The 35mm Threshold: How Maximalist Running Shoes Alter Foot Eversion and Hip Stability

When barefoot running and minimalist shoes dominated the endurance world a decade ago, the biomechanical trade-off was clear: less material meant more ground feel, but a higher risk of metatarsal stress fractures and Achilles tendinopathy. The modern shift toward maximalist running shoes—defined by thick, highly cushioned midsoles—was designed to solve exactly that problem by absorbing impact before it reaches the foot. But while a minimalist shoe strips away support to force the foot to stabilize itself, a maximalist shoe differs in one critical respect: it places the foot on an elevated, unstable platform that the rest of the leg must now actively control.[7]

The appeal of maximalist footwear is undeniable, with brands routinely releasing daily trainers and race-day models featuring up to 40 millimeters of foam under the heel. However, a growing body of biomechanical literature, including a 2024 systematic review published in Footwear Science analyzing data across multiple independent trials, demonstrates that this extra cushioning fundamentally alters how the human body interacts with the ground.[5]

The primary mechanism at play is a loss of local dynamic stability. When a runner's foot strikes the ground in a standard shoe—typically featuring 20 to 25 millimeters of foam—the ankle makes micro-adjustments to keep the leg aligned. As the stack height pushes past a 35-millimeter threshold, the lever arm between the ground and the ankle joint lengthens. This increased distance amplifies the rotational forces acting on the foot, specifically driving greater foot eversion, which is the inward rolling of the ankle during the stance phase.[7]

Researchers writing in Frontiers in Bioengineering and Biotechnology examined this exact phenomenon, measuring running style and stability across different speeds. While the technical literature does not offer direct quotations from the lead authors, the quantitative consensus across the data is clear: the increased stack height alters the sensory feedback from the plantar surface of the foot, muting proprioception and forcing the body to rely on secondary stabilization strategies to maintain an upright posture.[1]

Because the ankle cannot fully manage the instability of a 40-millimeter foam block, the mechanical demand travels up the kinetic chain. The hip abductors, particularly the gluteus medius, are forced to engage earlier and fire harder to prevent the knee from collapsing inward under the increased lateral torque.[7]

A study published in The American Journal of Sports Medicine tracked the influence of maximal running shoes on biomechanics before and after a 5-kilometer run. The data revealed that as runners fatigued over the 3.1-mile distance, their compensatory mechanisms began to fail. The hip stabilization required to manage the high-stack shoes led to altered kinematics and a 15 to 20 percent increase in proximal joint workload that was not present when the same athletes ran in traditional footwear.[6]

Interestingly, this instability is not uniform across all types of terrain or gradients. A preprint study hosted on bioRxiv investigated running style and stability during uphill running, testing whether a 10-degree incline exacerbated the wobble of thick-soled shoes.[4]

The researchers discovered that during uphill running, stability and running style are largely preserved regardless of shoe sole thickness. Because uphill running naturally shifts the foot strike toward the forefoot and shortens the flight phase, the ankle is subjected to lower peak impact forces, temporarily neutralizing the negative effects of the 35-millimeter stack height.[4]

For the everyday runner, these clinical findings require a practical translation rather than a panic. Maximalist shoes are not inherently dangerous, and for many athletes dealing with plantar fasciitis or chronic calf issues, the impact reduction heavily outweighs the stability cost.[7]

As highlighted in a point-counterpoint editorial by the HMP Global Learning Network, the debate between maximalist and minimalist shoes often misses the individual runner's structural capacity. The editorial emphasizes that runners adopting high-stack shoes must actively train their proximal stabilizers—the hips and core—to handle the workload that the feet are no longer managing.[3]

Running Research News echoed this sentiment in their analysis of recent biomechanical studies, pointing out that the foam itself is only half the equation. The density of the midsole material interacts directly with the stack height; a 40-millimeter shoe made of ultra-soft, compliant foam will demand significantly more hip stabilization than a 40-millimeter shoe constructed with a firmer, denser compound.[2]

The most effective intervention for runners utilizing maximalist footwear is not to abandon the shoes, but to supplement their weekly mileage with targeted strength work. Exercises that isolate the gluteus medius, such as single-leg deadlifts and lateral band walks, build the specific hip capacity required to control the increased foot eversion during a standard 12-week training block.[7]

The evolution of running footwear has simply traded one set of mechanical stresses for another. The critical variable is no longer just how much impact the foam absorbs, but whether the athlete's hips possess the endurance to control the platform beneath them. For runners logging heavy mileage in shoes taller than 35 millimeters, the deciding factor in injury prevention will be how consistently they train the muscles that the foam leaves behind.[7]