Bike World News has partnered with cycling coach Todd Parker. Todd is an exercise physiologist, endurance sports coach, personal trainer, author, public speaker, guest lecturer, and strength and conditioning specialist with a Masters Degree in Exercise Physiology & Human Performance. He is a former professional triathlete and has raced competitively in swimming, cycling, running and triathlon.
Those who exercise for more than 4 hours and are highly vigilant about hydration, to the extent they drink more fluid than they lose in sweat, over time they accumulate a large enough intake of water to dilute the blood sodium.
Consuming sodium-containing sports drinks helps, but does not protect against hyponatremia because a sports drink offers far more water than sodium. The typical sports drink may have only 1/5th the concentration of normal blood serum.
While dehydration is the far more common concern than over-hydration, all endurance athletes can avoid either problem by knowing their sweat rates. To learn your sweat rate, weigh yourself naked before and after you exercise. A one-pound drop equates to losing 16 ounces of sweat, and generally translates that you should target drinking at least 8-16 ounces of fluid during similar exercise bouts. It is rare that one can keep up with the rate of water loss, but we need to strive to find our optimal hydration intake rates.
Unfortunately, we’re all different, and therefore it’s “trial and error” through the range of experiences until you know how much and how often to drink under various conditions.
Having knowledge about your sweat rate takes the guesswork out of drinking during long training sessions and races , and reduces the risk of health problems associated with consuming too much or too little water.
Let’s revisit “The Big 4” that were covered in Part I of these article series, those being Sodium, Potassium, Magnesium, and Calcium.
Chloride is often referred as the 5th electrolyte that affects performance; however, at a much less significant level, and is also highly dependent upon the intake amounts of sodium and potassium.
As important as maintaining adequate hydration, the sometimes arduous task of figuring out how to maintain adequate balance of these minerals know as electrolytes which facilitate electrical nerve impulses to aid in long-term muscular contraction (i.e. multi-hour endurance training and racing).
As imbalances “initially surface”, muscles often begin to spasm and twitch, and as the imbalance(s) progress, muscles start to cramp, followed by a muscular “contractile locking” – ultimately inhibiting the affected muscle(s) from further contraction. When this stage is reached, the muscle seizes up and further performance is often not possible until homeostasis (a normal functioning balance) is reestablished.
Below are the general amounts of these electrolytes are normally within the body, estimated loss rates, and intake guidelines during multi-hour endurance training and racing.
Normal Daily Dietary Intake Guide for the Big 4:
- Sodium: variable; average 5.6–7.2 g
- Potassium: 1,950 – 3,900mg
- Chloride: Varies with potassium and sodium intake: ~2.5-3.6g/day (or 2,500-3,600mg/day)
- Magnesium: 300–400 mg
- Calcium: ~1,000-1,200 mg
Many endurance athletes will require much more than the tolerable Upper Intake Level (UIL) for sodium (2.3 g/day) and chloride (3.6g/day).
Let’s continue with Sodium. For example, it is estimated that the average American consumes somewhere between 8 and 12 g of table salt per day. (Table salt—sodium chloride—is 40% sodium, so there are 3.2-4.8 g sodium in 8-12 g of salt). This amount of sodium intake is about 20 to 30 times the amount of sodium needed to replace obligatory losses from urine (~ 25 mg/day), skin (~100mg /day), and feces (~25 mg /day).
Athletes need more sodium because they lose more sodium in sweat. The range of sodium lost in the sweat of athletes is wide because some athletes are salty sweaters and others are not. Sweat is saltier during the early stages of training and heat acclimation more so than a highly fit athlete that’s fully acclimated to exercise in the heat.
We will continue this series with the other 3 of what I call the Big 4, as well as how best to prevent electrolyte imbalances, as well as how to “come back” once signs of the onset of an imbalance surfaces. If you haven’t already, now is the time to experiment with different products in order to find out which ones may make you nauseous, or those not palatable (which means you won’t consume it often enough, and which one(s) contribute to your training success and optimal event performances.
Stay tuned to coverage on the next installment of the critical topics of maintaining adequate hydration and electrolyte balance.