FORCE, MOTION, SPEED: A GROUNDED PERSPECTIVE ON HUMAN RUNNING PERFORMANCE

Sprint running performance can be investigated relatively simply at the whole-body level by examining the timing of the phases of the stride and the forces applied to the ground in relation to a runners body weight. Research using this approach has been used to address a number of basic questions regarding the limits and determinants of human running speed. The primary differentiating factor for the top speeds of human runners is how forcefully they can strike the ground in relation to body mass. A general relationship between mass-specific force application and maximum running speeds results from from the similar durations of the aerial and swing phases of the stride for different runners. Recent work has elucidated the mechanism by which faster runners are able to apply greater mass-specific ground forces in the very brief foot-ground contact times sprinting requires

ANY OLYMPIC JUMP THAT WOMEN CAN DO, MEN CAN DO NEARLY 20% BETTER

Men clearly outperform women in events that depend on moving the body’s mass through space. However, the between-sex differences may vary with event specific mechanical demands. Existing observations suggest between-sex differences are relatively greater for jumping than running events. We tested this sytematically by comparing the top 50 performances for men and women in Olympic running (n=9) and three jumping (n=3) events over a recent 15-year period. We found that mean male–female difference across the three jumping events (17.8± 2.7%) was 1.5 times greater than the respective mean for the nine running events (11.2 ± 1.4%) examined. We conclude that male–female differences are substantially greater for all-out jumping versus running events

Cutting Sex-Performance Differences Down to Size: Are Females Closer to Males in Shorter Sprint Races?

The body size and composition differences between men and women are set by genetic factors with relatively constant offsets, particularly in homogeneous athletic populations. However, performance differences between the sexes appear to be more variable, potentially due to the mechanical demands of different events. Here, we set out to analyse the sex performance differences across sprint running events that differ in mechanical demands due to race length. Based on the scaling of tissue areas in relation to body mass, shorter, smaller athletes should be more forceful per kg body mass than larger ones. Greater force per kg body mass capabilities should be most advantageous during the acceleration portion of any race. Therefore, we hypothesized that the shorter sex, would fare relatively better in shorter vs longer races. We tested this by gathering performance, height and mass data from open sources on the top 40 performers in the 60, 100, 200 and 400 meter races over a 15 year period. As hypothesized, the shorter the sprint race, the smaller the male-female performance difference. These differences ranged from 8.6% at 60 m to 10.9% at 400 m. We conclude that male-female performance differences appear to be smaller for accelerated vs. steady-speed running

Are Men Cheaper Than Women? Insights From Walking Economy

ARE MEN CHEAPER THAN WOMEN? INSIGHTS FROM WALKING ECONOMY Nicole S. Schultz and Peter G. Weyand Southern Methodist University, Locomotor Performance Laboratory, Department of Applied Physiology and Wellness, Dallas, TX 75205 Introduction: The metabolic energy cost of human walking has been extensively studied. However, whether men and women require the same amount of energy (per kg of body mass) to walk at the same speed or cover the same distance remains unresolved. While most predictive algorithms incorporate only body mass and walking speed, we have recently found that mass-specific walking metabolic rates are inversely related to stature. Objective: We tested the specific hypothesis that walking economy does not differ between males and females when stature is controlled. We evaluated our hypothesis by comparing stature-matched adult males vs. females in each of three categories: short, medium and tall, at their respective most economical walking speeds. We predicted that minimum transport costs (COTmin, ml O2·kg-1·m-1) would not vary between gender groups of each stature. Methods: 30 subjects (15 male, 15 female) walked on a level treadmill at speeds ranging from 0.4 m·s-1 to 1.9 m·s-1. Indirect calorimetry was used to measure rates of oxygen uptake under steady-state conditions (Parvo Medics TrueOne 2400, Sandy, UT). Analysis: Minimum net transport cost, or net transport cost at the most economical walking speed, was determined for each subject by: 1) subtracting resting rates of oxygen uptake from the gross rates measured (VO2net, ml O2·kg-1·min-1), and 2) dividing VO2net by walking speed to identify the minimum COT. Unpaired t-tests were used to compare males and females within each stature group. Results: Transport costs were essentially identical for male and female groups of all three statures: short, medium and tall, and were inversely related to stature as expected. Conclusion: We conclude that men and women are equally cheap and gender does not influence walking energy expenditure. The mass-specific energy cost of transport does not differ in males and females of the same stature

DEVELOPMENT OF A SUSTAINABLE ONLINE ABORIGINAL & TORRES STRAIT ISLANDER GARDEN FOR LEARNING IN HEALTH SCIENCES

Aboriginal and Torres Strait Islander (ATSI) heritage trails are becoming increasingly important in Australia as they can translate intergenerational knowledge, culture and experiential learning for everyone (Muecke & Eadie, 2020). There is a need for virtual tours of gardens and online maps such as those utilised by the national botanical gardens in Victoria so access to natural resources is easier for both education purposes and public enjoyment (Royal Botanical Gardens Victoria, n.d.). At Australian Catholic University (ACU) we plan to digitise the ATSI Brisbane campus garden and create a sustainable and accessible learning environment for everyone by co-creating an online video and interactive ATSI heritage garden map at ACU with students. The project will involve recruitment of students to assist in creation of photos and videos, consultation with local community and Weemala Indigenous Higher Education Unit at ACU. The project celebrates collaborative ATSI knowings in science and sustainability that can be shared nationally and globally for community engagement, and in teaching of health sciences disciplines such as biomedical science, nutrition and nursing. REFERENCES Muecke, S. & Eadie, J. (2020). Ways of life: Knowledge transfer and Aboriginal heritage trails. Educational Philosophy and Theory, 52(11), 1201-1213. Royal Botanical Gardens Victoria (n.d.). https://www.rbg.vic.gov.au/#mai

Quantifying Getting High Under One’s Own Power – A Comparison of Vertical Jump Height Measurement Methods

Countermovement jump (CMJ) height is widely used as a performance test, but the methods for assessing jump height are not standardized. Some assessment methods include the use of aerial time, take-off velocity or jump and reach systems such as the Vertec commonly seen in the NFL combine. The Vertec tests an athlete’s vertical jump by having the athlete jump and reach for the highest rotating vane they can tap with their hand. However, the validity of these different methods is not well established even though the governing force-motion relationships have been known for centuries. Specifically, motion of the body’s center of mass (COM) is determined by the vertical impulse (force x Δtime) prior to take-off. At present, the agreement, or lack thereof, between the commonly used field assessment methods and the actual height the COM attains during a CMJ is not known. Here, we hypothesized that body positional changes during jump and reach tests result in jump height overestimations. PURPOSE: To compare one of the most widely utilized field methods, the Vertec to the gold standard of impulse determined jump height. METHODS: Thirty total (n=15 male, n=15 female) participants ranging in athletic ability from recreational to competitive collegiate level athletes completed three maximal effort CMJs. Jump height was determined simultaneously from the impulse collected using Bertec force plates and a Vertec system. Only the athlete’s highest jump was used in analysis. Vertec and impulse determined jump heights were compared using paired samples t-tests, with alpha level set at 0.05. RESULTS: Vertec jump heights significantly exceeded impulse determined jump heights by an average of 14 cm: 54 ± 14 vs. 40 ±11 cm (P\u3c0.001) respectively. [Vertec range: 32 to 81 cm; Impulse range: 23 to 59 cm.] CONCLUSION: The Vertec measurement system appreciably overestimates the elevation of the body’s COM during vertical jumping, here by an average of 14 cm or 5.5 inches. There was also a trend for individuals with higher jump heights to have a greater difference between the two measurements. Suggesting that reaching ability may be more of a determinant of Vertec jump height than vertical impulse. This should be of interest to sports performance professionals that use this method to analyze progress. This disparity in quantification exists because the difference between standing and reaching hand height at jump apex over-represents the vertical elevation of the COM. This phenomenon is most likely to result from the asymmetrical nature of the reaching action as athletes strike the Vertec vanes. It is also important for sport performance professionals that use the Vertec method to recognize that their athlete’s do not jump as high as they currently believe

UPPER EXTREMITY MOTION AND SPRINT RUNNING: A FAREWELL TO ARMS?

Despite a lack of prior research on the topic, the sport coaching community has popularized the use of arm drills for athletes with the intent to enhance sprinting performance. The purpose of this study was to identify the effect of self-restricted arm motion on sprint running velocity. Track & field athletes and team sport athletes (n=15) completed 12 30-meter sprints (six with normal arm motion, six with restricted arm motion) while radar data was collected to quantify running velocity. Using a mono-exponential function, velocity profiles were created for each trial which produced four outcome variables: vmax, amax, τ, and 30-meter sprint time. Differences in group means for all four outcome variables were not substantial between the two experimental conditions. It was concluded that the use of arm motion during maximal effort sprinting does not play a major role in running velocity enhancement

GROUND REACTION FORCES DURING COMPETITIVE TRACK EVENTS: A MOTION BASED ASSESSMENT METHOD

A motion based approach to generating vertical ground reaction forces (VGRF) from the motion of sprint running could be a useful analytical tool. The spring-mass model has been used for this purpose; however, the invariant pattern predicted by the model is not fully consistent with the force-time waveforms of competitive sprint athletes. The recently introduced two-mass model provides an alternative method that might generate better representations of sprinter’s force-time waveforms. Here we used both models to generate kinematic-averaged force-time waveforms from 4 sprint athletes in an IAAF 100-meter race from 360 Hz video data. We found substantial differences in the waveform patterns predicted by the two models. The two-mass model predicted waveform had greater peak forces (4.75 Wb) that occurred earlier in contact (28 ms) vs that of the spring mass model

Human Sprint Running Mechanics: Do Right and Left Legs Apply Equal Ground Forces?

Introduction: A growing body of research has focused on between-leg asymmetry as a critical factor for athletic performance and dysfunction. Specifically, various measures of between-leg asymmetry during running have been investigated in both healthy and injured populations. However, while the most important factor for running performance is the magnitude and rate of ground force application, it is not known whether the right and left legs typically apply equal ground forces at faster running speeds. Objective: In a healthy population of athletic female participants, we aimed to: 1) compare the mechanics of ground force application between right and left legs during moderate and top speed running, and 2) evaluate if the right vs. left leg asymmetries observed at intermediate speeds are more pronounced at faster speeds. Hypothesis: We hypothesized that the forces applied by the right and left legs of healthy athletes would agree to within 10% or less at both moderate and top speed. Participants: Nine female intercollegiate soccer players volunteered for the study (age: 19.4 ± 1.0 years, height: 1.72 ± 0.04 m, mass: 69.0 ± 7.2 kg). Data Collection: Ground force data was acquired at 1,000 Hz using a custom high-speed, three-axis force treadmill (AMTI, Watertown, MA). Data was analyzed for trials at 5.0 m•s-1 and each individual’s top speed. Top speed was defined as the fastest speed where the participant could complete eight consecutive steps on the treadmill without drifting backward more than 0.2 m. Outcome Measures: Ground contact time, vertical force, and vertical impulse were analyzed. Vertical force was normalized to body weight (Wb) and vertical impulse was calculated in body weight • seconds (Wb•s). For all trials, these variables were averaged for right vs. left footfalls, and percentage difference was calculated to quantify between-leg asymmetry. Results: Top speeds ranged from 7.21 to 8.26 m•s-1 (7.83 ± 0.38 m•s-1). At 5.0 m•s-1, the mean between-leg asymmetry was 2.3 ± 1.2 % for ground contact time, 1.9 ± 1.3 % for vertical force, and 2.3 ± 1.9 % for vertical impulse. At top speed, the mean between-leg asymmetry was 3.5 ± 2.8 % for ground contact time, 5.5 ± 3.0 % for vertical force, and 8.3 ± 4.8 % for vertical impulse. Conclusions: We conclude that the right and left legs apply ground force similarly during moderate and top-speed sprint running in healthy female athletes

A general relationship links gait mechanics and running ground reaction forces

The relationship between gait mechanics and running ground reaction forces is widely regarded as complex. This viewpoint has evolved primarily via efforts to explain the rising edge of vertical force– time waveforms observed during slow human running. Existing theoretical models do provide good rising-edge fits, but require more than a dozen input variables to sum the force contributions of four or more vague components of the body’s total mass (mb). Here, we hypothesized that the force contributions of two discrete body mass components are sufficient to account for vertical ground reaction force– time waveform patterns in full (stance foot and shank, m1=0.08mb; remaining mass, m2=0.92mb). We tested this hypothesis directly by acquiring simultaneous limb motion and ground reaction force data across a broad range of running speeds (3.0–11.1 m s−1 ) from 42 subjects who differed in body mass (range: 43–105 kg) and foot-strike mechanics. Predicted waveforms were generated from our two-mass model using body mass and three stride-specific measures: contact time, aerial time and lower limb vertical acceleration during impact. Measured waveforms (N=500) differed in shape and varied by more than twofold in amplitude and duration. Nonetheless, the overall agreement between the 500 measured waveforms and those generated independently by the model approached unity (R2 =0.95 ±0.04, mean±s.d.), with minimal variation across the slow, medium and fast running speeds tested (ΔR2 ≤0.04), and between rear-foot (R2 =0.94±0.04, N=177) versus fore-foot (R2 =0.95±0.04, N=323) strike mechanics. We conclude that the motion of two anatomically discrete components of the body’s mass is sufficient to explain the vertical ground reaction force–time waveform patterns observed during human running