publications

2025

1. Maximal active force in skinned muscle fibres from children with cerebral palsy

   Venus Joumaa ,  Faizan Syed ,  Jason J Howard , and 8 more authors

   Journal of Biomechanics, 2025

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   The aim of this study was to gain insight into the origins of muscle weakness in children with cerebral palsy (CP) by investigating active force in single muscle fibres isolated from the adductor longus (AL) of children with CP. Single skinned muscle fibres (n = 43, from 11 children with CP) were isolated and tested for their maximal active stress, instantaneous stiffness, and the ratio of active stress to stiffness at a sarcomere length (SL) of 2.4 µm, and passive stress at SLs of 2.4, 2.6, 2.8, 3.0, 3.2, and 3.4 µm. The muscle biopsies were tested for their total myofibrillar protein content using a BCA assay, and myosin heavy chain, actin, titin and nebulin content using gel electrophoresis. Muscle biopsies from the vastus lateralis of healthy adults (HA; n = 19 fibres from 4 subjects) were used for comparison. The maximal active stress and the instantaneous stiffness, expressed as active elastic modulus, were lower in the CP fibres compared to the HA fibres (79 ± 4 vs. 170 ± 11 kPa, and 5479 ± 381 vs. 8943 ± 402 kPa, respectively). The maximal active stress to stiffness ratio was not different between CP and HA fibres (0.016 ± 0.001 vs. 0.020 ± 0.002). Actin, titin and nebulin content was reduced in the CP compared to the HA samples. Passive stress was also reduced in the CP fibres at SLs of 2.8, 3.0, 3.2 and 3.6 µm. These results suggest that the contractile ability of muscles from children with CP is compromised at the fibre level and this is likely the result of a decrease in sarcomeric proteins such as actin, titin and nebulin.

2. Wearable Technology in Orthopaedic Surgery: Applications and Future Directions

   Alexander W. Iwasyk ,  Sia S. Gaur ,  Alyssa Federico , and 4 more authors

   JBJS Reviews, 2025

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   » Wearable technologies (wearables), including smartphones, smartwatches, and sensors, such as accelerometers and inertial measurement units, enable continuous, real-time, and objective data collection on physical function, health behaviors, and patient perceptions.» Wearables can track mobility metrics such as step count, activity duration, and joint range of motion, providing valuable longitudinal insights into recovery trajectories.» In orthopaedic surgery, wearables support timely, personalized patient education and improve communication between patients and surgical teams, contributing to better functional outcomes and patient satisfaction.» Smart implants and virtual/augmented reality systems are emerging as innovative approaches to enhancing engagement and adherence during postoperative rehabilitation.» Key challenges to implementation include concerns about data privacy, accessibility, and integration into clinical workflows.

2024

1. Technological Breakthroughs in Sport

   Victor R. A. Cossich ,  Dave Carlgren ,  Robert John Holash , and 1 more author

   2024

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2. Cardiac Function in Exercise.

   B R MacIntosh ,  and  R J Holash

   2024

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3. A Ramp- Versus Step-Transition to Constant-Work Rate Exercise Decreases Steady-State Oxygen Uptake

   Gabriele Marinari ,  Danilo Iannetta ,  John R. Holash , and 5 more authors

   Medicine & Science in Sports & Exercise, May 2024

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   ABSTRACT Within the initial minutes of square-wave exercise transitions above the moderate-intensity domain, the reliance on the anaerobic energy sources may induce some levels of metabolic instability; however, no study has attempted to limit metabolic instability at exercise onset by manipulating the exercise transition phase to a target work-rate (WR). Purpose To investigate whether a ramp-to-constant-work rate (rCWR) transition compared to a square-wave-to-constant-work rate (CWR) transition within the heavy-intensity domain can reduce metabolic instability and decrease the oxygen cost of exercise.

4. Heavy-intensity priming exercise extends the V̇o2max plateau and increases peak-power output during ramp-incremental exercise

   Gabriele Marinari ,  Danilo Iannetta ,  Robert John Holash , and 3 more authors

   American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, Aug 2024

   PMID: 38842514

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   This study investigated whether a heavy-intensity priming exercise precisely prescribed within the heavy-intensity domain would lead to a greater peak-power output (POpeak) and a longer maximal oxygen uptake (V̇o2max) plateau. Twelve recreationally active adults participated in this study. Two visits were required: 1) a step-ramp-step test [ramp-incremental (RI) control], and 2) an RI test preceded by a priming exercise within the heavy-intensity domain (RI primed). A piecewise equation was used to quantify the V̇o2 plateau duration (V̇o2plateau-time). The mean response time (MRT) was computed during the RI control condition. The delta (Δ) V̇o2 slope (S; mL·min−1·W−1) and V̇o2-Y intercept (Y; mL·min−1) within the moderate-intensity domain between conditions (RI primed minus RI control) were also assessed using a novel graphical analysis. V̇o2plateau-time (P = 0.001; d = 1.27) and POpeak (P = 0.003; d = 1.08) were all greater in the RI primed. MRT (P < 0.001; d = 2.45) was shorter in the RI primed compared with the RI control. A larger ΔV̇o2plateau-time was correlated with a larger ΔMRT between conditions (r = –0.79; P = 0.002). This study demonstrated that heavy-intensity priming exercise lengthened the V̇o2plateau-time and increased POpeak. The overall faster RI-V̇o2 responses seem to be responsible for the longer V̇o2plateau-time. Specifically, a shorter MRT, but not changes in RI-V̇o2-slopes, was associated with a longer V̇o2plateau-time following priming exercise.NEW & NOTEWORTHY It remains unclear whether priming exercise extends the maximal oxygen uptake (V̇o2max) plateau and increases peak-power output (POpeak) during ramp-incremental (RI) tests. This study demonstrates that a priming exercise, precisely prescribed within the heavy-intensity domain, extends the plateau at V̇o2max and leads to a greater POpeak. Specifically, the extended V̇o2max plateau was associated with accelerated RI-V̇o2 responses.

2023

1. Skeletal Muscle Structure.

   B R MacIntosh ,  and  R J Holash

   Aug 2023

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2. Technological Breakthroughs in Sport: Current Practice and Future Potential of Artificial Intelligence, Virtual Reality, Augmented Reality, and Modern Data Visualization in Performance Analysis

   VRA Cossich ,  D Carlgren ,  RJ Holash , and 1 more author

   Aug 2023

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   We are currently witnessing an unprecedented era of digital transformation in sports, driven by the revolutions in Artificial Intelligence (AI), Virtual Reality (VR), Augmented Reality (AR), and Data Visualisation (DV). These technologies hold the promise of redefining sports performance analysis, automating data collection, creating immersive training environments, and enhancing decision-making processes. Traditionally, performance analysis in sports relied on manual data collection, subjective observations, and standard statistical models. These methods, while effective, had limitations in terms of time and subjectivity. However, recent advances in technology have ushered in a new era of objective and real-time performance analysis. AI has revolutionised sports analysis by streamlining data collection, processing vast datasets, and automating information synthesis. VR introduces highly realistic training environments, allowing athletes to train and refine their skills in controlled settings. AR overlays digital information onto the real sports environment, providing real-time feedback and facilitating tactical planning. DV techniques convert complex data into visual representations, improving the understanding of performance metrics. In this paper, we explore the potential of these emerging technologies to transform sports performance analysis, offering valuable resources to coaches and athletes. We aim to enhance athletes’ performance, optimise training strategies, and inform decision-making processes. Additionally, we identify challenges and propose solutions for integrating these technologies into current sports analysis practices. This narrative review provides a comprehensive analysis of the historical context and evolution of performance analysis in sports science, highlighting current methods’ merits and limitations. It delves into the transformative potential of AI, VR, AR, and DV, offering insights into how these tools can be integrated into a theoretical model.

3. Active properties of skinned muscle fibres from children with cerebral palsy.

   Venus Joumaa ,  Jason Howard ,  Gavin Thomas , and 7 more authors

   In European Muscle Conference. Florence, Italy , Aug 2023

2019

1. A stochastic simulation of skeletal muscle calcium transients in a structurally realistic sarcomere model using MCell

   Robert John Holash ,  and  Brian R. MacIntosh

   PLOS Computational Biology, Mar 2019

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   Skeletal muscle contraction is initiated when an action potential triggers the release of Ca2+ into the sarcomere in a process referred to as excitation-contraction coupling. The speed and scale of this process makes direct observation very challenging and invasive. To determine how the concentration of Ca2+ changes within the myofibril during a single activation, several simulation models have been developed. These models follow a common pattern; divide the half sarcomere into a series of compartments, then use ordinary differential equations to solve reactions occurring within and between the compartments. To further develop this type of simulation, we have created a realistic structural model of a skeletal muscle myofibrillar half-sarcomere using MCell software that incorporates the myofilament lattice structure. Using this simulation model, we were successful in reproducing the averaged calcium transient during a single activation consistent with both the experimental and previous simulation results. In addition, our simulation demonstrated that the inclusion of the myofilament lattice within our model produced an asymmetric distribution of Ca2+, with more Ca2+ accumulating near the Z-disk and less Ca2+ reaching the m-line. This asymmetric distribution of Ca2+ is also apparent when we examine how the Ca2+ are bound to the troponin-C proteins along the actin filaments. Our simulation model also allowed us to produce advanced visualizations of this process, including two simulation animations, allowing us to view Ca2+ release, diffusion, binding and uptake within the myofibrillar half-sarcomere.

2018

1. An innovative ergometer to measure neuromuscular fatigue immediately after cycling.

   Douglas Doyle-Baker ,  John Temesi ,  Mary E Medysky , and 2 more authors

   Medicine and Science in Sports and Exercise, Feb 2018

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2017

1. A test to measure neuromuscular fatigue during and immediately after cycling exercise.

   Douglas Doyle-Baker ,  John Temesi ,  Mary E Medysky , and 2 more authors

   In Peer Beyond Graduate Research Symposium Conference Program , Feb 2017

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2. Three dimensional stochastic computer model of the skeletal muscle half sarcomere: changes in calcium diffusion caused by the myofilament lattice.

   Robert John Holash

   The University of Calgary , May 2017

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3. Increased occupation of sarcomeric calcium buffers reduces required calcium release for similar troponin-c binding of subsequent activation.

   Robert John Holash ,  Ian Smith ,  Walter Herzog , and 1 more author

   In European Muscle Conference. Montpelier, France , May 2017

2015

1. Effect of sarcomere length on calcium diffusion in a 3-D sarcomere model.

   Robert John Holash ,  and  Brian R MacIntosh

   In European Muscle Conference. Strasbourg, Austria , May 2015

2013

1. The importance of structure on: calcium release, diffusion, and binding in a spatially realistic 3-D sarcomere model.

   Robert John Holash ,  and  Brian R MacIntosh

   In Biomedical Basis for Human Performance Across the Lifespan , May 2013

2012

1. Skeletal muscle fatigue–regulation of excitation–contraction coupling to avoid metabolic catastrophe.

   Brian R MacIntosh ,  Robert J Holash ,  and  Jean-Marc Renaud

   Journal of Cell Science, May 2012

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2. A comparison of exer-gaming interfaces for use in rehabilitation programs and research.

   Kazumoto Tanaka ,  Jim Parker ,  Graham Baradoy , and 3 more authors

   Loading, May 2012

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   Exergames or active video games are video games with interfaces that require active involvement and the exertion of physical force by participants. These exergames are designed to track body motion and provide both fun and exercise for game players. Numerous video game console companies have designed exergaming interfaces that are becoming very popular. This paper examines the nature of the interfaces and explores the possibility of using these interfaces for rehabilitation programs and research. While many systems exist, this paper will focus on three major players: Sony PlayStation Move, Nintendo Wii, and Microsoft Xbox 360 Kinect. Comparisons include the technical specifications, the motion sensed by each interface, and the motion required in each therapeutic activity type. Discussion addresses the research implications of using these tools.

3. Modelling calcium diffusion, binding, and uptake in a spatially realistic 3-dimensional sarcomere model.

   Robert John Holash ,  and  Brian R MacIntosh

   In European Muscle Conference. Rhodes, Greece , May 2012
4. A comparison of exer-gaming interfaces for use in rehabilitation programs and research.

   Kazumoto Tanaka ,  Jim Parker ,  Graham Baradoy , and 3 more authors

   In Interactive Media Conference. Calgary, Alberta , May 2012
5. 3-Dimentional calcium kinetics; release, diffusion, binding, and uptake in a multicompartmental, skeletal muscle 1/2 sarcomere.

   Robert John Holash ,  and  Brian R MacIntosh

   In Canadian Society of Exercise Physiology Conference, CSEP , May 2012

2011

1. Procedures for rat in situ skeletal muscle contractile properties.

   Brian R MacIntosh ,  Shane P Esau ,  R John Holash , and 1 more author

   Journal of Visual Experimentation, May 2011

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2. Feasibility of the two-hour marathon is a burning issue.

   Jared R Fletcher ,  Shane P Esau ,  R John Holash , and 1 more author

   Journal of Applied Physiology (Bethesda, Md.: 1985), May 2011

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3. Verfahren für die Ratte

   Brian R MacIntosh ,  Shane P Esau ,  R John Holash , and 1 more author

   May 2011
4. Micro-physiological simulation of calcium diffusion in a 3-dimensional sarcomere model.

   Robert John Holash ,  and  Brian R MacIntosh

   In Canadian Society of Exercise Physiology Conference, CSEP , May 2011

2009

1. Skeletal muscle filament spacing changes with contraction.

   Robert John Holash ,  and  Brian R MacIntosh

   In Canadian Society of Exercise Physiology Conference, CSEP , May 2009
2. Can the second head of myosin bind to the adjacent thin filament?

   Robert John Holash ,  and  Brian R MacIntosh

   In Multi-scale Muscle Mechanics Conference. Woods Hole, Massachusetts , May 2009

2008

1. Modelling calcium release in a simplified two dimensional skeletal muscle model using the agent-based system Netlogo.

   Robert John Holash ,  and  Brian R MacIntosh

   In Canadian Society of Exercise Physiology Conference, CSEP , May 2008

2000

1. Validation of single maximal effort tests for peak power output.

   Robert John Holash ,  Igor Kopecky ,  Krista Sevdhal , and 1 more author

   In Canadian Society of Exercise Physiology Conference, CSEP , May 2000
2. Power output and force-velocity properties of muscle.

   B R MacIntosh ,  and  R J Holash

   May 2000
3. Validation of single maximal effort tests for power measurement.

   Robert John Holash

   The University of Calgary , Feb 2000

   Masters of Science Thesis, University of Calgary

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