Running Tips

by Jack Daniels, Ph.D.
National Team In Training Run Coach and Advisor

Jack Daniels, Ph.D., is a past winner of silver and bronze Olympic medals in the modern pentathlon.  He has coached 24 NCAA national individual champions, seven NCAA national team championships, 110 All Americans collegiate athletes, and four Olympic marathon medalists.  Daniels is a two-time recipient of the National Coach of the Year award, and is the author of Daniel's Running Formula, and more than 50 articles and research studies involving elite athletes.

Respect the Heat

Of all the adversities that marathoners (or any distance athletes, for that matter) face, heat is one of the worst. Although not necessarily so, excess heat often leads to dehydration, another major enemy of endurance athletes. Remember, it is possible to be adversely affected by the heat without becoming dehydrated, and you can also become dehydrated without getting over-heated.   These two conditions can affect the body independently.

Over-heating

An over-heated body is the result of inadequate cooling. And adequate body cooling depends on evaporation of water from the skin. It is not just wetting of the skin that counts, the fluid must evaporate (the process of which takes heat from the body's surface). You can easily prove to yourself how effective evaporation of fluid from the skin can be. On a warm day feel how warm your skin is at different locations. Often, the stomach is several degrees cooler than are some other areas (a bare middle can become a great site of cooling), and certainly, the skin is cooler than are the muscles, or the blood that helps carry the body's internal heat to the skin. So, the process is that when the body heats up, it starts to sweat and also starts to send more blood to the periphery (skin) where it is cooled by coming in contact with the relatively cooler skin. The cooler blood then circulates around the body, picking up heat from exercising muscles, which allows them to continue contracting more efficiently.

When the cooling mechanisms cannot keep up with heat buildup, the core temperature rises, and with even just a few degrees higher temperature, body functions start to suffer. We always hear about the need to "warm-up" before a race, and an increase of about one degree among the exercising muscles is desirable for improved performance. However, when the temperature rises more than just a degree or two, function is adversely affected.

Also, consider the effect heat has on providing oxygen to the exercising muscles. When blood flow increases to the skin (for improved cooling), this means less blood is being directed to the muscles. And with less blood going to the muscles, less oxygen gets to the muscles, which affects performance. The body is more interested in self-preservation than it is in ideal race performance, so it usually chooses to maintain a desirable temperature before it allows you to keep a particular pace that would interfere with cooling. It really boils down to either going at a pace slower than you want, or over-heating (which the body despises). Give in to your body under these circumstances - it knows best. Slow down in the heat, if you must be in the heat. 

Minimize the Effects of Hot Weather

You can acclimatize somewhat to hot weather, and exercising in the heat will speed up that process. However, it is not advisable to purposely exercise in the hottest part of the day, with the idea that facing greater heat will help acclimatization. Rather, seek out the cooler times of hot days - early morning and evening. Early mornings are the coolest part of the day, but are often more humid. Evenings are often less humid, but considerably warmer. It is really a matter of personal choice - higher humidity and lower temperature or higher temperature and lower humidity. Either is certainly better than exercising when the sun is up and radiation is adding its effect to that of high temperature and humidity.

Wear light, loose-fitting clothing. Experiment with different types of garments, caps (that can provide some shade, but also may produce a very hot head), socks, etc.

Dehydration

Dehydration is most often associated with the heat, but can occur even in cool weather. It is simply the process of losing fluid from the body. Again, the body knows what is best for it and when fluid levels get below a certain desired amount, the body protests by slowing down (in hopes of lowering the stress that is leading to the loss of fluid). If fluid levels get low enough, the body will just about stop functioning and you will pass out (lowering functions to a very low level in hopes of continuing on a little longer). Dehydration is a terrible way to go and must be avoided at all costs.

Naturally, the body can become dramatically dehydrated during certain illnesses - vomiting and diarrhea can quickly result in dehydration. Among healthy individuals, exercise is the most usual cause of becoming dehydrated, as a result of loss of fluid (via sweat) as you work to maintain desired temperature (explained above).

Just as in the case regarding many body functions, different people react differently to the same set of conditions - heat, for example. In a highly-controlled study that I performed a few years ago in Arizona, four groups of runners raced the same 25km road course on three consecutive weekends. The temperature varied from about 65 degree to 85 degrees for the three different runs. Each runner was weighed before and after each run and the exact amount of fluid that each drank was carefully monitored. Two of the subjects provided some interesting results. The two in question each weighed 165 pounds, each ran the 25,000 meters within one minute of the same time and each drank exactly 1,000ml of the same fluid. Both were also residents of the Phoenix area and well acclimatized to the local weather conditions. At the end of the run in question, one runner had lost a net of 1,500ml of water (3.3 pounds), the other weighed 8.8 pounds. Less, which means he lost 4,000ml more than he took in (5,000ml - 1,000ml = 4,000ml, or 8.8 pounds). What it boiled down to was that the first runner had a net water loss of 100m. per km run (100 X 25 = 2,500ml, minus the 1,000ml intake = 1,500ml or 1.5 liters or 3.3 pounds). The second runner lost 200ml per km run (200 X 25 - 5,000ml, minus 1,000ml intake = 4,000ml or 4.0 liters or 8.8 pounds).

Look at the difference in fluid loss between these two runners - 100ml vs. 200ml per km run. In a marathon (42km) this would mean fluid losses of 4.2 litters (5.64 pounds) and 8.4 liters (18.48 pounds), for the two runners respectively. These losses represent 3.4 percent and 11.2 percent of the runners' body weights. A loss of about 5 percent will negatively affect performance; more than 7 percent or 8 percent will not be tolerated - someone who loses 200ml per km will not make it to the end of a marathon. Actually, this 200ml per km net loss was the result of a 240ml per km gross fluid loss, coupled with a 40ml per km replacement (1,000ml over the course of 25km run).

Minimize the Effects of Fluid Loss

First, learn to drink during long runs or walks. Drink a lot with higher ambient temperatures. Figure your body can absorb about 1,000ml of fluid per hour, so learn to be able to take in that much, if necessary - just over a cup every 15 minutes. On the other hand, drinking more than about 1,000ml per hour may not be beneficial, if not more than that can be absorbed anyway. In fact, if you lose 240ml per km (10 liters) and drink 4 liters in a 4-hour marathon, the net loss is 6 liters (13.2 pounds - 8 percent of a 165-pound runner's body weight - not good).

My point is, some people will have real trouble completing a marathon, others very well may not. But, if it is hot enough, almost everyone will have trouble, and under some conditions, a run must be given up or the approach altered (walk/jog or just walk, which will lengthen the time taken to complete the distance, but which allows for greater fluid intake).

There is more to sweat than just plain water

As you sweat, you lose water and electrolytes, which is the reason specialized sport drinks have become popular - they provide you with water, electrolytes and energy, all three of which are good for an endurance athlete. Unfortunately, many distance athletes become serious about what they consume only during races, but the body can gradually become lacking in electrolytes if fluid intake during daily training sessions is water only. Get in the habit of consuming a reputable sport drink during practice sessions. This will get you used to that particular drink and will also keep your body supplied with needed nutrients. I often think that the trouble some endurance athletes have in competitions is brought on by inadequate attention to what they do during practice, and they go into a competitive effort already partially depleted in some important nutrients.

How To Calculate Your Reaction To Warm Weather

Follow these steps to prepare your own guide to determine how much you need to drink to avoid dehydration during a marathon.

1. Record your nude body weight prior to and following runs or walks of 40 to 60 minutes at the intensity you expect to perform in your marathon.

2. Record the temperature and humidity conditions for each of these test efforts.

3. If you drink during any of these runs or walks, record exactly how much you drink.

4. Generate a table that presents the rate at which your body loses fluid under different temperature conditions, and what the loss would be over the course of a full marathon.

5. Take the steps necessary to counteract the predicted loss, to stay under a 5-percent loss.

The table below indicates how much slower you might expect to complete a marathon under different temperature conditions (compared to a nice day of about 55 degrees and moderate humidity). Under the indicated temperatures and with abnormally high humidity, these adjustments may underestimate the effect. Walkers will face similar reductions in time, but they have more time to inject and absorb fluids so the problem should not be as great.