Stomach problems in the heat

Below are some snip bits from dan empfield's “slowtwitch” site commenting on stomach probs in the heat during ironman

a lot of good points here on the temp of fluids in your stomach, but don’t get carried away with this because yes it is a factor in my opinion, but you also must get your intake of fluid , electrolytes and calories in as well as pace…

it's all a process of elimination and in extreme situations every one of these factors must be in the ball park to eliminate the tum problems

Read on for dans comments:-

Regards

jh

**

It has also been demonstrated––though just anecdotally––that the stomach will often "shut off" during long, hot-weather races. Those of us who've followed Hawaii Ironman racing for many years can all relate the same stories of pro racers who continued to eat and drink on schedule but whose stomachs just expanded, absorbing nothing.

What causes the stomach to decide not to cooperate? There are several possible culprits.

One might be tempted to blame the well-established shunting of blood under exertion to other, temporarily more important, areas of the body. Perhaps such athletes simply misjudge their pace and their heart rates rise to a level that inhibits gastric emptying.

Another culprit may be the osmotic potential in the stomach––too much solute, not enough solvent. Related to this might be the choice of food in the evening prior and morning before the race––the contents of which are still hanging around, inhibiting uptake.

All that noted, there are seasoned pros who will tell you that, in their experience, stomach temperature plays a big part.It is difficult to determine just why a person might stop absorbing, but while the causes might be unrelated to stomach contents' temperature, I cannot see a downside to cooling off the stomach.

What is the strategy for ensuring that what one drinks during competition is always cold?

Sports Medicine, Sept/Oct, 1987, Murray R., John Stuart Research Laboratories, Quaker Oats Company, Barrington, The effects of consuming carbohydrate-electrolyte beverages on gastric emptying and fluid absorption during and following exercise.

The author says, "Gastric emptying rate may be influenced by a variety of factors including, but not limited to, the caloric content, volume, osmolality, temperature, and pH of the ingested fluid, diurnal and interindividual variation, metabolic state (rest/exercise), and the ambient temperature.

Int J Sport Nutr Exerc Metab, December, 2000, Gastric emptying of cold beverages in humans: effect of transportable carbohydrates, Shi X, Bartoli W, Horn M, Murray R., Gatorade Sports Science Institute, Barrington, IL 60010, USA.

The authors say, "Within 5 minutes after ingestion, cold beverages are warmed to above 30 C in the stomach. This infers that the effect of cold solution temperature on gastric emptying rate is likely to be small and transitory."

Those two articles above seem to contradict each other and they do. They're by the same author, Dr. Bob Murray, who is a friend of mine (and who runs the Gatorade Sports Institute).

The former study is 13 years older, and supports earlier work by David Costill. The latter statement––made last year––is made in the light of further study (as explained to me by Dr. Murray). He is certainly one of the honchos in this field, and if he says fluid temperature is not a big issue in stomach emptying, one must pay attention to that.

Yet a honcho of similar (or perhaps greater) size in this field is Dr. Tim Noakes of South Africa, who writes, "Fluid consumption during exercise is enhanced by the ingestion of cold, sweet fluids." (Exerc Sport Sci Rev 1993, Fluid replacement during exercise. Noakes TD).

And here's from: 1996 American College of Sports Medicine position stand: Exercise and fluid replacement, (Med Sci Sports ExercJanuary, , Convertino VA, Armstrong LE, Coyle EF, Mack GW, Sawka MN, Senay LC Jr, Sherman WM.

"It is recommended that ingested fluids be cooler than ambient temperature [between 15 degrees and 22 degrees C (59 degrees and 72 degrees F.]"

Also interesting (but only tangentially germaine) is a variety of studies (of which Noakes is often the auther) on body mass and thermoregulation. The idea is to draw a line between light runners and fast running (perhaps suggesting that one important reason elite runners run so fast is that they don't generate so much heat).

Noakes says, "It is concluded that, compared to heavier runners, those with a lower body mass have a distinct thermal advantage when running in conditions in which heat-dissipation mechanisms are at their limit. Lighter runners produce and store less heat at the same running speed; hence they can run faster or further before reaching a limiting rectal temperature."I bring this up because one might assume that in a race like the Ironman––especially the Hawaiian Ironman––lighter is better.

Yet while elite runners average perhaps 125 pounds, Greg Welch is the only male athlete under 145 pounds ever to win the race (and perhaps 150 pounds, I'm not quite sure of the weight of Thomas Hellriegel or Luc Van Lierde), and "optimal" (based on results) seems to suggest that 155 - 160 pounds is best.

Most Ironman winners have fallen into that range. I bring this up simply to suggest that for whatever reason triathlon––and long, arduous triathlon in particular––seems to buck scientific intuitive thinking.

http://www.slowtwitch.com/