During the development of my manual therapy workshop there have been 4 or 5 researchers who I have routinely referenced.
One of these researchers is Dr. Luke Kelly PhD from University of Queensland, Australia. I was interested in how he and his group have described the versatile adaptor of the foot which I thought complemented with how midfoot joints should freely move to allow this adaptor system to work.
For more than a century, textbooks taught that the human foot must become a rigid “lever” during walking and running: a stiff, locked structure that propels the body forward like a plank. Research led by Kelly has now challenged that long-standing view.
Across nineteen high-quality scientific studies, his team has shown that the foot is not a passive block of bone and ligament. It is a versatile adaptor: a dynamic, responsive, energy-shaping system powered in part by small but important muscles within the arch.
This shift represents an important advance in foot science, with direct implications for how we understand pain, build strength, and approach our treatment plans.
From “Rigid Lever” to “Versatile Adaptor”
The Kelly research group suggests that the foot remains mobile throughout the gait cycle. Rather than locking rigidly, it continuously adapts, absorbs shock, stores energy, and helps the ankle generate power.
At the centre of this discovery is the active arch-buttressing mechanism.
The Intrinsic Foot Muscles: Your Built‑In Suspension System
Using fine-wire EMG (electrodes placed inside the muscles), Kelly’s team proved that three key intrinsic muscles are essential:
- Abductor hallucis
- Flexor digitorum brevis
- Quadratus plantae
These muscles function like an active suspension system. They contract at precisely the right moments to stiffen the arch, control deformation, and support the ankle above.
This process is not passive or automatic. It is an example of active biological control built into human movement.
What made Kelly’s work especially innovative was the way his group evaluated the intrinsic foot muscles directly. Using ultrasound guidance, they temporarily blocked the tibial nerve with local anaesthetic to switch off the plantar intrinsic muscles while leaving the larger extrinsic muscles intact. When the active intrinsic muscular support was decoupled from the nervous system, this gave them a rare, gold-standard way to observe exactly how foot mechanics changed.
What Kelly’s Group Discovered
1. The Foot Is Energetically Versatile
The foot is not just a spring. During landing, it acts as a damper; during push-off, it acts as a motor, absorbing energy when needed and generating power when required.
2. Intrinsic Muscles Are Essential for Balance
These muscles fire in a tightly coordinated pattern to control side-to-side sway. Weakness in this system may appear as instability, fatigue, or wobbling during single-leg tasks.
3. The Foot and Ankle Are Mechanically Coupled
The intrinsic muscles influence ankle torque and gearing, especially during explosive movements like jumping. A stronger foot means a more powerful ankle.
4. The Arch’s Ability to Recoil Is an Evolutionary Advantage
Humans walk upright efficiently because the arch does not simply lock; it recoils. That recoil helps keep the tibia upright, improves calf muscle function, and reduces the energy cost of walking and running.
What About the Windlass Mechanism?
In short, the windlass mechanism is a passive facilitator that helps the foot’s active motor, its muscles, optimize propulsion. It does not “lock” the foot. Instead, it supports arch recoil and power generation, helping the motor work more efficiently during acceleration.
How This Changes Clinical Practice: The Forward‑Lean Strategy
One of the most clinically useful applications of Kelly’s recent work is both simple and effective.
1. Leaning Forward Turns on the Foot Muscles
Kelly’s team found that a gentle forward lean, just until the heels lift, can increase intrinsic muscle activation. This posture may produce more useful torque than adding external weights and can reach activation levels like walking.
2. Torque Matters More Than “Feeling the Burn.”
Traditional exercises such as “short foot” drills or toe scrunches can create high EMG activity while generating little force. They can also be cognitively demanding and mechanically inefficient.
The forward-lean strategy addresses these limitations. It is simple, intuitive, and capable of producing the higher-force stimulus needed for running, hiking, and everyday function.
3. It is Scalable for Every Patient
No equipment is required. There are no complicated cues, only a gradual increase in lean angle as strength improves.
Patients can begin in an upright position and progressively lean forward to load the foot’s active suspension system safely and effectively.
Why This Matters for Chiropodists/Podiatrists
The Kelly research provides a clearer and more accurate model of how the foot functions and how injury may develop.
It also offers a more practical way to rebuild strength:
- More natural than short‑foot drills
- More effective at generating real torque.
- More accessible for patients of all ages
- More aligned with how the foot behaves during walking and running.
The emerging “active suspension” model from Kelly research group is groundbreaking, but most high‑resolution datasets still come from young, healthy adults. As a result, these insights may not yet fully apply to children, older adults, or people with existing foot conditions. Broader and more diverse datasets will be essential to understand how these dynamic mechanisms function across the lifespan and within clinical populations, ensuring truly personalized care. However, I do think there will be implications for the prescription of foot orthoses and balance in the elderly especially people with diabetes.
With respect to manual foot therapy when we restore midfoot mobility, the forward-lean strategy reinforces that work by helping the foot function as intended: a dynamic, adaptable, energy-shaping system.
My next blog will discuss the Chris Nestor research group.
References
- Smith, R., Lichtwark, G., Farris, D., & Kelly, L. (2023). Examining the intrinsic foot muscles’ capacity to modulate plantar flexor gearing and ankle joint contributions to propulsion in vertical jumping. Journal of Sport and Health Science, 12, 639–647.
- Stephen, C. H. N., Kelly, L. A., Schuster, R. W., & Diamond, L. E. (2025). The effects of running shoe longitudinal bending stiffness and midsole energy return on oxygen consumption and ankle mechanics and energetics: A systematic review and meta-analysis. Journal of Sport and Health Science, 14, 101069.
- Osborne, J. W. A., Menz, H. B., Landorf, K. B., Whittaker, G. A., Cotchett, M., & Kelly, L. A. (2026). The influence of body posture and added mass on intrinsic and extrinsic foot muscle activation and force output during common foot strengthening exercises. Journal of Sport and Health Science, 15, 101110.
- Behling, A.-V., Welte, L., Michael, J. R., & Kelly, L. (2025). Human in vivo talocrural contributions to ankle joint complex kinematics during walking, running, and hopping. Heliyon, 11, e41301.
- Welte, L., Holowka, N. B., Kelly, L. A., Arndt, T., & Rainbow, M. J. (2022). Mobility of the human foot’s medial arch enables upright bipedal locomotion. bioRxiv (Preprint).
- Pemasiri, A., Goan, E., Lichtwark, G., Schuster, R., Kelly, L., & Fookes, C. (2026). Biomechanically accurate gait analysis: A 3D human reconstruction framework for markerless estimation of gait parameters.
- BMJ Open Sport & Exercise Medicine (2025). Publication metadata (10.1136/bmjsem-2025-sportskongres.50).
- Behling, A.-V., Rainbow, M. J., Welte, L., & Kelly, L. (2023). Chasing footprints in time – reframing our understanding of human foot function in the context of current evidence and emerging insights. Biological Reviews, 98, 2136–2151.
- Kelly, L. A., Cresswell, A. G., Racinais, S., Whiteley, R., & Lichtwark, G. (2014). Intrinsic foot muscles have the capacity to control deformation of the longitudinal arch. Journal of The Royal Society Interface, 11, 20131188.
- Kelly, L. A. (2014). In-vivo function of human plantar intrinsic foot muscles (Doctoral dissertation). The University of Queensland.
- Kelly, L. A., Kuitunen, S., Racinais, S., & Cresswell, A. G. (2012). Recruitment of the plantar intrinsic foot muscles with increasing postural demand. Clinical Biomechanics, 27, 46–51.
- Behling, A.-V., Welte, L., Michael, J. R., & Kelly, L. (2025). Human in vivo talocrural contributions to ankle joint complex kinematics during walking, running, and hopping. Heliyon, 11, e41301 (Second entry for this article).
- Behling, A.-V., Welte, L., Michael, J. R., & Kelly, L. (2025). Human in vivo talocrural contributions to ankle joint complex kinematics during walking, running, and hopping. Heliyon, 11, e41301 (Third entry for this article).
- Smith, R. E., Lichtwark, G. A., & Kelly, L. A. (2021). The energetic function of the human foot and its muscles during accelerations and decelerations. The Journal of Experimental Biology, 224, jeb242263.
- Behling, A.-V., Kelly, L., Welte, L., & Rainbow, M. J. (2024). The influence of talus size and shape on in vivo talocrural hopping kinematics. Royal Society Open Science, 11, 231997.
- Treherne, P., Kelly, L. A., & Rainbow, M. J. How Morphology and Mobility Shape Subtalar Joint Mechanics During Increased Loading (Short abstract/report).
- Birch, J. V., Farris, D. J., Riddick, R., Cresswell, A. G., Dixon, S. J., & Kelly, L. A. (2022). Neuromechanical adaptations of foot function when hopping on a damped surface. Journal of Applied Physiology, 133, 1302–1308.
- Behling, A.-V., Welte, L., Kelly, L., & Rainbow, M. J. (2024). Human in vivo midtarsal and subtalar joint kinematics during walking, running and hopping. Journal of The Royal Society Interface, 21, 20240074.
- Schuster, R. W., Cresswell, A. G., & Kelly, L. A. (2024). Human foot form and function: variable and versatile yet sufficiently related to predict function from form. Proceedings of the Royal Society B: Biological Sciences, 291, 20232543.