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\"In Sprint Cars, early readers will go to the racetrack and learn about sprint cars, their drivers, and how these fast cars win races. Vibrant, full-color photos and carefully leveled text will engage emergent readers as they discover the unique features of these cars. A picture diagram labels the parts of a sprint car, while a picture glossary reinforces new vocabulary. Children can learn more about sprint cars online using our safe search engine that provides relevant, age-appropriate websites. Sprint Cars also features reading tips for teachers and parents, a table of contents, and index. Sprint Cars is part of Jump!'s Need for Speed series\"-- Provided by publisher.

In athletics sprint events, the block start performance can be fundamental to the outcome of a race. This Systematic Review aims to identify biomechanical factors of critical importance to the block start and subsequent first two steps performance. A systematic search of relevant English-language articles was performed on three scientific databases (PubMed, SPORTDiscus, and Web of Science) to identify peer-reviewed articles published until June 2021. The keywords “Block Start”, “Track and Field”, “Sprint Running”, and “Kinetics and Kinematics” were paired with all possible combinations. Studies reporting biomechanical analysis of the block start and/or first two steps, with track and field sprinters and reporting PB100m were sought for inclusion and analysis. Thirty-six full-text articles were reviewed. Several biomechanical determinants of sprinters have been identified. In the “Set” position, an anthropometry-driven block setting facilitating the hip extension and a rear leg contribution should be encouraged. At the push-off, a rapid extension of both hips and greater force production seems to be important. After block exiting, shorter flight times and greater propulsive forces are the main features of best sprinters. This systematic review emphasizes important findings and recommendations that may be relevant for researchers and coaches. Future research should focus on upper limbs behavior and on the analysis of the training drills used to improve starting performance.

Introduction: Sprint performance is governed by the interplay of acceleration, maximum velocity, and speed endurance. Although these components have been studied independently, their combined influence on 100m and 400m performance remains underexplored. A comprehensive understanding of their interdependence is critical for refining evidence-based training strategies. Objective: This study investigates the relative contributions of acceleration, maximum velocity, and speed endurance to sprint performance in elite and sub-elite athletes, aiming to inform optimized training interventions for both short- and long-distance sprints. Methodology: Thirty competitive sprinters participated in a 12-week longitudinal training intervention. Biomechanical assessments included high-speed motion capture and laser timing systems to evaluate acceleration time, peak velocity, and speed endurance (assessed via repeated sprint decrement). Pearson correlation and multiple regression analyses were employed to identify associations between these variables and sprint outcomes. Results: Acceleration was strongly associated with 100m performance (r = -0.84, p < 0.001), while maximum velocity contributed significantly to performance across both sprint distances. In 400m events, speed endurance emerged as the primary determinant of performance (r = -0.79, p < 0.001). Athletes demonstrating balanced development across all three components achieved the most significant performance gains. Discussion: The findings align with previous biomechanical and physiological research on sprinting but underscore the need for integrated training approaches targeting all performance domains simultaneously. Conclusion: Acceleration and maximum velocity are key determinants of 100m success, whereas speed endurance is critical for 400m performance. These results highlight the importance of individualized, multidimensional training frameworks. Future research should examine long-term neuromuscular adaptations and periodized strategies to optimize sprint performance.

The purpose of this study was to investigate the postactivation potentiation effect after a heavy resistance stimulus (HRS) on running speed (RS). Fifteen amateur team game players (basketball, volleyball, handball, and soccer players), ages 18-23 years running the 30-m dash and the intermediate phase of 0-10 and 0-30 m sprints, were used to evaluate RS. Resistance training consisted of 10 single repetitions at 90% of 1 repetition maximum. The running tests were performed 3 times- (a) 3 minutes prior the HRS, (b) 3 minutes after the HRS, and (c) 5 minutes after the HRS-in separated training sessions. Results showed that RS was not affected 3 minutes after the resistance training, but it increased for both selected running phases (0-10 and 0-30 m) 5 minutes after the HRS (p < 0.05). These findings indicate that heavy resistance exercise improves 10- and 30-m sprint performance when performed 5 minutes after the exercise bout.

This study investigated how the acceleration-speed profile (ASP) of the weaker and stronger side changes at different radii. Twenty male youth soccer players completed 30 m linear and curvilinear sprints (12.15, 11.15, 9.15, 7.15, and 6.15 m radius) in three training sessions. Sprint speed and acceleration over time and distance were recorded using a GNSS device. The maximum theoretical speed (S0), the acceleration (A0), slope of the ASP (ASslope), the area under the ASslope (ASParea), the acceleration at a sprint speed of 3 m/s (A3), and the curvilinear sprint deficit (ASPdeficit) of the individual sprints were analyzed. The effects of side, radius, and their interaction were evaluated with 2 × 5 ANOVA and the post hoc tests. A significant effect of radius and side was observed for all variables (F ≥ 3.50, p ≤ 0.037, η2 ≥ 0.15). The ASParea and S0 decreased at tighter radii. The A3 and A0 remained relatively unchanged, resulting in a steeper ASslope, and a larger ASPdeficit. At the same radius, the weaker side CS had a smaller ASParea, S0, A3, and a larger ASPdeficit. The ASP of the curvilinear sprint in youth soccer players is side-dependent at both ends (acceleration and top speed), while radii mainly affect late acceleration and top speed performance. These observations should be considered when adapting soccer players’ sprint training and monitoring external load based on acceleration.

The aim of this study was to establish the anthropometric and physiological profiles of young nonelite soccer players according to their playing position, and to determine their relevance for the selection process. Two hundred forty-one male soccer players who were members of the Getxo Arenas Club (Bizkaia) participated in this study. Players, age 17.31 (+/- 2.64) years, range 14-21 years, were classified into the following groups: forwards (n = 56), midfielders (n = 79), defenders (n = 77), and goalkeepers (n = 29). Anthropometric variables of participants (height, weight, body mass index, 6 skinfolds, 4 diameters, and 3 perimeters) were measured. Also, their somatotype and body composition (weights and percentages of fat, bone, and muscle) were calculated. Participants performed the Astrand test to estimate their absolute and relative VO2max, an endurance test, sprint tests (30 meters flat and 30 meters with 10 cones) and 3 jump tests (squat jump, counter movement jump and drop jump). Forwards were the leanest, presenting the highest percentage of muscle. They were the best performers in all the physiological tests, including endurance, velocity, agility, and power. In contrast, goalkeepers were found to be the tallest and the heaviest players. They also had the largest fat skinfolds and the highest fat percentage, but their aerobic capacity was the lowest. In the selection process, agility and the jump tests were the most discriminating for forwards. In contrast, agility, height, and endurance were the key factors for midfielders. The defenders group was characterized by a lower quantity of fat. Thus, we may conclude that anthropometric and physiological differences exist among soccer players who play in different positions. These differences fit with their different workload in a game. Therefore, training programs should include specific sessions for each positional role.The aim of this study was to establish the anthropometric and physiological profiles of young nonelite soccer players according to their playing position, and to determine their relevance for the selection process. Two hundred forty-one male soccer players who were members of the Getxo Arenas Club (Bizkaia) participated in this study. Players, age 17.31 (+/- 2.64) years, range 14-21 years, were classified into the following groups: forwards (n = 56), midfielders (n = 79), defenders (n = 77), and goalkeepers (n = 29). Anthropometric variables of participants (height, weight, body mass index, 6 skinfolds, 4 diameters, and 3 perimeters) were measured. Also, their somatotype and body composition (weights and percentages of fat, bone, and muscle) were calculated. Participants performed the Astrand test to estimate their absolute and relative VO2max, an endurance test, sprint tests (30 meters flat and 30 meters with 10 cones) and 3 jump tests (squat jump, counter movement jump and drop jump). Forwards were the leanest, presenting the highest percentage of muscle. They were the best performers in all the physiological tests, including endurance, velocity, agility, and power. In contrast, goalkeepers were found to be the tallest and the heaviest players. They also had the largest fat skinfolds and the highest fat percentage, but their aerobic capacity was the lowest. In the selection process, agility and the jump tests were the most discriminating for forwards. In contrast, agility, height, and endurance were the key factors for midfielders. The defenders group was characterized by a lower quantity of fat. Thus, we may conclude that anthropometric and physiological differences exist among soccer players who play in different positions. These differences fit with their different workload in a game. Therefore, training programs should include specific sessions for each positional role.

The aim of this study was to investigate the effects of heavy sled towing using a load corresponding to a 50% reduction of the individual theoretical maximal velocity (ranged 57–73% body mass) on subsequent 30 m sprint performance, velocity, mechanical variables (theoretical maximal horizontal force, theoretical maximal horizontal velocity, maximal mechanical power output, slope of the linear force–velocity relationship, maximal ratio of horizontal to total force and decrease in the ratio of horizontal to total force) and kinematics (step length and rate, contact and flight time). Twelve (n = 5 males and n = 7 females) junior running sprinters performed an exercise under two intervention conditions in random order. The experimental condition (EXP) consisted of two repetitions of 20 m resisted sprints, while in the control condition (CON), an active recovery was performed. Before (baseline) and after (post) the interventions, the 30 m sprint tests were analyzed. Participants showed faster 30 m sprint times following sled towing (p = 0.005). Running velocity was significantly higher in EXP at 5–10 m (p = 0.032), 10–15 m (p = 0.006), 15–20 m (p = 0.004), 20–25 m (p = 0.015) and 25–30 m (p = 0.014). No significant changes in sprint mechanical variables and kinematics were observed. Heavy sled towing appeared to be an effective post-activation potentiation stimulus to acutely enhance sprint acceleration performance with no effect on the athlete’s running technique.

This study aimed to evaluate in vivo oxidative capacity and relative resistance to O2 diffusion using near‐infrared spectroscopy (NIRS) in the m. triceps brachii of recreational to world class swimmers and evaluate their relationships with swimming performance. Twenty‐eight swimmers were enrolled and assigned into three subgroups according to their level: ‘recreational/trained’ (Tier 1/2; n = 8), ‘national’ (Tier 3; n = 12) and ‘international/world class’ (Tier 4/5; n = 8). Performance was evaluated by 100 m freestyle trials. Training volume was measured by self‐reported distance (km/week). The mV̇O2 ${\\mathrm{m}}{{\\dot{V}}_{{{\\mathrm{O}}}_{\\mathrm{2}}}$recovery k of m. triceps brachii was non‐invasively estimated by NIRS through repeated intermittent occlusions under two conditions: well‐oxygenated (kHIGH) and low O2 availability (kLOW). The difference between kHIGH and kLOW (Δk) was calculated as an index of relative resistance to O2 diffusion. FINA points and 100 m performance differed among all groups. Training volume was greater in Tier 4/5 (34.0 ± 5.5 km week−1) and Tier 3 (35.5 ± 11.6 km week−1) than in Tier 1/2 (6.4 ± 1.8 km week−1). kHIGH was greater in Tier 4/5 and Tier 3 (3.18 ± 0.41 and 2.79 ± 0.40 min−1) versus Tier 1/2 (2.10 ± 0.36 min−1; all P < 0.002). kHIGH correlated with FINA points, 100 m performance and training volume. ∆k was not different among tiers and was not associated with training volume or performance. M. triceps brachii oxidative capacity (kHIGH) was positively associated with performance and training volume in swimmers. ∆k, which reflects relative resistance to O2 diffusion, was not different among athletes. These data suggest that m. triceps brachii oxidative capacity is associated with swimming performance and that muscle O2 diffusing capacity exerts a similar relative resistance to O2 diffusive flow across swimmers. What is the central question of this study? Do highly trained swimmers have greater muscle oxidative capacity but higher sensitivity to reductions in O2 availability, that is, are relatively more ‘O2 diffusion limited’, than recreational swimmers? What is the main finding and its importance? We found that m. triceps brachii oxidative capacity varied significantly among swimmers of different competitive levels, and that it was associated with both training volume and performance. However, relative resistance to O2 diffusion was not different among swimmers of all levels, suggesting that training‐induced adaptations to support muscle oxidative capacity were matched well to adaptations to support muscle O2 diffusion.

This study elucidated kinetic and kinematic changes between control and weighted vest sprinting with a load of 7% body mass. Fourteen male sprinters completed 60 m control and vest sprints over a long force platform system. Step-to-step ground reaction force and spatiotemporal variables were grouped, representing the initial acceleration (1st–4th steps), middle acceleration (5th–14th steps), later acceleration (15th step–step before maximum velocity reached) and maximum velocity (stride where maximum velocity reached) phase during each trial. Two-way ANOVA with post hoc Tukey HSD and a Cohen’s d effect size with 95% confidence intervals elucidated the difference between trials and phases. Between control and vest trials the velocity decreased (3.41–3.78%) through trivial–small step length (1.95–2.72%) and frequency (0.87–1.54%) decreases. Vertical impulse increased (6.46–6.78%) through moderate support time increases (4.84–6.00%), coupled with no effective vertical mean force differences during the vest trial, compared to the control. There was no significant interaction between trials and phases. Therefore, although weighted vest trials did not increase vertical mean force production, vests did induce an increased vertical force application duration during the support phase step-to-step while supporting a larger total load (body mass plus vest mass).

This study explored the impact of short rest intervals on resisted sprint training in elite youth soccer players, specifically targeting enhanced initial-phase explosive acceleration without altering sprint mechanics. Fifteen U19 soccer players participated in a randomized crossover design trial, executing two sprint conditions: RST2M (6 sprints of 20 m resisted sprints with 2 min rest intervals) and RST40S (6 sprints of 20 m resisted sprints with 40 s rest intervals), both under a load equivalent to 30% of sprint velocity decrement using a resistance device. To gauge neuromuscular fatigue, countermovement jumps were performed before and after each session, and the fatigue index along with sprint decrement percentage were calculated. Interestingly, the results indicated no significant differences in sprint performance or mechanical variables between RST2M and RST40S, suggesting that the duration of rest intervals did not affect the outcomes. Horizontal resistance appeared to mitigate compensatory patterns typically induced by fatigue in short rest periods, maintaining effective joint movement and hip extensor recruitment necessary for producing horizontal ground forces. These findings propose a novel training strategy that could simultaneously enhance sprint mechanics during initial accelerations and repeated sprint abilities for elite youth soccer players—a methodology not previously employed