Bodily Fluids

Part I

Lonnie Lowery

Now that I’ve got your attention with the title, let’s try to raise our thinking from the lower centers of bodily function and get more cerebral, shall we? (Admittedly there are those, like a certain editor around here, who can weave both into an entertaining editorial but we’ll try to stay on track.) Let’s go beyond the obvious as we did in the recent breakfast article here on the site, “Why Breakfast?”. Today let’s talk “advanced hydration”. We must understand why seemingly obvious recommendations are made – then we must go a step further so we can tweak such things as circumstances dictate. I’ve always hated blind obedience and I bet you do to. As warrior nerds and T-men we have no time for neon-colored sweat or corporate gimmicks. We want to actually understand because there’s a clear link between knowledge and success. Summer is upon us and there are some things that you should know beyond what sports drink commercials try to spoon-feed you. So let’s fill our tanks – both physical and mental.

Training Without Draining

I was stunned when I first learned where water losses came from. As we lose weight during a workout and our clothes grow heavy with sweat, that water doesn’t just appear. A significant portion used to be blood (plasma) volume! Plasma, or similarly serumcomprises a bit over half of whole blood. Here’s a picture of what healthy amber-colored plasma looks like and a graph of how it goes away under different conditions…

--Insert plasma loss graph w/ plasma tube pic--

Data in graph from references below.

Whether it’s exercise (which seriously affects plasma volume), heat (which affects it even more), or even a squat workout that induces a shift of fluids into the interstitial space (a “pump”), we sacrifice a little bit of our overall blood volume as we exercise. If you’re anything like me, you’ve actually suffered the effects of all three of these stressors at once! Ugh! This is a big deal considering that we can only lose as estimated 1% of body weight from dehydration before side effects occur like performance decrements, weakness, fatigue, and eventually heat illness (especially as we go beyond 5% dehydration).(23) Once heat illness does hit (heat exhaustion and god forbid heat stroke) it can be three months before heat tolerance resumes.(23) Some individuals can irreversibly lose heat tolerance as thermoregulatory centers of the brain become permanently damaged. So dehydration in the heat is no joke.

Perhaps even more disturbing, acute body mass loss from ramped-up sweating and panting can be doubly dangerous for us men. According to some late 90s data from a researcher named White and his colleagues, men’s losses can double that of women!(22) This research was done both indoors and outdoors during steady state running so it’s fairly representative of what many of us endure.

We need to appreciate that the heart muscle is pulling double duty as we exercise in the heat, perfusing both working muscles and the skin (for cooling). As exercise continues, heart rate rises beyond the needs of the muscular workload, a phenomenon called cardiac drift. Without sufficient plasma volume to push around, the stroke volume of the heart falls-off (stroke volume x heart rate = cardiac output). This effect actually reduces peak oxygen usage, called VO2-peak or even aerobic capacity.(7) Even if you’re not an endurance athlete, general conditioning still requires some level of aerobic capacity.

And on the skin perfusion side of things, it’s important to realize that sweating is our number one way to cool off. A liter of sweat, about the amount evaporating over 60-90 minutes of exercise, carries away an amazing 580 kcal of heat! Of course, this doesn’t mean that sweating in a sauna can replace dieting, as heat can be injected from the environment; it doesn’t all come from muscular work and burning of stored fat. At any rate, sweating is good and the more fit you are, the better you are at it!

Muscle Jerky

How does flat, shrunken, dry and cooked sound to you? These adjectives are a desirable description of turkey or beef jerky – not of your biceps or quads! And such descriptions are less of an exaggeration than you might realize. First, cells do dehydrate and shrink. As a generality, this causes catabolism (breakdown) within the cell, as has been described by the likes of Dieter Haussinger (whose work has admittedly been exaggerated by unscrupulous supplement companies). You might think of cell shrinkage and catabolism as a kind of anti-insulin effect. Instead of swelling muscle glycogen concentrations and protein synthesis making you bigger, the opposite type of effect is making you smaller. Sure, about two-thirds of our bodies’ water is within our cells (the “intracellular compartment”) but it’s not impervious to loss. And from a larger tissue-level viewpoint, blood flow (perfusion) to the muscle suffers when you dehydrate. Forgetting about the water issue for a moment, low perfusion is not conducive to nutrient delivery either (and again looks like the opposite of how insulin helps us grow).

Second, there is at least some connection between lifting, hot environments, muscle temperature and heat shock proteins.(4) Heat shock proteins, or HSPs are a protective cellular response to stress, and were first described in relation to - you guessed it – heat. It’s not news that our muscle proteins can and do denature in response to various stressors, not unlike the way an egg protein turns white in a frying pan. Yikes!Dehydration hurts our ability to cool off and muscle contractions add to the stress by raising local temperatures. Again, flat, shrunken, dry and cooked sounds like a meat product Randy “Macho Man” Savage would hock in a commercial (Oooh yeah, brother!);no bodybuilder wants to shrink up and bring new meaning to the term “Slim Jim”. Keep you muscles full with pre-, mid-, and post-workout drinks.

Also, there are fairly new data suggesting that eccentric exercise (lengthening contractions or “negatives”) leave even more muscle trauma when done in the presence of dehydration and hyperthermia... that is, at least from a muscle soreness perspective.(4) Now, negatives are great for hypertrophy but they are also brutal so do not dehydrate when lifting in the heat! All bodybuilding exercise involves negatives on some level so your recovery time frames could become even longer. If you’re interested in muscle structural damage beyond simple soreness, go check out Muscle Masochism here on the site. The take home message here yet again is: Don’t be a “jerk”. Take along a cold sports drink during hot summer training!

Okay, that’s enough to fill-up on until next time. As described in the introduction of this article, understanding why we make our nutrition/ hydration choices is a big deal. It’s not enough to know how to do something! When you see the underlying physiology it becomes possible to tailor your own plans and stick to them. Hydration is so fundamental to performance and growth that I’ll discuss just how high it ranks among all the things you can do for your body in the second half of this topic. Part II will deal with hormonal consequences of exercising without a bottle of fluid in-hand, broadly-accepted hydration guidelines and even hydration supplements that “work”. We may even get into ways to assess your own dehydration status and sweat rate! Stay tuned…

Dr. Lonnie Lowery is an exercise physiologist and licensed nutrition professional, working – and working out - with collegiate athletes in hot environments. He can be reached at or via the Staley Coaching Club ().

References and Further Reading

  1. AmericanCollege of Sports Medicine. Exercise and fluid replacement. Med. Sci. Sports Exerc.1996; 28(1): i-vii. June 28, 2006.
  2. Armstrong, L., et al. Urinary indices during dehydration, exercise, and rehydration.Int J Sport Nutr. 1998 Dec;8(4):345-55.
  3. Cleary, M., et al. Dehydration and symptoms of delayed-onset muscle soreness in normothermic men.J Athl Train. 2006 Jan-Mar;41(1):36-45.
  4. Cleary, M., et al. Dehydration and symptoms of delayed-onset muscle soreness in hyperthermic males. J Athl Train. 2005 Oct–Dec; 40(4): 288–297.
  5. Cochrane, D. and Sleivert, G. Do changing patterns of heat and humidity influence thermoregulation and endurance performance?J Sci Med Sport. 1999 Dec;2(4):322-32.
  6. Deuster, P., et al. Hormonal responses to ingesting water or a carbohydrate beverage during a 2 h run. Med Sci Sports Exerc. Jan;24(1):72-9,1992.
  7. Ganio, M., et al. Fluid ingestion attenuates the decline in VO2peak associated with cardiovascular drift.Med Sci Sports Exerc. 2006 May;38(5):901-9.
  8. Goulet, E. et al. Effect of glycerol-induced hyperhydration on thermoregulatory and cardiovascular functions and endurance performance during prolonged cycling in a 25 degrees C environment.Appl Physiol Nutr Metab. 2006 Apr;31(2):101-9.
  9. Graham, T. Caffeine and exercise: metabolism, endurance and performance.Sports Med 2001;31(11):785-807.
  10. Jimenez, C., et al. Plasma volume changes during and after acute variations of body hydration level in humans.Eur J Appl Physiol Occup Physiol. 1999 Jun;80(1):1-8.
  11. Jimenez, C., et al. Plasma compartment filling after exercise or heat exposure.Med Sci Sports Exerc. 2002 Oct;34(10):1624-31.
  12. Lowery, L. Assessing Post-Workout Recovery:An Issue of Timing. Sports Cardiovasc Well Nutr 19th Annual Symposium. Chicago, IL: 2003.
  13. Lowery, L. Physical Recovery & Improvement: It Happens Outside of Practice!Ohio Dept. Education Broadcast Seminar. Akron, OH: 2006.
  14. Melin, B., et al. Effects of hydration state on hormonal and renal responses during moderate exercise in the heat.Eur J Appl Physiol Occup Physiol. 1997; 76(4): 320-7.
  15. Nieman D. Influence of mode and carbohydrate on the cytokine response to heavy exertion. Med Sci Sports Exerc May;30(5):671-678, 1998
  16. Nieman, D. and Bishop, N. Nutritional strategies to counter stress to the immune system in athletes, with special reference to football.J Sports Sci. 2006 Jul;24(7):763-72.
  17. Neumayr, G., et al. Short-term effects of prolonged strenuous endurance exercise on the level of haematocrit in amateur cyclists. Int J Sports Med. 2002 Apr;23(3):158-61.
  18. Ploutz-Snyder, L., et al. Resistance exercise-induced fluid shifts: change in active muscle size and plasma volume.Am J Physiol. 1995 Sep;269(3 Pt 2):R536-43.
  19. Robergs, R. and Griffin, S. Glycerol. Biochemistry, pharmacokinetics and clinical and practical applications.Sports Med. 1998 Sep;26(3):145-67.
  20. Wagner, D. Hyperhydrating with glycerol: implications for athletic performance.J Am Diet Assoc. 1999 Feb;99(2):207-12.
  21. Watson, G., et al. Creatine use and exercise heat tolerance in dehydrated men.J Athl Train. 2006 Jan-Mar;41(1):18-29.
  22. White, J., et al. Fluid replacement needs of well-trained male and female athletes during indoor and outdoor steady state running.J Sci Med Sport. 1998 Sep;1(3):131-42.
  23. Williams, M. Nutrition for Health, Fitness and Sport. Boston, MA: McGraw-Hill Higher Education.