Does Dehydration Cause Cramps and Heat Illness?

[Wildhorse]

The New York Times published an interesting article today dealing with this question. According to the results of research studies described in the NYT article, the answer appears to be that dehydration does not cause heat illness or cramps, which is, of course, contrary to what we have been told.

The article specifically addresses problems caused by coaches encouraging young athletes to drink a lot of water, so much that they get sick from that. But it has broader implications. Note that the article mentions hiking in Grand Canyon.

It seems that heat illness is merely caused by overexertion in the heat, with or without water. Cramps happen when a muscle is fatigued, with or without water.

I remember a fellow who experienced bad cramps climbing Skyline. His hiking companions loaded him up with water - just following conventional wisdom.

Based on the research, it seems that the key to hiking Skyline in the summer is being physically prepared, including having sufficient heat acclimation. This, plus other variables always at play in a human body, would explain why some people are able to do this, while others totally fail. Lack of water is not the explanation for heat illness or cramps, but it remains, of course, a major risk for dehydration.

The article is at http://well.blogs.nytimes.com/2015/08/2 ... ottom-well

[7birdies]

From my personal experience, I would go with muscle fatigue as the culprit. I like to run vertically, and it seems the only time my legs start cramping is when I transition to hiking from running after a long steep climb. As an example, when I do Skyline, I like to run non-stop to Flat Rock and then hike from there to the Tram and most of the time I get leg cramps on the hike to the tram. On Skyline trips when I didn't run to Flat Rock, never cramped. I run mountain trails in Palm Desert area during the middle of the afternoon in the summer all the time and I've never cramped up, I know there are times my hydration levels aren't great and I feel like I'm on the verge of spontaneous combustion, but no cramps. So it seems that for me its likely a muscle fatigue issue. I sure wish I knew the answer for sure so I could try and make the hikes from Flat Rock to the Tram after running more pleasurable as its no picnic shuffling up that steep terrain all cramped up.

[halhiker]

I think we've discussed this here at some point by making the point that it's the heat and not dehydration that's getting people in trouble. You can get heat illness no matter how well hydrated you are. At a certain point it would be better to pour your water over your body rather than drinking it.

[Ed]

Thanks for the article link, Wildhorse. Makes sense to me. This idea that forced hydration was a solution to problems with fatigue and heat always seemed a bit trendy and questionable.

[cynthia23]

Thanks so much for posting this, Wildhorse. As Hal mentions, this point has come up a lot of late. As I've said before, some people have an idea that water is a magical elixir that protects you from heat stroke, and that's not the case at all.

[7birdies]

I agree Hal, in certain situations its much better to douse yourself with the water rather drinking. I started a 5 mile mountain run in Palm Desert today at Noon. I started with two 22 oz. frozen water bottles (only used approx 3/4 of the total) I sipped only a small amount of water during the run and used most of it for dripping over my head. As long as I kept dumping the cold water over my head I felt pretty good.

[Sally]

I am lucky in that I seldom cramp up. However, I come to feel EXTREMELY poorly hiking in heat. For example, during two hikes I did this month (Vivian Creek trail to San G and John's Meadow to San Bernardino Peak) I was fine going uphill as we started very early in the morning. Although I was well hydrated, coming downhill later in the day in the heat I suffered GREATLY. Only when we finally came to the stream crossings and I was able to get thoroughly wet did I find relief. There is nothing that feels better than a cold, wet head, wet shirt, and wet bandana around the neck. And yes, Hikin Jim...Ellen, Marilyn, and I did plenty of bandana-dipping!

[Wildhorse]

The association of fatigue with cramps seems sound, and yet, from what I read, it also seems that we do not fully understand cramps. In spite of empirical and anecdotal evidence to the contrary, we are likely to continue hearing that drinking lots of water prevents them. The association of heat illnesses with heat, surely seems sound. Surely that is why they are called heat stroke and heat exhaustion. And yet, we are likely to continue hearing that drinking lots of water prevents them.

Nothing is is quite linear it seems. Certainly not our bodies, or our minds.

For a few weeks my leg muscles were fatigued. No cramps, but tired. I had hiked almost every day, and it was hot. That must be the reason, I thought. I was careful to drink plenty of water, and sometimes I slowed down to give my legs a break. But hiking too fast or hard on hot days was not the reason, as I discovered later. I should have thought about it starting with my back, but I did not. I had stressed my back recently from lifting heavy rocks that I was arranging in my back yard (building a switchback to remind me of a mountain trail.) But it did not occur to me that this would cause my leg fatigue. I went to my chiropractor, knowing from prior experience that this would help relieve the stress in my back. I described my back stress to him, but did not mention that my legs had felt fatigued lately, even while we spent the whole time talking about our mutual interest in hiking, and though I had felt the fatigue walking up the stairs to his office. He adjusted my spine in several places from my tailbone to my neck - it was quite crooked. After that visit, walking down the stairs to my car, I noticed that the fatigue had vanished. Just like that, gone.

From what 7birdies has written, and Sally, and Zippetydude (in his account of ascending Skyline in summer), I realize now that I have been missing a great thing by not pouring water on my head, by not hiking with a spray bottle or mister. I intend to start doing this immediately. When I bike too.

We are not linear beings. As Isaiah Berlin wrote, and Kant before him, the timber of humanity is crooked. Our limits and boundaries, the reasons for things, and the straight path: they all elude us. But the mist is cool.

[apage]

I think there are several pathophysiological issues at play in this post. Muscle cramps are a symptom of heat related illnesses and the cause of heat related illnesses can be different for every person. A persons ability to tolerate exposure to heat and exertion is determined by their overall physical fitness level, there level of acclamation to heat and their hydration status. You'll see people on the trail all day long that outwardly don't look like they're fit but due to acclimation, conditioning and proper hydration (with electrolytes) they can hike all day long in heat.
Hydration is very important to prevention of heat related illness but may not alone prevent cramping. Cramping is caused when there's an imbalance of electrolytes in and around a particular muscle group. When muscles contract there's a shift of electrolytes at a cellular level. Once a muscle has contracted the electrolytes must shift again to "reset" and if there's an imbalance of electrolytes the muscle may not be able to "re-polarize" or return to it's relaxed state, resulting in a cramp (Potassium is the major player in re-polarization).
Hydration is also very important. From personal experience, I can loose 3 pounds of weight during a 5 mile run in 90 degree heat. I'm not loosing fat during that time, it's all water. Water weighs about 8 pounds per gallon so, in theory, would have lost almost a half gallon of water during that run. That's a lot of fluid lost and fluid shifting becomes very pronounced to keep the body in equilibrium as a result. The fluid shifting pulls water from the vascular system and other areas to keep the body in equilibrium and my blood pressure begins to drop and my heart rate has to increase to keep me functioning correctly. This is why our heart rate is a little high for hours following long hikes or prolonged workouts. A study published in 1996 stated, in a nutshell, stated that athletes should strive to keep water loss at less than 1% of body weight during strenuous activity in order to prevent cardiac strain and maintain performance. http://www.mhhe.com/hper/nutrition/will ... ndix_k.pdf
So, if I were to add anything useful to this conversation, conditioning and acclimation are as important and hydration on the trail and don't underestimate to importance of sodium, magnesium, calcium and potassium. One last comment, when a person is sick on the trail due to heat and exhaustion (nausea, vomiting, dizziness) they are no longer absorbing fluids but rejecting them. This is a true medical emergency and they should seek shade, rest and maybe medical assistance. Pressing on isn't always the right choice as the mountain will always be there for another day.

[Ellen]

Howdy All

Thanks to Apage for his excellent post on the physiology of fluid balance during exercise AND for posting the American College of Sports Medicine position stand on exercise and fluid replacement.

I agree that heat cramps have multiple etiologies.

From personal experience and working with cramp prone athletes/hikers, I always include table salt in my medical kit. Some of us are salty sweaters -- my hiking companions are always entertained by the varying salt patterns on my t-shirt post hike. No matter how fit and acclimated some folks are, they will lose a substantial amount of salt in sweat. Heavy sweaters also lose a lot of salt due to high fluid losses.

The average endurance athletes loses 800 mg for every two pounds (quart or liter) of sweat. A half teaspoon of table salt supplies 1,000 mg.

It's true that most Americans consume too much salt. However, for a heavily sweating athlete/hiker, salt is a friend, not a villain.

There are multiple ways to obtain salt during a hike:

1) Sports drinks -- coconut water is high in potassium but low in sodium
2) Salt supplements such as Salt Stick
3) Salty foods such as pretzels and chips
4) Fast food salt packets or a small container of table salt

Miles of smiles,
Ellen