate architecture of—and co-adaptations among—ecologically relevant complex phenotypes. A large number of studies have looked at the relationships between locomotor performance and behaviour at the inter-specific, among-individual, and within-individual levels, with mixed results. We found a significant and negative relationship between sprint speed and distance moved during an open-field test, which goes against the prediction of the pace-of-life syndrome and the “phenotypic compensation” hypotheses. Instead, these results support the “trait co-specialisation” hypothesis. In refuging animals such as chipmunks, reactive behaviours (being shy and less exploratory) may reduce exposure to predators and high sprint speed may further the probability of escaping given an encounter with a predator. Taken all together, the negative among- and within-individual correlations and sensitivity to the same covariates (parasites, and to a less extent body mass) suggest that sprint speed and exploratory behaviour are co-adapted in eastern chipmunks.

Critical determinants of combined sprint and endurance performance: an integrative analysis from muscle fiber to the human body.

Optimizing physical performance is a major goal in current physiology. However, basic understanding of combining high sprint and endurance performance is currently lacking. This study identifies critical determinants of combined sprint and endurance performance using multiple regression analyses of physiologic determinants at different biologic levels. Cyclists, including 6 international sprint, 8 team pursuit, and 14 road cyclists, completed a Wingate test and 15-km time trial to obtain sprint and endurance performance results, respectively. Performance was normalized to lean body mass2/3 to eliminate the influence of body size. Performance determinants were obtained from whole-body oxygen consumption, blood sampling, knee-extensor maximal force, muscle oxygenation, whole-muscle morphology, and muscle fiber histochemistry of musculus vastus lateralis. Normalized sprint performance was explained by percentage of fast-type fibers and muscle volume ( R2 = 0.65; P < 0.001) and normalized endurance performance by performance oxygen consumption ( V̇o2), mean corpuscular hemoglobin concentration, and muscle oxygenation ( R2 = 0.92; P < 0.001). Combined sprint and endurance performance was explained by gross efficiency, performance V̇o2, and likely by muscle volume and fascicle length ( P = 0.056; P = 0.059). High performance V̇o2 related to a high oxidative capacity, high capillarization × myoglobin, and small physiologic cross-sectional area ( R2 = 0.67; P < 0.001). Results suggest that fascicle length and capillarization are important targets for training to optimize sprint and endurance performance simultaneously.-Van der Zwaard, S., van der Laarse, W. J., Weide, G., Bloemers, F. W., Hofmijster, M. J., Levels, K., Noordhof, D. A., de Koning, J. J., de Ruiter, C. J., Jaspers, R. T. Critical determinants of combined sprint and endurance performance: an integrative analysis from muscle fiber to the human body.

Effects of Soccer Training on Anthropometry, Body Composition, and Physical Fitness during a Soccer Season in Female Elite Young Athletes: A Prospective Cohort Study.

The objectives of this study were to (i) describe soccer training (e.g., volume, types), anthropometry, body composition, and physical fitness and (ii) compute associations between soccer training data and relative changes of anthropometry, body composition, and physical fitness during a soccer season in female elite young athletes. Seasonal training (i.e., day-to-day training volume/types) as well as variations in anthropometry (e.g., body height/mass), body composition (e.g., lean body/fat mass), and physical fitness (e.g., muscle strength/power, speed, balance) were collected from 17 female elite young soccer players (15.3 ± 0.5 years) over the training periods (i.e., preparation, competition, transition) of a soccer season that resulted in the German championship title in under-17 female soccer. Training volume/types, anthropometrics, body composition, and physical fitness significantly varied over a soccer season. During the two preparation periods, higher volumes in resistance and endurance training were performed (2.00 ≤ d ≤ 18.15; p < 0.05), while higher sprint and tactical training volumes were applied during the two competition periods (2.22 ≤ d ≤ 11.18; p < 0.05). Body height and lean body mass increased over the season (2.50 ≤ d ≤ 3.39; p < 0.01). In terms of physical fitness, significant performance improvements were found over the soccer season in measures of balance, endurance, and sport-specific performance (2.52 ≤ d ≤ 3.95; p < 0.05). In contrast, no statistically significant changes were observed for measures of muscle power/endurance, speed, and change-of-direction speed. Of note, variables of muscle strength (i.e., leg extensors) significantly decreased (d = 2.39; p < 0.01) over the entire season. Our period-specific sub-analyses revealed significant performance improvements during the first round of the season for measures of muscle power/endurance, and balance (0.89 ≤ d ≤ 4.01; p < 0.05). Moreover, change-of-direction speed significantly declined after the first round of the season, i.e., transition period (d = 2.83; p < 0.01). Additionally, significant medium-to-large associations were observed between training and anthropometrics/body composition/physical fitness (−0.541 ≤ r ≤ 0.505). Soccer training and/or growth/maturation contributed to significant variations in anthropometry, body composition, and physical fitness outcomes throughout the different training periods over the course of a soccer season in female elite young soccer players. However, changes in components of fitness were inconsistent (e.g., power, speed, strength). Thus, training volume and/or types should be carefully considered in order to develop power-, speed- or strength-related fitness measures more efficiently throughout the soccer season.

Histone deacetylase activity modulates exercise-induced skeletal muscle plasticity in zebrafish (Danio rerio).

Aerobic exercise has a positive impact on animals by enhancing skeletal muscle function and locomotor performance. Responses of skeletal muscle to exercise involve changes in energy metabolism, calcium handling, and the composition of contractile protein isoforms, which together influence contractile properties. Histone deacetylases (HDAC) can cause short-term changes in gene expression and may thereby mediate plasticity in contractile properties of skeletal muscle in response to exercise. The aim of this project was to determine (in zebrafish, Danio rerio) the traits that mediate interindividual differences in sustained and sprint performance and to determine whether inhibiting class I and II HDACs mediates exercise-induced changes in these traits. High sustained performers had greater aerobic metabolic capacity [citrate synthase (CS) activity], calcium handling capacity [sarco/endoplasmic reticulum ATPase (SERCA) activity], and slow contractile protein concentration [slow myosin heavy chain (MHC)] compared with low performers. High sprint performers had lower CS activity and slow MHC concentrations compared with low performers, but there were no significant differences in lactate dehydrogenase activity or fast MHC concentrations. Four weeks of aerobic exercise training increased sustained performance, CS activity, SERCA activity, and slow MHC concentration. Inhibiting class I and II HDACs increased slow MHC concentration in untrained fish but not in trained fish. However, inhibiting HDACs reduced SERCA activity, which was paralleled by a reduction in sustained and sprint performance. The regulation of muscle phenotypes by HDACs could be a mechanism underlying the adaptation of sustained locomotor performance to different environmental conditions, and may therefore be of therapeutic and ecological significance.

Digit ratio (2D:4D) and physical fitness (Eurofit test battery) in school children

BackgroundThe relative lengths of the index finger to the ring finger (2D:4D) is sexually dimorphic and is thought to be a correlate of prenatal sex steroids (low 2D:4D=high prenatal testosterone and low prenatal oestrogen). In adults there have been reports that low 2D:4D is consistently associated with high sports performance. AimsTo investigate correlations between 2D:4D and fitness levels in children. Study designRight 2D:4D and body size were measured, in addition to flexibility, speed, endurance and strength (Eurofit tests). Subjects: 922 boys and 835 girls (mean ages (years): 10.8±1.01 and 10.07±1.00 respectively). Outcome measures: height, mass, BMI, triceps and subscapular skinfolds, 20m shuttle run, sit and reach, standing broad jump, hand grip strength, 10×5m sprint, and the sit and reach test. ResultsBoys significantly outperformed the girls in the 10×5m sprints, the 20m shuttle run, standing broad jump, and hand grip strength. In boys but not girls, 2D:4D was significantly negatively correlated with scores in all these tests except the standing broad jump. In girls but not boys, 2D:4D was significantly positively correlated to stature, mass, BMI and waist circumference. ConclusionsIt is suggested that high prenatal testosterone and low prenatal oestrogen (low 2D:4D) is implicated in high sprinting speed, endurance and hand grip strength in boys. In girls low prenatal testosterone and high prenatal oestrogen is associated with large body size.

Understanding sprint velocity fluctuations for improved project plans with Scrum: a case study

ABSTRACTStarting from the documentation of high sprint velocity fluctuations in a Scrum project, this paper presents a thorough approach to identify the sources of issues arising in the context of Scrum implementation. Given that Scrum provides guidance on identifying process issues but not their root causes, various approaches are explored. This is of great relevance because Scrum defines project schedules relying heavily on sprint velocity and because it is the most widely used agile methodology. The findings provide a new approach to evaluate such fluctuations and establish a more realistic project assessment than what is currently defined by Scrum. In this respect, this paper contributes to improve the understanding of the software development process using this agile framework. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Investigation of Varied Intensity Interval Sprint Training and Detraining Impact on Selected Speed Parameters

The objective of this study is to determine the effect of varied intensity interval sprint training and detraining impact on selected speed parameters. To achieve the purpose of the study 45 male students were selected and randomly assigned into three groups of 15 each. Group-I (n=15) underwent high intensity interval sprint training, group-II (n=15) underwent moderate intensity interval sprint training and group-III (n=15) acted as control. The duration of the training programme was 12 weeks with three sessions per week on alternative days. Speed, speed endurance and anaerobic power were assessed prior to and immediately after 12 weeks of training and also during the period of cessation of experimental treatment for 40 days at an interval of every 10 days, from high and moderate intensity interval sprint training groups and control group. The obtained data was analyzed statistically by analysis of covariance and 3 x 5 factorial ANOVA with repeated measures on last factor. Findings of the study revealed significant improvement on selected speed parameters whereas significant decrease during the detraining period.

The Symmetry of Children’s Knees Is Linked to Their Adult Sprinting Speed and Their Willingness to Sprint in a Long-Term Jamaican Study

Jamaican athletes are prominent in sprint running but the reasons for their success are not clear. Here we consider the possibility that symmetry, particularly symmetry of the legs, in Jamaican children is linked to high sprinting speed in adults. Our study population was a cohort of 288 rural children, mean age 8.2 (±1 SD = 1.7) years in 1996. Symmetry was measured in 1996 and 2006 from the fluctuating asymmetry (FA) of three lower-body traits and we constructed a lower body composite FA trait (Comp lb-FA). In 2010 we measured sprinting speed (for 90 m and 180 m races) in participants recruited from our original cohort. There were 163 untrained adults in our sample. We found: (i) high Comp lb and knee symmetry in 1996 and 2006 were linked to fast sprinting times in our 2010 runners and (ii) our sample of sprinters appears to have self-selected for greater symmetry. We conclude that high knee symmetry in childhood is linked to an ability to sprint fast in adult Jamaicans as well as a readiness to sprint.

The effect of coloration and temperature on sprint performance in male and female wall lizards

Phenotypic coloration in animals is often expected to have a signalling function, but it may also evolve as a correlated trait that reflects life-history strategy, social strategy, or ecological divergence. Wall lizards (Podarcis muralis) exhibit substantial colour variation, with both males and females being red, white, yellow, or a mixture of these colours. However, the biological significance of these colour morphs remains unknown. Here we investigate the relationship between coloration and temperature-dependent locomotor performance in an attempt to identify the adaptive significance of colour variation in this species. We investigate the maximum sprint speed of males and females of each of these colour morphs across seven different temperatures, using general additive mixed models (GAMMs). We predicted that the different sexes and colour phenotypes would exhibit differences in sprint speed performance, potentially indicating a correlation between coloration and adaptation into different ecological niches. We found no difference in performance of the discrete colour morphs, but amongst individuals that exhibited red coloration, those with a greater percentage of red were slower than those with less red coloration. This suggests a trade-off between red coloration and high sprint performance in this species. Furthermore, larger animals performed better, independent of colour and sex. Finally, we found no relative or absolute difference between males and females in their sprint performance. Taken together, our results suggest that there is no sex-specific or colour morph-specific differentiation in the use of microhabitats in this species. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 107, 573–582.