PK Gill, JM Donelan, KM Steele, MH Schwartz, AJ Ries (2025) Quantifying altered oxygen kinetics and reducing metabolic test times for children with cerebral palsy: a dual-exponential Bayesian modeling approach

Journal Article in Journal of Applied Physiology

Prior research using indirect calorimetry has shown that children with cerebral palsy (CP) exhibit significantly increased energetic costs during walking. However, metabolic testing to obtain oxygen cost is challenging. As a result, differences in oxygen uptake kinetics (V̇o2) in CP compared with their typically developing peers remain unexplored. Step changes in work rate have been shown to result in an exponential V̇o2 response with three distinct phases 1) cardiodynamic, 2) primary, and 3) steady-state.

Infographic titled “Slower oxygen kinetics and reduced metabolic testing times for children with cerebral palsy.” The conclusion states "“Conclusion: Time constants are longer in CP; only 3 minutes of data are needed for reliable steady- state walking estimates.Aim: This study aimed to apply a dual-exponential Bayesian model to assess the time constant of the primary phase V̇o2 response from resting to walking in children with CP. In addition, evaluate the model’s ability to estimate steady-state V̇o2 using shorter test durations.

Methods: A dual-exponential Bayesian model was applied to metabolic data from a sample of 263 children with CP. The model estimated the time constant of the primary phase V̇o₂ response and tested the accuracy of steady-state V̇o₂ estimation using only the first 3 minutes of data, compared to the standard 6-minute duration.

Results: The median V̇o2 time constant was 33.1 s (5th–95th percentile range: 14.5–69.8 s), significantly longer than reported values for typically developing children (range of means: 10.2–31.6 s). Furthermore, the model accurately estimated steady-state V̇o2 using only the first 3 min of metabolic data compared with the typical 6 min used in current clinical practice. The 3-min estimate explained >95% of the 6-min estimate variance, with <5% mean absolute error.

Interpretation: Slower oxygen kinetics in children with CP suggest impairments in metabolic control, potentially contributing to their higher energy demands. Although the exact mechanisms remain unclear, this study provides valuable insights into the walking energetics of children with CP and presents a more efficient method for analyzing V̇o2 for this population.

Neuromechanics & Mobility Lab presents at ASB 2025

The Neuromechanics & Mobility Lab had a fantastic showing at the 2025 American Society of Biomechanics (ASB) Annual Meeting in Pittsburgh, PA! From student awards to impactful presentations, our team contributed to advancing the science of human movement and rehabilitation engineering.

We’re proud to celebrate Ally Clarke, who received a Student Travel Award for her abstract titled “Influence of Bodyweight Support on Motor Control in Children with Cerebral Palsy.” Her work was recognized by the ASB community for its contribution to pediatric motor control research. Congratulations, Ally!

Lab members presented posters across multiple themes. Madeleine McCreary explored toddler muscle activation during joystick driving in her poster “Kicking it off: Does toddler leg muscle activation while driving change with posture?” Mackenzie Pitts shared insights on “Mechanisms of split-belt treadmill adaptation in children with cerebral palsy.” Ally Clarke presented her award-winning work on bodyweight support and motor control, and Katie Landwehr-Prakel showcased her research on “Muscle activity during walker-based exoskeleton use in children with cerebral palsy.

Beyond the science, our team engaged in workshops, debates, and networking events that emphasized advocacy, inclusion, and the integration of lived experiences into biomechanics research. The ASB 2025 program featured sessions on AI in biomechanics, wearable tech, and neuromechanics – all aligning with our lab’s mission to enhance mobility and participation.

Thank you to ASB and the biomechanics community for an inspiring week. We’re already looking forward to connecting again at the World Congress of Biomechanics (WCB) in Vancouver in 2026!

  • Four people standing together on a rooftop at sunset with a scenic view of the Pittsburgh city skyline, yellow bridges, and river in the background during ASB 2025
  • Four individuals standing in front of a research poster at ASB 2025, representing the University of Washington.
  • Group of individuals standing and discussing research in front of scientific posters at ASB 2025, with charts and graphs visible on the posters
  • Researcher presenting findings to an attendee in front of scientific posters at ASB 2025, showcasing graphs and charts related to biomechanics research.
  • Two individuals standing in front of three research posters on cerebral palsy at ASB 2025

Congratulations – Kate Bokowy earns Outstanding Research Award

We’re excited to celebrate Kate Bokowy, who recently earned her Bachelor of Science in Mechanical Engineering from the University of Washington!

Kate was also recognized with the Department of Mechanical Engineering Outstanding Research Award for her impactful work in the Neuromechanics & Mobility Lab. Under the mentorship of Ph.D. student Mia Hoffman, Kate contributed to the development of the Switch Kit—a DIY toolkit designed to facilitate digital accessibility using accessible switches.

Congratulations, Kate, on your graduation and this well-deserved recognition!

Congratulations – Mia Hoffman receives Dennis Lang Award!

We’re thrilled to share that Mia Hoffman, a Ph.D. student in the Neuromechanics & Mobility Lab, has been honored with the Dennis Lang Award from the University of Washington Disability Studies Program.

Mia is currently pursuing a Graduate Certificate in Disability Studies, and this award recognizes her outstanding academic work and spirited commitment to the field. The Dennis Lang Award celebrates the legacy of Dennis Lang, a co-founder of the UW Disability Studies Program, whose dedication and service were instrumental in shaping the program and its community.

Mia received a merit-based monetary award and was recognized at the Disability Studies convocation on June 4.

Congratulations, Mia! Your work continues to inspire and advance the values of inclusion, equity, and excellence in disability studies.

Congratulations – Ally Clarke receives ASB Student Travel Award!

A young woman with blonde hair is wearing a green sweater and blue jeans while standing in front of a blossoming tree.

We’re excited to share that Ally Clarke has been selected to receive a Student Travel Award from the American Society of Biomechanics (ASB) to attend the 2025 ASB Annual Meeting in Pittsburgh, PA. This award supports students who have authored abstracts accepted for presentation. Ally’s abstract Influence of Bodyweight Support on Motor Control in Children with Cerebral Palsy was selected for presentation at the meeting, and we’re proud to see her work recognized and supported by the biomechanics community.

Congratulations, Ally!