Re: Hydration

  • Alain Jaques
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15 years 7 months ago #393 by Alain Jaques
Re: Hydration was created by Alain Jaques
I attended a lecture by Prof Tim Noakes a few years ago and one of the things he covered in detail was hydration. The talk was aimed a ultra-marathon runners and he warned of the dangers of over-hydration.

Over-hydration can kill you (and has killed quite a few runners) whereas dehydration is relatively harmless. The levels of dehydration in marathon runners will affect performance but is unlikely to kill you. He gave the example of the most dehydrated person every measured - this guy got lost in the Gobi desert for a week, his level of dehydration was several degrees of magnitude greater than anybody could achieve on a marathon or ultra-marathon, and he survived.

With surfskiing I think it would be difficult to over-hydrate, you need around 4+ hours to get over-hydrated and you will need to carry a lot of liquid or be resupplied often. Surfskiing races are not like running races where you pass a refreshment station every few kilometers.

At the end of the lecture and all the scientific explanations Tim Noakes concluded by saying "just drink when you are thirsty".

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15 years 7 months ago #394 by NigelWall
Replied by NigelWall on topic Re: Hydration
Never heard of Tim Noakes, but their are some inconsistencies in the facts put forward.

1. This is fact "Dehydration hurts your performance, and slows your ability to recover for the next workout. Continuing to run (exercise) when dehydrated can lead to heat stroke and death." Pfitzinger
2. It is still true that when you are thirsty you are already suffering from mild dehydration. The smart athletes drink little and often on long sessions.
3. To better understand the dangers of dehydration, take a look at what happens in the body when you workout on a warm day. First, your body automatically sends more blood to the skin for evaporative cooling, leaving less oxygen-rich blood going to your working muscles. Second, the warmer it is, the more you sweat, and the more your blood volume decreases. Less blood returns to your heart, so it pumps less blood per contraction. Your heart rate must increase, therefore, to pump the same amount of blood. The result is that you cannot maintain as fast a pace on a warm day. Also the thickening of the blood ups your blood pressure.

This is a real case

I was 5 hours into a multi sport race and on a trail trek. I caught up with another competitor. He was coherent and jogging, but didn't look in great shape. I chatted and he seemed OK, but decided to report at the next check point (we were in deep bush). I reported the competitor at a check point 15 minutes later and the search crew went back into the bush right away. The guy was semi concious and was rushed to hospital suffering from dehydration and electrolyte imbalance. He was on a drip for 3 days and hospitalised for 7.

In the same race the following year a guy was choppered off the kayak section with the same symptoms, but caught earlier. He was OK after 3 hours in the medevac tent with water, salts and rest.

Don't under estimate the effects.

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15 years 7 months ago #395 by mckrouk
Replied by mckrouk on topic Re: Hydration
I suggest anyone who has not heard of Noakes should search for his published articles on sports science on www.pubmed.com. Particularly with reference to hydration, from 2004 to 2007.

Paddling is not like running. Paddlers stay cooler (as they are getting splashed and perhaps because they slow down more readily) as opposed to runners who have to rely on their own cooling mechanisms. In 6 years of paddling races averaging 2 per week, I've never seen anyone seriously dehydrated enough to require medical attention. When I used to work in medical tents at several ultra marathons, marathons and half marathons and in Emergency departments of hospitals, I saw runners dehydrate often, all of whom responded to rehydration, and some of whom required hospitalisation with IV fluids. The danger of dying is due to hyponatraemia (blood sodium below 125) which occurs more readily with over-hydration. Again, I've never seen this in a paddler.

What is well known and accepted is that any athlete should be well hydrated in order to perform, so drink about 500ml to 1 litre before you race and drink about 200ml/hr (add up to 200ml more per hour in hot and humid conditions) while you race to avoid dehydration. This will keep you safe and able to perform. Don't overdo the fluids and drink a bit more if you feel thirsty, especially while running!

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  • Alain Jaques
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15 years 7 months ago #396 by Alain Jaques
Replied by Alain Jaques on topic Re: Hydration
Professor Timothy Noakes is a world-renowned professor of exercise and sports science at the University of Cape Town. He has run more than 70 marathons and ultramarathons, and is the author of the running book "Lore of Running". See the Wikipedia for more.. en.wikipedia.org/wiki/Tim_Noakes

Check out this article for more insight into dehydration/over-hydration, www.pponline.co.uk/encyc/rehydration.html

Noakes makes the provocative claim that current guidelines on hydration, which have been in existence for the past 30 years, have been biased by sports drink sponsorship, do not take account of athletes? individual needs and have led to the over-consumption of fluids during exercise.

My point is that adequate hydration is important, as per the guidelines of Rob M and Dr Kroukamp, but be aware that there is a lethal danger of everdoing it.

I also speak from personal experience, I mildly over-hydrated on the Two Oceans Ultra Marathon in 2004 and collapsed with cramps and delerium 1km from the finish. I made the finish only because I knew there was medical help there, and I felt I really needed it.

Runners and cyclists in long distance events are now asked to write their normal body weight on the back of their race numbers. This can be used as quick check to see if the athlete is over or under-hydrated.

For your average athlete Noake's advice is to drink no more than required, as indicated by thirst, rather than as much as possible. All athletes should also ensure adequate salt intake in the fluids they take on board during and after exercise to counteract salt losses in sweat.

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15 years 7 months ago #397 by HI Paddler
Replied by HI Paddler on topic Re: Hydration
According to Merck's online pages, if you have normal kidney functions you would have to drink more than two gallons of water a day on a regular basis. This is excluding heat or exercise.

www.merck.com/mmhe/sec12/ch158/ch158c.html

Another source agrees: www.healthatoz.com/healthatoz/Atoz/commo...cy/overhydration.jsp

I don't believe my intake of a gallon of water the day before the race is excessive. Of course, if your kidneys are not working property you must be much more careful about your intake of water.

On one six man Molokai crossing I consumed a bit more than 2 gallons over the six hour crossing. I avoided dehydration which makes a paddler totally ineffective in the crew.

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15 years 7 months ago #398 by NigelWall
Replied by NigelWall on topic Re: Hydration
Thanks for those refs Alain, they do make interesting reading. Glad you made it OK at Two Oceans. I'm coming to SA and doing Comrades in June, so I'm working hard and doing very long running sessions (as well as still paddling) so very aware of hydration at present. Temps are rarely below 30c so I have a constant fine balancing act.

My 'record' consumption was last October on Day 1 of the 2 day Coast to Coast race where I consumed 9 litres of approx 75/25 water/sportsdrink in just under 8 hours. After the day finished I was still thirsty and downed another 2 litres (water) over the next 4 hours in carefully measured short bursts of 2-300mls. That was a mix of trail running and cycling.

On a 4 hour paddling session I would only use 2-3 litres in similar temps.

Hi P - a gallon the day before race day sounds right for the 'average' bloke. The sites I have visited suggest 8-10 glasses of water.

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15 years 3 months ago #399 by [email protected]
Replied by [email protected] on topic Re: Hydration
Here's some great info on nutrition and hydration:

petalumarivermarathon.blogspot.com/

Rob

Currently Fenn Swordfish S, Epic V10 Double.
Previously: Think Evo II, Carbonology Zest, Fenn Swordfish, Epic V10, Fenn Elite, Red7 Surf70 Pro, Epic V10 Sport, Genius Blu, Kayak Centre Zeplin, Fenn Mako6, Custom Kayaks ICON, Brian's Kayaks Molokai, Brian's Kayaks Wedge and several others...

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15 years 1 month ago #400 by stuartknaggs
Replied by stuartknaggs on topic Re: Hydration
Wow, heated discussion. I am well acquainted with over hydration, we had a runner collapse on a club half marathon from over hydration and another died in the Comrades this year.

Hydration definitely depends on where you are and what sort of workout you are doing.

My personal program is as follows (with close reference to Dr Tim Noakes):

No specific hydration program in the days before a race.

Races shorter than 1hr - no hydration but some water just to wash the salt away and to wet the throat - around 500ml

Races over 1hr, about 1litre per hour.

Note that in cooler conditions (SA) I mix my supliment to about 15% sugar using the tried and tested, universally available, Coca Cola at 50% coke / water.

At home in the tropics I mix it weaker, about 8-10% sugar - 25% to 1/3 coke / water.

I usually end up with some mix left at the end and have never had to down litres of water or energy drink at the finish of a race.

I sip as I race, with the tube continually in my mouth. It has become so natural that I sometimes forget to spit it out at the finish. I ended up with my juice tube still clamped in my teeth after I wiped out coming in at Toti in the 2006 Scottburgh to Brighton :).

But - as was pointed out earlier - it is very personal and combinations should be tried in practise to get the mix, quantity and favourite additive right. Don't just use the suppliment that the big boys use - they are probably being paid to use it - do your own research and stick with what works for you.

Also note - I am a C to D grade social paddler but have been around a while and have competed at very high level at other sports.

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