Super shoes: A double-edged sword for runners
The world of running footwear is a fascinating one, with the latest technology promising to make athletes faster and more efficient. But what happens when these so-called 'super shoes' come with a hidden cost to the body's mechanics? A recent study by researchers at Mass General Brigham (MGB) delves into this question, revealing some surprising insights.
The study, published in PM&R, tested the effects of carbon-plated running shoes, known as 'advanced footwear technology' (AFT), on the body mechanics of healthy elite runners. The findings suggest that while these shoes can significantly improve performance, they may also come with a price tag in terms of increased risk of bone stress injuries.
The research team, led by Michelle M. Bruneau, PT, DPT, PhD, and Adam Tenforde, MD, recruited 23 healthy elite distance runners, who were already familiar with AFT. The runners completed trials in three different shoe types: a neutral cushioned trainer, a lightweight foam shoe, and the AFT model, running at various paces.
The study revealed some interesting findings. Firstly, runners in the super shoes took fewer steps per minute, which led to longer strides and more overstriding. This pattern has been linked to higher loading on the lower leg, which could potentially increase the risk of bone stress injuries.
Secondly, the arch of the foot rolled inward more in the super shoes, causing a slight sideways collapse on each landing. This motion has been associated with navicular stress injuries, a slow-healing condition affecting a small midfoot bone with limited blood supply.
However, not all changes pointed towards higher risk. Interestingly, runners in the super shoes pushed off less forcefully with their ankles, which was unexpected. Previous studies have linked higher ankle loading with a history of bone stress injuries, so this finding suggests that the super shoes may actually reduce the risk of certain injuries.
The study also noted that some measures remained largely unchanged across all three shoe types, such as the up-and-down bounce of the body, the overall impact force at landing, and how long the foot stayed planted each step. This indicates that while the super shoes do alter running form, the impact on overall impact force and foot placement may not be as significant as previously thought.
The concerns about bone health and these shoes are not unfounded. A 2023 report from the same research group described five elite runners who developed navicular stress injuries while training and racing in carbon plate footwear. While this case series could not prove causation, it raised important questions that motivated the lab work.
The study's limitations include the relatively small sample size (23 runners) and the fact that 11 participants had prior bone stress injuries. Additionally, the analysis captured only a single lab session, and the shoes differed in various aspects beyond the carbon plate, making it challenging to isolate the specific effects of the plate itself.
Despite these limitations, the study provides valuable insights. It highlights the need for sports medicine clinicians to closely monitor athletes with prior bone stress injuries and suggests rotating between shoe types to gradually adapt to AFT. For recreational runners, the takeaway is to wear these shoes with awareness, not on every run, and to balance the performance benefits with the potential risks.
In conclusion, while 'super shoes' can significantly improve running performance, the study underscores the importance of considering the potential trade-offs. As Bruneau, the lead author, advises, runners should weigh the benefits against the possibility of subtle changes in body loading, ensuring they stay informed and make informed choices about their footwear.
