This study investigated the influence of pacer body size on the aerodynamic drag experienced by elite marathon runners. Using 3D numerical simulations, various drafting configurations were analyzed at a running speed of 21  km/h with 1.2 m spacings between runners. The modeled runner groups comprised one elite protected marathoner (1.80 m) and one or two pacers of different heights (1.70  m, 1.80  m, and 1.90  m). Isosurfaces of total pressure and pressure coefficient maps revealed that taller pacers generate a wider wake and a more favorable pressure field for downstream runners. Specifically, compared to running solo, a 1.80 m runner positioned between two 1.90  m pacers benefits from a maximum drag reduction of 61.6%, resulting in a 6.48% improvement in running economy and a time gain of 5 min 02 s over the marathon distance. The relationship between projected frontal area, group configuration, and pressure field variations underscores the critical role of fluid-structure interactions on running performance. This study demonstrates that drag reduction depends not only on positioning but also on runner morphology, and opens promising avenues for fine-tuning drafting strategies in elite pack running.

The metabolic cost of running (Cr) is one of the three main determinants of performance in distance running, along with maximum oxygen consumption and lactate threshold. However, level Cr is only weakly correlated with performance in trail running, which almost always involves uphill and downhill sections. Through a secondary analysis of published data, the primary aim of this study was to characterize the correlations between individuals’ level and graded (downhill and uphill) Cr. We took advantage of this database to also re-evaluate the pattern and critical points (i.e., optimum slope) of the relationship between Cr and slope. We analyzed 23 studies evaluating level and graded Cr, published before August 2024. Both Cr and Pearson correlation coefficients between level and graded Cr were plotted as functions of slope. Using third-order polynomial functions, a correlation between level and graded Cr was a continuous function of slope in which correlation coefficients declined with progressively steep uphill or downhill slopes. Downhill Cr was minimized at − 18.8

Runners are susceptible to bone stress injuries (BSI), due in part to cumulative loading, which is affected by force magnitude and frequency. We identified biomechanical variables that may predict BSI incidence by following 30 collegiate distance runners over three years. Athletes were classified as either uninjured (n = 8 male, 16 female) or injured (n = 3 male, 3 female) if they sustained a BSI. We measured ground reaction forces while athletes ran on a force-instrumented treadmill, and analysed step frequency (fstep), contact length (Lc), and bodyweight-normalised stance average vertical ground reaction force (Favg) alongside asymmetry (expressed as symmetry index, SI). A secondary analysis examined inter-limb biomechanical changes in six runners prior to sustaining a BSI. We found an interaction between injury status, sex, and speed on Favg values (p = 0.026). Forty-seven weeks prior to injury, Favg values were greater in the unaffected leg than the affected leg (p = 0.022). In addition, female injured runners exhibited 1.62 percentage points greater fstep SI than uninjured females at 4.9 m/s (p = 0.030). Future research that incorporates more frequent data collection is needed to integrate biomechanical variables and physiological risk factors for injury prediction and prevention among collegiate distance runners.

In 2023, Faith Kipyegon set the female world record for running one mile (4:07.64). Here, we quantitatively explore if improved aerodynamic drafting could allow her to run just 3.19% faster and thus break the 4-minute mile barrier. Drafting involves other athletes (pacers) running in formation around a designated athlete to reduce the aerodynamic drag force acting on the designated runner. Drafting allows the designated athlete to run faster at the same rate of metabolic energy consumption. Our overall approach was to estimate Kipyegon's metabolic energy consumption during her mile world record performance. Then, we used empirically established relationships between horizontal resistive force, running velocity and metabolic power to estimate how much faster she could run at the same metabolic power if the aerodynamic force was reduced via drafting. Our calculations suggest that Kipyegon could run ~3:59.37 with drafting provided by one pacer in front and one in back who change out with two other pacers at 800 m.

To extend the Running Energy Expenditure Estimation (RE3) model for predicting metabolic rates during uphill and downhill running as well as to enhance the Hoogkamer-Taboga-Kram (HTK) equation for estimating metabolic rates during level and uphill running. We combined running metabolic data from an original dataset (n = 62) with individual subject data from 26 studies (n = 424) and group mean data from 12 studies (n = 187). Using this integrated dataset, we derived a new graded running term for the empirical RE3 model and updated the HTK equation coefficients for level and uphill running. We then compared the accuracy and precision of these new equations with the established American College of Sports Medicine (ACSM) and Minetti et al. equations based on the root-mean-square deviation (RMSD). Accuracy and precision of estimating level Ṁ were high for the Minetti et al. (RMSD, 1.44 W kg−1), HTK (1.30 W kg−1), and RE3 (1.27 W kg−1) equations, but much worse for the ACSM equation (1.82 W kg−1). Agreement on uphill slopes was highest for the HTK (RMSD, 1.45 W kg−1) and RE3 (1.41 W kg−1) equations with less precision noted for the ACSM (2.17 W kg−1) and Minetti et al. (2.18 W kg−1) equations. When estimating Ṁ during downhill running, the RE3 equation performed marginally better (RMSD, 1.45 W kg−1) than the Minetti et al. equation (1.57 W kg−1). The improved RE3 and HTK equations estimate metabolic rates during level and graded running with improved accuracy and precision. We provide a publicly available web-based metabolic rate calculator that simplifies estimation for researchers, practitioners, and runners alike.

The incidence of lower extremity injuries in collegiate distance runners is ∼20%. Identification of a runner sustaining a potential injury remains challenging. This exploratory, cross-institutional study sought to determine whether ground reaction force (GRF) characteristics during steady-state running could identify competitive collegiate distance runners who would later sustain lower extremity injuries. Normative boundaries for 10 GRF variables during braking and propulsion were established for noninjured runners using median ± scaled median absolute deviation. A subanalysis was conducted on runners with and without impact peaks in vertical GRF to mitigate the influence of impact peaks on GRF variables. We hypothesized that prior to injury, runners who later developed an injury would have more GRF variables outside of the normative boundaries than noninjured runners. Using Cliff's method, a rank-based, nonparametric method for comparing 2 independent groups, we found no statistically significant difference between the number of variables outside the boundaries for injured and noninjured runners overall (P = .17). However, injured runners without impact peaks had more variables outside the normative boundaries than noninjured runners (P < .001). This novel analytical approach demonstrates the potential for preidentifying collegiate distance runners without impact peaks who may be at risk for injury.

Competitive and recreational cyclists use stiff-soled shoes that firmly attach to 'clipless' pedals. When compared to very flexible running shoes, very stiff cycling shoes with clipless pedals enhance power output during sprint cycling. However, a recent study showed no difference in power output or sprint performance between commercially available cycling shoes that span a range of longitudinal bending stiffnesses (similar to 200 to 500 Nm/rad). Thus, we sought to identify the likely range of sole stiffnesses below 200 Nm/rad over which reduced cycling shoe sole stiffness begins to decrease maximal power output. We measured the mechanical power outputs of 25 road cyclists during maximal sprints wearing shoes with identical uppers but with three different sole stiffnesses. Each participant completed nine 50 m sprints (three trials for each shoe) on a road with a steady, uphill grade of 9.1%. The three shoe sole conditions were: injected nylon (longitudinal bending stiffness 194 Nm/rad), moderate stiffness thermoplastic polyurethane (medium TPU) (43 Nm/rad), and low stiffness TPU (soft TPU) (9 Nm/rad) all ridden with the same clipless pedals. Stiffness was quantified using a simple testing apparatus. Power output decreased below the sole stiffness of similar to 200 Nm/rad but only moderately. Maximal 1 s crank power (Pmax1) decreased -3.1% (ES = -0.59, p = 0.020) from Nylon to medium TPU and then further decreased -2.4% (ES 16 = -0.50, p = 0.054) from medium TPU to soft TPU. Interpolating our results suggests just a similar to 1% loss in Pmax1 at a sole stiffness of 100 Nm/rad. Within reasonable limits, cycling shoe sole stiffness has only a small effect on power output.

Background: Wearable exoskeletal devices can enhance locomotor performance, but their mass results in a metabolic penalty. Previous studies have quantified the metabolic cost of running with added mass on the feet, but less is known about the effects of adding mass to the thigh and shank segments.Aim: To quantify the metabolic cost of running with additional leg mass.Methods: 15 participants (7 F, 8 M) completed treadmill running trials (3 m/s) normally and with lead mass (300-1350 g) attached to either the thigh, shank, or foot, bilaterally. We measured metabolic power using expired gas analysis. Results: Per 1000 g of added mass per leg, gross metabolic power increased by approximately 16% (foot) and 11% (shank) for females which was slightly greater than the 11% and 8% increases for males, respectively. For thigh loading, metabolic power increased by just 4% per 1000 g in both sexes. Conclusion: Adding mass more distally on the leg increases the metabolic cost of running to a greater extent. For the same absolute added mass on the foot or shank, metabolic power increases more in females.

A total of 200,000+ large timbers were transported >75 km to Chaco Canyon, a political and religious center in the precontact U.S. Southwest, using only human power. Previous researchers reported that typical primary roof beams (vigas) of Chacoan Great Houses averaged 0.22 m in diameter and 5 m in length with a mass of 275 kg. However, the 275 kg mass appears to be a miscalculation. Here, we calculate that a ponderosa pine timber of the stated dimensions would have a mass between 85–140 kg depending on the water content. While still a prodigious load, this recalculated mass requires revisions to estimates of the labor, time, and energy required to build Great Houses at Chaco. Based on contemporary measurements on professional load carriers and soldiers, we estimate that as few as two people could have carried an 85 kg timber across 100 km in as few as 21 h of active walking.200,000+ maderas grandes fueron transportadas >75 km hasta el Cañón del Chaco, un centro político y religioso precolombino en el suroeste de los EE.UU., utilizando únicamente fuerza humana. Investigadores anteriores informaron que las vigas principales del techo de las Casas Grandes Chacoanas tenían un diámetro promedio de 0.22 m y una longitud de 5 m con una masa de 275 kg. La masa de 275 kg parece ser un error de cálculo. Aquí, calculamos que una madera de pino ponderosa de las dimensiones indicadas tendría una masa entre 85 y 140 kg dependiendo del contenido de agua. Aunque sigue siendo una carga prodigiosa, esta masa recalculada requiere revisiones de las estimaciones de la fuerza laboral, el tiempo y la energía totales necesarios para construir las Casas Grandes en Chaco. Basado en medidas contemporáneas sobre profesionales de carga y soldados, nosotros estimamos que tan solo 2 personas podrían cargar una madera de 85 kg a través de 100 km en tan solo ∼ 21 horas de caminata activa.

Looney, DP, Hoogkamer, W, Kram, R, Arellano, CJ, and Spiering, BA. Estimating metabolic energy expenditure during level running in healthy, military-age women and men. J Strength Cond Res 37(12): 2496-2503, 2023-Quantifying the rate of metabolic energy expenditure (.) of varied aerobic exercise modalities is important for optimizing fueling and performance and maintaining safety in military personnel operating in extreme conditions. However, although equations exist for estimating oxygen uptake during running, surprisingly, there are no general equations that estimate.. Our purpose was to generate a general equation for estimating. during level running in healthy, military-age (18-44 years) women and men. We compiled indirect calorimetry data collected during treadmill running from 3 types of sources: original individual subject data (n545), published individual subject data (30 studies; n5 421), and published group mean data (20 studies, n 5 619). Linear and quadratic equations were fit on the aggregated data set using a mixed-effects modeling approach. A chi-squared (x 2) difference test was conducted to determine whether the more complex quadratic equation was justified (p, 0.05). Our primary indicator of model goodness-of-fit was the root-mean-square deviation (RMSD). We also examined whether individual characteristics (age, height, body mass, and maximal oxygen uptake [V.O2max]) could minimize prediction errors. The compiled data set exhibited considerable variability in. (14.54 6 3.52 W center dot kg21), respiratory exchange ratios (0.8960.06), and running speeds (3.5060.86m center dot s21). The quadratic regression equation had reduced residual sum of squares compared with the linear fit (x2, 3,484; p, 0.001), with higher combined accuracy and precision (RMSD, 1.31 vs. 1.33 W center dot kg21). Age (p 5 0.034), height (p 5 0.026), and body mass (p 5 0.019) were associated with the magnitude of under and overestimation, which was not the case for V.O2max (p50.898). The newly derived running energy expenditure estimation (RE3) model accurately predicts level running. at speeds from 1.78 to 5.70 m center dot s21 in healthy, military-age women and men. Users can rely on the following equations for improved predictions of running. as a function of running speed (S, m center dot s21) in either watts (W center dot kg21 5 4.43 + 1.51 center dot S + 0.37 center dot S2) or kilocalories per minute (kcal center dot kg21 center dot min21 5 308.8 + 105.2 center dot S + 25.58 center dot S2).

Between 850 and 1200 CE, approximately 200,000+ large timbers were transported >75 km to Chaco Canyon using only human power. Researchers have proposed various load-carriage methods, speculated about how many porters would be needed and their speed of transport, but none have conducted empirical investigations. Here, we explore the feasibility of long-distance timber transport using tumplines, a technology well-evidenced in Chaco's archaeological record. Two authors trained themselves to use tumplines and together carried a 60 kg timber 25 km with the timber oriented transverse to the walking direction. Total elapsed time was <10 h and walking speed averaged 4.5 km/hr. Individual walking speed with a 30 kg tumpline load was only similar to 10 % slower than the preferred unladen walking speed. Timber transport to Chaco using tumplines is clearly feasible. We close by considering the implications of tumpline timber transport on the socio-political dynamics of Chacoan society.

We quantify that the common practice of using single-value oxygen uptake energy equivalents for exercising subjects can incur systematic errors of up to 7%. We argue that such errors can be greatly reduced if researchers measure both V̇o2 and V̇co2 and adopt appropriate stoichiometry equations.

AIM:We analyzed the biomechanical response (joint angles, moments, and powers) to running with added leg mass. These data may help guide the design of wearable locomotor assistive devices (i.e., exoskeletons), which are becoming more prevalent. METHODS:15 participants (7 females, 8 males) completed treadmill running trials (3m•s-1) normally and with lead mass (300-1350 g) attached to the thigh, shank, or foot, bilaterally. We quantified the lower limb biomechanics combining motion capture and ground reaction force data using standard inverse dynamics analysis. RESULTS:Only moderate kinematic changes occurred in response to the distal added limb mass. Maximum hip flexion and maximum knee flexion angles during swing phase increased by approximately 9% and 6% respectively for each 1 kg added to each foot. However, adding even small masses made dramatic changes to the joint moments and powers, mostly during the swing phase. For example, adding 1 kg to each foot increased maximum joint moments by as much as 40% (knee extension in late swing) and maximum joint power by as much as 50% (hip generation in late swing). CONCLUSION:Leg joint kinematics were largely conserved in response to adding mass to the legs. Adding mass to the leg distally increased joint power mainly at the knee and hip joints during the swing phase, whereas adding mass proximally mainly affected the ankle joint mechanics during the stance phase. These changes have implications for shoe designs, people who run with added mass on their legs for sport/strength training and for the design of wearable devices.

Triathletes almost universally use two shoe types; one for cycling and one for running. Though equally as efficient as cycling shoes during steady-state cycling, traditional running shoes impair cycling sprint performance. Newly developed running shoes, containing stiff carbon-fibre plates, may allow triathletes to use one pair of shoes for both cycling and running without sacrificing performance. Here, we describe a hybrid running-cycling shoe system, consisting of carbon-plated running shoes with magnetic pedal attachments and test whether it facilitates similar crank power and sprint cycling performance compared to a traditional road cycling shoe-pedal combination. The purpose of the present study was to quantify the possible disadvantage of cycling in running shoes during accelerations, even though accelerations comprise only a small portion of a triathlon cycling leg. Participants completed four standing, all-out, 50 m sprints in both shoe-pedal conditions on an uphill road (4.9% slope). On average, maximum 1 s mechanical power and 50 m mean power decreased by 8.5% (p < .001) and 7.5% (p < .001), respectively, when using the hybrid shoe-pedal combination. The decrease in power translated to only a 2.8% decrease in 50 m mean velocity (p < .001). Some participants expressed apprehension about the novel magnetic shoe-pedal interface which may explain a portion of the decrease in performance. Overall, we find that for triathletes, using hybrid running-cycling shoes would incur little performance disadvantage during accelerations on the bike. Not having to change shoes would allow for a faster bike-to-run transition.

Recently developed shoes that are highly-cushioned and have a curved stiff plate embedded in the midsole are “ergogenic” in that they reduce the rate of metabolic energy required to run at a defined speed. These energy savings are not due to low mass but rather to their foam midsoles which are unusually compliant and resilient. The function of the plate has not yet been elucidated, but evidence is clear that the plate itself does not act as a spring or a teeter-totter. The plate may act synergistically with the foam to create an area-elastic structure, akin to a gymnastics floor. Future studies of ergogenic shoes should: focus on muscle function using EMG and ultrasound, explore footstrike pattern effects, only utilize stiff treadmills, and seek to define a consistent baseline shoe condition for comparison.

Background: Compared to conventional racing shoes, Nike Vaporfly 4% running shoes reduce the metabolic cost of level treadmill running by 4%. The reduction is attributed to their lightweight, highly compliant, and resilient midsole foam and a midsole-embedded curved carbon-fiber plate. We investigated whether these shoes also could reduce the metabolic cost of moderate uphill (+3 degrees) and downhill (-3 degrees) grades. We tested the null hypothesis that, compared to conventional racing shoes, highly cushioned shoes with carbon-fiber plates would impart the same similar to 4% metabolic power (W/kg) savings during uphill and downhill running as they do during level running. Methods: After familiarization, 16 competitive male runners performed six 5-min trials (2 shoes x 3 grades) in 2 Nike marathon racing-shoe models (Streak 6 and Vaporfly 4%) on a level, uphill (+3 degrees), and downhill (-3 degrees) treadmill at 13 km/h (3.61 m/s). We measured submaximal oxygen uptake and carbon dioxide production during Minutes 4-5 and calculated metabolic power (W/kg) for each shoe model and grade combination. Results: Compared to the conventional shoes (Streak 6), the metabolic power in the Vaporfly 4% shoes was 3.83% (level), 2.82% (uphill), and 2.70% (downhill) less (all p < 0.001). The percent of change in metabolic power for uphill running was less compared to level running (p = 0.04; effect size (ES) = 0.561) but was not statistically different between downhill and level running (p = 0.17; ES = 0.356). Conclusion: On a running course with uphill and downhill sections, the metabolic savings and hence performance enhancement provided by Vaporfly 4% shoes would likely be slightly less overall, compared to the savings on a perfectly level race course.