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Improving Mechanical Effectiveness During Sprint Acceleration: Practical Recommendations and Guidelines
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Measuring the ground reaction forces (GRF) underlying sprint acceleration is important to understanding the performance of such a common task. Until recently direct measurements of GRF during sprinting were limited to a few steps per trial, but a simple method (SM) was developed to estimate GRF across an entire acceleration. The SM utilizes displacement- or velocity-time data and basic computations applied to the runner's center of mass and was validated against compiled force plate (FP) measurements; however, this validation used multiple-trials to generate a single acceleration profile, and consequently fatigue and error may have introduced noise into the analyses. In this study, we replicated the original validation by comparing the main sprint kinetics and force-velocity-power variables (e.g. GRF and its horizontal and vertical components, mechanical power output, ratio of horizontal component to resultant GRF) between synchronized FP data from a single sprinting acceleration and SM data derived from running velocity measured with a 100 Hz laser. These analyses were made possible thanks to a newly developed 50-m FP system providing seamless GRF data during a single sprint acceleration. Sixteen trained male sprinters performed two all-out 60-m sprints. We observed good agreement between the two methods for kinetic variables (e.g. grand average bias of 4.71%, range 0.696 ± 0.540-8.26 ± 5.51%), and high inter-trial reliability (grand average standard error of measurement of 2.50% for FP and 2.36% for the SM). This replication study clearly shows that when implemented correctly, this method accurately estimates sprint acceleration kinetics.
Sprint running is a common feature of many sport activities. The ability of an athlete to cover a distance in the shortest time relies on his/her power production. The aim of this study was to provide an exhaustive description of the mechanical determinants of power output in sprint running acceleration and to check whether a predictive equation for internal power designed for steady locomotion is applicable to sprint running acceleration. Eighteen subjects performed two 20 m sprints in a gym. A 35‐camera motion capture system recorded the 3D motion of the body segments and the body center of mass (BCoM) trajectory was computed. The mechanical power to accelerate and rise BCoM (external power, Pext) and to accelerate the segments with respect to BCoM (internal power, Pint) were calculated. In a 20 m sprint, the power to accelerate the body forward accounts for 50% of total power; Pint accounts for 41% and the power to rise BCoM accounts for 9% of total power. All the components of total mechanical power increase linearly with mean sprint velocity. A published equation for Pint prediction in steady locomotion has been adapted (the compound factor q accounting for the limbs' inertia decreases as a function of the distance within the sprint, differently from steady locomotion) and is still able to predict experimental Pint in a 20 m sprint with a bias of 0.70±0.93 W·kg−1. This equation can be used to include Pint also in other methods that estimate external horizontal power only. This article is protected by copyright. All rights reserved.
Aims
We analysed the changes in force-velocity-power variables and jump performance in response to an individualized training program based on the force-velocity imbalance (FVimb). In particular, we investigated (i) the individual adaptation kinetics to reach the optimal profile and (ii) de-training kinetics over the three weeks following the end of the training program.
Methods
Sixty subjects were assigned to four sub-groups according to their initial FVimb: high or low force-deficit (FD) and high or low velocity-deficit (VD). The duration of training intervention was set so that each individual reached their “Optimal force-velocity (F-v) profile”. Mechanical and performance variables were measured every 3 weeks during the program, and every week after the end of the individualized program.
Results
All subjects in the FD sub-groups showed extremely large increases in maximal theoretical force output (+30±16.6% Mean±SD; ES = 2.23±0.28), FVimb reduction (-74.3±54.7%; ES = 2.17±0.27) and large increases in jump height (+12.4±7.6%; ES = 1.45±0.23). For the VD sub-groups, we observed moderate to extremely large increases in maximal theoretical velocity (+15.8±5.1%; ES = 2.72±0.29), FVimb reduction (-19.2±6.9%; ES = 2.36±0.35) and increases in jump height (+10.1±2.7%; ES = 0.93±0.09). The number of weeks needed to reach the optimal F-v profile (12.6 ± 4.6) was correlated to the magnitude of initial FVimb (r = 0.82, p<0.01) for all participants regardless of their initial subgroup. No significant change in mechanical variables or jump performance was observed over the 3-week de-training period.
Conclusions
Collectively, these results provide useful insights into a more specific, individualized (i.e. based on the type and magnitude of FVimb) and accurate training prescription for jumping performance. Considering both training content and training duration together with FVimb may enable more individualized, specific and effective training monitoring and periodization.
The force-vector theory contends that horizontal exercises are more specific to horizontal sports skills. In this context, the focus is on horizontal force production relative to the global coordinate frame. However, according to the principle of dynamic correspondence, the direction of force relative to the athlete is more important, and thus the basis for the force-vector theory is flawed. The purpose of this study was therefore to test the force-vector theory. According to the force-vector theory, hip thrust is a horizontally loaded exercise, and so hip thrust training would be expected to create greater improvements in horizontal jump performance than vertical jump performance. Eleven collegiate female athletes aged 18–24 years completed a 14-week hip thrust training programme. Pre and post testing was used to measure the following: vertical squat jump, vertical countermovement jump, horizontal squat jump, horizontal countermovement jump and hip thrust 3 repetition maximum (3RM). Subjects improved their 3 repetition maximum hip thrust performance by 33.0% (d = 1.399, p < 0.001, η² = 0.784) and their vertical and horizontal jump performance (improvements ranged from 5.4–7.7%; d = 0.371–0.477, p = 0.004, η² = 0.585). However, there were no differences in the magnitude of the improvement between horizontal and vertical jumping (p = 0.561, η² = 0.035). The results of this study are contrary to the predictions of the force-vector theory. Furthermore, this paper concludes with an analysis of the force-vector theory, presenting the mechanical inconsistencies in the theory. Coaches should use the well established principle of dynamic correspondence in order to assess the mechanical similarity of exercises to sports skills.
This study aimed (i) to explore the relationship between vertical (jumping) and horizontal (sprinting) force–velocity–power (FVP) mechanical profiles in a large range of sports and levels of practice, and (ii) to provide a large database to serve as a reference of the FVP profile for all sports and levels tested. A total of 553 participants (333 men, 220 women) from 14 sport disciplines and all levels of practice participated in this study. Participants performed squat jumps (SJ) against multiple external loads (vertical) and linear 30–40 m sprints (horizontal). The vertical and horizontal FVP profile (i.e., theoretical maximal values of force ( F0 ), velocity ( v0 ), and power ( Pmax )) as well as main performance variables (unloaded SJ height in jumping and 20-m sprint time) were measured. Correlations coefficient between the same mechanical variables obtained from the vertical and horizontal modalities ranged from −0.12 to 0.58 for F0 , −0.31 to 0.71 for v0 , −0.10 to 0.67 for Pmax , and −0.92 to −0.23 for the performance variables (i.e, SJ height and sprint time). Overall, results showed a decrease in the magnitude of the correlations for higher-level athletes. The low correlations generally observed between jumping and sprinting mechanical outputs suggest that both tasks provide distinctive information regarding the FVP profile of lower-body muscles. Therefore, we recommend the assessment of the FVP profile both in jumping and sprinting to gain a deeper insight into the maximal mechanical capacities of lower-body muscles, especially at high and elite levels.
Sprinting is a key action in team sports such as Rugby Sevens, a new Olympic sport. Recent research has shown at length the importance of technical or mechanical proficiency for sprinting performance. Simple methods of profiling mechanical characteristics of athletes have been developed utilizing three sprints reaching maximal velocities and demonstrated in a number of elite cohorts. These methods were applied with 16 athletes (age = 23 ± 7 years; height = 1.73 ± 0.82 m; body mass = 69.9 ± 7.2 kg) from the New Zealand Women’s Rugby Sevens team. Mechanical proficiency in the form of horizontal-to-vertical force application ratio (RF) showed strong Pearson’s correlations (r=-0.60 p=0.001, r=-0.61 p=0.002) between 10 m and 40 m sprinting performances, respectively. Further r values (r=>-0.71) were observed for relationships between peak relative horizontal power expression and sprinting performances. This study expands, via a newly observed population, the body of knowledge contending the relationship between mechanical proficiency and sprinting performance and supports the usage of profiling methods to individualizing training for speed and power. Profiling can identify among a cohort whom is “force dominant” and “velocity dominant” as well as simply which athletes are more and less proficient at applying forces efficiently to propel themselves in sprinting actions.
The aim of this study was to investigate the impact of timing gate setup on mechanical outputs in sprinting athletes. Twenty-five male and female team sport athletes (mean ± SD: 23 ± 4 y, 185 ± 11 cm, 85 ± 13 kg) performed two 40-m sprints with maximal effort. Dual-beamed timing gates covered the entire running course with 5-m intervals. Maximal horizontal force (F0), theoretical maximal velocity (v0), maximal horizontal power (Pmax), force-velocity slope (SFV), maximal ratio of force (RFmax) and index of force application technique (DRF) were computed using a validated biomechanical model and based on twelve varying split time combinations, ranging from three to eight timing checkpoints. When no timing gates were located after the 20-m mark, F0 was overestimated (mean difference, ±90%CL: 0.16, ±0.25 to 0.33, ±0.28 N•kg-1 ; possibly to likely; small), in turn affecting SFV and DRF by small to moderate effects. Timing setups covering only the first 15 m displayed lower v0 than setups covering the first 30-40 m of the sprints (0.21 ±0.34 to 0.25 ±0.34 m•s-1 ; likely; small). Moreover, poorer reliability values were observed for timing setups covering the first 15-20 m vs. the first 25-40 m of the sprints. In conclusion, the present findings showed that the entire acceleration phase should be covered by timing gates to ensure acceptably valid and reliable sprint mechanical outputs. However, only three timing checkpoints (i.e., 10, 20 and 30 m) are required to ensure valid and reliable outputs for team sport athletes.
The capacity to rapidly generate and apply a great amount of force seems to play a key role in sprint running. However, it has recently been shown that, for sprinters, the technical ability to effectively orient the force onto the ground is more important than its total amount. The force-vector theory has been proposed to guide coaches in selecting the most adequate exercises to comprehensively develop the neuromechanical qualities related to the distinct phases of sprinting. This study aimed to compare the relationships between vertically-directed (loaded and unloaded vertical jumps, and half-squat) and horizontally-directed (hip-thrust) exercises and the sprint performance of top-level track and field athletes. Sixteen sprinters and jumpers (including three Olympic athletes) executed vertical jumps, loaded jump squats and hip-thrusts, and sprinting speed tests at 10-, 20-, 40-, 60-, 100-, and 150-m. Results indicated that the hip-thrust is more associated with the maximum acceleration phase (i.e., from zero to 10-m; r = 0.93), whereas the loaded and unloaded vertical jumps seem to be more related to top-speed phases (i.e., distances superior to 40-m; r varying from 0.88 to 0.96). These findings reinforce the mechanical concepts supporting the force-vector theory, and provide coaches and sport scientists with valuable information about the potential use and benefits of using vertically- or horizontally-based training exercises.
This study aimed to evaluate whether an individualised sprint-training program was more effective in improving sprint performance in elite team-sport players compared to a generalised sprint-training program. Seventeen elite female handball players (23 +/- 3 y, 177 +/- 7 cm, 73 +/- 6 kg) performed two weekly sprint training sessions over eight weeks in addition to their regular handball practice. An individualised training group (ITG, n = 9) performed a targeted sprint-training program based on their horizontal force-velocity profile from the pre-training test. Within ITG, players displaying the lowest, highest and mid-level force-velocity slope values relative to body mass were assigned to a resisted, an assisted or a mixed sprint-training program (resisted sprinting in the first half and assisted sprinting in the second half of the intervention period), respectively. A control group (CG, n = 8) performed a generalised sprint-training program. Both groups improved 30-m sprint performance by ~ 1% (small effect) and maximal velocity sprinting by ~ 2% (moderate effect). Trivial or small effect magnitudes were observed for mechanical outputs related to horizontal force-or power production. All between-group differences were trivial. In conclusion, individualised sprint-training was no more effective in improving sprint performance than a generalised sprint-training program.
Aims
In the current study we investigated the effects of resisted sprint training on sprinting performance and underlying mechanical parameters (force-velocity-power profile) based on two different training protocols: (i) loads that represented maximum power output (Lopt) and a 50% decrease in maximum unresisted sprinting velocity and (ii) lighter loads that represented a 10% decrease in maximum unresisted sprinting velocity, as drawn from previous research (L10).
Methods
Soccer [n = 15 male] and rugby [n = 21; 9 male and 12 female] club-level athletes were individually assessed for horizontal force-velocity and load-velocity profiles using a battery of resisted sprints, sled or robotic resistance respectively. Athletes then performed a 12-session resisted (10 × 20-m; and pre- post-profiling) sprint training intervention following the L10 or Lopt protocol.
Results
Both L10 and Lopt training protocols had minor effects on sprinting performance (average of -1.4 to -2.3% split-times respectively), and provided trivial, small and unclear changes in mechanical sprinting parameters. Unexpectedly, Lopt impacted velocity dominant variables to a greater degree than L10 (trivial benefit in maximum velocity; small increase in slope of the force-velocity relationship), while L10 improved force and power dominant metrics (trivial benefit in maximal power; small benefit in maximal effectiveness of ground force orientation).
Conclusions
Both resisted-sprint training protocols were likely to improve performance after a short training intervention in already sprint trained athletes. However, widely varied individualised results indicated that adaptations may be dependent on pre-training force-velocity characteristics.
This review covers underlying physiological characteristics and training considerations that may affect muscular strength including improving maximal force expression and time-limited force expression. Strength is underpinned by a combination of morphological and neural factors including muscle cross-sectional area and architecture, musculotendinous stiffness, motor unit recruitment, rate coding, motor unit synchronization, and neuromuscular inhibition. Although single- and multi-targeted block periodization models may produce the greatest strength-power benefits, concepts within each model must be considered within the limitations of the sport, athletes, and schedules. Bilateral training, eccentric training and accentuated eccentric loading, and variable resistance training may produce the greatest comprehensive strength adaptations. Bodyweight exercise, isolation exercises, plyometric exercise, unilateral exercise, and kettlebell training may be limited in their potential to improve maximal strength but are still relevant to strength development by challenging time-limited force expression and differentially challenging motor demands. Training to failure may not be necessary to improve maximum muscular strength and is likely not necessary for maximum gains in strength. Indeed, programming that combines heavy and light loads may improve strength and underpin other strength-power characteristics. Multiple sets appear to produce superior training benefits compared to single sets; however, an athlete’s training status and the dose–response relationship must be considered. While 2- to 5-min interset rest intervals may produce the greatest strength-power benefits, rest interval length may vary based an athlete’s training age, fiber type, and genetics. Weaker athletes should focus on developing strength before emphasizing power-type training. Stronger athletes may begin to emphasize power-type training while maintaining/improving their strength. Future research should investigate how best to implement accentuated eccentric loading and variable resistance training and examine how initial strength affects an athlete’s ability to improve their performance following various training methods.
Purpose:
Our aim was to quantify the mechanical outputs developed during horizontal squat jumps, and notably the movement velocity, in comparison to vertical squat jumps with and without loads.
Methods:
Thirteen healthy male athletes performed squat jumps without additional loads (SJ0), with a load of ~60% of body mass (SJ60) and during horizontal squat jumps performed lying down on a roller device with (AHSJ) and without (HSJ) a rubber band assistance. Instantaneous lower limb extension velocity, force and power output were measured and averaged over the push-off phase.
Results:
The force was significantly higher during SJ60 than during SJ0, which was higher than during HSJ and AHSJ. Extension velocity was significantly different across all conditions with 0.86 ± 0.07, 1.29 ± 0.10, 1.59 ± 0.19 and 1.83 ± 0.19 m.s-1 for SJ60, SJ0, HSJ and AHSJ conditions, respectively. Differences in force and velocity values between SJ0 and the other conditions were large to extremely large. Differences were observed in power values only between SJ60 and SJ0, SJ60 and AHSJ and SJ0 and HSJ.
Conclusion:
Horizontal squat jump modalities allow athletes to reach very to extremely largely higher limb extension velocities (HSJ: +24.0±16%, AHSJ: +42.8±17.4%) than during SJ0. HSJ and AHSJ modalities are cheap and practical modalities to train limb extension velocity capabilities, i.e. the ability of the neuromuscular system to produce force at high contraction velocities.
PurposeWe sought to compare force–velocity relationships developed from unloaded sprinting acceleration to that compiled from multiple sled-resisted sprints. Methods
Twenty-seven mixed-code athletes performed six to seven maximal sprints, unloaded and towing a sled (20–120% of body-mass), while measured using a sports radar. Two methods were used to draw force–velocity relationships for each athlete: A multiple trial method compiling kinetic data using pre-determined friction coefficients and aerodynamic drag at maximum velocity from each sprint; and a validated single trial method plotting external force due to acceleration and aerodynamic drag and velocity throughout an acceleration phase of an unloaded sprint (only). Maximal theoretical force, velocity and power were determined from each force–velocity relationship and compared using regression analysis and absolute bias (± 90% confidence intervals), Pearson correlations and typical error of the estimate (TEE). ResultsThe average bias between the methods was between − 6.4 and − 0.4%. Power and maximal force showed strong correlations (r = 0.71 to 0.86), but large error (TEE = 0.53 to 0.71). Theoretical maximal velocity was nearly identical between the methods (r = 0.99), with little bias (− 0.04 to 0.00 m s−1) and error (TEE = 0.12). Conclusions
When horizontal force or power output is considered for a given speed, resisted sprinting is similar to its associated phase during an unloaded sprint acceleration [e.g. first steps (~ 3 m s−1) = heavy resistance]. Error associated with increasing loading could be resultant of error, fatigue, or technique, and more research is needed. This research provides a basis for simplified assessment of optimal loading from a single unloaded sprint.
Rugby Sevens, a new Olympic sport, features high intensity intermittent running and contact efforts over short match durations, normally six times across two to three days in a tournament format. Elite Rugby Sevens seasons often include over a dozen competitive tournaments across less than nine months, demanding deliberate and careful training-stress balance and workload management alongside development of the necessary physical qualities required for competition. Focus on running and repeated power skills, strength, and match-specific conditioning capacities is advised. Partial taper approaches in combination with high velocity running (>5m/s from GPS measures) exposures before and between tournaments in succession may reduce injury rates and enhance performance. In a sport with substantial long-haul intercontinental travel and repetitive chronic load demands, management of logistics including nutrition and recovery is inclusive of the formula for success in the physical preparation of elite Rugby Sevens athletes.
The purpose of this study was to examine the effects of an 8-week barbell hip thrust strength training program on sprint performance. Twenty-one collegiate athletes (15 males and 6 females) were randomly assigned to either an intervention (n = 11, age 27.36 ± 3.17 years, height 169.55 ± 10.38 cm, weight 72.7± 18 kg) or control group (n = 10, age 27.2 ± 3.36 years, height 176.2 ± 7.94 cm, weight 76.39 ± 11.47 kg). 1RM hip thrust, 40m sprint time, and individual 10m split timings: 0-10, 10-20, 20-30, 30-40m, were the measured variables; these recorded at both the baseline and post testing time points. Following the 8-week hip thrust strength training intervention significantly greater 1RM hip thrust scores for the training group were observed (p < 0.001, d = 0.77 [mean difference 44.09 kg]), however this failed to translate into changes in sprint time for any of the measured distances (all sprint performance measures: p > 0.05, r = 0.05 - 0.37). No significant differences were seen for the control group for 1RM hip thrust (p = 0.106, d = 0.24 [mean difference 9.4 kg]) or sprint time (all sprint performance measures: p > 0.05, r = 0.13 - 0.47). These findings suggest that increasing maximum hip thrust strength through use of the barbell hip thrust does not appear to transfer into improvements in sprint performance in collegiate level athletes.
THE USE OF VERTICALLY LOADED EXERCISES, SUCH AS THE BACK SQUAT, DEADLIFT, AND OLYMPICSTYLE LIFTS, ARE COMMONLY PRESCRIBED BY STRENGTH AND CONDITIONING PROFESSIONALS TO ENHANCE THE PHYSICAL QUALITIES OF ATHLETES. THESE METHODS HAVE BEEN SUPPORTED AS EFFECTIVE MEANS, MAINLY FOR NOVICE SUBJECTS, BUT THEIR EFFECTIVENESS AND TRANSFER HAS BEEN QUESTIONED IN MORE ADVANCED ATHLETES AND IN TRANSFER TO SPECIFIC PHYSICAL QUALITIES. THE EFFECTIVENESS OF VERTICALLY LOADED EXERCISE TO ENHANCE SPRINTING SPEED AND CHANGE OF DIRECTION (COD) SPEED IS EQUIVOCAL IN ADVANCED ATHLETES, AND THE USE OF HORIZONTALLY LOADED MOVEMENT MAY HAVE BETTER TRANSFER FOR SPRINTING SPEED AND COD SPEED.
Ballistic performances are determined by both the maximal lower limb power output (Pmax) and their individual force-velocity (F-v) mechanical profile, especially the F-v imbalance (FVimb): difference between the athlete's actual and optimal profile. An optimized training should aim to increase Pmax and/or reduce FVimb. The aim of this study was to test whether an individualized training program based on the individual F-v profile would decrease subjects' individual FVimb and in turn improve vertical jump performance. FVimb was used as the reference to assign participants to different training intervention groups. Eighty four subjects were assigned to three groups: an “optimized” group divided into velocity-deficit, force-deficit, and well-balanced sub-groups based on subjects' FVimb, a “non-optimized” group for which the training program was not specifically based on FVimb and a control group. All subjects underwent a 9-week specific resistance training program. The programs were designed to reduce FVimb for the optimized groups (with specific programs for sub-groups based on individual FVimb values), while the non-optimized group followed a classical program exactly similar for all subjects. All subjects in the three optimized training sub-groups (velocity-deficit, force-deficit, and well-balanced) increased their jumping performance (12.7 ± 5.7% ES = 0.93 ± 0.09, 14.2 ± 7.3% ES = 1.00 ± 0.17, and 7.2 ± 4.5% ES = 0.70 ± 0.36, respectively) with jump height improvement for all subjects, whereas the results were much more variable and unclear in the non-optimized group. This greater change in jump height was associated with a markedly reduced FVimb for both force-deficit (57.9 ± 34.7% decrease in FVimb) and velocity-deficit (20.1 ± 4.3%) subjects, and unclear or small changes in Pmax (−0.40 ± 8.4% and +10.5 ± 5.2%, respectively). An individualized training program specifically based on FVimb (gap between the actual and optimal F-v profiles of each individual) was more efficient at improving jumping performance (i.e., unloaded squat jump height) than a traditional resistance training common to all subjects regardless of their FVimb. Although improving both FVimb and Pmax has to be considered to improve ballistic performance, the present results showed that reducing FVimb without even increasing Pmax lead to clearly beneficial jump performance changes. Thus, FVimb could be considered as a potentially useful variable for prescribing optimal resistance training to improve ballistic performance.
Purpose:
To ascertain whether force-velocity-power relationships could be compiled from a battery of sled-resisted overground sprints and to clarify and compare the optimal loading conditions for maximizing power production for different athlete cohorts.
Methods:
Recreational mixed-sport athletes (n = 12) and sprinters (n = 15) performed multiple trials of maximal sprints unloaded and towing a selection of sled masses (20-120% body mass [BM]). Velocity data were collected by sports radar, and kinetics at peak velocity were quantified using friction coefficients and aerodynamic drag. Individual force-velocity and power-velocity relationships were generated using linear and quadratic relationships, respectively. Mechanical and optimal loading variables were subsequently calculated and test-retest reliability assessed.
Results:
Individual force-velocity and power-velocity relationships were accurately fitted with regression models (R2> .977, P < .001) and were reliable (ES = 0.05-0.50, ICC = .73-.97, CV = 1.0-5.4%). The normal loading that maximized peak power was 78% ± 6% and 82% ± 8% of BM, representing a resistance of 3.37 and 3.62 N/kg at 4.19 ± 0.19 and 4.90 ± 0.18 m/s (recreational athletes and sprinters, respectively). Optimal force and normal load did not clearly differentiate between cohorts, although sprinters developed greater maximal power (17.2-26.5%, ES = 0.97-2.13, P < .02) at much greater velocities (16.9%, ES = 3.73, P < .001).
Conclusions:
Mechanical relationships can be accurately profiled using common sled-training equipment. Notably, the optimal loading conditions determined in this study (69-96% of BM, dependent on friction conditions) represent much greater resistance than current guidelines (~7-20% of BM). This method has potential value in quantifying individualized training parameters for optimized development of horizontal power.
The ability of the human body to generate maximal power is linked to a host of performance outcomes and sporting success. Power-force-velocity relationships characterize limits of the neuromuscular system to produce power, and their measurement has been a common topic in research for the past century. Unfortunately, the narrative of the available literature is complex, with development occurring across a variety of methods and technology. This review focuses on the different equipment and methods used to determine mechanical characteristics of maximal exertion human sprinting. Stationary cycle ergometers have been the most common mode of assessment to date, followed by specialized treadmills used to profile the mechanical outputs of the limbs during sprint running. The most recent methods use complex multiple-force plate lengths in-ground to create a composite profile of over-ground sprint running kinetics across repeated sprints, and macroscopic inverse dynamic approaches to model mechanical variables
Background:
Sprint running acceleration is a key feature of physical performance in team sports, and recent literature shows that the ability to generate large magnitudes of horizontal ground-reaction force and mechanical effectiveness of force application are paramount. The authors tested the hypothesis that very-heavy loaded sled sprint training would induce an improvement in horizontal-force production, via an increased effectiveness of application.
Methods:
Training-induced changes in sprint performance and mechanical outputs were computed using a field method based on velocity-time data, before and after an 8-wk protocol (16 sessions of 10- × 20-m sprints). Sixteen male amateur soccer players were assigned to either a very-heavy sled (80% body mass sled load) or a control group (unresisted sprints).
Results:
The main outcome of this pilot study is that very-heavy sled-resisted sprint training, using much greater loads than traditionally recommended, clearly increased maximal horizontal-force production compared with standard unloaded sprint training (effect size of 0.80 vs 0.20 for controls, unclear between-groups difference) and mechanical effectiveness (ie, more horizontally applied force; effect size of 0.95 vs -0.11, moderate between-groups difference). In addition, 5-m and 20-m sprint performance improvements were moderate and small for the very-heavy sled group and small and trivial for the control group, respectively. Practical Applications: This brief report highlights the usefulness of very-heavy sled (80% body mass) training, which may suggest value for practical improvement of mechanical effectiveness and maximal horizontal-force capabilities in soccer players and other team-sport athletes.
Results:
This study may encourage further research to confirm the usefulness of very-heavy sled in this context.
A more horizontally oriented ground reaction force vector is related to higher levels of sprint acceleration performance across a range of athletes. However, the effects of acute experimental alterations to the force vector orientation within athletes are unknown. Fifteen male team sports athletes completed maximal effort 10-m accelerations in three conditions following different verbal instructions intended to manipulate the force vector orientation. Ground reaction forces (GRFs) were collected from the step nearest 5-m and stance leg kinematics at touchdown were also analysed to understand specific kinematic features of touchdown technique which may influence the consequent force vector orientation. Magnitude-based inferences were used to compare findings between conditions. There was a likely more horizontally oriented ground reaction force vector and a likely lower peak vertical force in the control condition compared with the experimental conditions. 10-m sprint time was very likely quickest in the control condition which confirmed the importance of force vector orientation for acceleration performance on a within-athlete basis. The stance leg kinematics revealed that a more horizontally oriented force vector during stance was preceded at touchdown by a likely more dorsiflexed ankle, a likely more flexed knee, and a possibly or likely greater hip extension velocity.
The barbell hip thrust may be an effective exercise for increasing horizontal force production and may thereby enhance performance in athletic movements requiring a horizontal force vector, such as horizontal jumping and sprint running. The ergogenic ability of the squat is well known. The purpose of this study was to compare the effects of six-week front squat and hip thrust programs in adolescent male athletes. Vertical jump height, horizontal jump distance, 10 m and 20 m sprint times, and isometric mid-thigh pull peak force were among the measured performance variables, in addition to front squat and hip thrust three-repetition maximum (3 RM) strength. Magnitude-based effect-sizes revealed potentially beneficial effects for the front squat in both front squat 3 RM strength and vertical jump height when compared to the hip thrust. No clear benefit for one intervention was observed for horizontal jump performance. Potentially beneficial effects were observed for the hip thrust compared to the front squat in 10 m and 20 m sprint times. The hip thrust was likely superior for improving normalized isometric mid-thigh pull strength, and very likely superior for improving hip thrust 3 RM and isometric mid-thigh pull strength. These results support the force vector theory.
Purpose:
To explore the effects of training against mechanically different types of loads on muscle force (F), velocity (V), and power (P) outputs.
Methods:
Subjects practiced maximum bench throws over 8 wk against a bar predominantly loaded by approximately constant external force (weight), weight plates (weight plus inertia), or weight plates whose weight was compensated by a constant external force pulling upward (inertia). Instead of a typically applied single trial performed against a selected load, the pretest and posttest consisted of the same task performed against 8 different loads ranging from 30% to 79% of the subject's maximum strength applied by adding weight plates to the bar. That provided a range of F and V data for subsequent modeling by linear F-V regression revealing the maximum F (F-intercept), V (V-intercept), and P (P = FV/4).
Results:
Although all 3 training conditions resulted in increased P, the inertia type of the training load could be somewhat more effective than weight. An even more important finding was that the P increase could be almost exclusively based on a gain in F, V, or both when weight, inertia, or weight-plus-inertia training load were applied, respectively.
Conclusions:
The inertia training load is more effective than weight in increasing P and weight and inertia may be applied for selective gains in F and V, respectively, whereas the linear F-V model obtained from loaded trials could be used for discerning among muscle F, V, and P.
This review article discusses previous literature that has examined the influence of muscular strength on various factors associated with athletic performance and the benefits of achieving greater muscular strength. Greater muscular strength is strongly associated with improved force-time characteristics that contribute to an athlete’s overall performance. Much research supports the notion that greater muscular strength can enhance the ability to perform general sport skills such as jumping, sprinting, and change of direction tasks. Further research indicates that stronger athletes produce superior performances during sport specific tasks. Greater muscular strength allows an individual to potentiate earlier and to a greater extent, but also decreases the risk of injury. Sport scientists and practitioners may monitor an individual’s strength characteristics using isometric, dynamic, and reactive strength tests and variables. Relative strength may be classified into strength deficit, strength association, or strength reserve phases. The phase an individual falls into may directly affect their level of performance or training emphasis. Based on the extant literature, it appears that there may be no substitute for greater muscular strength when it comes to improving an individual’s performance across a wide range of both general and sport specific skills while simultaneously reducing their risk of injury when performing these skills. Therefore, sport scientists and practitioners should implement long-term training strategies that promote the greatest muscular strength within the required context of each sport/event. Future research should examine how force-time characteristics, general and specific sport skills, potentiation ability, and injury rates change as individuals transition from certain standards or the suggested phases of strength to another.
Recent studies have brought new insights into the evaluation of power-force-velocity profiles in both ballistic push-offs (e.g. jumps) and sprint movements. These are major physical components of performance in many sports, and the methods we developed and validated are based on data that are now rather simple to obtain in field conditions (e.g. body mass, jump height, sprint times or velocity). The promising aspect of these approaches is that they allow for a more individualized and accurate evaluation, monitoring, and training practices; the success of which are highly dependent on the correct collection, generation and interpretation of athletes' mechanical outputs. We therefore wanted to provide a practical vade mecum to sports practitioners interested in implementing these power-force-velocity profiling approaches. After providing a summary of theoretical and practical definitions for the main variables, we have first detailed how vertical profiling can be used to manage ballistic push-off performance with emphasis on the concept of optimal force-velocity profile and the associated force-velocity imbalance. Further, we have discussed these same concepts with regards to horizontal profiling in the management of sprinting performance. These sections have been illustrated by typical examples from our own practice. Finally, we have provided a practical and operational synthesis, and outlined future challenges that will help in further developing these approaches.
At the end of this chapter, you will be able to: • Explain the multidimensional nature of sprint running and its implications for training and testing • Describe the mechanical aspects of sprint running • Describe the biomechanical aspects of sprint running • Explain the etiology of some of the common musculoskeletal injuries associated with sprint running • Develop a qualitative analysis of sprint running • Develop specifi c workouts targeting muscular strength commensurate with the biomechanical aspects of sprint running • Explain agility performance and its importance in sport • Develop specifi c workouts based on representative learning that enhance the attunement of the athlete's sprinting and agility movements to environmental information
Very little is currently known about the effects of acute hamstring injury on over-ground sprinting mechanics. The aim of this research was to describe changes in power-force-velocity properties of sprinting in two injury case studies related to hamstring strain management: Case 1: during a repeated sprint task (10 sprints of 40 m) when an injury occurred (5th sprint) in a professional rugby player; and Case 2: prior to (8 days) and after (33 days) an acute hamstring injury in a professional soccer player. A sports radar system was used to measure instantaneous velocity-time data, from which individual mechanical profiles were derived using a recently validated method based on a macroscopic biomechanical model. Variables of interest included: maximum theoretical velocity (V0) and horizontal force (FH0), slope of the force-velocity (F-v) relationship, maximal power, and split times over 5 and 20 m. For Case 1, during the injury sprint (sprint 5), there was a clear change in the F-v profile with a 14% greater value of FH0 (7.6-8.7 N/kg) and a 6% decrease in V0 (10.1 to 9.5 m/s). For Case 2, at return to sport, the F-v profile clearly changed with a 20.5% lower value of FH0 (8.3 vs. 6.6 N/kg) and no change in V0. The results suggest that the capability to produce horizontal force at low speed (FH0) (i.e. first metres of the acceleration phase) is altered both before and after return to sport from a hamstring injury in these two elite athletes with little or no change of maximal velocity capabilities (V0), as evidenced in on-field conditions. Practitioners should consider regularly monitoring horizontal force production during sprint running both from a performance and injury prevention perspective.
Investigating the differences between distinct phases of sprint running may increase the knowledge about the specific physical abilities needed for different phases of sprinting. Differences between the mid-acceleration and the maximum velocity phase of sprint running have not yet been adequately investigated. Twenty male sprinters performed maximum-effort sprint runs, and measurements were made at 12m from start for the mid-acceleration phase and at 40m from the start for the maximum velocity phase. Kinematic data and ground reaction forces (GRF) were collected at a rate of 200 and 1000 Hz, respectively. Intersegmental dynamics analysis (ISD) was performed to investigate the interaction of muscle torque (MUS) with other passive torques. The peak horizontal braking force was significantly lower for the acceleration compared to the maximal velocity phase, while the peak horizontal propulsive force was similar for the two phases. The peak MUS torques at the hip and knee joints for the braking phase were significantly smaller in the acceleration than the maximum velocity phase. In conclusion, compared with the maximum velocity phase, the lower horizontal braking force was the primary cause for the increase in running velocity during the mid-acceleration phase. The force produced by lower limb muscles required to counteract external torques (EXT) caused by the horizontal braking force in the braking phase was smaller during the acceleration phase than the maximum velocity phase. Therefore, training aimed at reducing the horizontal braking force might be more important than increasing the force produced by the lower limb muscles for success of the mid-acceleration phase. Copyright (C) 2015 by the National Strength & Conditioning Association.
The process of strength–power training and the subsequent adaptation is a multi-factorial process. These factors range from the genetics and morphological characteristics of the athlete to how a coach selects, orders, and doses exercises and loading patterns. Consequently, adaptation from these training factors may largely relate to the mode of delivery, in other words, programming tactics. There is strong evidence that the manner and phases in which training is presented to the athlete can make a profound difference in performance outcome. This discussion deals primarily with block periodization concepts and associated methods of programming for strength–power training within track and field.
The aim of this study was to investigate the effects of adding vertical/horizontal plyometrics to the soccer training routine on jumping and sprinting performance in U-20 soccer players. The vertical jumping group (VJG) performed countermovement jumps (CMJ), while the horizontal jumping group (HJG) executed horizontal jumps (HJ). Training interventions comprised 11 sessions, with volume varying between 32-60 jumps per session. The analysis of covariance revealed that CMJ height and peak force improved only in the VJG, and that HJ distance and peak force improved in both groups. Velocity in 20 m (VEL 20 m) did not improve in either group; however, velocity in 10 m (VEL 10 m) presented a moderate positive effect size (ES = 0.66) in the HJG, while the ES was large (1.63) for improvement in the 10-20 m acceleration in the VJG and largely negative (-1.09) in the HJG. The transference effect coefficients (calculated by the equation: TEC = result gain (ES) in nontrained exercise/result gain (ES) in trained exercise) between CMJ and VEL 20 m and ACC 10-20 m were 1.31 and 2.75, respectively. The TEC between HJ and VEL 10 m, VEL 20 m and ACC 0-10 m were 0.44, 0.17, and 0.44, respectively. The results presented herein indicate that the plyometric training-axis is decisive in determining the neuromechanical training responses in high-level soccer players.
This study determined the effects of simulated technique manipulations on early acceleration performance. A planar seven-segment angle-driven model was developed and quantitatively evaluated based on the agreement of its output to empirical data from an international-level male sprinter (100 m personal best = 10.28 s). The model was then applied to independently assess the effects of manipulating touchdown distance (horizontal distance between the foot and centre of mass) and range of ankle joint dorsiflexion during early stance on horizontal external power production during stance. The model matched the empirical data with a mean difference of 5.2%. When the foot was placed progressively further forward at touchdown, horizontal power production continually reduced. When the foot was placed further back, power production initially increased (a peak increase of 0.7% occurred at 0.02 m further back) but decreased as the foot continued to touchdown further back. When the range of dorsiflexion during early stance was reduced, exponential increases in performance were observed. Increasing negative touchdown distance directs the ground reaction force more horizontally; however, a limit to the associated performance benefit exists. Reducing dorsiflexion, which required achievable increases in the peak ankle plantar flexor moment, appears potentially beneficial for improving early acceleration performance.
This study aimed to validate a simple field method for determining force- and power-velocity relationships and mechanical effectiveness of force application during sprint running. The proposed method, based on an inverse dynamic approach applied to the body center of mass, estimates the step-averaged ground reaction forces in runner's sagittal plane of motion during overground sprint acceleration from only anthropometric and spatiotemporal data. Force- and power-velocity relationships, the associated variables, and mechanical effectiveness were determined (a) on nine sprinters using both the proposed method and force plate measurements and (b) on six other sprinters using the proposed method during several consecutive trials to assess the inter-trial reliability. The low bias (<5%) and narrow limits of agreement between both methods for maximal horizontal force (638 ± 84 N), velocity (10.5 ± 0.74 m/s), and power output (1680 ± 280 W); for the slope of the force-velocity relationships; and for the mechanical effectiveness of force application showed high concurrent validity of the proposed method. The low standard errors of measurements between trials (<5%) highlighted the high reliability of the method. These findings support the validity of the proposed simple method, convenient for field use, to determine power, force, velocity properties, and mechanical effectiveness in sprint running.
© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
The objective of this study was to characterize the mechanics of maximal running sprint acceleration in high-level athletes. Four elite (100-m best time 9.95–10.29 s) and five sub-elite (10.40–10.60 s) sprinters performed seven sprints in overground conditions. A single virtual 40-m sprint was reconstructed and kinetics parameters were calculated for each step using a force platform system and video analyses. Anteroposterior force (FY), power (PY), and the ratio of the horizontal force component to the resultant (total) force (RF, which reflects the orientation of the resultant ground reaction force for each support phase) were computed as a function of velocity (V). FY-V, RF-V, and PY-V relationships were well described by significant linear (mean R2 of 0.892 ± 0.049 and 0.950 ± 0.023) and quadratic (mean R2 = 0.732 ± 0.114) models, respectively. The current study allows a better understanding of the mechanics of the sprint acceleration notably by modeling the relationships between the forward velocity and the main mechanical key variables of the sprint. As these findings partly concern world-class sprinters tested in overground conditions, they give new insights into some aspects of the biomechanical limits of human locomotion.
Background:
Although lower-body strength is correlated with sprint performance, whether increases in lower-body strength transfer positively to sprint performance remain unclear.
Objectives:
This meta-analysis determined whether increases in lower-body strength (measured with the free-weight back squat exercise) transfer positively to sprint performance, and identified the effects of various subject characteristics and resistance-training variables on the magnitude of sprint improvement.
Methods:
A computerized search was conducted in ADONIS, ERIC, SPORTDiscus, EBSCOhost, Google Scholar, MEDLINE and PubMed databases, and references of original studies and reviews were searched for further relevant studies. The analysis comprised 510 subjects and 85 effect sizes (ESs), nested with 26 experimental and 11 control groups and 15 studies.
Results:
There is a transfer between increases in lower-body strength and sprint performance as indicated by a very large significant correlation (r = -0.77; p = 0.0001) between squat strength ES and sprint ES. Additionally, the magnitude of sprint improvement is affected by the level of practice (p = 0.03) and body mass (r = 0.35; p = 0.011) of the subject, the frequency of resistance-training sessions per week (r = 0.50; p = 0.001) and the rest interval between sets of resistance-training exercises (r = -0.47; p ≤ 0.001). Conversely, the magnitude of sprint improvement is not affected by the athlete's age (p = 0.86) and height (p = 0.08), the resistance-training methods used through the training intervention, (p = 0.06), average load intensity [% of 1 repetition maximum (RM)] used during the resistance-training sessions (p = 0.34), training program duration (p = 0.16), number of exercises per session (p = 0.16), number of sets per exercise (p = 0.06) and number of repetitions per set (p = 0.48).
Conclusions:
Increases in lower-body strength transfer positively to sprint performance. The magnitude of sprint improvement is affected by numerous subject characteristics and resistance-training variables, but the large difference in number of ESs available should be taken into consideration. Overall, the reported improvement in sprint performance (sprint ES = -0.87, mean sprint improvement = 3.11 %) resulting from resistance training is of practical relevance for coaches and athletes in sport activities requiring high levels of speed.
The overall objective of this review was to investigate the role and development of sprinting speed in soccer. Time motion analyses show that short sprints occur frequently during soccer games. Straight sprinting is the most frequent action prior to goals, both for the scoring and assisting player. Straight line sprinting velocity (both acceleration and maximal sprinting speed), certain agility skills and repeated sprint ability are shown to distinguish groups from different performance levels. Professional players have become faster over time, indicating that sprinting skills are becoming more and more important in modern soccer. In research literature, the majority of soccer related training interventions have provided positive effects on sprinting capabilities, leading to the assumption that all kinds of training can be performed with success. However, most successful intervention studies are time consuming and challenging to incorporate into the overall soccer training program. Even though the principle of specificity is clearly present, several questions remain regarding the optimal training methods within the larger context of the team sport setting. Considering time-efficiency effects, soccer players may benefit more by performing sprint training regimes similar to the progression model used in strength training and by world leading athletics practitioners, compared to the majority of guidelines that traditionally have been presented in research literature.
This series of reviews focuses on the most important neuromuscular function in many sport performances: the ability to generate maximal muscular power. Part 1, published in an earlier issue of Sports Medicine, focused on the factors that affect maximal power production while part 2 explores the practical application of these findings by reviewing the scientific literature relevant to the development of training programmes that most effectively enhance maximal power production. The ability to generate maximal power during complex motor skills is of paramount importance to successful athletic performance across many sports. A crucial issue faced by scientists and coaches is the development of effective and efficient training programmes that improve maximal power production in dynamic, multi-joint movements. Such training is referred to as 'power training' for the purposes of this review. Although further research is required in order to gain a deeper understanding of the optimal training techniques for maximizing power in complex, sports-specific movements and the precise mechanisms underlying adaptation, several key conclusions can be drawn from this review. First, a fundamental relationship exists between strength and power, which dictates that an individual cannot possess a high level of power without first being relatively strong. Thus, enhancing and maintaining maximal strength is essential when considering the long-term development of power. Second, consideration of movement pattern, load and velocity specificity is essential when designing power training programmes. Ballistic, plyometric and weightlifting exercises can be used effectively as primary exercises within a power training programme that enhances maximal power. The loads applied to these exercises will depend on the specific requirements of each particular sport and the type of movement being trained. The use of ballistic exercises with loads ranging from 0% to 50% of one-repetition maximum (1RM) and/or weightlifting exercises performed with loads ranging from 50% to 90% of 1RM appears to be the most potent loading stimulus for improving maximal power in complex movements. Furthermore, plyometric exercises should involve stretch rates as well as stretch loads that are similar to those encountered in each specific sport and involve little to no external resistance. These loading conditions allow for superior transfer to performance because they require similar movement velocities to those typically encountered in sport. Third, it is vital to consider the individual athlete's window of adaptation (i.e. the magnitude of potential for improvement) for each neuromuscular factor contributing to maximal power production when developing an effective and efficient power training programme. A training programme that focuses on the least developed factor contributing to maximal power will prompt the greatest neuromuscular adaptations and therefore result in superior performance improvements for that individual. Finally, a key consideration for the long-term development of an athlete's maximal power production capacity is the need for an integration of numerous power training techniques. This integration allows for variation within power meso-/micro-cycles while still maintaining specificity, which is theorized to lead to the greatest long-term improvement in maximal power.
Forces applied to the ground during sprinting are vital to performance. This study aimed to understand how specific aspects of ground reaction force waveforms allow some individuals to continue to accelerate beyond the velocity plateau of others. Twenty‐eight male sprint specialists and 24 male soccer players performed maximal‐effort 60‐m sprints. A 54‐force‐plate system captured ground reaction forces, which were used to calculate horizontal velocity profiles. Touchdown velocities of steps were matched (8.00, 8.25 and 8.50 m·s⁻¹) and the subsequent ground contact forces were analysed. Mean forces were compared across groups and statistical parametric mapping (t‐tests) assessed for differences between entire force waveforms. When individuals contacted the ground with matched horizontal velocity, ground contact durations were similar. Despite this, sprinters produced higher average horizontal power (15.7‐17.9 W·kg⁻¹) than the soccer players (7.9‐11.9 W·kg⁻¹). Force waveforms did not differ in the initial braking phase (0‐~20% of stance). However, sprinters attenuated eccentric force more in the late braking phase and produced a higher anteroposterior component of force across the majority of the propulsive phase, for example from 31‐82% and 92‐100% of stance at 8.5 m·s⁻¹. At this velocity, resultant forces were also higher (33‐83% and 86‐100% of stance) and the force vector was more horizontally orientated (30‐60% and 95‐98% of stance) in the sprinters. These findings illustrate the mechanisms which allowed the sprinters to continue accelerating beyond the soccer players’ velocity plateau. Moreover, these force production demands provide new insight regarding athletes’ strength and technique training requirements to improve acceleration at high velocity.
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A macroscopic view of sprint mechanics during an acceleration phase, and notably athlete’s propulsion capacities, can be given by Force-velocity (F-v) and Power-velocity (P-v) relationships. They characterize the change in athlete’s maximal horizontal force and power production capabilities when running speed increases and directly determine sprint acceleration performance. This chapter presents an accurate and reliable simple method to determine these mechanical capabilities during sprinting. This method, based on a macroscopic biomechanical model and validated in laboratory conditions in comparison to force plate measurements, is very convenient for field use since it only requires anthropometric (body mass and stature) and spatio-temporal (split times or instantaneous velocity) input variables. It provides different information on athlete’s horizontal force production capabilities: maximal power output, maximal horizontal force, maximal velocity until which horizontal force can be produced and mechanical effectiveness of force application onto the ground. This information presents interesting practical applications for sport practitioners to individualize training focusing on sprint acceleration performance, but also perspectives in injury management. This chapter presents different examples of such applications. Moreover, this simple method can also help to bring new insight into the limits of human locomotion since it makes possible to estimate sprinting mechanical properties of the fastest men and women without testing them in a laboratory.
Training or rehabilitation programs have to induce changes in force(F)- velocity(v)-power(P) capabilities according to both mechanical demands of the targeted task and actual athlete’s muscle capabilities. To determine individual strengths and weaknesses and then individualize strength training modalities, it is essential to know which mechanical capabilities lower limb muscles have to present to maximize ballistic push-off performances. In this chapter, we explore the relationship between the different lower limb muscle mechanical capabilities and ballistic push-off performances. A biomechanical model is presented to bring new insights on the effect of F-v profile on ballistic performances, notably on the existence of an optimal F-v profile. The latter can be accurately determined for each athlete using equations given in this chapter and usual squat jump FvP profile evaluations, including testing using the simple field method presented in Chap. 4. This makes possible the determination of F-v imbalance (towards force or velocity capabilities) and the quantification of the magnitude of the associated force or velocity deficits. These indexes constitute interesting tools to individualize athlete’s training programs aiming to improve athletes’ ballistic performance. These individual programs should focus on increasing lower limb maximal power and/or decreasing force-velocity imbalance. The effectiveness of such an individualized “optimized” training was shown to be greater than a traditional strength training similar for all athletes. This supports the great interest for strength and conditioning coaches, who aim to improve athlete’s ballistic performance, to evaluate FvP profile on each of their athlete and to consider F-v imbalance to design individually training regimen.
We aimed to clarify the mechanical determinants of sprinting performance during acceleration and maximal speed phases of a single sprint, using ground reaction forces (GRFs). While 18 male athletes performed a 60-m sprint, GRF was measured at every step over a 50-m distance from the start. Variables during the entire acceleration phase were approximated with a fourth-order polynomial. Subsequently, accelerations at 55%, 65%, 75%, 85%, and 95% of maximal speed, and running speed during the maximal speed phase were determined as sprinting performance variables. Ground reaction impulses and mean GRFs during the acceleration and maximal speed phases were selected as independent variables. Stepwise multiple regression analysis selected propulsive and braking impulses as contributors to acceleration at 55%-95% (β > 0.724) and 75%-95% (β > 0.176), respectively, of maximal speed. Moreover, mean vertical force was a contributor to maximal running speed (β = 0.481). The current results demonstrate that exerting a large propulsive force during the entire acceleration phase, suppressing braking force when approaching maximal speed, and producing a large vertical force during the maximal speed phase are essential for achieving greater acceleration and maintaining higher maximal speed, respectively.
This study aimed to describe changes in step width (SW) during accelerated sprinting, and to clarify the relationship of SW with sprinting performance and ground reaction forces. 17 male athletes performed maximal-effort 60 m sprints. The SW and other spatiotemporal variables, as well as ground reaction impulses, over a 52 m distance were calculated. Average values for each 4 steps during acceleration were calculated to examine relationships among variables in different sections. The SW rapidly decreased up to the 13th step and slightly afterward during accelerated sprinting, showing a bilinear phase profile. The ratio of SW to the stature was significantly correlated with running speed based on average values over the 52 m distance and in the 9th-12th step section during accelerated sprinting. The SW ratio positively correlated with medial, lateral and mediolateral impulses in all step sections, except for medial impulse in the 17th-20th step section. These results indicate the importance of wider SW for better sprinting performance, especially in the 9th-12th step section. Moreover, the wider SW was associated with larger medial impulse and smaller lateral impulse, suggesting that a wide SW contributes to the production of greater mediolateral body velocity during accelerated sprinting.
No abstract is available for this article.
SUMMARY: THE ABILITY TO EXPRESS HIGH POWER OUTPUTS IS CONSIDERED TO BE ONE OF THE FOUNDATIONAL CHARACTERISTICS UNDERLYING SUCCESSFUL PERFORMANCE IN A VARIETY OF SPORTING ACTIVITIES, INCLUDING JUMPING, THROWING, AND CHANGING DIRECTION. NUMEROUS TRAINING INTERVENTIONS HAVE BEEN RECOMMENDED TO ENHANCE THE ATHLETE'S ABILITY TO EXPRESS HIGH POWER OUTPUTS AND IMPROVE THEIR OVERALL SPORTS PERFORMANCE CAPACITY. THIS BRIEF REVIEW EXAMINES THE FACTORS THAT UNDERLIE THE EXPRESSION OF POWER AND VARIOUS METHODS THAT CAN BE USED TO MAXIMIZE POWER DEVELOPMENT. (C) 2012 National Strength and Conditioning Association
Are the fastest running speeds achieved using the simple-spring stance mechanics predicted by the classic spring-mass model? We hypothesized that a passive, linear-spring model would not account for the running mechanics that maximize ground force application and speed. We tested this hypothesis by comparing patterns of ground force application across athletic specialization (competitive sprinters vs. athlete non-sprinters; n=7 each) and running speed (top speeds vs. slower ones). Vertical ground reaction forces at 5.0 m•s(-1), 7.0 m•s(-1) and individual top speeds (n=797 total footfalls) were acquired while subjects ran on a custom, high-speed force treadmill. The goodness of fit between measured vertical force vs. time waveform patterns and the patterns predicted by the spring-mass model were assessed using the R(2) statistic (where an R(2) of 1.00 = perfect fit). As hypothesized, the force application patterns of the competitive sprinters deviated significantly more from the simple-spring pattern than those of the athlete, non-sprinters across the three test speeds (R(2) < 0.85 vs. R(2) ≥ 0.91, respectively), and deviated most at top speed (R(2)=0.78±0.02). Sprinters attained faster top speeds than non-sprinters (10.4±0.3 vs. 8.7±0.3 m•s(-1)) by applying greater vertical forces during the first half (2.65±0.05 vs. 2.21±0.05 body weights), but not the second half (1.71±0.04 vs. 1.73±0.04 body weights) of the stance phase. We conclude that a passive, simple-spring model has limited application to sprint running performance because the swiftest runners use an asymmetrical pattern of force application to maximize ground reaction forces and attain faster speeds.
The purpose of this review was to consider the association of measures of maximum strength inrelation to sports performance and performance variables, which rely on high levels of power and speed, in essence it is an expansion of the ideas and concepts presented by 39. Evidence from different types of cross-sectional research as well as observational data was considered. Collectively the data indicate that the association between maximum strength and sport performance related variables such as peak power and peak rate of force development is quite strong. While explaining performance in strength/power sports is a multi-factorial problem, there is little doubt that maximum strength is a key component.
Weighted sled towing is used by athletes to improve sprint acceleration ability. The typical coaching recommendation is to use relatively light loads, as excessively heavy loads are hypothesized to disrupt running mechanics and be detrimental to sprint performance. However, this coaching recommendation has not been empirically tested. This study compared the effects of weighted sled towing with two different external loads on sprint acceleration ability. Twenty-one physically active men were randomly allocated to heavy- (n = 10) or light-load weighted sled towing (n = 11) groups. All subjects participated in two training sessions per week for 8 weeks. The subjects in the heavy and light groups performed weighted sled towing using external loads that reduced sprint velocity by ∼30% and ∼10%, respectively. Before and after the training, the subjects performed a 10-m sprint test, in which split time was measured at 5 and 10 m from the start. The heavy group significantly improved both the 5- and 10-m sprint time by 5.7 ± 5.7% and 5.0 ± 3.5%, respectively (P < 0.05), whereas only 10-m sprint time was improved significantly by 3.0 ± 3.5% (P < 0.05) in the light group. No significant differences were found between the groups in the changes in 5-m and 10-m sprint time from pre- to post-training. These results question the notion that training loads that induce greater than 10% reduction in sprint velocity would negatively affect sprint performance, and point out the potential benefit of using a heavier load for weighted sled towing.
THE TRAINING OF HORIZONTAL PROPULSIVE FORCE GENERATION IS ONE ASPECT OF MANY SPORTS THAT IS NOT EASILY SIMULATED WITH TRADITIONAL GYM-BASED RESISTANCE TRAINING METHODS, WHICH PRINCIPALLY WORK THE LEG MUSCULATURE IN A VERTICAL DIRECTION. GIVEN THAT MOST MOTION INVOLVES AN INTEGRATION OF BOTH VERTICAL AND HORIZONTAL FORCE PRODUCTION, TRANSFERENCE OF GYM-BASED STRENGTH GAINS MAY BE IMPROVED IF EXERCISES WERE USED THAT INVOLVED BOTH VERTICAL AND HORIZONTAL FORCE PRODUCTION.
The relationships between ground reaction forces, electromyographic activity (EMG), elasticity and running velocity were investigated
at five speeds from submaximal to supramaximal levels in 11 male and 8 female sprinters. Supramaximal running was performed
by a towing system. Reaction forces were measured on a force platform. EMGs were recorded telemetrically with surface electrodes
from the vastus lateralis and gastrocnemius muscles, and elasticity of the contact leg was evaluated with spring constant
values measured by film analysis. Data showed increases in most of the parameters studied with increasing running speed. At
supramaximal velocity (10.36±0.31 m×s−1; 108.4±3.8%) the relative increase in running velocity correlated significantly (P<0.01) with the relative increase in stride rate of all subjects. In male subjects the relative change in stride rate correlated
with the relative change of IEMG in the eccentric phase (P<0.05) between maximal and supramaximal runs. Running with the towing system caused a decrease in elasticity during the impact
phase but this was significant (P<0.05) only in the female sprinters. The average net resultant force in the eccentric and concentric phases correlated significantly
(P<0.05−0.001) with running velocity and stride length in the maximal run. It is concluded that (1) increased neural activation
in supramaximal effort positively affects stride rate and that (2) average net resultant force as a specific force indicator
is primarily related to stride length and that (3) the values in this indicator may explain the difference in running velocity
between men and women.