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"Super-shoes" are designed to improve endurance running performance by reducing the metabolic demands of running. Although the research on "super-shoes" is still developing and has mostly been studied in male runners, it is not clear how possible mediating factors, such as foot strike pattern, influence the metabolic cost and joint mechanics in competitive female runners. Purpose: The objective of this study is to assess the influence of "super-shoes" on metabolic cost and joint mechanics in competitive female runners and to understand how foot strike patter may influence the footwear effects. Methods: Eighteen competitive female runners ran four 5-min bouts on a force instrumented treadmill at 12.9 km⋅h-1 in 1) Nike Vaporfly Next% 2™(SUPER) and 2) Nike Pegasus 38™(CON) in a randomized and mirrored order. Results: Metabolic power was improved by 4.2% (P < 0.001; d = 0.43) and metatarsophalangeal (MTP) negative work (P < 0.001; d = 1.22), ankle negative work (P = 0.001; d = 0.67), and ankle positive work (P < 0.001; d = 0.97) were all smaller when running in SUPER compared with CON. There was no correlation between foot strike pattern and the between-shoe (CON to SUPER) percentage change for metabolic power (r = 0.093, P = 0.715). Conclusions: Metabolic power improved by 4.2% in "super-shoes" (but only by ~3.2% if controlling for shoe mass differences) in this cohort of competitive female runners, which is a smaller improvement than previously observed in men. The reduced mechanical demand at the MTP and ankle in "super-shoes" are consistent with previous literature and may explain or contribute to the metabolic improvements observed in "super-shoes"; however, foot strike pattern was not a moderating factor for the metabolic improvements of "super-shoes." Future studies should directly compare the metabolic response among different types of "super-shoes" between men and women. [ABSTRACT FROM AUTHOR]

In the quest to uncover the underlying mechanisms responsible for the performance-enhancing benefits imparted by advanced footwear technology (AFT), footwear researchers are employing an individual-level approach. In doing so, they hope to unveil individual-specific responses to AFT otherwise masked by a group-level approach. Classifying an individual's response on the basis of running economy (RE) is a logical strategy given that the intended purpose of AFT is to enhance performance; however, caution should be taken when doing so. Metabolic measurement devices are far from perfect, and given the known errors associated with metabolic measurements we would like to reiterate a suggestion first made 40 years ago: when seeking to quantify the interindividual variability of improvement in RE associated with running in AFT, the best practice is to rely on a minimum of two same-day measurements of RE. [ABSTRACT FROM AUTHOR]

Background: Ethylene and vinyl acetate (EVA) and polyether block amide (PEBA) are recently the most widely used materials for advanced footwear technology (AFT) that has been shown to improve running economy (RE). This study investigated the effects of these midsole materials on RE and biomechanics, in both fresh and worn state (after 450 km). Methods: Twenty‐two male trained runners participated in this study. Subjects ran four 4‐min trials at 13 km‧h−1 with both fresh EVA and PEBA AFT and with the same models with 450 km of wear using a randomized crossover experimental design. We measured energy cost of running (W/kg), spatiotemporal, and neuromuscular parameters. Results: There were significant differences in RE between conditions (p = 0.01; n2 = 0.17). There was a significant increase in energy cost in the worn PEBA condition compared with new (15.21 ± 1.01 and 14.87 ± 0.99 W/kg; p < 0.05; ES = 0.54), without differences between worn EVA (15.13 ± 1.14 W/kg; p > 0.05), and new EVA (15.15 ± 1.13 w/kg; ES = 0.02). The increase in energy cost between new and worn was significantly higher for the PEBA shoes (0.32 ± 0.38 W/kg) but without significant increase for the EVA shoes (0.06 ± 0.58 W/kg) (p < 0.01; ES = 0.51) with changes in step frequency and step length. The new PEBA shoes had lower energy cost than the new EVA shoes (p < 0.05; ES = 0.27) with significant differences between conditions in contact time. Conclusion: There is a clear RE advantage of incorporating PEBA versus EVA in an AFT when the models are new. However, after 450 km of use, the PEBA and EVA shoes had similar RE. [ABSTRACT FROM AUTHOR]

Introduction/purpose: Previous results about shoe longitudinal bending stiffness (LBS) and running economy (RE) show high variability. This study aimed to assess the effects of shoes with increased LBS on RE and performance in trained and national runners. Methods: Twenty-eight male runners were divided into two groups according to their 10-km performance times (trained, 38-45 min and national runners, <34 min). Subjects ran 2 - 3 min (at 9 and 13 km·h-1 for trained, and 13 and 17 km·h-1 for national runners) with an experimental shoe with carbon fiber plate to increase the LBS (Increased LBS) and a control shoe (without carbon fiber plate). We measured energy cost of running (W·kg-1) and spatiotemporal parameters in visit one and participants performed a 3000 m time trial (TT) in two successive visits. Results: Increased LBS improved RE in the trained group at slow (11.41 ± 0.93 W·kg-1 vs 11.86 ± 0.93 W·kg-1) and fast velocity (15.89 ± 1.24 W·kg--1 vs 16.39 ± 1.24 W·kg-1) and only at the fast velocity in the national group (20.35 ± 1.45 W·kg-1 vs 20.78 ± 1.18 W·kg-1). The improvements in RE were accompanied by different changes in biomechanical variables between groups. There were a similar improvement in the 3000 m TT test in Increased LBS for trained (639 ± 59 vs 644 ± 61 s in control shoes) and national runners (569 ± 21 vs 574 ± 21 s in control shoes)withmore constant pace in increased LBS compared with control shoes in both groups. Conclusions: Increasing shoe LBS improved RE at slow and fast velocities in trained runners and only at fast velocity in national runners. However, the 3000m TT test improved similarly in both levels of runners with increased LBS. The improvements in RE are accompanied by small modifications in running kinematics that could explain the difference between the different levels of runners. [ABSTRACT FROM AUTHOR]

• We showed that reducing the longitudinal bending stiffness in the forefoot of the Nike Vaporfly 4% has minimal effect on overall running economy • Biomechanically, the curved carbon-fiber plate in the Nike Vaporfly 4% has the most influence on the metatarsophalangeal joint, with no significant effect on the ankle or knee joints • The forefoot longitudinal bending stiffness alone likely has minimal effect on performance. Instead, improved performance is likely due to an interaction of the foam, shoe geometry, and other effects of the curved carbon-fiber plate not related to bending stiffness. This study aimed to determine the independent effect of the curved carbon-fiber plate in the Nike Vaporfly 4% shoe on running economy and running biomechanics. Fifteen healthy male runners completed a metabolic protocol and a biomechanics protocol. In both protocols participants wore 2 different shoes, an intact Nike Vaporfly 4% (VF intact) and a cut Nike Vaporfly 4% (VF cut). The VF cut had 6 medio-lateral cuts through the carbon-fiber plate in the forefoot to reduce the effectiveness of the plate. In the metabolic protocol, participants ran at 14 km/h for 5 min, twice with each shoe, on a force-measuring treadmill while we measured metabolic rate. In the biomechanics protocol, participants ran across a runway with embedded force plates at 14 km/h. We calculated running economy, kinetics, and lower limb joint mechanics. Running economy did not significantly differ between shoe conditions (on average, 0.55% ± 1.77% (mean ± SD)) worse in the VF cut compared to the VF intact ; 95% confidence interval (–1.44% to 0.40%). Biomechanical differences were only found in the metatarsophalangeal (MTP) joint with increased MTP dorsiflexion angle, angular velocity, and negative power in the VF cut. Contact time was 1% longer in the VF intact. Cutting the carbon-fiber plate and reducing the longitudinal bending stiffness did not have a significant effect on the energy savings in the Nike Vaporfly 4%. This suggests that the plate's stiffening effect on the MTP joint plays a limited role in the reported energy savings, and instead savings are likely from a combination and interaction of the foam, geometry, and plate. [Display omitted] [ABSTRACT FROM AUTHOR]

In the wake of the quest to break the 2-h marathon barrier, carbon-fiber plates have become commonplace in marathon racing shoes. Despite the controversy surrounding this shoe technology, studies on the effects of increased longitudinal bending stiffness on running economy report mixed results. Here, we provide a comprehensive review of the current literature on midsole bending stiffness and carbon-fiber plates in distance running shoes, focusing on how longitudinal bending stiffness affects running energetics and lower limb mechanics. The current literature reports changes in running economy with increased longitudinal bending stiffness ranging from ~ 3% deterioration to ~ 3% improvement. In some studies, larger improvements have been observed, but often those shoes varied in many aspects, not just longitudinal bending stiffness. Biomechanically, increased longitudinal bending stiffness has the largest impact on metatarsal–phalangeal (MTP) and ankle joint mechanics. Plate location [top loaded (an insole), embedded (in between midsole foam), and bottom loaded (along the bottom of the shoe)] and geometry (flat/curved) affect joint moments and angular velocities at the MTP and ankle joint differently, which partly explains the mixed running economy results. Further research investigating how carbon-fiber plates interact with other footwear features (such as foam and midsole geometry), scaling of those with shoe size, body mass, and strike pattern, and comparing various plate placements is needed to better understand how longitudinal bending stiffness affects running economy. [ABSTRACT FROM AUTHOR]

Eliud Kipchoge made two attempts to break the 2-hour marathon, in Monza and then Vienna. Here we analyse only the effects of course elevation profile and turn curvatures on his performances. We used publicly available data to determine the undulations in elevation and the radii of the curves on the course. With previously developed equations for the effects of velocity, slope, and curvature on oxygen uptake, we performed simulations to quantify how much the elevation changes and curves of the Vienna course affect a runner's oxygen uptake (at a fixed velocity) or velocity (at a fixed oxygen uptake). We estimate that, after the initial downhill benefit, the course led to an overall oxygen uptake penalty of only 0.03%. When compared to a perfectly level straight course, we estimate that the combined effects of the undulations and curves of the Vienna course incurred a penalty of just 1.37 seconds. Kipchoge ran 2:00:25 in Monza Italy. Comparison with the Monza course profile indicates a 46.2 second (1.09% oxygen uptake) advantage of Vienna's course while the fewer curves of Vienna contributed ~ 1 second. The Vienna course was very well-chosen because it minimized the negative effects of elevation changes and curves. Abbreviations: CoT: Oxygen cost of transport; C V ˙ O2: Curved rate of oxygen consumption; V ˙ O2: Rate of oxygen consumption; WA: World Athletics [ABSTRACT FROM AUTHOR]

The article focuses on research examining if marathon runner Eliud Kipchoge could reduce his time running the Berlin, Germany marathon to under two hours by using cooperative drafting (CD). It states on September 16, 2018 he eclipsed the previous world record for the Berlin marathon by one minute, 18 seconds for a time of 2:01:39. It utilizes mathematical models to examine how CD would benefit running speed and found three Kipchoge-like-runners could together beat the two-hour marathon barrier.

Background: We have shown that a prototype marathon racing shoe reduced the metabolic cost of running for all 18 participants in our sample by an average of 4%, compared to two well-established racing shoes. Gross measures of biomechanics showed minor differences and could not explain the metabolic savings.Objective: To explain the metabolic savings by comparing the mechanics of the shoes, leg, and foot joints during the stance phase of running.Methods: Ten male competitive runners, who habitually rearfoot strike ran three 5-min trials in prototype shoes (NP) and two established marathon shoes, the Nike Zoom Streak 6 (NS) and the adidas adizero Adios BOOST 2 (AB), at 16 km/h. We measured ground reaction forces and 3D kinematics of the lower limbs.Results: Hip and knee joint mechanics were similar between the shoes, but peak ankle extensor moment was smaller in NP versus AB shoes. Negative and positive work rates at the ankle were lower in NP shoes versus the other shoes. Dorsiflexion and negative work at the metatarsophalangeal (MTP) joint were reduced in the NP shoes versus the other shoes. Substantial mechanical energy was stored/returned in compressing the NP midsole foam, but not in bending the carbon-fiber plate.Conclusion: The metabolic savings of the NP shoes appear to be due to: (1) superior energy storage in the midsole foam, (2) the clever lever effects of the carbon-fiber plate on the ankle joint mechanics, and (3) the stiffening effects of the plate on the MTP joint. [ABSTRACT FROM AUTHOR]

Background: During a race, competing cyclists often cooperate by alternating between leading and drafting positions. This approach allows them to maximize velocity by using the energy saved while drafting, a technique to reduce the overall drag by exploiting the leader’s slipstream. We have argued that a similar cooperative drafting approach could benefit elite marathon runners in their quest for the sub-2-hour marathon.Objective: Our aim was to model the effects of various cooperative drafting scenarios on marathon performance by applying the critical velocity concept for intermittent high-intensity running.Methods: We used the physiological characteristics of the world’s most elite long-distance runners and mathematically simulated the depletion and recovery of their distance capacity when running above and below their critical velocity throughout a marathon.Results: Our simulations showed that with four of the most elite runners in the world, a 2:00:48 (h:min:s) marathon is possible, a whopping 2 min faster than the current world record. We also explored the possibility of a sub-2-hour marathon using multiple runners with the physiological characteristics of Eliud Kipchoge, arguably the best marathon runner of our time. We found that a team of eight Kipchoge-like runners could break the sub-2-hour marathon barrier.Conclusion: In the context of cooperative drafting, we show that the best team strategy for improving marathon performance time can be optimized using a mathematical model that is based on the physiological characteristics of each athlete. [ABSTRACT FROM AUTHOR]

Fatigue, developed over the course of a run, may cause changes in running kinematics. Training status may influence the effect of fatigue on running kinematics, since well trained, competitive runners are used to running until exhaustion, whereas novice runners are not. This study aimed to determine changes in running kinematics during an exhaustive run in both novice (NOVICE) and competitive (COMP) longdistance runners. About 15 NOVICE and 15 COMP runners performed a treadmill run, until voluntary exhaustion at 3,200 m time trial pace. Joint angles and global trunk and pelvis angles were recorded at the beginning and at the end of the run. In both groups, peak pelvic anterior tilt, pelvic rotation range of motion (both during stance phase) and ankle plantar flexion during swing phase increased after the exhaustive run. There was a significant interaction effect between group and exhaustion for peak forward trunk lean, which increased only in the NOVICE group, and for hip abduction during mid-swing, which increased in NOVICE and decreased in COMP runners. In conclusion, NOVICE runners showed larger kinematic adjustments when exhausted than COMP runners. This may affect their running performance and should be taken into account when assessing a runner's injury risk. [ABSTRACT FROM AUTHOR]

A sub-2-hour marathon requires an average velocity (5.86 m/s) that is 2.5% faster than the current world record of 02:02:57 (5.72 m/s) and could be accomplished with a 2.7% reduction in the metabolic cost of running. Although supporting body weight comprises the majority of the metabolic cost of running, targeting the costs of forward propulsion and leg swing are the most promising strategies for reducing the metabolic cost of running and thus improving marathon running performance. Here, we calculate how much time could be saved by taking advantage of unconventional drafting strategies, a consistent tailwind, a downhill course, and specific running shoe design features while staying within the current International Association of Athletic Federations regulations for record purposes. Specifically, running in shoes that are 100 g lighter along with second-half scenarios of four runners alternately leading and drafting, or a tailwind of 6.0 m/s, combined with a 42-m elevation drop could result in a time well below the 2-hour marathon barrier. [ABSTRACT FROM AUTHOR]

Purpose: Our goal was to quantify if small (1%-3%) changes in running economy quantitatively affect distance-running performance. Based on the linear relationship between metabolic rate and running velocity and on earlier observations that added shoe mass increases metabolic rate by ~1% per 100 g per shoe, we hypothesized that adding 100 and 300 g per shoe would slow 3000-m time-trial performance by 1% and 3%, respectively. Methods: Eighteen male sub-20-min 5-km runners completed treadmill testing, and three 3000-m time trials wearing control shoes and identical shoes with 100 and 300 g of discreetly added mass. We measured rates of oxygen consumption and carbon dioxide production and calculated metabolic rates for the treadmill tests, and we recorded overall running time for the time trials. Results: Adding mass to the shoes significantly increased metabolic rate at 3.5 m⋅s-1 by 1.11% per 100 g per shoe (95% confidence interval = 0.88%-1.35%). While wearing the control shoes, participants ran the 3000-m time trial in 626.1 ± 55.6 s. Times averaged 0.65% ± 1.36% and 2.37% ± 2.09% slower for the +100-g and +300-g shoes, respectively (P < 0.001). On the basis of a linear fit of all the data, 3000-m time increased 0.78% per added 100 g per shoe (95% confidence interval = 0.52%-1.04%). Conclusion: Adding shoe mass predictably degrades running economy and slows 3000-m time-trial performance proportionally. Our data demonstrate that laboratory-based running economy measurements can accurately predict changes in distance-running race performance due to shoe modifications. [ABSTRACT FROM AUTHOR]

Purpose: Runners naturally adopt a stride frequency closely corresponding with the stride frequency that minimizes energy consumption. Although the concept of self-optimization is well recognized, we lack mechanistic insight into the association between stride frequency and energy consumption. Altering stride frequency affects lower extremity joint power; however, these alterations are different between joints, possibly with counteracting effects on the energy consumption during ground contact and swing. Here, we investigated the effects of changing stride frequency from a joint-level perspective. Methods: Seventeen experienced runners performed six running trials at five different stride frequencies (preferred stride frequency (PSF) twice, PSF ± 8%, PSF ± 15%) at 12 km⋅h-1. During each trial, we measured metabolic energy consumption and muscle activation, and collected kinematic and kinetic data, which allowed us to calculate average positive joint power using inverse dynamics. Results: With decreasing stride frequency, average positive ankle and knee power during ground contact increased (P < 0.01), whereas average positive hip power during leg swing decreased (P <0.01). Average soleus muscle activation during ground contact also decreased with increasing stride frequency (P < 0.01). In addition, the relative contribution of positive ankle power to the total positive joint power during ground contact decreased (P = 0.01) with decreasing stride frequency, whereas the relative contribution of the hip during the full stride increased (P < 0.01) with increasing stride frequency. Conclusions: Our results provide evidence for the hypothesis that the optimal stride frequency represents a trade-off between minimizing the energy consumption during ground contact, associated with higher stride frequencies, without excessively increasing the cost of leg swing or reducing the time available to produce the necessary forces. [ABSTRACT FROM AUTHOR]

Footwear interventions are a potential avenue to correct walking asymmetry in neurologic populations, such as stroke. However, the motor learning mechanisms that underlie the changes in walking imposed by asymmetric footwear are unclear. The objectives of this study were to examine symmetry changes during and after an asymmetric shoe height intervention in (1) vertical impulse and (2) spatiotemporal gait parameters and (3) joint kinematics, in healthy young adults Eleven healthy young adults (3 males, 8 females; 21.2 ± 3.1 years old) participated in this study. Participants walked on an instrumented treadmill at 1.3 m/s for four conditions: (1) a 5-minute familiarization with equal shoe height, (2) a 5-minute baseline with equal shoe height, (3) a 10-minute intervention, where participants walked with asymmetric shoe height with a 10 mm shoe insert in one shoe, and (4) a 10-minute post-intervention, where participants walked with equal shoe height. Asymmetry in kinetics and kinematics were used to identify changes during intervention and aftereffects, a hallmark of feedforward adaptation Participants did not alter vertical impulse asymmetry (p = 0.667) nor stance time asymmetry (p = 0.228). During the intervention, step time asymmetry (p = 0.003) and double support asymmetry (p < 0.001) were greater compared to baseline. Leg joint asymmetry during stance (Ankle plantarflexion: p < 0.001; Knee flexion: p < 0.001; Hip extension: p = 0.011) was greater during the intervention compared to baseline. However, changes in spatiotemporal gait variables and joint mechanics did not demonstrate aftereffects. Our results show that healthy human adults change gait kinematics, but not weight-bearing symmetry with asymmetrical footwear. This suggests that healthy humans prioritize maintaining vertical impulse by changing their kinematics. Further, the changes in gait kinematics are short-lived, suggesting feedback-based control, and a lack of feedforward motor adaptations • Kinetic asymmetry is not adapted with asymmetrical shoe height. • Gait kinematic asymmetry are altered with asymmetrical shoe height. • Gait kinematic asymmetry changes may be due to reactive learning mechanisms. [ABSTRACT FROM AUTHOR]