Stride Frequency Research Articles

Maximum aerobic speed, maximum oxygen consumption, and running spatiotemporal parameters during an incremental test among middle- and long-distance runners and endurance non-running athletes.

BackgroundMaximal aerobic speed (MAS) is a useful parameter to assess aerobic capacity and estimate training intensity in middle- and long-distance runners. However, whether middle- and long-distance runners reach different levels of MAS compared to other endurance athletes with similar V̇O2max has not been previously studied. Therefore, we aimed to compare V̇O2max, MAS and spatiotemporal parameters between sub-elite middle- and long-distance runners (n = 6) and endurance non-runners (n = 6). In addition, we aimed to compare the maximal blood lactate concentration [BLa] experienced by participants after conducting these tests.MethodsTelemetric portable respiratory gas analysis, contact and flight time, and stride length and rate were measured using a 5-m contact platform during an incremental test at a synthetic athletics track. V̇O2, heart rate, respiratory quotient values in any 15 s average period during the test were measured. [BLa] was analyzed after the test . Running spatiotemporal parameters were recorded at the last two steps of each 400 m lap. A coefficient of variation (%CV) was calculated for each spatiotemporal variable in each participant from 8 km h−1 onwards.ResultsWhereas runners reported faster MAS (21.0 vs. 18.2 km h−1) than non-runners (p = 0.0001, ES = 3.0), no differences were found for V̇O2max and maximum blood lactate concentration during the running tests (p > 0.05). While significant increases in flight time and stride length and frequency (p < 0.001, 0.52 ≤ n}{}{eta }_{p}^{2} ≤ 0.8) were observed throughout the tests, decreases in contact time (p < 0.001, n}{}{eta }_{p}^{2}=0.9) were reported. Runners displayed a greater %CV (p = 0.015) in stride length than non-runners. We conclude that middle- and long-distance runners can achieve a faster MAS compared to non-running endurance athletes despite exhibiting a similar V̇O2max. This superior performance may be associated to a greater mechanical efficiency. Overall, runners displayed a greater ability to modify stride length to achieve fast speeds, which may be related to a more mechanically efficient pattern of spatiotemporal parameters than non-runners.

Mechanics of bipedal and quadrupedal locomotion on dry and wet granular media

AbstractThe effectiveness of exploration robots is contingent upon their capability and efficiency to locomote on contorted and multifaceted terrains. Traditional wheeled robots do not suffice at overcoming such terrains and complications they introduce. The proposed work explores the performance of WhegRunner, a whegged (i.e., wheel‐legged) robotic platform used to examine the mechanics of running on granular media at different saturation levels. In particular, the effect of bipedal/quadrupedal gait, saturation level, stride length, and stride frequency on robot's forward body velocity and cost of transport (COT) was studied. To increment nominal stride length, the robot was fitted with different number of spoked whegs from 3 to 7. In addition, eight evenly spaced motor speeds ranging from 2.33 to 7.43 Hz were used to observe the effect of stride frequency. Similar trends were observed between the two gaits, with the quadrupedal gait showing better overall performance. On dry sand, wider strides were attained at reduced motor speeds with lower spoked whegs. However, on wet sand (15% and 30% saturation), wider strides were achieved with higher motor speeds and lower spoked whegs. As a result, lower spoked whegs accomplished higher body forward velocity and lower COT as saturation increased. The acquired knowledge elucidates underexplored mechanics of locomotion on granular media at different saturation levels. The WhegRunner can be used as a platform to obtain a greater insight on how to develop more proficient exploration robots, ones which can face complex and deformable terrains and mediums.

IDENTIFIKASI PANJANG LANGKAH DAN FREKUENSI LANGKAH SEBAGAI FAKTOR PENENTU KECEPATAN LARI SPRINT 100 M

This study aims to identify the variability of stride length and stride frequency of junior-level 100 m sprinters with different performance levels and to verify the kinematics parameters of the phases of sprinting. Data were collected from a sample of 9 junior sprinter athletes determined by purposeful sampling. The analysis results show that the average number of steps for 100 m is 52.8. For the variable stride length, the average is 1.88 m. The step frequency variable shows an average of 4.77 steps/second (max step frequency). During the acceleration phase, the average stride frequency is 4.48 steps/second. The score in the last phase, i.e., the sprinters must maintain their velocity until the end of the race from a distance of 60 – 100 m, shows an average rate of 4.07 steps/second. The average sprinting time of the sprinters is 11.74 seconds, and the average speed of the sprinters is 8.54 ms-1, with a top speed of 8.95 ms-1 and the lowest speed of 7.99 ms-1. Based on the analysis of kinematic parameters, the different phase structures. The results show that stride length significantly contributes to the 100 m sprint performance than stride frequency, which is no longer considered the most critical determinant of performance at junior-level athletes.

An Alternative Athlete Monitoring System Using Cost-Effective Inertial Sensing Instrumentation.

An examination of the human gait is feasible using inertial sensing. The embedded accelerometer and gyroscope in an inertial measurement unit can evaluate physical activity-based sports and this unit is relatively affordable compared to global positioning systems or video recording quantification. This study developed a cost-effective sports monitoring investigation method with an inertial sensor attached to the right leg of the athletes. In total, four parameters were simultaneously tracked to assess the entire sensor performance in real-time. The accelerometer measured the typical leg angle when walking and running, whereas the gyroscope processed the raw data to obtain the stride frequency from the time-domain data. Moreover, a comparison between the accelerometer and gyroscope was presented while simultaneously attaining the signal to convert the time-domain data to frequency results. Also, the number of strides and linear velocity was expressed as results in this study. To confirm the results, a statistical hypothesis test was implemented for all obtained results. The results indicated that the inertial sensing instrumentation used in this study is promising and could be an affordable alternative option for a sports monitoring system.

Construction of Sports Rehabilitation Training Method Based on Virtual Reality

The introduction of virtual reality technology into rehabilitation training can avoid various shortcomings of traditional rehabilitation training, and can efficiently complete training tasks. Based on the basic theory of virtual reality, this paper constructs a sports rehabilitation training method to achieve the consistency of the virtual upper limbs and the real upper limbs of the human body. The model provides a background environment in the virtual reality training, realizes the systematic maintenance of the patient’s training mode, provides the patient with a scientifically based training mode and evaluation results, solves the quantitative index problem of sports rehabilitation training, and builds a virtual upper limb platform at the same time. During the simulation process, the system used the Berg balance assessment scores to conduct four-stage assessments. Before treatment, the three-dimensional gait analysis, FMAL lower extremity function scores and Berg balance assessment results were not significantly different between the control group and the experimental group ([Formula: see text]). The experimental results showed that the three-dimensional gait analysis was used to analyze the pace, left and right step length, left and right support percentage, and stride frequency. Compared with the evaluation data before treatment, the index values of the control group and the experimental group were significantly improved ([Formula: see text]); after the treatment, the two groups of patients were evaluated for motor function, the evaluation values of the experimental group were higher than those of the control group when compared between the two groups. It effectively meets the human–computer interaction needs of rehabilitation training.

The Effects Of Self-Myofascial Release On Flight Time And Step Frequency In Trained Runners

Running performance can be measured by flight time and stride frequency. Self-myofascial release (SMR), such as foam rolling, has gained much popularity in athletes for mobilization and releasing fascial adhesions in the working muscles. PURPOSE: The purpose of this study was to examine whether SMR will affect flight time and step frequency in trained runners. METHODS: Eight trained runners (ages: 41.38 ± 8.68, VO2max: 47.4 ± 6.87) volunteered to participate. During their first session they were video recorded completing a 4-minute treadmill run with a 1% incline at self-selected 5-km pace, followed by a VO2max test. During their second session, the participants completed guided foam rolling and repeated the 4 min run test. The videos were used to analyze flight time and stride frequency through Runmatic. RESULTS: There were no significant differences for the t-tests for flight time (p > .05), however there was a significant difference in stride frequency (p = 0.44). CONCLUSIONS: These findings suggest that foam rolling may improve stride frequency. Previous research has found stride frequency to be improved with improved flexibility, foam rolling has been found to improve range of motion in the hips. Future studies are still needed to determine how SMR effects running performance.

12-Week Nordic Walking Training Improves Gait in Community Seniors

&lt;p&gt;目的 : 探討12週北歐式健走訓練對於社區高齡者步態的影響。方法：70名高齡者分為無任何運動訓練介入的控制組，以及為期12週、每週3次、每次60分鐘的北歐式健走訓練組，訓練前後以光學步態分析系統，量測受試者行走5公尺的步態參數。結果：經12週北歐式健走訓練後，高齡者的步行速度顯著變快6.25 %、步幅顯著變大3.39%、步伐距離顯著變大1.70 % (p &lt; .05)，其他步態參數則無顯著變化 (p &gt; .05)。然而，12週僅維持正常生活作息的控制組，步行速度變慢、步幅變短、步態週期變長、步頻變慢、站立期時間變長、步伐距離變短、步伐時間變長、雙腳支撐期時間變長等衰退現象 (p &lt; .05)。結論：本研究以造成高齡者跌倒的重要因素：「步態」為主題，發現12週、每週3次、每次60分鐘北歐式健走訓練，能提高高齡者的步行速度與步幅，並維持其他步態參數，不因12週時間而有衰退情形；但是，僅維持正常生活作息，未不做任何有指導性專業運動訓練的高齡者，經過12週時間後的步行速度、步幅、步頻、站立期時間、雙腳支撐期時間等步態參數，皆有老化衰退現象。因此，北歐式健走訓練是一項對高齡者的步態，具有維持或促進效益的訓練方式。&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;&lt;p&gt;Purpose: The purpose of this study was to investigate the effect of 12-week Nordic walking training on the gait of the elderly in the community. Methods: 70 elderly people were divided into a control group without any exercise training intervention, and a Nordic walking training group for 12 weeks, 3 times a week, 60 minutes each time. The gait parameters were collected when participants walking for 5 meters, and was analyzed when by the optical gait analysis system before and after intervention. Results: After 12 weeks of Nordic walking training, the walking speed of the elderly was significantly increased by 6.25%, the stride length was significantly increased by 3.39%, and the step length was significantly increased by 1.70% (p&lt; .05). Other gait parameters were not significantly different (p &gt; .05). However, the control group that only maintained a normal daily routine for 12 weeks had a significant decline in gait: the walking speed became slower, the stride length became shorter, the gait cycle became longer, the stride frequency became slower, the stance phase became longer, and the period of double support became longer (p&lt; .05). Conclusions: This study focuses on gait of the elderly, for it is one of the important factors causing falls. It is found that 12 weeks, 3 times a week, 60 minutes of Nordic walking training each time can improve the walking speed and stride length of the elderly, and maintain other gait parameters for 12 weeks. However, the gait parameters (walking speed, stride length, stride frequency, stance phase, period of double support) of the other elderly who are not trained became worse. Therefore, Nordic walking training is a training method that maintains or promotes the gait of the elderly.&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

Predicting 2d Ground Reaction Forces In Running: Combining Inertial Measurement Units With Neural Networks

Knowing the ground reaction force (GRF) helps to quantify biomechanical load during running. However, GRF measurement is restricted to the lab. Artificial neural networks (ANNs) are capable to model complex relations and thus could be used to predict GRF from inertial measurement units (IMUs). This prediction would be a step towards the quantification of biomechanical load in the field. PURPOSE: Show the possibilities of an ANN to estimate GRFs in vertical and posterior/anterior direction using three IMUs. METHODS: 6 experienced heel strike runners (3 F, 3 M; age 31.5y ± 11.7y, height 1.77 m ± 0.07 m, mass 60.7 kg ± 16.0 kg) ran 9 trials on a force-instrumented treadmill at combination of three velocities (10, 12 and 14 km/h) and three stride frequencies (preferred, -10% of preferred and + 10% of preferred). Subjects were instrumented with IMUs (240 Hz) mounted at both proximal tibias and pelvis. With a per subject approach, 40 strides were extracted per trial, 20% of this data was used as validation and 80% as training set. Two layer ANNs (250 and 100 neurons) were then trained with the gravity subtracted acceleration in the global frame as input to fit the vertical and posterior/anterior GRF. Performance of the models was analysed with the root mean squared error (RMSE) and the Pearson’s correlation coefficient (r). The mean of the absolute error of the vertical peak during stance was calculated as an absolute value and percentage. The absolute and percentual error of the posterior/anterior breaking and push-off force peaks were determined. RESULTS: The ANN modelled peak GRF forces with high accuracy (vertical: r > 0.99, mean absolute peak error < 2.4%; posterior/anterior: r > 0.96, mean absolute peak error < 11.0%; Table 1). CONCLUSION: Deployment of ANNs to predict 2D GRFs directly from gravity subtracted acceleration in the global frame is very promising with a subject specific approach.

Does sex of the jockey influence racehorse physiology and performance

The racing industry is supported by a predominance of female stablehands and work riders, but few become professional jockeys. Female jockeys have recently had notable race success. No study has assessed whether the sex of the rider may subtly influence racehorse physiology to affect performance. Here, using a validated exercise tracking system (the 'Equimetre'™) that records many physiological parameters simultaneously, this study characterised racehorse cardiovascular (heart rate, heart rate recovery) and biomechanical (stride length and frequency) parameters at various exercise intensities (slow canter to hard gallop) to address the question whether any parameter varied according to sex of the rider. A total of 530 Thoroughbreds, varying in age (2-7 years old) and sex (including geldings), from one racing yard in Australia, completed a total of 3,568 exercise sessions, monitored by a single trainer, on varying track surfaces (sand, turf, or fibre). Different work riders,103 in total (male, n = 66; female, n = 37) of which n = 43 were current or past registered professional jockeys, participated in the study. Data were analysed using analysis of variation (ANOVA) or mixed-effect models, as appropriate. Sex of the rider did not influence (P > 0.05) racehorse speed nor stride length at any training intensity. Racehorse heart rate and peak heart rate increased with training intensity (P < .001), with no difference according to sex of rider (P > 0.05). Racehorse heart rate recovery was influenced by sex of the rider, but only at the extremes of the reversed, usual training intensity on each surface (e.g. heart rate after galloping on sand was significantly lower with male riders, P = 0.03). Finally, analysis of 52,464 race results indicated a similar chance of a top-three placing for male and female jockeys. In conclusion, this study, using objectively obtained data, demonstrates for the first time no overt effect of the rider's sex on racehorse physiology in training and performance in racing. Such data could encourage greater female participation in racing and improve access of female jockeys to better quality mounts in racing events.

Effects of personal protective clothing on firefighters’ gait analyzed using a three-dimensional motion capture system

Objectives. The effects of personal protective clothing (PPC) on firefighters’ gait were investigated to develop high-performance PPC. Methods. Thirteen participants participated in human trials with three types of PPC (firefighter protective clothing [FPC], semi-enclosed chemical protective clothing [CPC_semi] and fully enclosed chemical protective clothing [CPC_full]) and a T-shirt (control clothing [CON]). A three-dimensional (3D) motion capture system was used to obtain gait parameters (step length, step width, stride frequency, gait speed and toe-out angle) and the range of motion (ROM) of the joints (hip, knee and ankle). Results. PPC produced an increase in step width (23.4%, p > 0.05), but the gait speed (9.1%) and stride frequency (6.4%) decreased compared with the CON results. ROM is affected by the PPC type and joint. FPC and CPC_semi had no significant effect in terms of ROM of the hip and knee besides the landing angle of the knee. However, CPC_full had a significant effect on the maximum extension angle of the hip and maximum flexion angle of the knee, which reached up to 27.2%. Conclusion. The ROM of the firefighter’s lower limbs was limited by PPC. This study offers insights into next-generation PPC design and development, as well as guidelines for training and firefighting.

Evaluating the discriminatory power of the velocity field diagram and timed-up-and-go test in determining the fall status of community-dwelling older adults: a cross-sectional observational study

BackgroundSystematic reviews demonstrated that gait variables are the most reliable predictors of future falls, yet are rarely included in fall screening tools. Thus, most tools have higher specificity than sensitivity, hence may be misleading/detrimental to care. Therefore, this study aimed to determine the validity, and reliability of the velocity field diagram (VFD -a gait analytical tool), and the Timed-up-and-go test (TUG)-commonly used in Nigeria as fall screening tools, compared to a gold standard (known fallers) among community-dwelling older adults.MethodThis is a cross-sectional observational study of 500 older adults (280 fallers and 220 non-fallers), recruited by convenience sampling technique at community health fora on fall prevention. Participants completed a 7-m distance with the number of steps and time it took determined and used to compute the stride length, stride frequency, and velocity, which regression lines formed the VFD. TUG test was simultaneously conducted to discriminate fallers from non-fallers. The cut-off points for falls were: TUG times ≥ 13.5 s; VFD’s intersection point of the stride frequency, and velocity regression lines (E1) ≥ 3.5velots. The receiver operating characteristic (ROC) area under the curves (AUC) was used to explore the ability of the E1 ≥ 3.5velots to discriminate between fallers and non-fallers. The VFD’s and TUG’s sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were determined. Alpha was set at p < 0.05.ResultsThe VFD versus TUG sensitivity, specificity, PPV and NPV were 71%, 27%, 55%, and 42%, versus 39%, 59%, 55%, and 43%, respectively. The ROC’s AUC were 0.74(95%CI:0.597,0.882, p = 0.001) for the VFD. The optimal categorizations for discrimination between fallers/non-fallers were ≥ 3.78 versus ≤ 3.78 for VFD (fallers versus non-fallers prevalence is 60.71% versus 95.45%, respectively), with a classification accuracy or prediction rate of 0.76 unlike TUG with AUC = 0.53 (95% CI:0.353,0.700, p = 0.762), and a classification accuracy of 0.68, and optimal characterization of ≥ 12.81 s versus ≤ 12.81 (fallers and non-fallers prevalence = 92.86% versus 36.36%, respectively).ConclusionThe VFD demonstrated a fair discriminatory power and greater reliability in identifying fallers than the TUG, and therefore, could replace the TUG as a primary tool in screening those at risk of falls.

Pycnogenol improves kinematic parameters of donkeys (Equus asinus) subjected to packing during the dry season

The administration of pycnogenol (PYC) prior to physical exertion had earlier shown to improve gait variables after work. The aim of this study was to determine the effect of PYC on kinematic parameters of donkeys subjected to packing during the dry season. Ten male donkeys served as experimental subjects. Five donkeys were administered with PYC (10 mg/kg) in feed (test group) while another five donkeys were given feed only (control group) for one week pre-packing. Thermal environmental parameters of ambient temperature (AT), relative humidity (RH) and temperature humidity index (THI) were recorded. Kinematic parameters of speed (SP), stride length (SL), stride frequency (SF) and stride duration (SD) using videographic recordings 5 minutes post-packing with each animal walking at a self-selected speed were recorded. The THI values obtained pre- (95.4 ± 3.9) and during (85.3 ± 1.6) packing in the cold-dry season were significantly lower than the values of 148.8 ± 1.8 and 134.8 ± 1.1, respectively obtained during the hot-dry season. The speed recorded in test group (2.0 ± 0.3 m/s) was significantly (P &lt; 0.05) higher when compared to the value (1.3 ± 0.2 m/s) obtained in control group during the hot-dry season while, during the cold-dry season, the test group recorded a significantly (P &lt; 0.05) higher speed (1.3 ± 0.3 m/s) when compared with 1.0 ± 0.2 m/s recorded in control group.The increased speed recorded in the test group indicated that the group performed better as they were less fatigued when compared with the control group. Thus, PYC could be used as a potential agent in the management of fatigue in donkeys used for packing purposes in the region.

Behavioral Study of Parkinson's Disease Rats Model with DigiGait&amp;lt;sup&amp;gt;TM&amp;lt;/sup&amp;gt; Imaging System

<bold>Objective</bold> To detect the feasibility of DigiGait^TM Imaging System in evaluating gait changes in rats model with Parkinson's disease (PD). <bold>Methods</bold> A total of 24 clean male SD rats were randomly divided into normal group, sham operation group and model group, with eight rats in each group. In the model group, 6-Hydroxydopamine (6-OHDA) was injected into the brain with unilateral 2-point method to establish PD rats model. The sham operation group was injected with 0.2% ascorbic acid solution with the same method, and the normal group did not receive any surgical treatment. After successful preparation of the model, DigiGait^TM Imaging System was used to analyze temporal subcomponent (swing duration, braking duration, stance duration, stance factor), spatial subcomponent (stride frequency, stride length, stance width, gait symmetry, paw overlap distance, paw placement positioning) and postural subcomponent (paw angle, step angle, paw area). <bold>Results</bold> 1) Temporal subcomponent: compared with the normal group, the swing duration, braking duration and stance duration of left front paw, left hind paw and right front paw in the model group were significantly prolonged (<italic>P</italic>&lt;0.05), and the braking duration and swing duration of right hind paw in the model group were significantly prolonged (<italic>P</italic>&lt;0.05). Compared with the sham operation group, the swing duration, braking duration and stance duration of left front paw, left hind paw and right front paw in the model group were significantly prolonged (<italic>P</italic>&lt;0.05), and the braking duration of right hind paw in the model group was significantly prolonged (<italic>P</italic>&lt;0.05). 2) Spatial subcomponent: compared with the normal group and the sham operation group, the front and hind limb stance width of the model group significantly increased (<italic>P</italic>&lt;0.05), step frequency of four paws, stride length of left paws and paw placement positioning and gait symmetry in the model group significantly decreased (<italic>P</italic>&lt;0.05). But stride length of right paws and overlap distance of left and right paws in the model group had no significant changes (<italic>P</italic>&gt;0.05). 3) Postural subcomponent: compared with the normal group and the sham operation group, the contact area of left front paw, left hind paw and right hind paw with running belt in the model group significantly decreased (<italic>P</italic>&lt;0.05), there was no significant difference in paw area, paw angle and gait angle between the right front paw and the running belt (<italic>P</italic>&gt;0.05). <bold>Conclusion</bold> DigiGait^TM Imaging System can objectively evaluate walking, balance and coordination functions of PD rats, which has the potential to be widely applied in PD related basic research.

Triceps surae muscle force potential and force demand shift with altering stride frequency in running.

While it is well recognized that the preferred stride frequency (PSF) in running closely corresponds to the metabolically optimal frequency, the underlying mechanisms are still unclear. Changes in joint kinematics when altering stride frequency will affect the muscle-tendon unit lengths and potentially the efficiency of muscles crossing these joints. Here, we investigated how fascicle kinematics and forces of the triceps surae muscle, a highly energy consuming muscle, are affected when running at different stride frequencies. Twelve runners ran on a force measuring treadmill, adopting five different frequencies (PSF; PSF ± 8%; PSF ± 15%), while we measured joint kinematics, whole-body energy expenditure, triceps surae muscle activity, and soleus (SOL; N=10) and gastrocnemius medialis (GM; N=12) fascicle kinematics. In addition, we used dynamic optimization to estimate SOL and GM muscle forces. We found that SOL and GM mean muscle fascicle length during stance followed an inverted U-relationship with the longest fascicle lengths occurring at PSF. Fascicle lengths were shortest at frequencies lower than PSF. In addition, average SOL force was greater at PSF-15% compared with PSF. Overall, our results suggest that reduced SOL and GM muscle fascicle lengths, associated with reduced muscle force potential, together with greater SOL force demand, contribute to the increased whole-body energy expenditure when running at lower than PSF. At higher stride frequencies, triceps surae muscle kinematics and force production were less affected suggesting that increased energy expenditure is rather related to higher cost of leg swing and greater cost of force production.

A Data Analytics Approach to Assess the Functional and Physical Performance of Female Soccer Players: A Cohort Design.

Background and Objectives: The aim of this study was twofold: (i) to observe the individual results of fitness status [countermovement jump (CMJ)], hop test, linear sprinting time, stride frequency, stride distance, force–power–velocity, peak power maximal and maximal speed, and repeated sprint ability (RSA) and functional performance (overhead squat, single-leg squat test, dumbbell hip-hinge, Thomas test, hip extension, and internal and external hip rotators) and (ii) to analyze the relationship between anthropometrical measures and values of fitness status with % of difference in the Thomas test, hip extension, and internal and external hip rotators. Materials and Methods: The study followed a cohort design. Sixteen female soccer players competing in the second division of the Spanish league were monitored during the first days of the pre-season. These players were evaluated three times during the preseason of the cohort period. The dataset showed a negative moderate correlation between time and percentage of difference in hip angle and another positive moderate correlation between maximal sprint and percentage of difference in hip angle (r = −0.54, p = 0.02 and r = 0.53, p = 0.04), respectively. The correlations of stride time and distance with hip extension are interesting, as professional soccer players should have higher levels of hip flexor flexibility during the stride phase, recoil of the instep kick action.

Hip Torque Is a Mechanistic Link Between Sprint Acceleration and Maximum Velocity Performance: A Theoretical Perspective.

Sprinting performance is critical for a variety of sports and competitive activities. Prior research has demonstrated correlations between the limits of initial acceleration and maximum velocity for athletes of different sprinting abilities. Our perspective is that hip torque is a mechanistic link between these performance limits. A theoretical framework is presented here that provides estimates of sprint acceleration capability based on thigh angular acceleration and hip torque during the swing phase while running at maximum velocity. Performance limits were calculated using basic anthropometric values (body mass and leg length) and maximum velocity kinematic values (contact time, thigh range of motion, and stride frequency) from previously published sprint data. The proposed framework provides a mechanistic link between maximum acceleration and maximum velocity, and also explains why time constant values (τ, ratio of the velocity limit to acceleration limit) for sprint performance curves are generally close to one-second even for athletes with vastly different sprinting abilities. This perspective suggests that specific training protocols targeted to improve thigh angular acceleration and hip torque capability will benefit both acceleration and maximum velocity phases of a sprint.

Analysis of the Bayesian Gait-State Estimation Problem for Lower-Limb Wearable Robot Sensor Configurations.

Many exoskeletons today are primarily tested in controlled, steady-state laboratory conditions that are unrealistic representations of their real-world usage in which walking conditions (e.g., speed, slope, and stride length) change constantly. One potential solution is to detect these changing walking conditions online using Bayesian state estimation to deliver assistance that continuously adapts to the wearer's gait. This paper investigates such an approach in silico, aiming to understand 1) which of the various Bayesian filter assumptions best match the problem, and 2) which gait parameters can be feasibly estimated with different combinations of sensors available to different exoskeleton configurations (pelvis, thigh, shank, and/or foot). Our results suggest that the assumptions of the Extended Kalman Filter are well suited to accurately estimate phase, stride frequency, stride length, and ramp inclination with a wide variety of sparse sensor configurations.

Influence of caste and subcaste characteristics on locomotion in the ant Camponotus fellah.

Worker polymorphism in ants has evolved repeatedly, with considerable differences in the morphometry of worker subcastes. Such body size differences and especially caste- and subcaste-specific characteristics might significantly influence locomotion. Therefore, we performed a comprehensive locomotion analysis along gradients in both body size and walking speed of Camponotus fellah worker subcastes, and of males, which have rarely been studied to date because of their short life spans associated with mating flights. We provide a detailed description of the morphometry and size differences of C. fellah castes and subcastes and analyse locomotion in the different polymorphic groups in terms of absolute and relative walking speeds (mesosoma lengths per second). Our results reveal that body size and shape affect locomotion behaviour to different extents in the worker subcastes (minor workers, medias, major workers) and in males. Nevertheless, C. fellah ants use the same overall locomotion strategy, with males and major workers reaching considerably lower walking speeds than minors and medias. Body size thus mainly affects walking speed. Minor workers reach the highest relative velocities by high relative stride lengths in combination with large vertical and lateral centre of mass oscillations and clearly higher stride frequencies of up to 25 Hz. Locomotion of males was characterised by clearly lower walking speeds, wider footprint positions, significant phase shifts and a notable dragging of the shorter hind legs. However, general walking parameters of males differed less from those of the female workers than expected as a result of division of labour in the colony.

Evolution of determinant factors of maximal sprinting and repeated sprint ability in women soccer players

The present study aimed to determine the influence of force–power–velocity, vertical and horizontal jumps, and repeated sprint ability on the sprinting performance of adult women soccer players. Eighteen women soccer players from one team participating in the first female national Spanish soccer league were analyzed. Fitness assessments were performed twice in a period of three months. The following assessments were made to reach the aim of the study: (1) anthropometric measures, (2) CMJ (0%, 20% and 40%), (3) hop test (dominant and nondominant leg), (4) linear sprinting at 30 m and (5) RSA test. The main evidence of this study revealed the meaningful contribution of lower-limb power (vertical and horizontal jump), maximal sprint and peak power on sprinting time performance, while stride frequency was meaningfully explained by vertical jump and maximal sprinting. In fact, positive moderate and large correlations were found between Time and CMJ, CMJ 20%, CMJ 40%, Hop Test Dominant and Non-dominant, and Pmax and MS of Force–Power–Velocity (r = − 0.73, p = 0.001; r = − 0.68, p = 0.002; r = − 0.51, p = 0.03; r = − 0.64, p = 0.004; r = − 0.57, p = 0.013; r = − 0.78, p = 0.001, and r = − 0.83, p = 0.001, respectively). In sum, peak power, maximal speed, and lower-limb power (in vertical and horizontal jumps) were significant determinants of sprinting performance (time), while vertical jump was the determinant of stride frequency. In addition, our findings suggest that potentiation and explosive vertical power could be the emphasis for sustaining the stride frequency of women soccer players, while sprinting performance should be supported by strong acceleration and maximal velocity sustained by both vertical and horizontal force and concentric and eccentric strength and power.

Experimental Investigation on Pedestrian Walking Load in Steel Footbridges

Accurate simulation of walking load is of great significance in conducting human-induced vibration analyses. However, accurate pedestrian walking load data obtained from long-span footbridges is scarce and data reliability depends on the sensor used for measurement. In the current work, Yanluo Footbridge with 102 m span was adopted as test site and Xnode high-precision acceleration wireless sensor was applied for measurements. An experimental investigation was performed on walking loads according to bipedal walking force model. In experimental studies, single-person and multi-person walking tests were performed at Yanluo Footbridge to measure corresponding stride frequency and dynamic load factor. The acceleration time-histories of walking pedestrians were accurately recorded using three-axis wireless acceleration sensor Xnode. Furthermore, the equation of dynamic load factor was derived by analyzing time-histories and power spectra and the design models of pedestrian walking load and crowd load were developed based on a great number of experimental data. Time histories of pedestrian walking loads showed regular periodic changes and dynamic load factor increased by increasing stride frequency. Using the walking load model developed in this work, the reliable structure response of human-induced vibration analysis can be obtained.