I'm Dr Alfie Gordon — a performance scientist with a PhD in the cardiovascular physiology of sunlight. Sun Endurance is where I figure out, in public, how athletes can use light to perform better. 

My background is in sport and exercise science — the study of what actually happens inside the body when you load it. But my first real lesson in light didn't come from a lab. It came in the army, watching night-time light wreck soldiers' sleep and readiness: same training, same food, worse output.

I moved into sport nutrition and started making videos reviewing Hexis, a behaviour-change app that tells athletes not what they ate but what to do next. That work got me hired there. The mechanic is the part that matters — Hexis doesn't passively log the past, it gives you the what now — and I'd already come to believe light needed exactly that same layer, and that nobody had built it.

Elite sport introduced me to the people already treating light as a lever. Tom Clark, Esteban Ocon's Head of Performance and the founder of Phaze, manages drivers' light exposure and circadian timing as a genuine performance input across an F1 calendar built on jet lag. The operators building the most data-driven companies in this space do the same for themselves: blue-light blockers to work late, morning light to anchor the day. Light is already a variable at the top. It just isn't a discipline yet.

Underneath all of it, I was doing a PhD on the seasonal use of nitric oxide in the skin and what it does to vascular health — built on Professor Richard Weller's work, and approached from cardiovascular disease rather than sport. Most people in performance can recite the nitrate–nitrite and L-arginine pathways; far fewer think about the skin, the largest organ we have and the surface we actually interface the world through. Weller showed that UVA on skin releases nitric oxide into the circulation and lowers blood pressure, independently of vitamin D — and that last part matters, because vitamin D's role is well characterised, but D supplementation doesn't reduce cardiovascular disease, and it ignores the nitric oxide half of the equation entirely.

The performance angle was wide open. My supervisor, Dr David Muggeridge, had already tried UVA as an adjunct to dietary nitrate for performance — but the literature on UV and performance is thin, and what exists doesn't yet separate light's own contribution cleanly. I'm not going to pretend it does.

Light is now, belatedly, being treated as a variable: managing jet lag, red light for recovery, covering up to protect against skin cancer. But that framing is almost entirely defensive. Weller has been blunt about the trade-off — an exclusive focus on avoiding the sun protects the skin while costing the heart — and he's now Chief Medical Officer of The90, a company built around a wearable that monitors UV load. It's positioned for skin ageing, but it solves the genuinely hard problem underneath: measuring UV exposure well, at scale, on the body. Brands like Pelotan have started estimating UV load from activity data, with all the limitations a proxy like that implies; the Gem points at something more robust.

And here's the connection most people miss: what that hardware actually does is profile people into sun-avoiders and sun-seekers, then tell them what to do next. That isn't tracking — it's the what now layer, the same thing Hexis does for nutrition. A discipline is forming in real time, and the performance seat in it is empty.

So this is the site that surfaces how athletes can use light to perform, across load, recovery and readiness — built by someone who studies the mechanism. 

Light is ubiquitous; of course it could influence everything. The work is taking it seriously as a training variable, and being accurate enough to be trusted while I do.