Increasing Running Speed Research Articles

EMG Activity of Lower Limb Muscles during Anti-Gravity Treadmill Running with Different Loads and Speeds

The study’s objective was to identify the features of internal movement structure that depend on speed and the importance of unloading when jogging on an anti-gravity treadmill. The aim was to investigate whether the internal structure of running changes under unloaded conditions, using an anti-gravity treadmill. Twenty male competitive middle- and long-distance runners with the following characteristics participated in the study: age, 25 ± 5 years; body weight, 67.2 ± 8.9 kg; body height, 177 ± 11 cm; and training experience, 9 ± 5 years. The gastrocnemius (GC), tibialis anterior (T), quadriceps femoris (Q), biceps femoris (B), and gluteus (G) were the five lower limb muscles whose muscle activity was evaluated. Surface electromyography (sEMG) was used to measure muscle activation while jogging and running on the AlterG Anti-Gravity Treadmill. The study method involved capturing the examined muscular activity at four different speeds: 6, 10, 14, and 18 km/h. At each of these speeds, four two-minute measurements were taken with varying body weight relief: 100%, 75%, 50%, and 25% of body weight. Repeated measures multivariate analysis of variance (RM-MANOVA) [F = 3.4663 p = 0.0001] showed that as running speed increases, the muscular activity of each muscle, expressed as a percentage of maximum muscle tension (%MVIC), decreases significantly. Results indicate that running pace affects the dynamics of the reduction in muscle activity in every examined muscle. As one runs faster, the decline in dynamics becomes more intense. At the slowest jogging pace (6 km/h), the variations were almost negligible (±4 percentage points between 25% and 100% body weight relief) as unloading increased. However, the discrepancies reached up to 14 percentage points at the fastest running speed (18 km/h). In every muscle studied, distinctive patterns and significant dynamics at high speeds were observed. The study’s findings suggest that using an anti-gravity treadmill for training can be beneficial, yet it is important to consider the significant relationships between speed and relief, as these variables could impact maintaining a proper movement pattern and running style. This knowledge may be useful when choosing the right training regimens and loads for runners recovering from injuries.

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.

Features of the development of speed skills in football players

This article examines the issues of speed training, training speed in football players aimed at increasing running speed and "transferring" this speed to running with the ball. This process of "transferring" speed abilities is more effective when an athlete in normal running emphasizes the frequency of movements, but not the length of running steps, that is, he overcomes training segments with slightly shortened steps, which in their rhythmic structure are similar to steps in running with m' cell. Speed training falls, in fact, on the pubertal phase of the body development of young athletes, when puberty is accompanied by a rapid increase in muscle mass, glycogen reserves, and an increase in the level of secretion of adrenaline and gonadal hormones. At this time, optimal biological prerequisites are created for the development of anaerobic capabilities, maximal strength, power endurance, and speed-power qualities. The volume of loads should increase at the fastest pace in the development of strength endurance, which reaches its maximum values by the end of the stage. Gradually, exercises with maximum efforts, performed in overcoming, yielding and isokinetic modes, are included in the training.
 Speed abilities are very difficult to develop. The possibility of speed increase in locomotor cyclic acts is very limited. In the process of sports training, an increase in the speed of movements is achieved both by influencing the actual speed abilities, and in another way - through the development of strength and speed-strength abilities, speed endurance, improvement of the technique of movements, etc., i.e. improvement of those factors that significantly depend on the manifestation of certain qualities of speed. Numerous studies have shown that the aforementioned types of speed abilities are specific. Direct positive transfer of speed takes place only in movements that have similar semantic and programming aspects, as well as motor composition. The specific features of speed abilities are noted, so they require the use of appropriate training tools and methods for each of their varieties.

Measurement of levitation force of high-temperature superconducting maglev under high-speed operation condition

High-temperature superconducting (HTS) pinning magnetic levitation (maglev) has garnered significant attention in high-speed maglev transportation due to its inherent self-stability, low energy consumption, and absence of mechanical friction. Ensuring the safe and stable operation of HTS pinning maglev systems necessitates a dedicated focus on the performance and stability of HTS bulks levitated above the permanent magnetic guideway (PMG). Previous research has indicated that variations in the temperature within the HTS bulk can impact the levitation performance of the system. This temperature-related phenomenon occurs when the external magnetic field applied to the HTS bulk changes. However, it is noteworthy that previous levitation force tests for HTS magnetic levitation systems have been limited to quasi-static or low-speed studies. The exploration of dynamic levitation forces, particularly at high speeds, has remained constrained due to the associated high costs. Therefore, the objective of this study is to investigate dynamic levitation forces while the HTS pinning maglev system is in motion at high speeds, utilizing a self-developed ultra-high-speed maglev test rig. Initially, the relationship between the levitation force and the vertical displacement of the HTS pinning maglev system is examined based on quasi-static experiments. Subsequently, comparative studies are conducted to measure levitation forces at varying speeds. Finally, the correlation between running speed and dynamic levitation force is discussed. The investigation reveals that the levitation force experiences only a marginal decrease as the running speed increases. At a running speed of 240 km/h, the attenuation rate of the levitation force is approximately 2.478 %, demonstrating the commendable stability of HTS pinning maglev systems. The article concludes by presenting the dynamic levitation characteristics and their attenuation trends to speed. These findings can serve as valuable references for future design and practical implementation of HTS pinning maglev systems.

Comparison of kinematics and kinetics between unassisted and assisted maximum speed sprinting

ABSTRACT Producing comparable/greater ground reaction forces (GRFs) at faster running speeds is beneficial for sprint performance, and assisted sprint training is used to induce faster running speed conditions. This study aimed to demonstrate the characteristics of assisted sprinting at the maximal speed phase and investigate acute differences to control sprinting. Fifteen sprinters completed control and assisted (5 kg) sprints over force platforms. Assisted sprinting increased running speed (9.3% mean difference), while propulsive mean force (−4.3%) and impulse (−12.4%) decreased, suggesting that running speed improvements were caused primarily by assisted pulling force rather than improvements in anteroposterior force production of athletes. In addition, vertical mean force increased (4.2%), probably due to braking mean force (34.2%) and impulse (32.5%) increases. Magnitude of control trial maximum speed was achieved earlier (during acceleration) in assisted trials, and net anteroposterior (includes both braking and propulsive components) mean force (67.2%) and impulse (67.9%) increased at this matched speed, suggesting that assisted sprints could be used to practice producing greater GRFs at comparable speeds. Running speed improvement by pulling force was associated with contact time decreases (r = -.565), suggesting that shortening contact time may be important for effective assisted sprinting.

A Synthetic Integrated Wireless Aerodynamic Evaluation System for Train–Bridge System

The development of high-speed railway networks and the increased running speeds of high-speed trains (HSTs) have made the aerodynamic interference between HSTs and their surrounding environments increasingly important. Compared with a traditional wind tunnel test, systematically understanding the aerodynamic characteristics of HSTs involves relatively more stringent requirements, highlighting the need to develop experimental methods and technologies with enhanced dynamic performance. Central South University (CSU) developed a wireless data acquisition system, named as the in-model sensory and wireless data acquisition — remote control and processing system (ISWDA-RCPS), which can operate onboard a novel moving train and infrastructure rig. The system was developed to meet current wind tunnel data collection needs, and it avoids the physical cables used in conventional devices, which are extremely susceptible to induced noise. The system accepts inputs from various sensors and transfers the data wirelessly to an access point outside a wind tunnel’s test section. To analyze the feasibility of the ISWDA-RCPS concerning its sensing capabilities and wireless communications, we conduct experiments in multiple operating conditions. Finally, pressure measurements are acquired from a moving Fuxing HST model at different points and used to analyze the aerodynamic behavior of the model.

Vibration comfort assessment of tractor drivers based on sEMG and vibration signals

In order to comprehensively evaluate the driver’s vibration comfort under different vibration conditions, eighteen subjects were required to drive a tractor at different speeds on field and asphalt roads respectively in the real vehicle experiment. The sEMG signals and vibration acceleration signals of the subjects were recorded. And the time-frequency domain analysis of sEMG signals and acceleration signals were used to determine the relationship among the characteristic indexes, tractor speed and road surfaces. The relevance analysis showed that there was a significant correlation between the integral electromyography (iEMG) and median frequency (MF) of the middle scalene muscle, erector spinae muscle and gastrocnemius muscle, the RMS of weighted acceleration (aw) of the neck, waist and legs, and the subjective comfort feelings. It was proven that the tractor speed had a significant impact on human body vibration based on the ANOVA result (p < 0.05). With the increase of running speed, the time domain indexes of sEMG signals including iEMG, RMS and the vibration acceleration signals of the testing body parts increased significantly, while the amplitudes of frequency domain indexes decreased. Therefore, a quantitative regression evaluation model for the comfort of the neck, waist and legs integrating the sEMG and vibration signals was established, and its relative errors were 5.05, 4.38 and 6.12% respectively. This proposed assessment model can combine characteristics of the partial and overall vibration response of human body effectively, predict the tractor driver’s vibration comfort accurately, provide a theoretical basis for the evaluation of tractor cab vibration comfort.

Effect of Train Vibrations on the Dynamic Response of a Multi-Span Double-Curved Brick Arch Thin-Shell Factory of Changleyuan

The dynamic characteristics of a multi-span double-curved brick arch thin-shell factory of Changleyuan in Baoji City and the dynamic response to train vibration load were studied using field dynamic tests and finite-element numerical simulations, and a vibration evaluation of the thin-shell factory was carried out. The results showed that the first-order frequency of the thin-shell factory was 6.24 Hz in the horizontal direction (east–west) and 9.31 Hz in the vertical direction. Moreover, it was established that the horizontal vibration is the overall vibration of the factory, while the vertical vibration is the individual vibration of the double-curved brick arch. In addition, the self-oscillation frequency obtained from the numerical simulation results was greater compared with the field measurements, with a maximum error rate of 7.14%. Both in acceleration and velocity, the vertical vibration for each measurement point was larger than the horizontal vibration, and the farther away from the railroad, the smaller the vibration. The vibration of the velocity at the bottom of the arch was almost the same as that at the top of the arch, while the acceleration vibration at the bottom of the arch was significantly larger than that at the top of the arch, with an average amplitude of 40.64%. For every 20 km/h increase in train running speed, the average increase in vertical acceleration amplitude, vertical velocity amplitude, horizontal acceleration amplitude, and horizontal velocity amplitude for each measurement point of the thin-shell factory was 35.4%, 29.8%, 23.7%, and 12.5%, respectively. When v = 150 km/h, the maximum velocity amplitude for each measurement point of the thin-shell factory was 1.163 mm/s, which is less than the security specification limit of 2.5 mm/s, such that the security of the thin-shell factory meets the requirement, and the maximum horizontal velocity amplitude was 0.272 mm/s, which is close to the integrity specification limit of 0.27 mm/s, such that the integrity of the thin-shell factory just exceeds the requirement; so it is suggested that train running speeds should not exceed 150 km/h and that the thin-shell factory needs to strengthen the monitoring and protection of its integrity.

Characteristics of the Linear Motor for Electrified High-Speed Maglev Transportation in the Rotational Motions Caused by Asymmetry Transverse Air-Gaps

The electromagnetic characteristics and running stability of the linear motor for electrified Maglev transportation under rotational motions caused by asymmetry transverse air-gaps are calculated and analyzed. Firstly, considering the end effect and the shape of the vehicle coils, the formulas of levitation and guidance currents, levitation and guidance forces, rolling torque, yawing torque, coupling stiffness between lateral and rolling direction, coupling stiffness between lateral and yawing direction and equivalent guidance stiffness are derived. Secondly, the variations of rolling torque, yawing torque, guidance force and levitation force with different lateral displacement, rolling angle and yawing angle are predicted. Then the two coupling stiffnesses and the equivalent guidance stiffness at different operating speeds are investigated. Finally, in order to verify the analysis results, not only the 3-D FEM model is established, but also the experiments are carried out. It shows that the combined levitation and guidance electrodynamic suspension (EDS) maglev train will roll and yaw, and its levitation height also changes after being disturbed laterally. In addition, the train will run more stably when being disturbed laterally as running speed increases.

Effect of increased running speed and weight carriage on peak and cumulative tibial loading.

Tibial stress injuries are a burdensome injury among military recruits. Military activities include running and the carriage of additional weight, and this may be related to the high risk of bone stress injuries. The aim of this study was to quantify tibial loading when running at two different speeds, with and without additional weight, and to quantify their combined influence. Fourteen male distance runners who ran at least 40 km per week ran barefoot on a force-instrumented treadmill in four conditions representing preferred running speed (mean (SD) 3.1 (0.3) m/s) and 20% increased running speed (3.8 (0.4) m/s), with and without 20% of body weight carried in a weight vest. Kinematics and kinetics were synchronously collected. Bending moments were estimated about the medial-lateral axis of the tibial centroid located 1/3rd of the length from distal to proximal. Static equilibrium was ensured at each 1% of stance. Peak bending moments were obtained in addition to cumulative-weighted loading, where weighted loading accounted for the relative importance of the magnitude of the bending moment and the quantity of loading using a bone-dependent weighting factor. There were no interaction effects for running speed and weight carriage on peak or cumulative tibial loading. Running at a 20% faster speed increased peak and cumulative loading per kilometer by 8.0% (p < 0.001) and 4.8% (p < 0.001), respectively. Carriage of an additional 20% of body weight increased peak and cumulative loading per kilometer by 6.6% (p < 0.001) and 8.5% (p < 0.001), respectively. Increasing the physical demand of running by increasing speed or weight carriage increased peak tibial loading and cumulative tibial loading per kilometer, and this may increase the risk of tibial stress injury. Running speed and weight carriage independently influenced tibial loading.

Biarticular mechanisms of the gastrocnemii muscles enhance ankle mechanical power and work during running.

The objective of the study was to explore how biarticular mechanisms of the gastrocnemii muscles may provide an important energy source for power and work at the ankle joint with increasing running speed. Achilles tendon force was quantified as a proxy of the triceps surae muscle force and the contribution of the monoarticular soleus and the biarticular gastrocnemii to the mechanical power and work performed at the ankle joint was investigated in three running speeds (transition 2.0 m s-1, slow 2.5 m s-1, fast 3.5 m s-1). Although the contribution of the soleus was higher, biarticular mechanisms of the gastrocnemii accounted for a relevant part of the performed mechanical power and work at the ankle joint. There was an ankle-to-knee joint energy transfer in the first part of the stance phase and a knee-to-ankle joint energy transfer during push-off via the gastrocnemii muscles, which made up 16% of the total positive ankle joint work. The rate of knee-to-ankle joint energy transfer increased with speed, indicating a speed-related participation of biarticular mechanisms in running. This energy transfer via the gastrocnemii seems to occur with negligible energy absorption/production from the quadriceps vasti contractile elements and is rather an energy exchange between elastic structures.

Analysis of Vehicle–Bridge Coupling System Under the Wind and Waves Combined Condition During Two Trains’ Meeting

Based on the theories of computational fluid dynamics, aerodynamics, bridge dynamics and vehicle dynamics, a sea-crossing cable-stayed bridge with a main span of 532 m is taken as the research object in this study to explore the characteristics of dynamic response when two CRH3 high-speed trains pass each other under the context of wind–wave combination. Firstly, the CFD method is used to construct an aerodynamic calculation model of the vehicle–bridge system under the context of wind–wave combination. Also, the first wind tunnel and wave flume tests are conducted to verify the numerical results of aerodynamic coefficients. Then, the bridge dynamics model and vehicle dynamics model are established by using both the finite element method and the multi-body dynamics method. Finally, a three-dimension vehicle–bridge coupled model is constructed by using the multi-body dynamic software SIMPACK to explore the effects of average wind and regular waves. It is demonstrated that the dynamic characteristics of the vehicle–bridge coupling system under the condition of wind–wave combination are different than under the context of average wind alone. According to the research result, wave effect can affect or make a difference to the aerodynamic characteristics of the vehicle–bridge coupling system. In general, there is only a slight increase in the dynamic responses of bridge structure including mid-span displacement when compared with the condition of average wind alone, including mid-span displacement. Meanwhile, the wind and waves combined condition also has a negative effect on the dynamic responses and running safety of high-speed trains. Especially for the leeward vehicle, the dynamic responses of the leeward train change more abruptly than under the single static wind condition with the increase of running speed.

Effects of S-Curve Runs and Sprint In-Out Exercise Methods Against The Increase of Speed, in 100 Meters Sprint Observed from Foot Length and Height Ratios

The purpose of this study was to find the effect of differences between S-Curve Runs and Sprint In-Out exercise methods against the increase of speed in 100 meters sprint; the different increases of speed in 100 meters sprints for the runners with big, medium, and small ratios of foot length and height; and the differences of interactions between S-Curve Runs and Sprint In-Out exercise methods and foot length and height ratios against the increase of speed in 100 meters sprint. This research was conducted at Chevron Football School in Pekanbaru for 8 weeks by using the experimental method of 2 x 3 factorial designs. The research population contained students of the school. Purposive Random Sampling was utilized as the sampling method included 42 students with big, medium, and small ratios of foot length and height, for each took 14 students as the samples. ANOVA was employed as the data analysis technique. Prerequisite tests of data analysis were conducted beforehand by using the sample normality test (Lilliefors Test at α = 0.05) and homogeneity of variance test (Bartlett’s Test at α = 0.05). Results of data analysis indicated that there were significant differences between S-Curve Runs and Sprint In-Out exercise methods against the increase of speed in 100 meters sprint with Fcount = 10.54758 &gt; Ftable = 4.07 in which the effects of S-Curve Runs exercise have better improvement than Sprint In-Out exercise, with the average increases for each are 2.17 and the 1.7; there were significant differences between the runners with big, medium, and small ratios of foot length and height with Fcount = 14.16068 &gt; Ftable = 3.22. The increase of 100 meters sprint result on samples with big ratios of foot length and height was better than samples with medium and small ratios, for each having average increase of 2:43, 1.89 and 1:51; and there was no correlation effect between the S-Curve Run and Sprint In-Out training methods and the foot length and height ratios against the increase of running speed, in which the Fcount = 0.29174 &lt; Ftable = 3:22.

Effects of Game-Specific Demands on Accelerations during Change of Direction Movements: Analysis of Youth Female Soccer

The aim of this study was to assess center of mass (COM) acceleration and movement during change of direction (COD) maneuvers during a competitive soccer game to elucidate situation-specific demands of COD performance. This information can assist in developing soccer-specific tests and training methods. Fifteen elite-level female youth soccer players were tracked for one game with inertial measurement units (IMU) attached to the lower back. COD movements in combination with situational patterns were identified using high-speed video. LASSO regression was used to identify the most important predictors associated with higher vertical peak accelerations (PAv) of the COM during COD movements. COD angle, running speed, contact, and challenge from the opposition were identified as important features related to higher PAv. This study adds to the literature on the demands of COD performance in soccer match-play. The unique approach with game-specific situational data from female youth players provides increased insight into the game-demands of COD and agility performance. PAv in games was higher with larger COD angles, increased running speed, or with contact when the player was challenged by the opposition. A larger study including more games is warranted to increase confidence in using these variables as a basis for training or testing agility.

Research on causes and countermeasures of wheel polygon wear based on Kik-Piotrowiski contact model

In order to study the wheel polygon wear problems in high-speed trains, an iterative model of wheel wear was established based on 1 ) the train-track rigid-flexible coupling dynamics model, 2 ) Kik-Piotrowiski + Fastsim wheel-rail contact model, and 3 ) Archard wear model to predict the developing process of wheel polygon. Taking a certain type of high-speed train in China as an example, the developing process of the 20-order wheel polygon is simulated. Compared with the Hertz model, the results of the Kik-Piotrowiski model are more consistent with the actual situation, and the prediction of the wheel polygon is more accurate. The results show that with the increase of vehicle running speed, the dominant order of the final wheel polygon decreases gradually, while the excitation frequency always locates between 550 and 600 Hz, which verifies the ‘frequency fixed’ mechanism. By comparing the development of wheel polygon wear results under three working conditions 1 ) flexible wheelset + flexible rail, 2 ) rigid wheelset + flexible rail, and 3 ) flexible wheelset + rigid rail), and by analysing the harmonic response of rail, it is concluded that the third-order bending modal vibration of rail plays an important role in the forming of wheel polygon. .

Increasing Step Frequency Reduces Patellofemoral Joint Stress and Patellar Tendon Force Impulse More at Low Running Speed.

Patellofemoral pain syndrome and patellar tendinopathy are important running-related overuse injuries. This study investigated the interaction of running speed and step frequency alterations on peak and cumulative patellofemoral joint stress (PFJS) and patellar tendon force (PTF) parameters. Twelve healthy individuals completed an incremental running speed protocol on a treadmill at habitual, increased and decreased step frequency. Peak PFJS and PTF, peak rate of PFJS and PTF development, and PFJS and PTF impulse per kilometer (km) were calculated using musculoskeletal modeling. With increasing running speed, peak PFJS ( P < 0.001) and PTF ( P < 0.001) and peak rate of PFJS ( P < 0.001) and PTF ( P < 0.001) development increased, whereas PFJS ( P < 0.001) and PTF ( P < 0.001) impulse per km decreased. While increasing step frequency by 10%, the peak PFJS ( P < 0.001) and PTF ( P < 0.001) and the PFJS ( P < 0.001) and PTF ( P < 0.001) impulse per kilometer decreased. No significant effect of step frequency alteration was found for the peak rate of PFJS ( P = 0.008) and PTF ( P = 0.213) development. A significant interaction effect was found for PFJS ( P < 0.001) and PTF ( P < 0.001) impulse per km, suggesting that step frequency alteration was more effective at low running speed. The effectiveness of step frequency alteration on PFJS and PTF impulse per km is dependent on the running speed. With regard to peak PFJS and PTF, step frequency alteration is equally effective at low and high running speeds. Step frequency alteration was not effective for peak rate of PFJS and PTF development. These findings can assist the optimization of patellofemoral joint and patellar tendon load management strategies.

Commercial Smart Watches and Heart Rate Monitors: A Concurrent Validity Analysis.

Montalvo, S, Martinez, A, Arias, S, Lozano, A, Gonzalez, MP, Dietze-Hermosa, MS, Boyea, BL, and Dorgo, S. Smartwatches and commercial heart rate monitors: a concurrent validity analysis. J Strength Cond Res 37(9): 1802-1808, 2023-The purpose of this study was to explore the concurrent validity of 2 commercial smartwatches (Apple Watch Series 6 and 7) against a clinical criterion device (12-lead electrocardiogram [ECG]) and a field criterion device (Polar H-10) during exercise. Twenty-four male collegiate football players and 20 recreationally active young adults (10 men and 10 women) were recruited and participated in a treadmill-based exercise session. The testing protocol included 3 minutes of standing still (resting), then walking at low intensity, jogging at a moderate intensity, running at a high intensity, and postexercise recovery. The intraclass correlation (ICC 2,k ), and Bland-Altman plot analyses showed a good validity of the Apple Watch Series 6 and Series 7 with increased error (bias) as jogging and running speed increased in the football and recreational athletes. The Apple Watch Series 6 and 7 are highly valid smartwatches at rest and different exercise intensities, with validity decreasing with increased running speed. Strength and conditioning professionals and athletes can confidently use the Apple Watch Series 6 and 7 when tracking heart rate; however, caution must be taken when running at moderate or higher speeds. The Polar H-10 can surrogate a clinical ECG for practical applications.

The Effects of Increasing Running Speed on the Displacement and Velocity of the Center of Pressure

The Effects of Increasing Running Speed on the Displacement and Velocity of the Center of Pressure

Der verflixte erste Posten – Laufzeitenanalyse von OL-Juniorinnen und -Junioren

Orienteering is a combination of cognitive and physical capabilities of cardiovascular and musculoskeletal system. However, especially for juniors, there is often the risk of running too fast compared to map-reading skills, which ends up in search actions. This yields directly to the aim of the study to analyze the steadiness of speed for course times in junior orienteering runners. Material and methods: Results from the Swiss long distance orienteering championships of the year 2020 were analyzed to calculate average speed and steadiness per control for the categories D14, D16, D18, D20 and H14, H16, H18, H20 with the concept of performance km. Results: Male juniors were significantly faster than female in all analyzed categories (p &lt; 0.01). Both, female (R2 = 0.6573) and male (R2 = 0.7937) juniors showed an age-dependent average performance kilometer decrease and in consequence increase of running speed. Analyses from the standard deviation of the percentage deviation to a control and the ranking position indicated that the steadier the run, the better the result, whereby for some categories high coefficients of determination, e.g., D18 (R2 = 0.679) were identified. Moreover, analyses by control indicated, that especially to the first control respectively the first part of the race was uneven paced. Discussion: Analyses show a clear age dependence of running speed in female and male junior orienteers. Furthermore, the steadier the run, the better the rank. This implies, that even pacing yields to faster course times, which is also supported by biological restrictions known from long-distance running. In addition, it is detectable, that particularly the first part of the orienteering course respectively the first control was uneven paced. This is probably a consequence of an often too high speed in the beginning of a course with corresponding search actions. In consequence, the first control should be consciously addressed in training and the ability to directly start highly focused should be in consequence specifically trained e.g., with starting exercises.

Effects of Running Velocity on Vertical Stiffness and Muscle Co-activations

The purpose of this study was to investigate the vertical stiffness and agonist-antagonist muscle co-activation according to running velocity. Eighteen runners asked to perform running on an instrumented treadmill (HP Cosmos, Germany) with a capacitance-based pressure platform at 40, 50, 60, 70, 80% of maximum velocities, 19 infrared cameras and surface electromyography were used to measure kinematics and muscle activation. Vertical stiffness increased significantly as running speed increased. On the other hand, co-activation decreased significantly as the running speed increased. We conclude that antagonist muscle groups decrease with increasing running speed and depend on agonist muscle group activity.