Running Velocity Research Articles

Smartwatch-Derived Data and Machine Learning Algorithms Estimate Classes of Ratings of Perceived Exertion in Runners: A Pilot Study.

The rating of perceived exertion (RPE) is a subjective load marker and may assist in individualizing training prescription, particularly by adjusting running intensity. Unfortunately, RPE has shortcomings (e.g., underreporting) and cannot be monitored continuously and automatically throughout a training sessions. In this pilot study, we aimed to predict two classes of RPE (≤15 “Somewhat hard to hard” on Borg’s 6–20 scale vs. RPE in runners by analyzing data recorded by a commercially-available smartwatch with machine learning algorithms. Twelve trained and untrained runners performed long-continuous runs at a constant self-selected pace to volitional exhaustion. Untrained runners reported their RPE each kilometer, whereas trained runners reported every five kilometers. The kinetics of heart rate, step cadence, and running velocity were recorded continuously ( 1) with a commercially-available smartwatch (Polar V800). We trained different machine learning algorithms to estimate the two classes of RPE based on the time series sensor data derived from the smartwatch. Predictions were analyzed in different settings: accuracy overall and per runner type; i.e., accuracy for trained and untrained runners independently. We achieved top accuracies of % for the whole dataset, % for the trained runners, and % for the untrained runners. We predict two classes of RPE with high accuracy using machine learning and smartwatch data. This approach might aid in individualizing training prescriptions.

Can match play kicking and physical performance outcomes be replicated in an Australian football small-sided game?

ABSTRACT Introduction: This study investigated if the technical and physical match performance outcomes can be replicated in a 5v6 small-sided game (SSG). Methods: Sixteen youth Australian Football (AF) players (mean ± SD; age 16.5 ± 1.0 years, height 179.1 ± 8.0 cm, weight 69.5 ± 9.5 kg) were randomly recruited. Participants were assessed in the SSG during the week prior to the assessed match play. The technical variables assessed were kicking proficiency, number of kicks executed and the amount of time each player had with the ball before kick execution (i.e., under 2s, 2-4s, over 4s). The physical variables assessed were odometer, meters travelled per minute, maximum velocity and percentage of high intensity running. Results: The results suggest kicking proficiency, the number of kicks executed, meters travelled per minute and percentage of high intensity running were all higher in the SSG than during match play. Furthermore, the SSG had less technical variability in comparison to match play. During match play, players had less time affordance to execute a kick and achieved higher maximum running velocities than during the SSG. Conclusion: This research provides coaches with greater insights into the technical and physical performance demands of match play.

Effect of an Eleven-Day Altitude Training Program on Aerobic and Anaerobic Performance in Adolescent Runners.

Background and Objectives: We evaluated the effect of an eleven-day altitude training camp on aerobic and anaerobic fitness in trained adolescent runners. Materials and Methods: Twenty adolescent (14–18 yrs) middle- and long-distance runners (11 males and 9 females; 16.7 ± 0.8 yrs), with at least two years of self-reported consistent run training, participated in this study. Eight of the subjects (4 females/4 males) constituted the control group, whereas twelve subjects (5 females/7 males) took part in a structured eleven-day altitude training camp, and training load was matched between groups. Primary variables of interest included changes in aerobic (VO2max) and anaerobic (30 s Wingate test) power. We also explored the relationships between running velocity and blood lactate levels before and after the altitude training camp. Results: Following 11 days of altitude training, desirable changes (p < 0.01) in VO2max (+13.6%), peak relative work rate (+9.6%), and running velocity at various blood lactate concentrations (+5.9%–9.6%) were observed. Meanwhile, changes in Wingate anaerobic power (+5.1%) were statistically insignificant (p > 0.05). Conclusions: Short duration altitude appears to yield meaningful improvements in aerobic but not anaerobic power in trained adolescent endurance runners.

Running mechanics adjustments to perceptually-regulated interval runs in hypoxia and normoxia

ObjectivesWe determined whether perceptually-regulated, high-intensity intermittent runs in hypoxia and normoxia induce similar running mechanics adjustments within and between intervals. DesignWithin-participants repeated measures. MethodsNineteen trained runners completed a high-intensity intermittent running protocol (4×4-min intervals at a perceived rating exertion of 16 on the 6–20 Borg scale, 3-min passive recoveries) in either hypoxic (FiO2=0.15) or normoxic (FiO2=0.21) conditions. Running mechanics were collected over 10 consecutive steps, at constant velocity (∼15.0±2.0km.h−1), at the beginning and the end of each 4-min interval. Repeated measure ANOVA were used to assess within intervals (onset vs. end of each interval), between intervals (interval 1, 2, 3 vs. 4) and FiO2 (0.15 vs. 0.21) main effects and any potential interaction. ResultsParticipants progressively reduced running velocity from interval 1–4, and more so in hypoxia compared to normoxia for intervals 2, 3 and 4 (P<0.01). There were no between intervals (across all intervals P>0.298) and FiO2 (across all intervals P>0.082) main effects or any significant between intervals×within intervals×FiO2 interactions (all P>0.098) for any running mechanics variables. Irrespective of interval number or FiO2, peak loading rate (+10.6±7.7%; P<0.001) and duration of push-off phase (+2.0±3.1%; P=0.001) increased from the onset to the end of 4-min intervals, whereas peak push-off force decreased (−4.0±4.0%; P<0.001). ConclusionsWhen carrying out perceptually-regulated interval treadmill runs, runners adjust to progressively slower velocities in hypoxia compared to normoxia. However, only subtle constant-velocity modifications of their mechanical behaviour occurred within each set, independently of FiO2 or interval number.

New Insights into Mechanical, Metabolic and Muscle Oxygenation Signals During and After High-Intensity Tethered Running

High-intensity exercises including tethered efforts are commonly used in training programs for athletes, active and even sedentary individuals. Despite this, the knowledge about the external and internal load during and after this effort is scarce. Our study aimed to characterize the kinetics of mechanical and physiological responses in all-out 30 seconds (AO30) tethered running and up to 18 minutes of passive recovery. Additionally, in an innovative way, we investigated the muscle oxygenation in more or less active muscles (vastus lateralis and biceps brachii, respectively) during and after high-intensity tethered running by near-infrared spectroscopy – NIRS. Twelve physically active young men were submitted to AO30 on a non-motorized treadmill to determine the running force, velocity and power. We used wearable technologies to monitor the muscle oxygenation and heart rate responses during rest, exercise and passive recovery. Blood lactate concentration and arterial oxygen saturation were also measured. In a synchronized analysis by high capture frequency of mechanical and physiological signals, we advance the understanding of AO30 tethered running. Muscle oxygenation responses showed rapid adjustments (both, during and after AO30) in a tissue-dependence manner, with very low tissue saturation index observed in biceps brachii during exercise when compared to vastus lateralis. Significant correlations between peak and mean blood lactate with biceps brachii oxygenation indicate an important participation of less active muscle during and after high-intensity AO30 tethered running.

Effects of Breast Motion on Lower-Body Kinematics during Running

We measured the effects of breast motion on lower-body kinematics during overground running. Thirty female participants aged 18–60 years completed two blocks of three trials each of overground running for 25 m at self-selected pace under two conditions: with and without breast support provided by a sports bra. Participants' body movements were analyzed with 18 parameters characterizing breast and lower-body kinematics. Sports bra use reduced breast motion and increased about 83% of the lower-body kinematic parameters, including running velocity; stride length; foot clearance; vertical and lateral center of mass displacement; and thorax, hip, knee, and ankle range of motion (all p < 0.05). Among the changed characteristics, the stride length, center of mass displacements, thorax and knee range of motions correlated negatively (r = –0.25 to –0.46) with the velocity of breast motion. Therefore, the reduction of breast motion may improve lower-body kinematics during running, which may influence sport and leisure performance.

Effect of bilateral lesions in the amygdala on the maximum running velocity and cardiovascular response in rats during treadmill running

The high intensity of exercise around/at maximum levels induces psychological distress. It is known that the amygdala in the limbic system is one of the regions of the brain controlling such emotion, as well as regulating the cardiovascular system. Therefore, we hypothesized that the amygdala could play an important role in limiting the high‐intensity exercise performance. To test this, we examined whether bilateral amygdala lesions increased maximal exercise performance with altered cardiovascular responses during exercise. The arterial pressure in rats was chronically measured using radio‐telemetry during treadmill running. The rats were subjected to forced running for 60 min per day (velocity ≤20 m/min) for 3 days to achieve treadmill habituation. Thereafter, an incremental exercise test was conducted until exhaustion (pre‐test). Exercise intensity was initiated at 10 m/min, and the velocity was increased by 2 m/min every 3 min. In the amygdala lesion group, the bilateral lesions in the amygdala were induced by electrical stimulation (direct current 1 mA for 5 s). In the sham group, the tip of the electrode was inserted into the amygdala and immediately removed without electrical stimulation. After surgery, re‐training was conducted similar to the habituation protocol, and the incremental exercise test was repeated (post‐test). In the sham group, there were no significant differences between pre‐ and post‐test in the mean maximum running velocities (pre‐test: 47.2 ± 1.8 m/min, post‐test: 44.0 ± 2.8 m/min) and running time (pre‐test: 56.5 ± 3.2 min; post‐test: 49.9 ± 4.7 min). However, the mean maximum running velocity was greater (pre‐test: 45.5 ± 2.3 m/min; post‐test: 54.0 ± 0.6 m/min; p &lt; 0.05) and the running time was longer (pre‐test: 57.9 ± 3.4 min; post‐test: 70.0 ± 0.8 min; p &lt; 0.05) in the post‐test as compared to the pre‐test of the lesion group. Moreover, we found that the mean arterial pressure in both groups of animals exhibited a gradual increase during submaximal exercise (low/moderate intensity) followed by a drastic increase during high/maximal‐intensity exercise. However, compared to the sham group, the mean arterial pressure response in the amygdala lesion group was significantly lower during submaximal exercise, whereas it was greater during high/maximal‐intensity exercise, suggesting that the amygdala could play a role in limiting the exercise performance by modulating the autonomic cardiovascular control.Support or Funding InformationGrant‐in‐Aid for JSPS Fellows (19J22706)

How do Amateur Endurance Runners Alter Spatiotemporal Parameters and Step Variability as Running Velocity Increases? a Sex Comparison.

This study aimed to analyse the effects of running velocity on spatiotemporal parameters and step variability in amateur endurance runners, according to sex. A group of 51 males and 46 females performed an incremental running test on a treadmill (10-16 km/h). Spatiotemporal parameters (contact and flight time, step length, step frequency and step angle [CT, FT, SL, SF, SA]) and step variability, in terms of within-participant standard deviation (SD), were recorded through the OptoGait System. The ANOVA showed significant differences in the magnitude of the spatiotemporal parameters as running velocity increased (p < 0.001). It also revealed significant differences in step variability (p < 0.005) over the entire running protocol. Between-sex differences in CT, SL, SL-normalized and SF (p < 0.05, ES = 0.4-0.8) were found. Differences were also found in step variability at high velocities (15-16 km/h), with males showing a greater SD than females. In conclusion, increasing running velocity makes CT shorter, FT and SL longer, and SF and SA greater in amateur endurance runners, changing step variability, regardless of sex. Additionally, some between-sex differences were found in spatiotemporal parameters and step variability.

Relationship Between Mechanical Effectiveness in Sprint Running and Force-Velocity Characteristics of a Countermovement Jump in Australian Rules Football Athletes.

Morris, CG, Weber, JA, and Netto, KJ. Relationship between mechanical effectiveness in sprint running and force-velocity characteristics of a countermovement jump in Australian rules football athletes. J Strength Cond Res 36(3): e59-e65, 2022-This study evaluated the mechanical determinants of 40-m sprint performance in elite Australian Rules Football (ARF) athletes and identified variables of countermovement jumps (CMJs) that related to the sprint. Fourteen elite male ARF athletes (age = 22.7 ± 3.6 years; height = 1.88 ± 0.08 m; mass = 88.2 ± 9.38 kg) completed two 40-m sprints and 3 CMJs. Sprint mechanics were calculated using inverse dynamic methods from sprint times, anthropometric and spatiotemporal data, whereas CMJ variables were obtained from in-ground force plates. Associations between sprint mechanics, sprint performance, and CMJ variables were identified using Pearson's correlation coefficient. A p-value of <0.036 was considered statistically significant for all analyses after performing Bonferroni correction adjustment. Relative peak running power was significantly correlated (p < 0.036, r = -0.781 to -0.983) with sprint split times across all distances (5-40 m). Relative maximum horizontal force significantly correlated with acceleration performance (0-20 m, p < 0.036, r = -0.887 to -0.989). Maximum running velocity was significantly correlated (p < 0.036, r = -0.714 to -0.970) with sprint times across 20-40 m. Relative peak force in the CMJ was significantly associated (p < 0.036, r = -0.589 to -0.630) with sprint kinetics (power and horizontal force) and 5-20-m sprint times. Jump height and concentric time in the CMJ were significantly (p < 0.036) correlated with sprint time at 20 m (r = -0.550 and r = 0.546), respectively. These results indicate emphasis should be placed on training protocols that improve relative peak power, particularly in time-constrained environments such as team sports, focusing on maximal force production or maximal running velocity ability. Furthermore, associations between CMJ variables and sprint performance provide practitioners with an approach to assess sprint performance in-season, monitor training adaptations and further individualize training interventions, without requiring maximal sprint testing.

Active steering control strategy for rail vehicle based on minimum wear number

ABSTRACT Active steering technology is an effective method to solve the contradiction between curving performance and running stability of traditional bogie. In this study, an integrated active steering device was developed to integrate wheelset constraints and actuators. In addition, to study the minimum wear number control strategy, the existence of an optimal steering level that minimises the wear number was corroborated by a theoretical derivation based on the single wheelset model. Later, this research method was extended to the complete vehicle lateral dynamics model and steady-state solutions at different active steering levels were analysed. The results demonstrate that at optimal steering control, wear number is the lowest. This state is less affected by the running velocity, stiffness of the primary suspension, tread taper, and creep state, which are determined by the wheelbase and track curvature. The lateral forces of rail-vehicle wheels with an active steering function at different steering levels were measured using instrumented wheelsets. Furthermore, the accuracy of the simulation model was verified by comparing the experimental data with simulation results. Finally, the wear number of test vehicles at different steering levels were predicted using this model, and the control strategy proposed in this investigation was validated.

Markov modeling of run length and velocity for molecular motors

ABSTRACT Molecular motors are nanometer scale proteins involved in various intracellular processes such as cargo transport, muscle contraction and cell division. The steps in the chemo-mechanical cycle that use ATP hydrolysis to generate motion along the cytoskeletal tracks can be characterized by stepping rates depending only on the current state, permitting modeling of the cycle as a Markov process. To learn more about the nature of motor motion, cell researchers have conducted in vitro experiments in which molecular motors pull beads along filaments attached to glass slides and their velocity and run length until detachment from the microtubule are recorded. A formula is derived for distance traveled until detachment. Four molecular motors for which there are run length and velocity measurements in the literature are considered. In each case the derived formulas for run length and velocity have a generalized Michaelis–Menten form as functions of ATP concentration. The degrees of the numerator and denominator polynomials increase with the complexity of chemo-mechanical cycle. The degrees of the Michaelis–Menten form determine the maximum number of reaction rates that can be determined from experimental data on run length and velocity, however consistency conditions may reduce this number and restrict which rates can be determined.

Physiological and Perceptual Demands of Running on a Curved Nonmotorized Treadmill Compared With Running on a Motorized Treadmill Set at Different Grades.

Schoenmakers, PPJM, Crisell, JJ, and Reed, KE. Physiological and perceptual demands of running on a curved nonmotorized treadmill compared with running on a motorized treadmill set at different grades. J Strength Cond Res 34(5): 1197-1200, 2020-The current study compared the physiological and perceptual demands of running on a commercially available curved nonmotorized treadmill (cNMT) with different incline grades on a motorized treadmill (MT). Ten male team-sport athletes completed, after a familiarization session, a 6-minute run at a target velocity of 2.78 m·s on the cNMT (cNMTrun). The mean individual running velocity of cNMTrun was then used as warm-up and experimental running velocity in 3 subsequent visits, in which subjects ran for 6 minutes on the MT set at different grades (4, 6, or 8%). In all experimental trials (cNMTrun, 4MTrun, 6MTrun, and 8MTrun) and in the warm-up of the subjects' third visit (1MTrun), oxygen consumption (V[Combining Dot Above]O2) and heart rate (HR) were monitored, and ratings of perceived exertion (RPE) were obtained. The HR in cNMTrun was significantly higher compared with all MT trials. V[Combining Dot Above]O2 and RPE were significantly higher in cNMTrun compared with 1MTrun and 4MTrun, but not different from 6MTrun and 8MTrun. The relationship between V[Combining Dot Above]O2 and MT grades was highly linear (V[Combining Dot Above]O2 = 34.36 + 1.7 MT grade; r = 0.99), and using linear interpolation, the concave curved design of the cNMT was estimated to mimic a 6.9 ± 3% MT grade. On matched running velocities, V[Combining Dot Above]O2 and RPE responses while running on the cNMT are similar to a 6-8% MT grade. These findings can be used as a reference value by athletes and coaches in the planning of cNMT training sessions and amend running velocities accordingly. Future studies are needed to determine whether this estimate is similar for female runners, or those of a lower body mass.

A Plyometric Warm-Up Protocol Improves Running Economy in Recreational Endurance Athletes.

This study explored the impact of two differing warm-up protocols (involving either resistance exercises or plyometric exercises) on running economy (RE) in healthy recreationally active participants. Twelve healthy university students [three males, nine females, age 20 ± 2 years, maximal oxygen uptake (38.4 ± 6.4 ml min–1 kg–1)] who performed less than 5 h per week of endurance exercise volunteered to participant in this study. All participants completed three different warm-up protocols (control, plyometric, and resistance warm-up) in a counterbalanced crossover design with trials separated by 48 h, using a Latin-square arrangement. Dependent variables measured in this study were RE at four running velocities (7, 8, 9, and 10 km h–1), maximal oxygen uptake; heart rate; respiratory exchange rate; expired ventilation; perceived race readiness; rating of perceived exertion, time to exhaustion and leg stiffness. The primary finding of this study was that the plyometric warm-up improved RE compared to the control warm-up (6.2% at 7 km h–1, ES = 0.355, 9.1% at 8 km h–1, ES = 0.513, 4.5% at 9 km h–1, ES = 0.346, and 4.4% at 10 km h–1, ES = 0.463). There was no statistically significant difference in VO2 between control and resistance warm-up conditions at any velocity. There were also no statistically significant differences between conditions in other metabolic and pulmonary gas exchange variables; time to exhaustion; perceived race readiness and maximal oxygen uptake. However, leg stiffness increased by 20% (P = 0.039, ES = 0.90) following the plyometric warm-up and was correlated with the improved RE at a velocity of 8 km h–1 (r = 0.475, P = 0.041). No significant differences in RE were found between the control and resistance warm-up protocols. In comparison with the control warm-up protocol, an acute plyometric warm-up protocol can improve RE in healthy adults.

Sprint versus isolated eccentric training: Comparative effects on hamstring architecture and performance in soccer players.

AimsThe purpose of this study was to compare the effects of hamstring eccentric (NHE) strength training versus sprint training programmed as complements to regular soccer practice, on sprint performance and its mechanical underpinnings, as well as biceps femoris long head (BFlh) architecture.MethodsIn this prospective interventional control study, sprint performance, sprint mechanics and BFlh architecture variables were compared before versus after six weeks of training during the first six preseason weeks, and between three different random match-pair groups of soccer players: “Soccer group” (n = 10), “Nordic group” (n = 12) and “Sprint group” (n = 10).ResultsFor sprint performance and mechanics, small to large pre-post improvements were reported in “Sprint group” (except maximal running velocity), whereas only trivial to small negative changes were reported in “Soccer group” and “Nordic group”. For BFlh architecture variables, “Sprint” group showed moderate increase in fascicle length compared to smaller augment for the “Nordic” group with trivial changes for “Soccer group”. Only “Nordic” group presented small increases at pennation angle.ConclusionsThe results suggest that sprint training was superior to NHE in order to increase BFlh fascicle length although only the sprint training was able to both provide a preventive stimulus (increase fascicle length) and at the same time improve both sprint performance and mechanics. Further studies with advanced imaging techniques are needed to confirm the validity of the findings.

Prosthetic model, but not stiffness or height, affects maximum running velocity in athletes with unilateral transtibial amputations

The running-specific prosthetic (RSP) configuration used by athletes with transtibial amputations (TTAs) likely affects performance. Athletes with unilateral TTAs are prescribed C- or J-shaped RSPs with a manufacturer-recommended stiffness category based on body mass and activity level, and height based on unaffected leg and residual limb length. We determined how 15 different RSP model, stiffness, and height configurations affect maximum running velocity (vmax) and the underlying biomechanics. Ten athletes with unilateral TTAs ran at 3 m/s to vmax on a force-measuring treadmill. vmax was 3.8–10.7% faster when athletes used J-shaped versus C-shaped RSP models (p < 0.05), but was not affected by stiffness category, actual stiffness (kN/m), or height (p = 0.72, p = 0.37, and p = 0.11, respectively). vmax differences were explained by vertical ground reaction forces (vGRFs), stride kinematics, leg stiffness, and symmetry. While controlling for velocity, use of J-shaped versus C-shaped RSPs resulted in greater stance average vGRFs, slower step frequencies, and longer step lengths (p < 0.05). Stance average vGRFs were less asymmetric using J-shaped versus C-shaped RSPs (p < 0.05). Contact time and leg stiffness were more asymmetric using the RSP model that elicited the fastest vmax (p < 0.05). Thus, RSP geometry (J-shape versus C-shape), but not stiffness or height, affects vmax in athletes with unilateral TTAs.

Evolutions of flow patterns and pressure fluctuations in a prototype pump-turbine during the runaway transient process after pump-trip

The runaway after pump-trip is a fast transient process, during which unit vibrations, water-hammer fluctuations, pressure pulsation changes and flow pattern transitions happen violently, endangering pump-turbine units of pumped-storage power stations. In this paper, based on validated CFD data from 1D-3D coupled simulation, we describe the evolutions of flow patterns and pressure fluctuations in a prototype pump-turbine during this working point fast sliding process, and try to reveal the influence mechanism of flow pattern transitions on pressure fluctuation changes. The results show that the general evolutions of flow patterns are dominated by the changes of the runner velocity triangles, which are controlled by the changes of the discharge and rotational speed. Inhomogeneous local flow also contributes to abundant local vortex structures, such as rotating-stall vortices in the vane and runner regions, skirt and helical vortices in the draft-tube, separation vortices in the blade channels, and the impinging jets on the blade surfaces. These unstable vortices appear, change, and vanish in a fast transitional and uneven manner, leading to great differences in pressure and runner force fluctuations in different working regions.

Analysis of the world record time for combined father and son marathon.

The aim of this study was to examine the physiological profiles and the pacing strategies of the father (59 yr old) and son (34 yr old) who broke the World Record time (4:59:22; father: 2:27:52, son: 2:31:30) for combined father and son marathon in 2019. Oxygen uptake (V̇o2), heart rate (HR), ventilation (V̇e), blood lactate concentration (La), and running economy (RE) were measured during treadmill-running tests. The total distance of the marathon was divided into eight sections of 5 km and one last section of 2.195 km, and the relative average running velocity on each section was calculated individually. V̇o2max, HRmax, V̇emax, and Lamax were 65.4 mL·kg-1·min-1, 165 beats/min, 115 L/min, 5.7 mmol/L for the father and 66.9 mL·kg-1·min-1, 181 beats/min, 153 L/min, 11.5 mmol/L for the son, respectively. At 17 km/h, RE was 210 mL·kg-1·km-1 for the father and 200 mL·kg-1·km-1 for the son, and % V̇o2max sustained was 90.9% for the father and 84.5% for the son, respectively. The father maintained an even running velocity during the marathon (running velocity CV <1%), while the son ran the second half-marathon 7% slower than the first one, and his running velocity markedly dropped from the 35th kilometer. Father and son who broke the World record time for combined father and son marathon had a similar level of performance, but their physiological profiles and pacing strategies during the marathon were different. A more even speed for the son could help them to improve their own record in the near future.NEW & NOTEWORTHY We provide novel data demonstrating that different physiological profiles can lead to the same level of performance in a marathon, even at different ages. The novelty of our study is that we report on the physiological characteristics, training routine, and in-race pacing strategy that allowed a father (59 yr old) and son (34 yr old) to break the World Record time for combined father and son marathon. The father also established a new World record marathon time for the age of 59.

Critical velocity estimates running velocity in a 10-km running race in recreational runners

Abstract The aim of this study was to compare the estimated running velocity in a critical velocity (CV) test with the real running velocity in a 10-km race. This is a cross-sectional study with a convenience sample of 34 runners, 20 males and 14 females (42,4 ± 11,0). The participants attended two days of testing and one day to participate in an official 10-km race. During the visits, the following tests were performed: i) 400-meter running track test and ii) 2000 meter running track test. They were randomly selected and held in official athletics track with at least 48 hours rest between them. The athletes were instructed to participate in the study properly recovered, fed and hydrated. The CV was calculated as the linear relation between distance and race time, corresponding to the slope of the linear regression line. Both tests occurred in similar climatic situations. We found good agreement between the velocities estimated through the CV test and the real running velocity of a 10-km race. Although there was a difference in velocities estimated by the CV test and the real 10-km race, the variation delta was low. Thus, these data indicate that the CV test seems to be a good tool for estimating the velocity of a 10-km race. The CV determined in the field with two fixed distances 400 and 2000 meter was valid to estimate the running velocity of a 10-km race.

A New Aircraft Taxiing Model Based on Filtering White Noise Method

The conversion relationship between power spectral density (PSD) and international roughness index (IRI) was studied based on the filtering white noise method with variable sampling frequency using a quarter vehicle model. Six-degree-of-freedom dynamic equations of the whole aircraft taxiing were obtained considering the lift, upstream and downward bump, roll and pitch motion of the airframe. And then the dynamic load factors of the aircraft wheels under different pavement roughness and various airspeeds were solved by SIMULINK toolbox. The results shown that the mean dynamic load is independent of the pavement roughness, whose values are approximately equal to the load when the aircraft glided on the smooth pavement. The worse the pavement roughness, the greater the maximum dynamic load factor. There are approximately linear relationships between IRI and the maximum dynamic load. When the aircraft glides at low airspeed, the dynamic load increases as the increasing of airspeed. Then the maximum dynamic load factor decreases with the increase of running velocity. Moreover, the formulas for calculating the wheel dynamic load factor under the coupling action of pavement roughness and airspeed were proposed, which could be used to calculated the distribution of the dynamic load in longitudinal direction of the runway and determine the dynamic load values in airport pavement design.

Validation of the Cosmed K4b2 Portable Metabolic System During Running Outdoors

Ross, R, ALDuhishy, A, and González-Haro, C. Validation of the cosmed K4b2 portable metabolic system during running outdoors. J Strength Cond Res 34(1): 124-133, 2020-The aim of this study was to determine the agreement of the K4b metabolic system in comparison with the Douglas bags (DB) method for determining gas-exchange variables during both indoor treadmill and outdoor running. Nineteen endurance-trained males undertook 3 maximal incremental running tests, separated by at least 2 days: K4b indoor test (K1), K4b outdoor test (K2), and DB indoor test. Gas-exchange parameters (VO2, VCO2, VE, VI, Respiratory Exchange Ratio, FEO2, and FECO2) and heart rate were measured during K1, K2, and DB tests. For most of the variables (VO2, %VO2, %VCO2, VE, and VI), the agreement was better for K2 when compared with DB than for K1 when compared with DB. For VCO2, FEO2, and FECO2, the agreement was better between K1 when compared with DB than for K2 when compared with DB. Respiratory Exchange Ratio showed a similar agreement between both conditions (K1 vs. DB and K2 vs. DB). K4b seems valid for measuring gas-exchange variables during submaximal and maximal running velocities in an outdoor environment. Although K2 mean systematic error (bias) was low, the aleatory error was moderate. These considerations should be taken into account when using K4b to measure gas-exchange parameters both during indoor and outdoor activities.