Hello Reader,

In this edition of the Coaching Prof, we delve into a compelling case study that highlights the critical concept of durability in relation to endurance performance. Taylor Knibb's recent experience in the Ironman marathon at the Kona Female World Championship event serves as a vivid illustration of the challenges athletes encounter when pushing the boundaries of their endurance and emphasizes the importance of preparing for durability, especially in longer races.

Earlier in the summer, Knibb showcased her prowess in middle-distance races, clinching victory at the PTO US Open and Ironman 70.3 World Championship by dominating the biking leg and achieving the third-fastest run split times for both events. However, when she ventured into her first full marathon distance at the Ironman, an entirely new set of challenges emerged. As revealed in her conversation with Jack Kelly on The Triathlon Hour, Knibb had been sidelined from running since late March due to a foot injury.

We believe that a combination of scorching heat and extended duration significantly altered her intensity domains, which was evident in her performance, particularly in her struggles towards the race's conclusion (including removing her sports bra in search of coolness, and the expression on her face at the finish line said it all).

The four exercise intensity domains are commonly referred to as moderate, heavy, severe, and extreme. These domains are defined by three essential thresholds: the gas exchange threshold (GET/VT1), critical power/speed (CP/CS), and power/speed at VO2max. The HIIT Science figure below clearly illustrates how a decrease in these thresholds shifts the intensity domains downward.

Thanks to the research efforts of esteemed colleagues, such as Professor Andrew Jones and Dr. Dan Plews, we now understand that these thresholds can deteriorate with prolonged exposure to heavy-intensity exercise. The ability to resist this physiological deterioration is what scientists have recently termed 'DURABILITY.'

At Athletica, we are diligently working to incorporate this '4th Dimension' into our AI logic. Stay tuned for exciting developments on this front.

Now, you might be wondering about the connection between heat and the concept of durability. My eyes widened with surprise when our Athletica intern, Filip Kolodziej, sent me the latest study from Experimental Physiology. Here Lei and colleagues demonstrate that exercising above critical power leads to an increase in core body temperature.

As we've explored in previous Coaching Professor instalments and as I experienced firsthand during the gruelling Ironman Western Australia, once your core body temperature reaches critically high levels, it feels like you're on a 'highway to hell' – both literally and figuratively!

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Now, let's compare Taylor's performance to Anne Haug's record marathon run, as depicted in the figure below. It's evident that Anne's years of consistent long-distance training have paid significant dividends when it comes to sustaining performance during an 8-hour exercise in scorching heat.

As we discussed with Peter Leo, it's essential to develop efficiency in the heavy domain (below CP) to enhance your durability. If you're an Athletica user, you'll find these workouts integrated into your running, cycling, triathlon, and duathlon plans throughout your build micro-cycles.

As for Taylor, whether she had this component in her training remains a mystery. However, it's clear that she ventured close to the severe domain, grappling with overheating and physical strain. Once she masters this crucial aspect of her training, there's no doubt she has the potential to become an Ironman world champion.
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Paul Laursen, PhD

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