Rodents don't complain
Now based on human studies we already know what happens in the blood, when we exercise vigorously, CK rises, LDH rises, the serum electrolyte levels get messed up, etc.
|Figure 1: Changes in serum electrolyte levels (chloride, magnesium, calcium, phoporus, potassium, natrium) after the HIIT-esque workout w/ or w/out electrolyte supplementation (Osman. 2013)|
"[...] sodium ions decreased significantly (P 0.05) after exercised while after supplementation by Rehydran-n and Rehydran-n+ (Mg+Ca) citrate in group III and IV the level of sodium ion restored near to the control value. While potassium ions level increased significantly (P 0.05) in exercised group. The supplementation by Rehydran-n and Rehydran n+ (Mg+Ca) citrate in group III and IV not affected on the level of potassium and not return the value near to control value." (Osman. 2013)One thing that is at odds with previous research in humans, is the acute -18.6% drop in magnesium levels. Interestingly, this drop was blunted even when the rodents received the magnesium free NaCl + K electrolyte supplement. The immediate provision of magnesium in the Rehydran-n + Mg + Ca arm of the study, on the other hand, raised the Mg2+ levels by +18% and did thus also result in a transient electrolyte imbalance.
Rehydration prevents organ stress
As I already hinted at in the introduction, having slightly screwed electrolyte levels, as well as elevated amounts of creatine kinase, lactate dehydrogenase and urea in the blood are more or less negligible problems compared to any direct ill health effects the dehydration and the corresponding loss of electrolytes could have on the structural integrity and health of your heart and kidneys. Effects such as those Osman and Atya saw when they analyzed the organs of the animals who did not compensate for the electrolyte loss by the immediate provision of adequate amounts of salt after a workout:
Now, these results certainly sound more frightening than they actually are. Our bodies are (just like those of rodents, by the way) well equipped to handle the occasional cell / organ damage. And the heart is - believe it or not - "only" a muscle. It works slightly different, but can take at least as much beatings as our skeletal muscle tissue. Beatings of which the creatine kinase (CK) and lactate dehydrogenase (LDH) levels in the supplemented groups clearly show that they are are ameliorated by the the provision of electrolytes.
"Figure  microscopic sections of heart from exercised group [2b] showed leucocytic cells infiltration in cardiac myocytes. Whereas other sections from Rehydran-n treatment group [2c] revealed few focal intermuscular inflammatory cells infiltration. While Rehydran-n+ (Mg+Ca)citrate treatment group [2d] showing no histopathological changeslike those in control group [2a]." (Osman. 2013)
Figure 2: Sections of heart tissue after the workout (Osman. 2013)
Kidney sections of rat from control group revealed no histopathological changes. While in prolonged exercising group showing hyalinosis [=degeneration] of glomerular tufts. Moreover in Rehydran-n group vacuolations of epithelial lining renal tubules [=accumulation of waste that will be flushed out later on]. Rehydran n+ (Mg+Ca) citrate treatment group congestion of renal blood vessel was observed [=one reason the better stick to salt, only].
Now you may be asking yourselves, whether similar effects can be expected in human beings!? Well, the answer should be obvious: "Similar", yes. 100% identical, no. Maughn et al., for example, demonstrated similar (re-)hydration benefits in human subjects in the 1994 - it should be obvious thought that they refrained from cutting their subjects open and checking what happened to their hearts so that we can only speculate about the extend of cellular / structural damage and the corresponding compensatory effects in humans.
"The present results are in accordance with the exhausted exercised rats resulted in an increased growth in serum CPK activity. This increase, however was markedly reduced in the rats after administration of antioxidant. For instance, 16h exercise in rats caused a marked rise in activity levels of serum LDH. Increase in serum LDH activity is mainly due to release from heart and skeletal muscles into blood stream. [...] Different types of stressors cause an increase in activities of serum creatine phosphokinase and lactate dehydrogenase in humans and animals which is an indication of tissue damage." (Osman. 2013)
Figure 3: Creatine kinase (CPK), lactate dehydrogenase (LDH) and urea elevations (in %) after 5x4min treadmill runs with 2 min rest in-between (Osman. 2013)
|Table 1: Ingredients of a single sachet of Rehydran-N which was bought by the reaserchers at a local pharmacy - no sponsorship involved|
No glucose no effective rehydration
What is however necessary is the inclusion of the sugar or rather glucose in the rehydration formula, because the latter increases the efficacy of the formula significantly.
"The discovery that sodium transport and glucose transport are coupled in the small intestine so that glucose accelerates absorption of solute and water was potentially the most important medical advance this century."(Anonymous in Lancet. 1978)So don't skip on the miniscule amount of glucose - even if you are suffering from carbophobia and believe that any amount of carbohydrates is going to make you hold water. Trust me, if anything will make you hold water its their absence and the suboptimal uptake of the electrolytes in the absence of glucose that will make you look like a watery version of the Michelin Man.
|NaHCO3 loading increases performance & decrease LDH activity.|
And as far as the ostensibly beneficial decrease in LDH in the Rehydran-N + Mg + Ca group is concerned, this may well be a simple result of the alkalizing effect of magnesium and calcium ions. Assuming this is correct, similar benefits should occur in response to sodium bicarbonate, aka baking soda supplementation (learn more). The latter is after all part of the standard anti-rhabdomyolysis (=rapid breakdown of damaged skeletal muscle tissue) protocol where it does prevent both, further damage to the musculature and permanent damage to the kidneys (Vanholder. 2000).
- Anonymous. Water with sugar and salt. Lancet. 1978 Aug 5;2(8084):300-1.
- Maughan RJ, Owen JH, Shirreffs SM, Leiper JB. Post-exercise rehydration in man: effects of electrolyte addition to ingested fluids. Eur J. Appl. Physiol. Occup Physiol., 69: 209-15.
- Vanholder R, Sever MS, Erek E, Lameire N. Rhabdomyolysis. J Am Soc Nephrol. 2000 Aug;11(8):1553-61. Review.