Biology subjects

Hoogkamer, W.

Publications and source records attributed to Hoogkamer, W..

At least 19 recordsLinked to original sources

bioRxiv2025

Gait adaptation to asymmetric foot-ground compliance applied by robotic footwear

Perturbing foot-ground interaction dynamics has shown promise for eliciting adaptations to inter-limb weight-bearing symmetry, a critical target for rehabilitation of asymmetrical neuromotor deficits affecting gait. To date, this perturbation paradigm has been delivered via adjustable stiffness treadmills, in which the treadmill deck displaces under the walkers foot during the stance phase of gait. Recently, we developed robotic footwear capable of delivering asymmetrical ground stiffness perturbations during walking, offering a portable experimental platform for asymmetrical ground stiffness perturbations, allowing it to be executed overground and on conventional treadmills. In this study, we quantified kinetic and spatio-temporal gait adaptation to a foot-ground compliance perturbation delivered by the novel robotic footwear. We found that participants shifted their vertical ground reaction force impulse, vertical pushoff peak, and peak braking force toward the unperturbed limb after the perturbation was removed, indicating a shift in neuromotor control elicited by the perturbation. We conclude that the robotic footwear can elicit weight bearing adaptations similar to adjustable stiffness treadmills, and that the dissipative mechanical properties of the shoes likely play a key role in the direction of the adaptation.

neuroscience↗

bioRxiv2025

Metabolic energy expenditure during level, uphill, and downhill running

PurposeTo 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. MethodsWe combined running metabolic data from an original dataset (n=63) 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). ResultsAccuracy and precision of estimating level [M] were high for the Minetti et al. (RMSD, 1.44 W{middle dot}kg-1), HTK (1.30 W{middle dot}kg-1), and RE3 (1.27 W{middle dot}kg-1) equations but much worse for the ACSM equation (1.82 W{middle dot}kg-1). Agreement on uphill slopes was highest for the HTK (RMSD, 1.45 W{middle dot}kg-1) and RE3 (1.41 W{middle dot}kg-1) equations with less precision noted for the ACSM (2.17 W{middle dot}kg-1) and Minetti et al. (2.18 W{middle dot}kg-1) equations. When estimating [M] during downhill running, the RE3 equation performed marginally better (RMSD, 1.45 W{middle dot}kg-1) than the Minetti et al. equation (1.57 W{middle dot}kg-1). ConclusionThe 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.

physiology↗

bioRxiv2025

Weight-bearing symmetry changes after asymmetric surface stiffness walking

Stroke is a leading cause of adult disability in the United States, often presenting as hemiparesis. A priority in hemiparetic gait rehabilitation is the restoration of gait symmetry. While split belt treadmill training has shown promise in correcting spatial gait asymmetry, weight bearing and propulsion asymmetry remain resistant to improvement. As an alternative approach, we tested asymmetric surface stiffness walking to induce signatures of neuromotor adaptation relevant to correcting weight bearing and propulsion asymmetries in hemiparetic stroke. We hypothesized that a bout of asymmetric stiffness walking would elicit aftereffects in the form of asymmetries in weight bearing, propulsion, and plantar flexor activity. Twelve healthy young adults performed a 10-minute bout of asymmetric stiffness walking on an adjustable stiffness treadmill. We measured baseline and post-perturbation ground reaction forces (GRF) and spatio-temporal measures during 5-minute walking bouts on a dual-belt instrumented treadmill. After asymmetric surface stiffness walking, participants walked with increased vertical GRF and plantar flexor muscle excitations during push-off on the perturbed side relative to unperturbed. Participants also decreased their mid-stance vertical GRF and increased their peak braking GRF on the perturbed side relative to unperturbed. Counter to our hypothesis, they did not increase their propulsion GRF on the perturbed side. We conclude that asymmetric stiffness walking elicited a neuromotor adaptation towards a relative increase in push-off in the target limb, albeit primarily vertically aligned in our cohort of healthy young adults, and that gait adaptation to asymmetric stiffness walking should be investigated in individuals with push-off asymmetries. New & NoteworthyWeight-bearing asymmetry in individuals with hemiparetic stroke is resistant to treatments that produce improvements in other gait function measures (e.g., spatio-temporal symmetry). We investigated a novel perturbed ground stiffness intervention applied by an adjustable surface stiffness treadmill and found significant aftereffects in vertical and braking ground reaction force peaks in healthy young adults, as well as increases in perturbed-side plantar flexor activity during push-off, indicating a strong potential for correcting persistent deficiencies in post-stroke gait.

neuroscience↗

bioRxiv2025

Wearable Assessment of Level and Uphill Running at Critical Intensity

PurposeWe used commercially available wearable devices that measure running power (foot- vs. wrist-based) and muscle oxygenation to investigate time-to-exhaustion during level and uphill running at critical intensity. Methods14 healthy recreational runners participated in this study. They first ran a 3-minute all-out test to derive their critical running intensity. They then performed two time-to-exhaustion trials (TTEs) at this intensity at separate slopes to assess time-to-exhaustion, muscle oxygenation, and rating of perceived exertion. ResultsWe observed a shorter time-to-exhaustion (539 {+/-} 160 vs. 936 {+/-} 336 s), a faster decline in muscle oxygenation over time (-2.48 {+/-} 1.32 vs. -1.62 {+/-} 2.11 %{middle dot}min-1), a higher rating of perceived exertion at matched time points, and a higher estimated metabolic rate (19.51 {+/-} 1.99 vs. 17.82 {+/-} 1.62 W{middle dot}kg-1) for the level time-to-exhaustion test (TTELevel) compared to the uphill time-to-exhaustion test (TTEIncline) at a 2.86{degrees} (5%) slope. ConclusionOur data suggests that athletes should be careful when using running power at critical intensity to guide their racing and training in non-level conditions.

physiology↗

bioRxiv2025

Data driven shoe design improves running economy beyond state-of-the-art Advanced Footwear Technology running shoes

Advanced Footwear Technology (AFT) has enabled remarkable improvements in running performance over traditional marathon racing shoes. However, reported differences between state-of-the-art AFT models are small, and vary across individuals. To assess if the benefits of AFT have been fully realized or if further running economy improvements can be unlocked using modern computational design and optimization techniques, we compared a prototype AFT shoe developed using a data-driven computational design process (PUMA Fast-R 3; FR3) against state-of-the-art AFT models. We quantified running economy for 15 trained runners (11M, 4F) in this prototype AFT shoe and three commercially available AFT models: the PUMA Fast-R 2 (FR2), the Nike Alphafly 3 (NIKE), and the Adidas Adios Pro Evo (ADI). Running economy in the FR3 was 3.15 {+/-} 1.24%, 3.62 {+/-} 1.25%, and 3.54 {+/-} 1.16% better than in the FR2, NIKE and ADI (all p < 0.001), respectively, and every individual performed best in the FR3 shoes. While step parameters were similar between FR3 and FR2, the FR3 had a lower step frequency than the ADI (p = 0.013) and longer contact time than the NIKE and ADI (both p<0.001). Our results suggest that computational design analysis is a promising frontier in performance running shoe design, offering potential for further improvements and personalized AFT models.

physiology↗

bioRxiv2025

Posterior parietal cortex activity during visually cued gait: a preliminary study

Safe gait requires visually cued (VC) step adjustments for negotiating targets and obstacles. Effective step adjustments rely on good visuospatial processing. The posterior parietal cortex (PPC) is implicated in visuospatial processing, yet empirical evidence is limited for the PPCs role during gait in humans. Increased cortical control of gait is associated with higher gait variability, a marker of gait performance and fall risk among older adults. However, the cortical underpinnings of gait variability in visually complex environments are not well established. The primary aim of this preliminary study was to assess PPC activity during VC gait and VC gait with perturbations (VCP). A secondary aim was to determine how PPC activity relates to gait variability during VC and VCP gait. Twenty-one healthy young adults completed three treadmill gait conditions at preferred speed: non-cued (NC) gait, VC gait, where stepping targets were presented in a regular pattern, and VCP gait, where stepping target positions were pseudorandomly shifted. Functional near-infrared spectroscopy quantified relative changes in deoxygenated and oxygenated hemoglobin ({Delta}HbO2) concentrations in the PPC. Inertial measurement units quantified gait variability. Moderate effects were observed for more positive {Delta}HbO2 from NC to both VC and VCP gait, likely reflecting the increased visuospatial processing demands. Stride time variability was positively correlated with PPC {Delta}HbO2 during VC gait, suggesting a potential role for the PPC in modulating temporal components of VC gait. Extending these findings to older adults will help to elucidate the PPCs role in gait adaptability and fall risk with aging.

neuroscience↗

bioRxiv2025

Adjustable Compliance Footwear Technology to Investigate Gait Adaptation

Kinetic asymmetries in gait caused by neurological impairments are a major factor in mobility deficiency. Gait perturbation training has shown promise for rehabilitating neurological gait asymmetry, but the transfer of benefits from treadmill training to overground walking is limited. To enable kinetic gait perturbation training on treadmills and overground, we developed novel adjustable compliance footwear technology. The system consists of a wearable pneumatic actuation module which controls the pressure of custom air pockets embedded in a soft lattice midsole, and is capable of independently and wirelessly adjusting the midsole compliance under each foot from 300 kN/m and 60% energy absorption to 18 kN/m and 75% energy absorption in under 4 seconds. Hindfoot and forefoot sole deflection data are measured via Hall effect sensors and paired magnets characterized to 1.7 mm accuracy. To demonstrate the experimental capability of the system, we successfully triggered multiple compliance changes during overground walking and recorded ground reaction forces and embedded sensor values during a prolonged asymmetric compliance walking bout on a treadmill. Future work will include a full experimental study of gait adaptation to asymmetric footwear compliance perturbations.

bioengineering↗

bioRxiv2025

Is increasing the effective leg length of a human runner metabolically beneficial?

The purpose of this study was to understand if footwear midsole thickness can decrease the metabolic cost of running by increasing the effective leg length of a runner. We also sought to understand the role of midsole compliance on these measures. Participants (n = 16) ran on a treadmill at 14 km h-1 in four mass-matched shoe conditions: 30, 40, and 60 mm thickness of a firm midsole foam and 60 mm thickness of a compliant midsole foam. Over two testing sessions, we measured metabolic cost (two 5-minute trials in each condition) and biomechanical measures (one 2-minute trial in each condition). Increasing thickness in the firm midsole conditions increased effective leg length during early, mid, and late stance (all p < 0.001). However, metabolic cost increased (p = 0.031). Changing material from firm to compliant decreased effective leg length during midstance (p < 0.001), but not during early or late stance, and decreased metabolic cost (p < 0.001). Results suggest that increasing midsole thickness can increase the effective leg length of a runner, but this isolated effect leads to increasing in metabolic cost. On the other hand, increasing midsole compliance leads to reductions in metabolic cost, agreeing with previous literature. We suggest that the performance benefits seen in advanced footwear technology with increased midsole thickness are likely due to increased capacity to return mechanical energy, not due increases in effective leg length. Summary StatementIncreased midsole compliance, not increased effective leg length, is responsible for decreased metabolic cost in running.

physiology↗

bioRxiv2024

Forward Simulations of Walking on Surfaces with Asymmetric Mechanical Impedance: Insights for Gait Rehabilitation

Gait asymmetry, prevalent in stroke survivors and various other neurological and musculoskeletal conditions, leads to abnormal joint loading, increased fall risk, and reduced walking efficiency. Traditional rehabilitation methods often fail to consistently reduce weight-bearing gait asymmetry, necessitating innovative approaches. This study explores the potential of an adjustable mechanical impedance treadmill to amplify weight-bearing asymmetries, leveraging the "error amplification" technique akin to split-belt treadmill training. We developed a 2D optimal control gait model in OpenSim to simulate walking on a rigid platform with one leg and a compliant platform, with adjustable stiffness and damping, with the other. We simulated 112 unique mechanical impedance conditions of the compliant platform and analyzed the effects of these conditions on stance time, ground reaction forces (GRFs), and muscle activations. Our results identified specific impedance parameters that can be utilized to amplify propulsion asymmetries, providing a potential new approach for gait rehabilitation post-stroke. Future work should validate these results in experimental settings and further explore optimal impedance parameters for effective gait therapy of various gait impairments.

bioengineering↗

bioRxiv2024

Could a female athlete run a 4-minute mile with improved aerodynamic drafting?

In 2023, Faith Kipyegon set the female world record for running one mile (4:07.64). Here, we quantitively 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 Kipyegons 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.

physiology↗

bioRxiv2024

Walking with increased step length variability increases the metabolic cost of walking

Older adults and neurological populations tend to walk with slower speeds, more gait variability, and a higher metabolic cost. This higher metabolic cost could be related to their increased gait variability, but this relationship is still unclear. The purpose of this study was to determine how increased step length variability affects the metabolic cost of waking. Eighteen healthy young adults completed a set of 5-minute trials of treadmill walking at 1.20 m/s while we manipulated their step length variability. Illuminated rectangles were projected onto the surface of a treadmill to cue step length variabilities of 0, 5 and 10% (coefficient of variation). Actual step lengths and their variability were tracked with reflective markers on the feet, while metabolic cost was measured using indirect calorimetry. Changes in metabolic cost across habitual walking (no projections) and the three variability conditions were analyzed using a linear mixed effects model. Metabolic power was largest in the 10% condition (4.30 {+/-} 0.23 W/kg) compared to 0% (4.16 {+/-} 0.18 W/kg) and habitual (3.98 {+/-} 0.25 W/kg). The participants actual step length variability did not match projected conditions for 0% (3.10%) and 10% (7.03%). For every 1% increase in step length variability, there is an 0.7% increase in metabolic cost. Our results demonstrate an association between the metabolic cost of walking and gait step length variability. This suggests that increased gait variability contributes to a portion of the increased cost of walking seen in older adults and neurological populations. Summary StatementFor every 1% increase in step length variability, there is an 0.7% increase in the metabolic cost of walking.

physiology↗

bioRxiv2024

Effects of longitudinal bending stiffness and midsole foam on running energetics

BackgroundAdvanced footwear technology has become commonplace in the competitive running world. However, a systematic exploration of the effects of each of the primary components has not yet been presented. PurposeTo quantify running economy and step parameters in four different shoe conditions: PEBA shoes with plate, PEBA shoes without plate, EVA shoes with plate and EVA shoes without plate. MethodsParticipants ran at 14 km/h (n = 8 males) or 12 km/h (n = 6 females) on a treadmill. The shoe order was randomly assigned for the four shoe conditions, where the participants wore each shoe twice in a mirrored order. ResultsThere was a significant reduction in metabolic power (1.0%) associated with the presence of a plate, as well as a similar reduction based on foam type (1.0%). However, there was no significant interaction between presence of plate and foam type. Adding a plate significantly reduced metabolic power for EVA by 1.3% but not for PEBA. PEBA foam significantly reduced metabolic power by 1.3% in shoes without a plate, but not for the shoes with a plate. Step frequency and contact time were similar between shoes and not correlated to running economy improvements. ConclusionsStarting from a baseline condition with traditional foam without a plate, either adding a plate or using PEBA foam improved running economy with a similar amount (1.3%). Adding the alternate second feature non-significantly improved running economy with an additional 0.6%. The benefit of both technologies combined (1.9%) was smaller than the sum of its parts (1.3% each). Key pointsO_LIThe use of a PEBA foam midsole or the addition of a carbon fiber plate improves running economy a similar amount when compared to a traditional EVA running shoe without a plate. C_LIO_LIContrary to our hypothesis, the benefit of both technologies combined (1.9%) was smaller than the sum of its parts (1.3% each). C_LI

physiology↗

bioRxiv2024

Assessing sprint technique with shoe-mounted inertial sensors

Negative foot speed (i.e., the speed of the backward and downward motion of the foot relative to the body at ground contact) is a strong predictor of sprinting performance. Inertial measurement units (IMUs) are becoming a popular approach for assessing sports performance. The primary aim of this study was to use IMUs to investigate the relationship between negative foot speed and top running speed attained during a sprint on an outdoor track. Seventeen participants performed 80-meter track sprints while wearing a shoe-mounted IMU. Anteroposterior and vertical components of negative foot speed were extracted from the IMU. For the mean peak stride speed of 7.98{+/-}0.78m/s, the adjusted R2 values were 0.27 and 0.42 versus the anteroposterior and vertical components of negative foot speed, respectively. In conclusion, our findings support the common coaching tip of increasing negative foot speed to improve sprint speed. In addition, the results of this study support the use of IMUs for quantifying sprinting technique with actionable metrics.

bioengineering↗

bioRxiv2024

Influence of advanced footwear technology spikes on middle- and long-distance running performance measures in trained runners

Two types of track spikes are commonly used, recently: spikes with a compliant and resilient midsole foam (e.g., PEBA), and spikes that combine such modern foam with a carbon fiber plate. Here we evaluated the effect of these different spike technologies on running performance measures for middle- and long-distance track events in trained runners. Fourteen females performed a single visit with six 200m trials at self-perceived 800m race pace in three different spike conditions (Control, PEBA and PEBA+Plate) twice in a mirrored order. Sixteen males completed four visits. During the first three visits they performed six 200m trials at self-perceived 800m race pace, twice in each condition. Subsequently, they performed a 3,000m time trial in one of the three spike conditions. During visit four, participants completed six 4-minute running economy trials at 5 m/s, twice in each condition. At 800m race pace females ran faster in PEBA (2.1%) and PEBA+Plate (2.0%) compared to Control. Males ran faster in PEBA (1.4%) and PEBA+Plate (2.4%) compared to Control, and in PEBA+Plate compared to PEBA (1.1%). Similarly, males ran the 3,000m time trial faster in PEBA (1.0%) and PEBA+Plate (2.4%) than in Control. Running economy was better in PEBA (5.1%) and PEBA+Plate (4.0%) than in Control. Performance benefits from modern foam spikes with and without a plate are equivalent for female middle-distance running, and for male long-distance running, but larger from modern foam spikes with a plate for male middle-distance running.

bioengineering↗

bioRxiv2024

AdjuSST: An Adjustable Surface Stiffness Treadmill

Humans have the remarkable ability to manage foot-ground interaction seamlessly across terrain changes despite the high dynamic complexity of the task. Understanding how adaptation in the neuromotor system enables this level of robustness in the face of changing interaction dynamics is critical for developing more effective gait retraining interventions. We developed an adjustable surface stiffness treadmill (AdjuSST) to trigger these adaptation mechanisms and enable studies to better understand human adaptation to changing foot-ground dynamics. The AdjuSST system makes use of fundamental beam-bending principles; it controls surface stiffness by controlling the effective length of a cantilever beam. The beam acts as a spring suspension for the transverse endpoint load applied through the treadmill. The system is capable of enforcing a stiffness range of 15-300kN/m within 340 ms, deflecting linearly downwards up to 10 cm, and comfortably accommodating two full steps of travel along the belt. AdjuSST offers significant enhancements in effective walking surface length compared to similar systems, while also maintaining a useful stiffness range and responsive spring suspension. These improvements enhance our ability to study locomotor control and adaptation to changes in surface stiffness, as well as provide new avenues for gait rehabilitation.

bioengineering↗

bioRxiv2023

Relationship between advanced footwear technology longitudinal bending stiffness and energy cost of running

Introduction/PurposeShoe longitudinal bending stiffness (LBS) is often considered to influence running economy (RE) and thus, running performance. However, previous results are mixed and LBS levels have not been studied in advanced footwear technology (AFT). The purpose of this study was to evaluate the isolated effects of increased LBS from curved carbon fiber plates embedded within an AFT midsole on RE and spatiotemporal parameters. MethodsTwenty-one male trained runners completed 3 times 4 minutes at 13km/h with two experimental shoe models with a curved carbon fiber plate embedded in an AFT midsole with different LBS values (Stiff: 35.5 N/mm and Stiffest: 43.1 N/mm), and a Control condition (no carbon fiber plate: 20.1 N/mm). We measured energy cost of running (W/kg) and spatiotemporal parameters in one visit. ResultsRE improved for the Stiff shoe condition (15.71 {+/-} 0.95 W/kg; p<0.001; n2 =0.374) compared to the Control condition (16.13 {+/-} 1.08 W/kg) and Stiffest condition (16.03 {+/-} 1.19 W/kg). However, we found no significant differences between the Stiffest and Control conditions. Moreover, there were no spatiotemporal differences between shoe conditions. ConclusionChanges in LBS in AFT influences RE suggesting that moderately stiff shoes are the most effective LBS to improve RE in AFT compared to very stiff shoes and traditional, flexible shoe conditions while running at 13 km/h.

physiology↗

bioRxiv2023

Quantifying the performance benefits of middle distance running super spikes

BackgroundQuantifying the potential benefits of advanced footwear technology (AFT) track shoes (i.e., "spikes") in middle-distance events is challenging, because repeated maximal effort trials (as in sprinting) or aerobic running economy trials (as in long-distance running) are not feasible. MethodsWe introduce a novel approach to assess the benefits of AFT spikes, consisting of a series of 200 m runs at self-perceived middle-distance race pace with 10 min recovery and conducted four experiments to evaluate its validity, sensitivity, reproducibility, and utility. ResultsIn experiment 1, participants ran 1.2% slower in spikes with 200 g added mass vs. control spikes, exactly equal to the known effects of shoe mass on running performance. In experiment 2, participants ran significantly faster in AFT prototype spikes vs. traditional spikes. In experiment 3, we compared two other AFT prototype spikes against traditional spikes, on three separate days. Group-level results were consistent across days, but our data indicates that at least two separate sessions are needed to evaluate individual responses. In experiment 4, participants ran significantly faster in two AFT spike models vs. traditional spikes (2.1% and 1.6%). Speed was similar between a third AFT spike model and the traditional spikes. These speed results were mirrored by changes in step length, as participants took significantly longer steps in the two faster AFT spike models (2.3% and 1.9%), while step length was similar between the other spikes. ConclusionOur novel, interval-based approach is a valid and reliable method to quantify differences between spikes at middle-distance running intensity.

physiology↗

bioRxiv2023

Gait adaptation to asymmetric hip stiffness applied by a robotic exoskeleton

Wearable exoskeletons show significant potential for improving gait impairments, such as interlimb asymmetry. However, a more profound understanding of whether exoskeletons are capable of eliciting neural adaptation is needed. This study aimed to characterize how individuals adapt to bilateral asymmetric joint stiffness applied by a hip exoskeleton, similar to split-belt treadmill training. Thirteen unimpaired individuals performed a walking trial on the treadmill while wearing the exoskeleton. The right side of the exoskeleton acted as a positive stiffness torsional spring, pulling the thigh towards the neutral standing position, while the left acted as a negative stiffness spring pulling the thigh away from the neutral standing position. The results showed that this intervention applied by a hip exoskeleton elicited adaptation in spatiotemporal and kinetic gait measures similar to split-belt treadmill training. These results demonstrate the potential of the proposed intervention for retraining symmetric gait.

neuroscience↗