NFL, Gatorade and bananas

It must have been the bananas

Superbowl Sunday has come and gone, and New York Giants played the part of giant slayers by upsetting the New England Patriots, a team that steam-rolled the competition during the regular season, and even when against the ropes always seemed to be able to pull out a win from somewhere. Not in Superbowl XLII however, and Manning (the younger one, amazingly) led the Giants to two fourth quarter scores to win the title.

There are plenty of talking heads and pundits on the web, television, and in print to provide you all the detailed analysis of the game you need. Neither of us have tremendous insight into the game of football, and so we will leave the breakdown to the other guys. However, there is one story that emerged from the Superbowl that does fall within our "playbook", so we thought we'd spend some time on that instead!

New York coach Tom Coughlin does not read The Science of Sport

Back in October of 2007 we did a series on muscle cramps. In it we looked at the different theories of cramps, looked at the prevailing and perhaps dogmatic theory, presented a novel theory to explain cramps, and finally used the debate around cramps to demonstrate how science and knowledge evolve as new evidence comes to light.

The gist of this debate is that for years cramps have been attributed to dehydration and electrolyte imbalances and deficiencies. We suspect many of you who played youth sports were told, when playing in hot weather, to eat lots of bananas. The hypothesis there is that potassium depletion causes muscle cramps, and it is commonly accepted that bananas are a food stuff that is rich in potassium. So, quite simply, to stave off cramps one must just eat plenty of bananas - elementary school knowledge (or so we thought), and it turns out that even in the Superbowl, they adhere to that same dogma!

So in the big game, late in the first half, the crack Fox TV broadcast team crossed to their onfield reporter, who informed the watching nation that as a result of the high humidity in the stadium (the roof was closed), the Giants players were having problems with cramps, and that the coaches, sharp as they are, immediately had boxes of bananas brought to the sidelines. Sure enough, a couple of minutes later the cameras spotted it---a pile of bananas on the Giants sideline!

The first important (though tongue-in-cheek) point here is that Tom Coughlin and his coaching staff clearly do not subscribe to The Science of Sport. . .or perhaps they do, but they missed our series on muscle cramps? The second interesting point is in spite of all of the technology the NFL teams and coaches have at their disposal, all the high-tech strategies they employ, their wealth of human resources---19 coaches for the Giants and 14 for the Patriots---they rely on techniques that are entirely unproven and which no scientific evidence supports.

And then thirdly, and perhaps most thought provoking, is that Gatorade are the Official sports drink of the NFL, and copious amounts of it are available on the side of the field. Yet for some reason, the Giants were not told this - they chose the banana instead of the Gatorade! So calling for the banana backup is an indication that...the Gatorade wasn't working...? That wasn't an ad you saw in the Superbowl! Imagine the tagline..."Gatorade appears NOT to prevent cramps. Try bananas instead..."

No, science does not always have the answer

Admittedly, science does not always have the answers. Human performance even in individual events is incredibly complex. One only has to look at our previous post for some insight into will power and motivation to understand that many factors, perhaps too many and too complicated to measure, predict performance.

But it is still fascinating that at what many consider the pinnacle of professional sports---the NFL---the coaching staff turns to bananas during a game to alleviate muscle cramps. This is a sport in which assistant coaches, perched high above, take moving and still pictures, analyze them, and relay information about their opponents down to the coach on the sidelines. It is a sport that makes exstensive use of video analysis as players watch hours of game film of opposing teams to "get to know" them and their offensive and defensivee formations. They appear to be on the edge of technology. . . or are they? The bananas suggest otherwise, and give hope that maybe there is room for basic science.

In any case, it was a cracker of a game, and in our honest opinion the better team on the day won the match. Somehow the Patriots never really looked like the team that dismantled their opponents 18 games in a row. The Giants found a way to get to them, and came out ahead as a result of their efforts.

Be sure to come back later this week as we move on to Part III of our series on exercise in the cold.

Sports drinks, sweat and electrolytes

The actual data from the lab and the field

In the last post we introduced you to Randy, our imaginary 70 kg average male runner, and we created some potential scenarios regarding his fluid and sodium losses and replacement. The biggest take home message was to listen to your body and to drink to thirst, as this has been shown again and again in the field and the lab to keep people from drinking either too little or too much. We have received tons of feedback and discussion, and as we stated in the comments to that post we are pleased that so many of you are participating in the discussion, sharing your stories, and asking relevant and insightful questions.

Just as we will admit that field studies are not the perfect experiment but play an important role, it is the same with prediction equations. We can predict all we want from imaginary scenarios, and some times the equations are pretty accurate, but there is no substitute for the real thing, and many readers wanted to see more actual data and references that demonstrated why sodium ingestion is not necessary, and how both sports drinks and water will can cause a fall in sodium concentration. So while it is important to go through the exercise in the prior post, the next logical step is to look at the actual data.

Baker LB, Munce TA, Kenney WL. "Sex differences in voluntary fluid intake by older adults during exercise." Med Sci Sports Exerc. 2005 May;37(5):789-96

This study examined ad libitum fluid ingestion in older adults during intermittent exercise in the heat. Basically, they had continual access to water in one trial and Gatorade in another, and they had to cycle for 15 min and then rest for 15 min. The total time of each trial was two hours (four work/rest bouts) followed by an additional 30 min recovery period. A number of variables were measured, but we will focus on the sodium concentrations. One limitation of this study for our purposes here is that it was performed in older adults, and there is a well-documented effect of age on the thirst mechanism so that as you become older you become less sensitive to thirst. That is, your plasma osmolality rises higher before thirst kicks in.

According to the authors, their main findings were (and we quote):

1. When cool palatable fluids were readily available, active adults aged 54–70 yr drank enough to match sweating rates and maintain their body mass;
2. Their fluid intake behavior was repeatable;
   
3. CES [note: Gatorade] promoted greater voluntary fluid intake and restored PV losses faster than water;
   
4. There were sex differences in the fluid intake behavior of older active adults, with women drinking more water per kilogram of BM than men

As we tried to explain in many of our prior posts, the ingestion of any hypotonic fluid in excess of thirst will cause a fall in the sodium concentration. In this case "in excess" means drinking more than to your thirst. This occurs even though sports drinks contain some sodium because they still have much less when compared to the body fluids. Therefore the end result is a fall in sodium concentration. The data from this study show that these older adults, even when drinking to thirst, experience a fall in sodium concentration when ingesting water or Gatorade:


What we see is the time on the x-axis and the sodium concentration on the y-axis. The black dots represent the Gatorade trial, and the white (open) dots represent the water trial. All the subjects started with a sodium concentration of 142 mM per Liter, and in both trials the average concentration fell over time to approximately 139-140. There were no differences between the groups, and the symbols you see on the graph means that those values are significantly (statistically) different from the baseline value. So water and Gatorade ingestion produced a similar effect, and so Gatorade did not prevent a fall in sodium concentration in these subjects.

However one female subject ingested 2.8 L of water and 2.7 L of Gatorade in the respective trials. She gained weight in both instances, indicating an excessive fluid ingestion, and here are the data that support the conclusion that ingesting Gatorade will not prevent hyponatremia:


The problem is that the authors herald this as proof that ingesting Gatorade is much better than water:

"Furthermore, this woman’s data support the notion that a CES [Gatorade] is superior to water in limiting reductions in serum sodium during exercise-heat stress. During the CES trial, this female subject consumed 2.7 L and had a final serum sodium of 131 mmol per L . Therefore, although she consumed similar amounts of CES and water, serum sodium was maintained above that of symptomatic hyponatremia during the CES trial."

While the authors are entitled to their interpretation of the data, we disagree and conclude that both fluids are producing a steady fall in sodium concentration, and that the 131 value in the Gatorade trial is just marginally outside the symptomatic range (< style="font-weight: bold;">ingesting either water or Gatorade produced a nearly identical fall (~2-3 mmol) in the sodium concentration.

The take-home part: Sports drinks do not prevent hyponatremia

In fact Jonathan tried to apply this finding to a more "real world" situation in a letter to the British Journal of Sports Medicine. In that letter he argued that since the mean finishing time of women marathoners in America is five hours, and if the ingestion of Gatorade at rates similar to those found in the study is advocated by races, coaches, scientist, etc., then there would likely be many women (and probably men, too) presenting with hyponatremia. These data demonstrate that sports drinks do not prevent this condition as their ingestion in these subjects and at these rates causes a fall in sodium concentration.

Again one limitation to this study is it was done on older subjects, who are less sensitive to thirst, and what we might see in younger subjects would be a slight rise in sodium concentration when ingesting Gatorade and a maintenance of sodium concentration when ingesting water. The evidence for that statement comes from a 1992 study by Robert Cade, the inventor of Gatorade who incidentally died this week at the age of 80. In that study three groups of runners completed a marathon. One ingested Gatorade, another "half-Gatorade" (50% water, 50% Gatorade), and the third group water:

So in fact ingesting Gatorade to thirst in younger subjects results in a rise in sodium concentration, which is why you drink more---you never lower your osmolality below the thirst threshold and therefore are thirstier when ingesting a sports drink, whereas with water you maintain the osmolality right around the thirst threshold and drink and abstain as your thirst comes and goes. With sports drinks you instead just get thirstier, which seems kind of ironic since their slogan is "The thirst quencher!"

So those are some of the data that support our conclusions, and we hope that helps to clarify some of our interpretation(s) and conclusions. We will still post a "wrap-up" for the series on cramping in which we will try to briefly summarize the main points but more importantly leave you with some practical advice on this complex topic!

Muscle Cramps: Part II

The electrolyte depletion model of muscle cramps

In part one of this new series we tried to set the scene by providing some history in this area of muscle cramps. At times it might seem like we are a bit heavy on the historical side, but as we mentioned in one of our comments to Part I, understanding the historical record is crucial as often it helps us understand why we think what we do---and this affects one's interpretation of the science. In this post we will focus on the prevailing premise that dehydration and electrolyte disturbances cause muscle cramps.

The first important thing about this area of research is that Professor Martin Schwellnus is hands down the one researcher who has consistently moved this area forward. As a sports physician he has treated many a runner with cramps, and his curiosity and what he was seeing in the medical tents lead him to challenge this paradigm that dehydration and electrolyte problems cause cramps. What he found was that this model was based on not one shred of scientific data, and instead relied heavily on anecdotal evidence. Since 1997 he has published some of the only evidence available that has even attempted to determine what actually is causing the cramps and who is prone to this condition. The first paper he published in 1997 proposed a novel hypothesis for muscle cramps, but we will address that in Part III of this series.

The lab vs. the field

In our series on dehydration we discussed how the lab is not always translatable to the field, and vice versa, but that each has its own important role. Field studies are often cross sectional in nature, and although important we cannot assign direct cause and effect from them. However it is observations and findings from field studies that often lead to the very precise and mechanistic lab studies that are important in advancing our knowledge.

However one major obstacle in this area (cramping), is that no one has yet created a laboratory protocol in which we can reproduce muscle cramps in a controlled manner. Being able to do this is a crucial step in eventually identifying what causes them because it will allow us to make specific interventions to test what the effect is on cramps. So although we are still in the infancy of this area of research, the field studies are a very important starting point and have so far yielded important findings.

One study published in 1990 showed that there was no association between potassium levels and cramps. In that study cyclists rode for up to five hours. Some of the subjects did cramp, but their potassium levels were not uniformly high or low, thus showing no association between that variable and the cramps. However beyond that study (and one more that was presented at a conference but apparently not published) there is little real data out there to support or refute this hypothesis that dehydration or electrolyte disturbances cause cramps.

Study 1: Two Oceans Ultra Marathon

In a 2004 study published in the British Journal of Sports Medicine, Professor Schwellnus and his colleagues examined runners before and after the Two Oceans 56 km marathon in Cape Town. They measured quite a few variables, but since we are discussing changes in electrolytes and hydration, we will talk about those results. Remember that many people, both scientist and personal trainer alike, will profess that cramps are caused by dehydration and/or some disturbance in the electrolytes (sodium, potassium, magnesium, etc.) So the important finding from this 2004 study was that when the crampers were compared to the controls---who were matched for body mass and finishing time---the only differences were that the crampers had lower sodiums and higher magnesiums. The problem with this is that a lower sodium concentration suggests overhydration and not dehydration, and also if magnesium deficiency is meant to cause cramps then surely the crampers should have been lower here?

	Crampers (N = 21)	Controls (N = 22)
Sodium	139.8 ± 2.1	142.3 ± 2.1
Potassium	4.9 ± 0.6	4.7 ± 0.5
Magnesium	0.73 ± 0.1	0.67 ± 0.1
Osmolality	280 ± 6	284 ± 10

The relevance of this study is that if dehydration and electrolyte disturbances really play such a large role in cramps (as they are proposed to), then the crampers should have much higher electrolyte concentrations since they would be losing fluid and causing the concentrations to rise. Yet instead we see something entirely different, first that the crampers had lower sodium concentrations, and second that the crampers were not really different compared to the controls.

What is also noteworthy from this study was that the crampers had an average loss of body weight of 2.9%, compared to 3.6% for the non-cramping controls. In otherwords, the people who DID NOT cramp lost more weight than the people who did. It goes further than this, because Schwellnus et al were able to measure the change in plasma volume as well - a more direct measure for what is happening to fluids. Here, they found that the crampers actually gained a small amount of 0.2% during the race. The non-cramping control subjects LOST 0.7%. So the sum effect of this data is that it suggests very strongly that cramping is not associated with dehydration, or with lower serum electrolyte levels, which is what we have had drilled into us for many years!

The follow-up study from Iron Man - further evidence against serum electrolytes

The next year they published a study in Medicine and Science in Sports and Exercise, and instead of runners it was Ironman triathletes. According to what most of us hear day in and day out, it is these ultra-distance athletes who are exercising for 10+ hours at a time that must be most susceptible to dehydration and electrolyte deficiencies. After all, they are sweating for hours on end, and the numbers tell us that with so many liters of sweat lost then they must also be losing grams and grams of "essential electrolytes" such as sodium. Below you will see the basic data on these athletes, and the important finding here is that we see the crampers and controls were the same age and were similar in mass, had similar pre to post cahnges in mass, and also finished the Ironman in similar times:

	Crampers (N = 11)	Controls (N = 9)
Age (years)	33.5 ± 8.8	35.4 ± 8.1
Pre-race mass (kg)	79.1 ± 5.9	77.7 ± 6.4
Post race mass (kg)	76.3 ± 5.6	74.6 ± 6.5
Body mass loss (%)	3.4 ± 1.3	3.9 ± 2.0
Total race time (min)	660.8 ± 77.9	685.7 ± 48.5

So the two groups were essentially the same in that the crampers did not spend longer in the course or lose more weight (a crude measure of dehydration). Yet again the crampers and the controls looked remarkably similar on paper---except as in the 2004 study the crampers again had a statistically significant lower sodium concentration, and, we will repeat this, that suggests they were more hydrated compared to the controls. . .yet they were cramping. Here are the data from the electrolytes in the two groups:

	Crampers (N = 11)	Controls (N = 9)
Sodium	140 ± 2	143 ± 3
Potassium	4.4 ± 0.06	4.2 ± 0.5
Magnesium	0.9 ± 0.2	0.8 ± 0.1

Recall that what is most often put forward as the cause of cramps is either dehydration or some electrolyte disturbance, but the data from these two studies do not support that hypothesis. Although these are field studies and we cannot assign a cause and effect relationship, this available evidence suggests that these (normal) levels of dehydration do not appear to cause cramps. If these levels of dehydration did cause cramps and were largely responsible for cramps, then what we should see is a very high incidence of cramps in all of the race finishers with the same physiological characteristics as these subjects----or in other words, the vast majority of the race finishers.

Rejecting the old models

In science when the available evidence does not support the hypothesis, we must change the model. Based on this available evidence we see clearly that dehydration and electrolyte levels are not associated with muscle cramping during or after exercise, and therefore we must adopt a different model to explain what is causing them. We cannot just ignore the data we have shown here and keep on telling people that it is dehydration and electrolytes when new evidence suggests otherwise.

So in Part III of this short series we will lay out the newest hypothesis that tries to explain the "why" and the "how" of muscle cramps. It is novel and, as you might have guessed already, has nothing to do with electrolytes and dehydration! So come back and join us for Part III of this series, and then join us for the comments and debate!

See also:
Part I: Theories and fallacies of muscle cramps

References:
Brouns F et al., "Ammonia accumulation during highly intensive long-lasting cycling: individual observations." International Journal of Sports Medicine. 1990 May;11 Suppl 2:S78-84.

Schwellnus MP et al., "Aetiology of skeletal muscle 'cramps' during exercise: a novel hypothesis." Journal of Sports Sciences. 1997 Jun;15(3):277-85.

Schwellnus MP et al., "Serum electrolyte concentrations and hydration status are not associated with exercise associated muscle cramping (EAMC) in distance runners." British Journal of Sports Medicine. 2004 Aug;38(4):488-92.

Schwellnus MP. "Muscle cramping in the marathon : aetiology and risk factors." Sports Medicine. 2007;37(4-5):364-7

Sulzer NU et al., "Serum electrolytes in Ironman triathletes with exercise-associated muscle cramping." Medicine and Science in Sports and Exercise. 2005 Jul;37(7):1081-5.