Is Hypoxanthine the future for monitoring endurance performance?

Super interesting article on the use of Hypoxanthine (from sweat) being used as a predictor of performance in athletes.

Having done HR tracking, Power and over the last couple of years, Lactate, it’s always interesting to hear of new methods and advancements in performance, and opportunities to improve metabolic health. So while I am still waiting for a reasonable/practical real-time Lactate monitoring solution, maybe I should skip to the next big thing …

Check it out here:


Purine metabolism reflects the exercise-induced muscle adaptations and training status. This study evaluated the utility of plasma hypoxanthine in the prediction of actual sport performance. We studied male athletes: 28 triathletes (21.4±2.9 years), 12 long-distance runners (23.2±1.9 years), 13 middle-distance runners (22.9±1.8 years) and 18 sprinters (22.0±2.7 years). Season-best race times were considered, achieved over standard triathlon, 5 000 m, 1 500 m and 100 m, respectively. Incremental treadmill test was administered to determine maximum and “threshold” oxygen uptake. Resting and post-exercise plasma concentrations of hypoxanthine, xanthine, uric acid and lactate were measured as well as resting erythrocyte hypoxanthine-guanine phosphoribosyltransferase activity. Simple and multiple regression analyses were used to identify significant contributors to the variance in performance. Hypoxanthine considered alone explained more variance in triathletes, long-distance runners, middle-distance runners and sprinters (r 2=0.81, 0.81, 0.88 and 0.78, respectively) than models based on aerobic capacity and lactate (R 2=0.51, 0.37, 0.59 and 0.31, respectively). Combining purine metabolites and cardiorespiratory variables resulted in the best prediction (R 2=0.86, 0.93, 0.93 and 0.91; r=0.93, 0.96, 0.96 and 0.95, respectively). In summary, hypoxanthine is a strong predictor of performance in highly trained athletes and its prediction ability is very high regardless of sport specialization, spanning the continuum from speed-power to endurance disciplines. read more

hDrop – Wearable Hydration Monitor

I *just* received my order of the hDrop gen 2 wearable hydration monitor, and used it for a short 45 min easy Zone 2 run. Based on my interest of sweat analysis, I was curious to compare my results to other tests I have done in the past. I plan to continue to use it for more sessions, and it will be interesting to see how the results fluctuate with the seasons.

MetricPrevious ValuePer hDropNotes
Avg Sweat Rate37Oz/h16.4Oz/hMy previous values were cycling, temps were relatively cool
Avg Sodium Concentration716mg/L – 1023mg/L901.1mg/LRange of 5 tests, last 3 were all at 1000mg/L +- 50.

After my first quick and dirty test, the unit is probably quite accurate on the sodium concentration, but I am unsure about the sweat rate. My past sweat tests were done based on weight loss during the exercise, cycling (not running) and majority were indoors. Based on the effort and ambient temp, I think around a 500ml sweat loss seems correct. read more

Endurance Racing – Sweat Analysis

Sweat, and specifically Sodium, is one of the three “levers” for endurance athletes when it comes to hydration and nutrition (fueling) and subsequently your performance. The other two key elements or levers are Carbohydrates and Fluids.

The most important part about sodium/sweat is that everyone has a unique sweat loss rate, and a unique sodium content ratio in their sweat. So while a more generalized approach can be defined for consuming carbohydrates, the same is not true for electrolyte loss. This is why having a sweat test is critical for athletes wanting to perform, understand and take advantage of their data to understand their personal needs and requirements. read more

2023 Ironman – Texas

Reasonably last minute, 11 weeks before the event, I decided to sign up for Ironman Texas … a full distance Triathlon has been on my bucket list for a while now. Overall the race did not go according to plan, but most importantly I finished and it was very rewarding experience. Doing something this long for the first time is hard 🙂 Here are a few photos from the event, my favorite was the fun area of “Hippie Hollow”.