The Performance Margin 

VO2 max is one of the most frequently cited metrics in endurance sport. Garmin watches estimate it, coaches reference it, and athletes compare values as a proxy for fitness. But what it actually represents, and what its limitations are, is less well understood than the number itself. This post explains what VO2 max measures, how it relates to race performance, and how to structure training to develop it effectively. What VO2 Max Actually Measures VO2 max is the maximum volume

Almost every training session ends with a feedback form, and almost every one of them is wasted. Not because feedback has no value, but because of what we ask for. Did you enjoy it. Was the room comfortable. Rate the facilitator out of five. We collect a mood, file it, and learn nothing we could act on. In the trade these are called happy sheets, and the name is the whole criticism. A happy sheet can only ever return a compliment, which means it can never tell you what to cha

Two runners with identical VO2 max values can produce very different performances. One runs a 3:15 marathon. The other manages 3:45. The difference is often running economy; the oxygen cost of running at a given pace. Running economy is one of the most important yet least discussed factors in endurance running performance. Unlike VO2 max, which is partly constrained by genetics and responds relatively slowly to training, running economy can be meaningfully improved through ta

In my work in human factors, a lot of what I do comes down to a single idea: you cannot manage what you cannot see. Before anyone makes a good decision, they first have to perceive the situation accurately. Pilots call that situational awareness, and most of the errors we study do not start with a bad choice. They start with an incomplete picture. So when I had the chance to see something I normally only guess at, my own blood glucose, I was always going to take it. Why I did

There is a spectrum of training-related fatigue in endurance sport. At one end sits the normal tiredness of a hard week that resolves after a rest day. Further along is functional overreaching; planned and temporary fatigue that, with adequate recovery, produces a supercompensation response. At the far end is overtraining syndrome; a prolonged state of performance degradation and systemic dysfunction that can take months to fully resolve. Most athletes will experience functio

I've spent a large part of my working life watching people perform under pressure. Not in a gym, and not at a finish line - in aviation, where the quality of someone's thinking under load isn't measured in seconds off a PB. The stakes are rather higher than that. That's where my coaching philosophy comes from. Not from a textbook on periodisation, and not from my own race results. From human factors; the discipline that studies how capable people make poor decisions when they

Bank Holiday weekend here in the UK was unseasonally sunny, and I was away with my family camping in the Peak District. As it was my 30th birthday weekend, I was free to exercise as I pleased, and I definitely took advantage of that! On the Saturday, I took part in the Monsal Trail parkrun in Bakewell. This out and back route along the trail brought the challenge of narrow paths, slightly uneven, gravel terrain and a chance to test my lactate threshold after spending a lot

Athletes will spend significant time and money on training equipment, nutrition products, recovery tools, and coaching - and then routinely get six hours of sleep. It is one of the most consistent patterns in amateur sport, and it undermines every other investment made in performance. Sleep is not passive recovery. It is the period during which the majority of the body's repair and adaptation processes occur - the reason training produces fitness gains at all. Shortchange sle

Of all the physiological concepts that underpin endurance performance, lactate threshold is the one that correlates most strongly with race performance across distances from 5k to the marathon. Yet it remains poorly understood by most recreational athletes, who often confuse it with maximum effort, anaerobic threshold, or simply 'the point where it starts hurting'. Understanding lactate threshold properly - what it is, where yours sits, and how to develop it - is one of the m