22 September 2012

Salt


So, electrolyte balancing is always a fun topic.  My friend, Lauri, asked me on Facebook after my DNF at P2P what happened.  I gave here the raw, simplified answer.  Andy Reed, who ended up taking 5th at P2P, chimed in that my cramping was due to fatigue and that I had too much salt in my body (as indicated by the salt on my clothes).  I disagree.

I'm always open to all points of view on stuff like this and would love to hear others' opinions on it, expert or not.


Tim Long
To answer lauri's question. I got behind on salt/water on the first climb and never got out of the hole. — with Lauri Abrahamsen.
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  • Dan Roed and Leslie Rundle like this.
  • Lauri Abrahamsen Really? That's a great lesson for me. I'm sorry about the DNF but I'm glad it was nothing too serious.
  • Patty Osorio-O'Dea I'm sorry to hear, Tim. Next time...
  • Karen Peterson Oh bubba... That looks rough.
  • Danni Baird wow the salt on those shorts!!!
  • Ellen Parsons Fletcher Sorry it was not a good day.....
  • Andy Reed The salty shorts indicate your body has too much salt, not too little. You need to look at the science/physiology. Tim Noakes explains it in Waterlogged. There is more than enough sodium in the body to support an ultramarathon. Cramps are caused by neuromuscular fatigue, not electrolyte disturbance. Fact.
  • Tim Long Electrolyte Deficit
    With exertional heat cramps, an athlete typically has been sweating extensively with appreciable sweat electrolyte losses as well, particularly sodium and chlor
    ide. Whether during a single long race, match, game, or training session or consequent to multiple same- or repeated-day exercise bouts, a sizeable whole-body exchangeable sodium deficit develops when sweat sodium and chloride losses measurably exceed salt intake (6,7,57). The deficit threshold required to prompt muscle cramping is not well described; however, an estimated sweat-induced loss of 20%Y30% of the exchange- able Na+ pool has been noted with severe muscle cramping (6,29). How readily this occurs depends upon sweating rate (10), sweat sodium concentration (typically 20Y80 mmolILj1) (7,12,28), and dietary intake (27). And with continuous physical activity over an extended period of time (e.g., 3Y4 h or more), a high sweat sodium concen- tration generally stays high, even as whole-body water and sodium deficits progressively increase. This is possible because sweating rate remains fairly consistent during such long-term activity and serum sodium concentration is typically maintained or elevated, along with potential changes in sweat gland function or sympathetic nervous system activity that would tend to increase sweat sodium concentration (33). Other electrolytes also are lost in sweat to a much lesser degree, and several of these (namely calcium, magnesium, and potassium) have been implicated falsely as the cause of muscle cramping during or after exercise when purported deficiencies are suspected (3,15, 23,24,31,56,62,63). However, exertional heat cramp-prone athletes characteristically develop a sodium deficit because their sweat sodium and chloride losses are not offset promptly and sufficiently by dietary intake (6,7,57). -National Institute for Youth Sports & Health at Sanford, Sanford USD Medical Center, Sioux Falls, SD, American College of Sports Medicine
    57 minutes ago · Like · 2
  • Dan Roed I got lost after "with"? Tim is an exceptional athlete and he knows a little bit of what he speaks. Anybody who runs enough will have a "bad day" sooner or later. This allows for reflection on how we may do things better in the future.
  • Ken Michal I have a feeling that "Waterlogged" is going to confuse just as many runners as "Lore of Running" did! ;) Didn't he say "drink to thirst" in both?!? 
    Salty shorts means that Tim stopped sweating. Once that happened, his already elevated core temperature started to climb even more... He didn
  • Tim Long Go grab a cup of coffee, this is a long comment...
  • Tim Long Below is a well stated response to a question that resembles what Andy Reed and I apparently disagree on. Individual athletes can (and do) have vastly different levels of sodium (and loss during exercise). I happen to sweat a lot of sodium (obvious in my salt-caked clothes in races). I've messed around with levels of salt in my daily diet, which yielded no obvious difference in performance. I've toyed with salt and electrolyte intake in races (a luxury of doing so many training races in my schedule allows me to test all sorts of things out, in the hopes of tuning my own performance and also sharing my findings with other runners). 

    I've gotten to the point where, based on my effort level and race day conditions, I can guess when I'll feel the first twinge of cramping (initially typically in the tibialis anterior muscle [shin area] and/or the vastus medialis [quad above and to the inside of the knee]). If the weather is cool, I may not take any salt (e.g. Turquoise Lake 20 mile snow shoe race done in 4:30. I took in no salt). If it's hot and exposed, 90+F, I'm in for a long day of 900+mg of sodium intake with 40-60 oz of water/hr intake. The point is that it's individual. I need the salt intake or my muscles lock up. When they lock up and I continue to try to run on them, the damage is substantial. Other athletes may lose much lower levels of sodium.

    About Human Sweat (H2ProHydrate)
    Firstly whilst we have a huge amount of respect for Tim Noakes and his work he has a record of being quite provocative in his approach to certain topics. He likes to challenge exists dogmas and this is both healthy and necessary in science. However, sometimes he adopts quite an extreme position (in this case that sports drinks are completely unnecessary and that the companies that sell them are conning us) partly, I think, to get people to sit up and take notice and this certainly works!

    For starters we do agree with his point that listening to thirst is a good idea. Too many people do force fluid down too frequently and suffer as a result and in our advice to athletes we take a similar position. 

    However, one of the main points that we'd disagree with in his new book is in the way it dismisses that there is a large variation in sweat sodium losses; saying that they are relatively similar between people and mainly driven by dietary sodium intake. Our own data (which is probably one of the most comprehensive sets available) shows a much wider variance in sweat sodium values (approximately 19mmol/l to 84mmol/l) in well trained athletes than he quotes in the book (around 20-40mmol). 

    It's certainly possible that at the extremes when people are taking in huge volumes of sodium, or virtually none at all, the body could respond by losing more or less in sweat but the fact remains that the main mechanism for regulation of sodium is in the kidneys absorbing or excreting more in urine. From the large numbers of people we have tested (some of whom in professional rugby and football teams all eat similarly controlled diets to one another yet still show this wide variation in sweat sodium levels) it is clear there must be something other than just sodium intake dictating sodium loss in sweat and it would appear that this is genetics. 

    On a personal level as I explained in the talk at All3Motion one of the biggest drivers for me in getting my own sweat tested many years ago and looking into this topic further was that I had found by trial and error that by taking in lots of sodium in races I a) stopped cramping (as I had done a lot beforehand) and b) generally my performances improved dramatically. The consistent way in which this happened (and from listening to the experiences of other athletes we've tested and talked to over the years) leads us to strongly believe it cannot just be put down to a placebo effect.
    Also, although Dr Noakes is very sure in his opinion that sodium loss has absolutely nothing to do with cramping a lot of anecdotal evidence would suggest otherwise. For sure we don't believe it to be the only factor involved but the amount of athletes who have stopped cramping when we've upped their sodium intake in endurance events is significant. Again our own data from sweat tests and questionnaires shows a statistically significant correlation between athletes who report that they cramp regularly and the fact they tend to have higher sweat sodium levels. This may not offer definitive 'proof' of a link but it ties up with enough anecdotal experience to be taken seriously.

    As with a lot of topics in science and sports performance if you search hard enough you can definitely come up with a lot of evidence to prove and disprove most theories. Do we agree with Dr Noakes that many of the big sports drink companies have 'hyped' the efficacy of their products in order to sell more of them? Absolutely. Do we think that there is no benefit to be derived from intelligent use of certain supplements (such as sodium) to prevent performance dropping off as the body gets depleted during extended periods of exercise? No.

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