Measuring your sweat rate and sodium loss
The reason we sweat is to regulate our internal body temperatures. If you are a heavy sweater, then it behooves you to find the amount of fluid you sweat during exercise and replace the deficit. For relatively short rides, water alone should suffice, assuming the athlete starts the session appropriately fueled and watered. When considering harder, hotter and more intense events the picture begins to change.
Sweat sodium levels typically fall between 200mg/l and 1700mg/l in healthy athletes and this information can direct you on how much sodium to consume before and during exercise. Most cyclists take in about 300 – 500 mg of sodium in a normal sized bottle. Record your weight changes pre and post exercise and how to estimate your fluid requirements by calculating your sweat rate:
Sweat rate = (body weight pre training – body weight post training + fluids ingested – urine volume)
(Maximum sweat rates of an adult can be up to 2–4 liters per hour or 10–14 liters per day)
About sodium sweat testing
With advances in technology and far more cyclists taking part in long endurance events in particular, sweat testing is becoming more readily available. In fact, in the very near future we may be reading our sodium and lactate levels in real time from our smart phones and watches. Sweat analysis gives the athlete an opportunity to understand their individual physiology in greater detail and the implications it may have for hydration and electrolyte replenishment.
A sweat test involves taking a sweat sample from an athlete and analyzing it for sodium concentration.
Various methods can be used including attaching absorbent patches to the skin that become soaked in sweat during exercise, then sent to a lab for analysis. Exercise free sweat testing is also possible and a result can be obtained in about 25 minutes.