Nearly a decade ago, Nike revolutionised distance running with super shoes featuring thick, cushy soles and embedded carbon-fibre plates. These shoes boosted efficiency and speed, leading to a cascade of world records. Other brands quickly followed, pushing shoe technology to new heights.
In response, World Athletics imposed a sole thickness limit, initially 40 mm, to curb the advantage these “Frankenshoes” provided for running shoes. However, running shoe companies have recently begun deliberately exceeding this limit. Creating even thicker soles that appeal to runners despite risking disqualification. Adidas, for example, markets its Adizero Prime X2 Strung with soles about 10mm over the legal limit and openly admits it is “not allowed in elite races.”
Patrick Nava, Adidas’ global VP of running product, explained the appeal: “The more foam you have under your foot, the more comfortable it is, and the longer, usually, you can run.” Adidas plans to push sole heights up to around 50mm, which they consider the practical safety limit before risking instability.
However, World Athletics has recently tightened regulations significantly. From November 1, 2024, the maximum allowed sole thickness for all track and field running shoes should be capped at 20mm for sprint and hurdle events up to 400m. For 800m events and above, the sole thickness should be 25mm. This is a sharp reduction from previous limits and aims to maintain fairness and safety in competition.
Meanwhile, the governing body enforces these rules through pre-event shoe declarations and post-race spot checks. Running Shoes containing embedded sensing or intelligent technology remain banned. However, there is an exception for heart rate or cadence monitors. Non-compliance can invalidate race results.
Despite these strict new rules, many runners continue to seek out super-stacked running shoes for training or non-elite competitions. Valuing comfort and performance benefits. Brands like Adidas openly sell models that exceed legal limits, catering to this demand.
The rapid rise of “illegal” running shoes reflects a tension between cutting-edge innovation and regulatory efforts to preserve fair competition. World Athletics’ 2024 rules marked a decisive attempt to rein in sole thickness, but the market’s appetite for super-sized soles remains strong.
