It’s not what you can do for 5 minutes, it’s what you can do for 5 minutes after five hours. As endurance athletes, we know that our endurance – our physiological and psychological ability to endure, to keep going as the hours tick up in our event – is fundamental to our performance.

‘Durability’ is an emerging concept in exercise physiology, and, more importantly, we think, a critical factor in endurance training and performance. In our 2021 paper, we defined durability as an athlete’s resilience to the effects of prolonged exercise on their physiological profiling characteristics – the thresholds we use to inform pacing strategies, programme training sessions, and monitor training load (1). Subsequently, durability has been proposed as a crucial factor in endurance performance, as it defines, physiologically at least, our ability to stave off the upward creep in effort required at a given speed or power output as exercise progresses...

Those of you that read our blogs, or subscribe to our monthly Training Science Summaries, will know that we often write about ‘durability’. Durability has been one of our key research areas over the last few years, and something that is seeing a lot of attention in our field by other researchers, too. I think durability has massive implications not only for endurance performance, but also for the day-to-day decisions we make in endurance training.

In this blog, I’m going to provide an update on the durability research – what we know, what we don’t know, and what the implications are for athletes. However, I’ll before we get into durability, I’ll discuss physiological profiling.

Physiological Profiling and Endurance Training

I often have my athletes perform incremental exercise tests. With an incremental exercise test, we can estimate the athlete’s overall aerobic capacity or VO₂max, how economical their movement is, and their speed or...

As readers of our blogs will know, I am involved in research with colleagues at AUT in New Zealand on ‘durability’. We defined durability as the time of onset and magnitude of deterioration in physiological profiling characteristics – such as the ventilatory and lactate thresholds that mark the boundaries between intensity domains – over time during prolonged exercise (4). More simply, physiologically and perceptually, a 300 W effort when 20 min into a session is not the same as a 300 W effort when 200 min into a session. An athlete’s durability refers to how big the effect of those 200 min is.

We published a study last year that found an ~10% reduction in power output at the first ventilatory threshold (VT₁) following 150 min of moderate-intensity cycling (9). VT₁ is used as a marker of the transition between moderate and heavy intensity exercise. I use it as the upper boundary of “Zone 2”, and encourage my athletes to perform the bulk of...