15th 4Days Marches Research concerns the heart, hydration and heat Researchers follow hundreds participants of the Nijmegen 4Days Marches

The heart, hydration and body temperature are what this year's 4Days Marches Research of Radboud university medical center is all about. With this, the researchers in the 15th edition return to where the study began in 2007. Since that year, they have followed hundreds of participants every year during the 4Days Marches. Professor of Physiology Maria Hopman is head of research. 

Black or white clothing?

It is a frequently asked question during heat waves: in hot weather, should you wear black or white clothing? What do people feel most comfortable in? Science doesn’t give the answer. Yet. Maria Hopman: ‘There are different theories about the color of clothing. Black clothes absorb heat and white clothes reflect it. But white clothing allows more UV radiation through, which may cause the body temperature to rise. We are looking for the answer.’

The participants in this study will wear alternating white and black clothing during the march days. The researchers then look at the effects on the body, measuring skin and body temperature, among other things. From previous 4Days Marches research, we know that during a walking day, body temperature rises by about 1 degree Celsius. The study should show the importance of clothing plays in this. 

Hydration

Dehydration is a major problem among walkers during the 4Days Marches. During the first, also toughest, day about 20 percent of the participants dehydrate. That's about 10,000 people. The body is then not yet used to the physical effort. Drinking enough is very important, and if it’s hot outside, it is even more important. How much more varies from person to person. One person can get by with an extra liter, while other walkers need as much as five liters a day. 

This year, researchers are focusing on walkers who are taking water pills, diuretics. Doctors routinely prescribe this medication for high blood pressure. Hopman and her team want to know whether people should lower the dose during a heat wave or exercise in the heat. Hopman: ‘During hot conditions, participants sweat more. As a result, they also lose more fluid. Perhaps a lower dose is better then, to prevent dehydration.’

Troponin

After prolonged exercise there is an increase in a certain signal substance in the blood: troponin. This protein is considered an indicator of a heart attack. For a long time it was thought that the harmful effects of exercise were not so bad. But previous 4Days Marches research showed that walkers with high levels of troponin after exercise were more likely to develop cardiovascular disease or die over the course of the study than walkers with low levels of troponin after exercise. Thus, walkers with elevated troponin levels may have a worse prognosis. 

The important question is whether that elevation signals an underlying heart disease or whether it is a physiological response to exertion. So in this follow-up study, the researchers aim to determine the troponin levels of walkers, in order to gauge from them what normal and abnormal levels are. The researchers are also following participants in various cycling and running events. 

Fifteen years of 4Days Marches Research

Led by Maria Hopman, a team of scientists from Radboud university medical center has been conducting various studies during the Nijmegen 4Days Marches every year since 2007. She started this after the cancellation of the 2006 edition, due to extremely high temperatures. To date, the 4Days Marches Research has resulted in no fewer than 56 scientific publications. And we’re still counting. Every year, more than 12,000 people participate in questionnaire surveys. Hundreds of participants report daily during the 4Days Marches at the research center, right next to the start and finish location. Here are some of the results: 

• During walking, body temperature rises by 1 degree Celsius. 
• 20 percent of the walkers drink too little during a walking day.
• Heart damage occurs after a walking day, this seems to be predictive of cardiovascular disease.
• The first walking day is physically the toughest.
• Higher walking speed is related to a better score on a cognition test.
• Type 2 diabetes patients need less medication the more they train for the 4Days Marches.
• Both extra collagen and extra exercise reduce knee pain in preparation for the 4Days Marches.
• Walkers around 80 years old are estimated to be 8.2 years younger.
• 4Days Marches participants of all ages have adequate Vitamin D in the summer.
• 30-40 minutes walking a day contributes to lower risk of cardiovascular disease.
• Extra protein for the 60+ walker improves muscle mass.
• Statin use walkers don’t have more muscle problems and muscle damage after walking than non-statin using walkers.
• The older the walker, the poorer the thermoregulation.
• Eating extra vegetables lowers blood pressure in walkers with high blood pressure.
• Walkers have to get used to insect protein, but there is evidence that it leads to an increase in muscle mass.

Research leader and professor of Physiology Maria Hopman.

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