ISPGR was delighted to award Dr Christopher McCrum its 2025 Promising Scientist Award (PSA). In his PSA Plenary Talk at the 2025 World Congress in Maastricht, Netherlands, Dr McCrum reflected on how viewing fall prevention through the lens of elite sprint coaching has influenced the questions he asks, the methods he uses, and the way he interprets results. This post summarizes the key ideas and messages from that lecture.

Last year at the 2025 ISPGR World Congress, I was honoured to receive this award and to give a presentation about the first stages of my scientific career. I discussed not so much about the scientific nuts and bolts of my research but on one of the perspectives that I look at my research from and how that has aided me throughout my research so far. In this blog post, I will give a brief summary of the key points and messages of my talk.

My background and main motivation for my studies during my bachelor and masters was (elite) sports coaching, specifically in sprinting. At first glance, elite sprint performance and fall prevention in older adults may seem worlds apart. But the central argument of my talk was that changing perspectives can unlock new insights and progress, particularly in a field as complex as fall prevention. This idea resonated strongly with the broader theme of the ISPGR conference, which emphasized interdisciplinary collaboration and the value of looking beyond traditional disciplinary boundaries [1].

In my work, fall prevention is not about preventing all falls, nor is it about minimizing movement or risk-taking. Most falls in older adults occur due to trips and slips during walking, often involving large, sudden balance disturbances. These are the events I am primarily interested in understanding and preventing. Equally important is recognizing that older adults are not a homogeneous group, and that the mechanisms underlying a fall matter. Preventing a slow collapse during a transfer is not the same problem as recovering from a sudden trip during walking.

In sprint coaching, performance can be viewed through interacting “targets”, for example: Structure (e.g. muscle–tendon properties); Capacity (e.g., strength and power); or Technique/skill/coordination. Crucially, coaching also forces you to ask where an individual sits on each of these dimensions relative to the point of diminishing returns. Strength is not always the limiting factor. More conditioning is not always the answer. Sometimes, what matters most, is skill or technique.

This perspective influenced how I approached fall prevention research from early on. Rather than asking only whether older adults are weaker, slower, or less active, I became interested in whether they are given the opportunity to practice the specific skills required to resist and recover from balance loss. As a result, a large part of my research has focused on perturbation-based balance training (PBT) – exposing people to repeated, unexpected balance disturbances during walking so that they can learn to recover more effectively [2]. My own and others’ research consistently shows that older adults are capable of rapid adaptation to repeated perturbations. Improvements in reactive gait recovery can occur within a single session, and can be partly retained over weeks and even years.

Ageing is associated with well-documented declines in muscle-tendon properties, strength, power, and Type II muscle fibre size. These factors are clearly relevant for movement and fall risk, and exercise interventions targeting them are effective at reducing falls at the population level. However, while muscle structure and capacity matter, they do not appear to be the primary limiting factors for learning to recover from a trip during walking [3]. From a coaching perspective, this is not surprising: improving strength does not automatically translate into improved skill unless the skill itself is trained.

Another recurring theme in the field is whether being physically active protects against age-related declines in reactive balance. Our data suggest a nuanced answer. Reactive gait recovery does decline with age, even when older adults are matched to younger individuals on habitual physical activity [4]. However, the capacity to adapt to repeated perturbations is largely preserved: Older adults can still learn, even if their baseline performance is lower. This distinction matters. It suggests that interventions do not only need to consider how to prevent physical decline but also how to leverage preserved adaptability through appropriate task-specific training.

One outcome of taking a more skill-based perspective is the recognition that the ability to resist or avoid falls is not actually a single ability. We can distinguish between:

• Proactive gait adaptability: detecting threats and adjusting gait accordingly (e.g., stepping over an obstacle)
• Gait robustness: resisting disturbances without losing balance (e.g., tolerating uneven cobblestones without tripping or losing balance)
• Reactive gait recovery: responding effectively once balance is lost (e.g., a recovery step after a trip)

Each of these processes might be improved through different overlapping and interacting mechanisms: direct skill improvements; indirect changes in gait; and psychological factors such as confidence or threat perception [5].

Looking back over more than a decade of research, what stands out is not a single result, but how much the questions themselves were shaped by perspective. Approaching fall prevention through the lens of a sprint coach led me to prioritize task specificity, skill acquisition, and considering dose–response and dose-generalisability relationships [6] – ideas that are familiar in sport, but historically underemphasized in fall prevention. This does not mean that this perspective is definitive, complete or correct. But it illustrates the value of interdisciplinary thinking, particularly in a field where progress depends on integrating biomechanics, neuroscience, psychology, and clinical practice.

If there is one takeaway from my ISPGR lecture, it is that fall prevention, and posture and gait research more broadly, may benefit as much from changing how we think as from changing what we measure. Societies and conferences that actively encourage cross-disciplinary dialogue play a crucial role in making that possible [1].

References

1: Filtjens B, McCrum C. (2026) Perspectives on interdisciplinary posture and gait research from the ISPGR 2025 World Congress: Where do we stand and what are the next steps? Gait & Posture 124: 110058. doi: 10.1016/j.gaitpost.2025.110058

2: McCrum C, Bhatt TS, Gerards MHG, Karamanidis K, Rogers MW, Lord SR, Okubo Y. (2022) Perturbation-based Balance Training: Principles, Mechanisms and Implementation in Clinical Practice. Frontiers in Sports and Active Living. 4:1015394. doi: 10.3389/fspor.2022.1015394

3: McCrum C, Grevendonk L, Schaart G, Moonen-Kornips E, Jörgensen JA, Gemmink A, Meijer K, Hoeks J. (2021) Type II muscle fibre properties are not associated with balance recovery following large perturbations during walking in young and older adults. bioRxiv doi: 10.1101/2021.11.26.470167

4: Grevendonk L. Connell NJ, McCrum C, Fealy CE, Bilet L, Bruls YMH, Mevenkamp J, Schrauwen-Hinderling VB, Jörgensen JA, Moonen-Kornips E, Schaart G, Havekes B, de Vogel-van den Bosch J, Bragt MCE, Meijer K, Schrauwen P, Hoeks J. (2021) Impact of aging and exercise on skeletal muscle mitochondrial capacity, energy metabolism, and physical function: a cross-sectional study. Nature Communications. 12: 4773. doi: 10.1038/s41467-021-24956-2

5: van der Hulst EG, Meijer K, Meyns P, McCrum C. (2025) Design Considerations for Technology-assisted Fall-Resisting Skills Training Trials in Older Adults: A Pilot and Feasibility Study. medRxiv doi: 10.1101/2025.10.03.25337262

6: Karamanidis K, Epro G, McCrum C, König M. (2020) Improving trip and slip-resisting skills in older people: perturbation dose matters. Exercise and Sport Sciences Reviews. 48(1): 40-47. doi: 10.1249/JES.0000000000000210

About the Author

ISPGR was delighted to award Dr Benjamin Filtjens its 2025 Emerging Scientist Award (ESA). In his ESA Plenary Talk at the 2025 World Congress in Maastricht, Netherlands, Dr Filtjens shared how artificial intelligence (AI) and wearable sensors are helping tackle one of the most challenging symptoms of Parkinson’s disease: walking difficulties and freezing of gait. This post summarizes the key points from this talk.

Walking difficulties are among the most disabling symptoms of Parkinson’s disease. Two important aspects of gait assessment in Parkinson’s are the severity of freezing of gait (FOG) and the overall gait severity rating. FOG refers to sudden episodes in which patients are unable to move forward despite intending to, while a global clinical impression of gait is measured using standardized rating scales such as the (MDS-)UPDRS. Traditionally, both are assessed visually by clinicians reviewing gait tasks or video recordings. While effective, this approach is time-consuming, subjective, and difficult to scale.

Artificial intelligence (AI) offers a promising way forward: Deep learning methods can automatically process wearable-sensor or video data to estimate FOG episodes or UPDRS gait scores. Yet, a persistent challenge in the field is cross-center generalization. Most AI models are trained on relatively small, single-center datasets, which limits their ability to handle the wide variability in patient gait patterns, clinical tasks, and sensor/video configurations. As a result, models that work well in one center often perform far less accurately when tested on data from another center (or a different group of patients).

Our two recent studies approached the generalization problem from complementary perspectives. The first examined how wearable-sensor–based deep learning models for FOG detection transfer across six independent cohorts, and whether we can improve transfer by means of FOG-IT, a web application that enables human–AI collaborative scoring of FOG episodes (Figure 1).  In this workflow, the AI provides an initial prediction and the user can verify and correct it, keeping clinical expertise in the loop. The second examined how video-based deep learning models for UPDRS gait severity estimation transferred across four independent cohorts, and whether this could be improved using CARE-PD, the first open-source, multi-center 3D gait dataset with clinical labels.

In our studies, we found that models performed well when trained and tested on data from the same site, but their robustness dropped notably when applied to data from other centers. Study-specific metrics decreased by approximately 14% for FOG detection and 46% for gait-score estimation compared to within-site results. However, we could mitigate this drop by adapting the source-site–trained model using a small local sample from the target site. For FOG detection, an AI-assisted annotation workflow such as FOG-IT can make collecting such a local sample more feasible: the model first proposes FOG episodes and clinicians then correct these predictions, producing clinician-verified annotations that can be used to fine-tune (update) the model for the new center, while also providing oversight during deployment. These findings show that between-center differences reduce model robustness and strongly underline two needs:  humans should remain involved in the scoring process to verify performance and enable safe, efficient local adaptation when  a model is applied in a new setting (e.g., via FOG-IT, Figure 1), and the field needs multi-center development and validation datasets with standardized benchmarking to improve generalization (e.g., CARE-PD).

Figure 1. FOG-IT AI-assisted workflow. A deep-learning model generates initial annotations of FOG episodes in gait tasks. A human evaluator reviews and corrects these annotations and makes the final decision, thereby enabling correction of cross-center algorithmic biases.

FOG-IT (now called AID-FOG):

More information about the study—including a demo of the AI-assisted annotation platform and a link to the manuscript—is available on its webpage: https://aidfog.be/

Yang, P. K., Carlon, J., Goris, M., Klaver, E., Nonnekes, J., van Wezel, R. J., … & Filtjens, B. (2025). Deep Learning for Freezing of Gait Assessment using Inertial Measurement Units: A Multicentre Study. medRxiv, 2025-06; doi:https://doi.org/10.1101/2025.06.27.25330405.

CARE-PD:

More information about the study—including links to the benchmarking codebase, the multicentre dataset, and the manuscript—is available on its webpage: https://neurips2025.care-pd.ca/

Adeli, V., Klabucar, I., Rajabi, J., Filtjens, B., Mehraban, S., Wang, D., … & Taati, B. (2025). CARE-PD: A Multi-Site Anonymized Clinical Dataset for Parkinson’s Disease Gait Assessment. arXiv preprint arXiv:2510.04312.; doi: https://doi.org/10.48550/arXiv.2510.04312.

About the Author

I have been asked to write a short blog as part of the Honorary Membership that was bestowed upon me in Maastricht. In particular I was asked to speak about my experience with ISPGR as well as to provide tips and advice to junior researchers for achieving a successful career in posture and gait research. Let me attempt the latter point first drawing from my experience over the past 44 years post BSc.

First, of course, always think critically and objectively, but I would add that it is also necessary to BE HUMBLE in such thinking. One can be confident within the framework of the current knowledge, but there is still so much yet to understand and there are still many limits in our tools and theories that beg a cautious confidence. One should certainly never camp a career within any one theory. Humbleness allows us to be open to change and to minimize, and maybe even recognize, our biases. Also, while big breakthroughs are wonderful and we may dream of being the ‘big name’ researcher that broke through an idea, in reality, science is mostly moved forward by chipping away and adding little new nuggets of knowledge. While these nuggets are often not shocking, if the science is based on sound logic and well-thought-out protocols or models, they often catalyse other ideas and approaches or, also important, confirm existing ideas.

Next, BE PASSIONATE about what you do. Don’t jump on a bandwagon topic just because it is popular, or at least not until it has an undercurrent pull on your genuine interest. If I and the collaborators with whom I have worked have had any success, it is that our passion for knowledge has allowed us to attack issues not yet seen or at least not in a certain way, or perhaps in a way that combines ideas not yet put together. When you feel your passion wane, close the office door and pull out recent (or older) data and swim in it for a while.

Another piece of advice, actually part of being humble, is to SEE EVERY SINGLE PERSON ON THE TEAM AS A COLLEAGUE. I have learned something from every person, from trainees to research assistants to co-PIs, even in cases that required more mentoring than anticipated. Remember that every research question begs a team of brains well beyond the principal investigator. You will also be surprised by the productivity related to true intellectual respect. Related to this point, I would suggest being less possessive about your research program, i.e., BE A MENTOR, A COORDINATOR, BUT NOT AN OWNER. This is, believe me, very difficult to practice within our environment of institution and publication competition and the ego is difficult to control. Only in the latter part of my career have I tried (still a work in progress) to avoid talking about MY students, MY program, MY lab.

Another point is to EMBRACE GRANT WRITING. While most of us complain about it, and are disheartened by grant refusals, realize that every grant preparation is an opportunity to take stock of where the science is and what exciting things should be next. Even unsuccessful grants advance your thinking and will nourish the team’s next work if you write them with passion. Finally, my wife has been a rock for me (and probably felt like throwing a few at me too) throughout my scientific career. RECOGNIZE THOSE OUTSIDE YOUR RESEARCH PROGRAM who act as sounding boards, provide moral support, try to tolerate your scientific distractions that generally keep you rooted…and let them know how important they are to you.

As to ISPGR, as I mentioned when thanking everyone in Maastricht for this honour, ISPGR is a great society and has naturally grouped together many researchers that hold many of the values noted above. It has always been a safe place to expose and mutually challenge ideas and to see what flies. Having been on the board for 11 years, and on the executive for 6 years, including 2 years as president, I have seen the political, academic and social sides of ISPGR. Sure, it “ain’t” perfect, but it is mostly a wonderful place for exchange and even fun. My last message to the young researchers is to invest in your society to continue its mission and keep it moving forward.

Thank you again to ISPGR for the Honorary Member award of 2025.

Brad McFadyen

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About the Author

Since my first ISPGR World Conference in Fort Lauderdale in 2017, I have seen many studies on functional near-infrared spectroscopy (fNIRS). Whilst its use is still controversial, research has demonstrated that fNIRS assessments are feasible, and their results not only reinforce previous theories related to motor control but also bring new hypotheses regarding the involvement of cortical areas in balance and gait tasks, shedding light on a better understanding of fall risk. It was a great pleasure to have received the ISPGR Emerging Scientist Award 2023 because of my work in this emerging scientific field. Below, I summarise my research findings using fNIRS to examine complex balance and gait.

In a series of studies, I examined older adults at low and high fall risk and people with Parkinson’s disease (PD). These participants performed a range of stepping tests (simple choice stepping reaction time test (CSRT), CSRT with inhibitory response (iCSRT) and a Stroop version of CSRT (SST)), along with an adaptive walking test. The cortical areas examined were the prefrontal cortex (PFC), supplementary motor area (SMA) and premotor cortex (PMC). Older adults at high fall risk exhibited increased PFC activity and stepping response variability when completing the SST test compared to older adults at low fall risk and compared to the CSRT test [1]. In PD, the pattern of cortical activity differed. Whilst older adults increased their cortical activity (PFC, SMA and PMC) to handle more complex stepping tests (iCSRT and SST), people with PD exhibited a “slowdown” phenomenon, demonstrating reduced cortical activity in the same areas [2]. Finally, during adaptive gait, people with PD had little or no additional PFC, SMA, and PMC capacity beyond what they needed for simple walking and, therefore, presented with a more conservative gait pattern than their healthy peers [3].

Altogether, these results elucidate that older adults may not cope with task demands, relying heavily on their cortical resources, which reflects their increased risk of falling. Moreover, this increased cortical activity seems to reflect a compensatory process for deficits in postural control or a degree of neural inefficiency in those at high fall risk. In PD, the reduced cortical activity during complex stepping tests might reflect multiple pathways and/or subcortical damage, resulting in deficient use of cognitive and motor resources and poor overall motor behavior.  Finally, the cortical activity and behavior exhibited by people with PD during adaptive gait appear consistent with concepts of compensatory over-activation and capacity limitation.

Publications

[1]  Paulo H S Pelicioni, Stephen R Lord, Daina L Sturnieks, Bethany Halmy, Jasmine C Menant. Cognitive and Motor Cortical Activity During Cognitively Demanding Stepping Tasks in Older People at Low and High Risk of Falling. Front Med (Lausanne). 2021; 8: 554231. doi: 10.3389/fmed.2021.554231

[2]  Paulo H S Pelicioni, Stephen R Lord, Yoshiro Okubo, Daina L Sturnieks, Jasmine C Menant. People With Parkinson’s Disease Exhibit Reduced Cognitive and Motor Cortical Activity When Undertaking Complex Stepping Tasks Requiring Inhibitory Control. Neurorehabil Neural Repair. 2020 Dec;34(12):1088-1098. doi: 10.1177/1545968320969943.

[3]  Paulo H S Pelicioni, Stephen R Lord, Yoshiro Okubo, Jasmine C Menant. Cortical activation during gait adaptability in people with Parkinson’s disease. Gait Posture. 2022 Jan:91:247-253. doi: 10.1016/j.gaitpost.2021.10.038.

About the Author

By Kaylena Ehgoetz Martens

Freezing of gait is characterised by a sudden inability to initiate or continue walking which significantly impacts quality of life in people living with Parkinson’s disease. Since dopaminergic replacement therapy only partially ameliorates freezing of gait, other non-dopaminergic contributions may play a role in freezing of gait. There is evidence that sympathetic arousal increases prior to a freezing episode, particularly when freezing is triggered by stress. This highlights a potential neural mechanism to underpin the relationship between anxiety and freezing of gait. Despite a growing body of evidence that suggests anxiety may be a crucial contributor to freezing of gait, no research study has investigated changes in functional network architecture as a result of induced-anxiety which often triggers freezing of gait. Here, we aimed to investigate how anxiety-inducing contexts might ‘set the stage for freezing’, through the ascending arousal system, by examining an anxiety-inducing virtual reality gait paradigm inside functional magnetic resonance imaging (fMRI).

We used a virtual reality gait paradigm to navigate a virtual plank that has been validated to elicit anxiety, whilst simultaneously collecting task-based fMRI data from individuals with idiopathic Parkinson’s disease with confirmed freezing of gait. First, we established that the threatening condition (i.e., navigating across a narrow plank above a deep pit) provoked more freezing when compared to the non-threatening condition. We established that the threatening condition was associated with heightened network integration. By utilizing a dynamic connectivity analysis, we identified patterns of increased ‘cross-talk’ within and between motor, limbic and cognitive networks in the threatening conditions. The sympathetic nature of this phenomenon was demonstrated by an increase in pupil dilation during the anxiety-inducing condition of the virtual reality gait paradigm outside of the MRI scanner.

Figure 1: Screenshots of the virtual-reality paradigm A) non-threatening and B) threatening walking conditions. C) Graphical representation of the noradrenergic Locus Coeruleus and its influence on pupil dilation. D) ‘Cross-talk’ model depicted graphically, with “cross-talk” visualized through heightened connectivity/network integration represented by the orange boldened lines, and its subsequent influences on the Striatum, which inhibits Globus Pallidus Internus (GPi), which inhibits the Mesencephalic Locomotor Regions (‘MLR’), leading to freezing of gait.

This work reveals a potential explanation for how anxiety could lead to freezing of gait. Heightened sympathetic arousal related to anxiety could increase ‘cross-talk’ between distributed cortical networks that ultimately manifest as episodes of freezing of gait. This research advances our understanding of a symptom that affects many people living with Parkinson’s disease and opens new avenues to explore for better clinical management.

Publication: Taylor, N.L., Wainstein, G., Quek, D., Lewis, S.J.G., Shine, J.M., Ehgoetz Martens, K.A. (2022) The contribution of noradrenergic activity to anxiety-induced freezing of gait. Movement Disorders, 37(7):1432-1443. DOI: 10.1002/mds.28999

About the Author