Can antidepressants influence the sweat rate?


Dr. Dr. med. Lutz Aderhold - temperature management for preparation and follow-up in long-distance running - © private

Humans belong to the group of homeothermal (uniformly warm) living beings which, with their temperature regulation system, keep the core body temperature as constant as possible at around 37ºC. The core of the body includes the trunk and the head. The body shell serves as a heat insulator and for heat exchange.

Body temperature is impaired internally (muscle work) and externally (climate) and thus has a significant impact on athletic performance. At rest and during low stress, the core body temperature is independent of the external temperature. In the case of higher stress intensity, there is a dependency on the ambient temperature from an ambient temperature of 15ºC (Jessen 2001). Endurance activities lasting several hours also lead to an increase in core body temperature (exercise-induced hyperthermia).

A core body temperature of 39 to 40ºC is common during strenuous exercise. An increase in core body temperature to over 40 degrees Celsius harbors health risks. What measures can be used to ensure effective temperature management before, during and after the sporting challenge?

About 75% of the energy developed by the body is given off as heat and only the smaller remainder is available for muscular work. In the case of high heat loads, up to 97% of the energy is given off as heat (de Marees 2003). Our body has various mechanisms at its disposal to give off heat. A distinction is made between heat conduction (conduction), heat transport (convection), heat radiation (radiation) and sweat evaporation (evaporation). The most effective way is the cooling effect through evaporation of sweat. With high humidity, evaporation is more difficult and the cooling effect is therefore less.

"Summer is the time when it is too hot to do what it was too cold to do in winter" (Mark Twain).

Endurance performance is negatively influenced by unfavorable climatic conditions (Zintl and Eisenhut 2004; Aderhold and Weigelt 2012). Of the climatic factors, the outside temperature has the greatest influence on mileage. In addition, high humidity can reduce performance. Other external influencing factors are air movement and radiation. Ideal temperatures for long-distance running are 10-15ºC with dry and windless conditions.

Endurance performance is severely affected by heat. The greater exposure is reflected in an increased heart rate and lactate formation. There is a greater rise in the core body temperature and the increased sweating leads to a faster loss of body fluid.

Our body can adapt to high outside temperatures (Huonker 2003), but it takes 5-10 days to do this. The production of sweat then starts earlier and the sweat becomes poorer in electrolytes, which promotes evaporation. At high outside temperatures, sweat quantities of 2 liters and more per hour can occur. The cardiovascular and endocrine systems also make adjustments with less increase in heart rate and body temperature. The plasma volume increases, the hematocrit drops and the blood becomes thinner.

These adaptations can only be made through training at higher temperatures (over 25ºC), but not when the body is at rest and in heat (sauna). Extensive training favors the transition more than intensive training. Those who have been trained have more effective thermoregulation thanks to increased blood circulation in the skin and an increased sweat rate. Small and light runners usually have a better heat tolerance than big and heavy runners. Seniors, women and children usually tolerate heat less. The heat tolerance of women is reduced by the hormonal rise in temperature in the second half of the mestruation cycle.

Women and men react differently to sweaty activities. Women only begin to sweat during high physical exertion; in men, the cooling system starts up more quickly. The female body has a lower proportion of water than the male, which means that women also develop a lack of water more quickly. The individually high variability in heat tolerance shows that genetic factors also play a role in addition to the influences mentioned.

A number of diseases reduce heat tolerance. These include infections, growth hormone deficiency, disorders of the thyroid function, reduction in the number of sweat glands and skin diseases. Alcohol reduces the heat tolerance. Alcohol has a catabolic (degrading) effect and inhibits the antidiuretic hormone (ADH), i.e. it has a diuretic effect, which can lead to water loss even before the competition. A number of drugs also have a negative effect on heat tolerance, e.g. by reducing the amount of sweat. These include diuretics, antihistamines, beta blockers, and antidepressants.

The optimal outside temperature is around 11 degrees Celsius, because our body then does not need any additional energy either to produce heat or to dissipate heat (sweating is an active process). As soon as the temperatures rise above 15ºC, a reduction in performance is to be expected. Every time the outside temperature rises by 1º C, a power decrease of 1-2% must be expected. Due to the increasing blood circulation in the skin for thermoregulation, the working muscles have less blood available, which leads to a decrease in performance.

In addition, there is increased carbohydrate burning in the heat, which causes earlier fatigue during longer endurance exercise. With increased humidity, the reduction in performance is correspondingly greater. High humidity increases the risk of heat-related complications because our body's cooling system does not work as well in humid conditions as it does in dry conditions.

In hot weather, the intensity and the scope of the training should be reduced. If possible, stressful units should be relocated to the cooler morning hours or late evening hours. For competitions under hot conditions, it is best to go to the start pre-cooled and start the first section at a reduced pace. Do not strive for your best performance, because this is definitely not possible under these conditions. You can protect your head with a white peaked cap.

Fluids with electrolytes and carbohydrates should be consumed at an early stage. Drinks that are too cold can lead to gastrointestinal complaints. You should drink enough fluids the day before. However, larger amounts of caffeinated drinks (coffee, black tea, cola drinks) and alcohol are bad, as they lead to fluid loss due to the diuretic effect. Also check the color of the urine. A dark color indicates a concentrated kidney excretion and thus a lack of fluids.

Adequate fluid intake (1 - 1.5 l / h) in small portions leads to a slower rise in the core body temperature and the risk of heat damage is reduced. Strongly chilled drinks have no advantages and often lead to stomach cramps. The fluid requirement is influenced by the intensity of exercise, outside temperature, humidity, solar radiation and the wind as well as body weight and sweat rate. After all, it makes a difference whether you weigh 50 or 90 kg.

Appropriate clothing should also be chosen according to the temperature. Wet sponges and water poured on the head can provide additional cooling. Heat-sensitive and non-acclimatized runners should better avoid a competition at high temperatures. Organizers must live up to their responsibility and also have the courage to abandon the competition in adverse weather conditions, as happened in 2007 at the marathons in Rotterdam and Chicago.

In the case of limited performance and fitness level, also in combination with inappropriate clothing and circulatory insufficiency, the heat production can lead to threatening heat stress. But healthy and productive people are also at risk from long-term physical peak performances such as long-distance running. In a warm and humid environment, even under resting conditions, there is a balance between heat production and possible heat emission. Under these conditions, even light physical exertion causes an increase in core body temperature.

The efficiency of the cardiovascular system is important for temperature regulation in order to transport a large volume of blood through the vascular system and to enable a high level of heat dissipation. Defective or inadequate mechanisms of heat dissipation result in a build-up of heat with increasing body core temperature. Circulatory diseases and fluid loss are the main contributors to heat damage. A particularly dangerous situation is when the air humidity is high, with greater heat exposure and physical exertion.

Risk factors for the occurrence of heat damage are: inadequate fitness, lack of heat adaptation, obesity, fluid deficit, cardiovascular disease, childhood and senior age, fever, the influence of alcohol, medication (diuretics, stimulants, high blood pressure drugs). According to Kleinmann (2009), early warning symptoms for heat damage are: headache, throbbing temples, dizziness, drowsiness, abdominal cramps, nausea, cold sweat.

Especially in the warm season, the right clothing, appropriate fluid intake and external cooling are of great importance for long-term stress.

While the application of cold is a tried and tested method in medical therapy, the application of cold to optimize performance in sport has only played a role for a relatively short time. Water, ice, air, gel and others are used as carriers. used.

Endurance performance is worse under warm conditions. When you run, a large part of your muscles are involved in movement. Effective heat regulation is therefore of particular importance when running. To optimize performance, it therefore makes sense to lower the body temperature. The longer the running route and the more heat-stressing the climatic conditions, the more important and effective precooling measures are. Studies have shown that moderate precooling can increase performance. This increases the heartbeat volume, the oxygen content in the blood is better utilized and the lactate levels are lower.

The higher the performance level, the lower the performance-enhancing effect of pre-cooling. Endurance performance seems to depend on the starting heart rate and the time it takes to reach the maximum heart rate, the starting body temperature and the ambient temperature. The higher the starting heart rate due to warming up, the lower the capacity for an increase in frequency under load up to the individual maximum heart rate with the consequence of a lower endurance performance. The critical core body temperature is only reached after a significantly longer period of exposure through pre-cooling (Ückert 2012). Studies that have shown that the training effect is greater under cool conditions are also interesting.

These results clearly speak in favor of a cold start. This applies even more to high outside temperatures. The body reacts with increased blood circulation and sweating in order to achieve cooling. As a result, blood is withdrawn from the working muscles, which leads to a reduction in performance. So, especially in hot weather, you should use all possibilities to go to the start pre-cooled (cooling gel, cooling vest, water, ice, wet T-shirt, wet hair) and use all possibilities for external cooling (water point, sponges, water shower, crash ice) on the way (Simultaneous cooling).

When pre-cooling with cold water, it should be noted that the high thermal conductivity of the water can lead to excessive cooling of the muscles. The cold application using a cooling vest has the advantage of being able to be used anywhere. A cold application in the form of precooling results in improvements in endurance of an average of 8%. The use of cold water leads to a 5% improvement in endurance performance. Whole-body air application at -110ºC is the most effective precooling method with an improvement of 10%, but its use will only be possible to a very limited extent. The cold vest application increases endurance performance by 8% (Ückert 2012). Cooling vests have proven themselves because of their ease of use when preparing for endurance competitions in hot and humid environments.

Nevertheless, you can see the extensive warm-up before the competition, which often runs like a ceremony, in many long-distance runners. You shouldn't try to force a cold start on a staunch fan of intensive warming up.If no increase in performance is to be expected, it probably has a psychological effect for him, with the feeling that he has done everything for a good performance. But you have to ask yourself what the intensive warm-up gymnastics with pre-gymnastics offered at many large city marathons is about. You can use up your energy even before the competition, because not only fat but also the limited glycogen, which is important for the competition, is consumed by running in slowly. Stretching is important in the training phase in order to prevent mobility restrictions.

Before a long distance competition, a few relaxing and carefully stretching dynamic exercises are sufficient. Too intensive a warm-up program can represent a fatigue-inducing preload during endurance exercise. On the other hand, precooling without previous activities in the form of warming up leads to performance improvements (Ückert 2012). The more unfavorable the climatic conditions (high temperature and humidity, solar radiation) are, the more so. Nevertheless, warming up is presented as a performance-enhancing and injury-prophylactic measure (Freiwald 1993; Schiffer 1997; de Marees 2003; Weineck 2010). The study situation on this question is inconsistent.

With a usual endurance run in training, you usually increase the pace and let it coast down at the end, but there can be no question of a regular run-in and run-out. It is different before tempo runs. In order to bring the muscles to operating temperature, to promote blood circulation (metabolism) and flexibility and thus to reduce the risk of injury, it is important to run in. But you don't have to overdo that either, 1-2 km is enough. After intense exertion, such as repetitive runs, you should also run out to loosen the muscles and promote the removal of acidic metabolic products from the muscles (sport-specific cool down).

In sports with abrupt or complicated movement sequences (sprint, jump, push, throw), on the other hand, a warm-up is necessary and also leads to better performance. In the case of cyclical and acyclical short-term requirements, a moderate preparation program has a positive effect on performance if it increases the muscle temperature slightly and there is no pre-exhaustion (Ückert 2012). The length of the break between warming up the muscles and the short-term requirement should not be longer than 5 minutes (Ückert 2012). However, it is known that static stretching directly before high-speed and maximum strength sports leads to a reduction in the performance of the muscles. In these sports, therefore, only a general warm-up, loosening and light dynamic stretching should be done.

Even with the medium-distance run (medium-time requirement), warm-up should be done to prepare for exercise by running-in and shorter climbing runs.This reduces the initial oxygen deficit and creates the conditions for increased oxygen uptake. Overall, one can say that the shorter the competition route, the more intense the warm-up program has to be. Warming up increases the blood flow to the muscles, accelerates the metabolism and the provision of energy, reduces the elastic and viscous resistance in the muscles and increases the speed of contraction. However, it is not necessary to increase the core body temperature in order to establish motivation. As a living being at the same temperature, humans are able to perform without restrictions regardless of the ambient temperature, which is referred to in specialist literature as "thermoregulatory freedom".

In the case of long-term demands, too intensive a warm-up has a negative effect on performance due to the stress on the muscle glycogen stores and the increased thermoregulatory stress.Pre-exhaustion and an increase in core body temperature should therefore be avoided.The aim is to warm the muscles slightly and increase oxygen uptake through mobilizing and activating preparation (Weineck 2010). Due to the complexity of the influencing parameters, however, there can be no general recommendation for the optimal duration and intensity. In addition, a muscular warm-up and a general precooling are not mutually exclusive.

As a rule of thumb for running in for well-trained runners up to the half marathon route, the following can apply:

- 10 minutes at 25 degrees Celsius
- 15 minutes at 20 degrees Celsius
- 20 minutes at 15 degrees Celsius
- 25 minutes at 10 degrees Celsius

Half the time is enough for runners with a best time of over 45 minutes for 10 km. Do not run in the sun in summer, but always look for shade. Short increases should be integrated into the running-in process.
A marathon or ultra runner can do without a break-in and use the first kilometers of the competition to "curl up" and warm up. A third of the times mentioned above are sufficient for these long stretches Runner also runs out, more likely to run out on the way to the shower. The lactate and other metabolic products are broken down more quickly by running out, but after very long competitions it is very difficult to continue, even if only slightly, after very long competitions due to the hours of muscular stress. to charge.

Leaking out after these efforts does not bring any great advantages, but rather a dehydration bath or an extensive shower bath and muscle care with a light massage. Only after the acidification of the muscle tissue has subsided and the loss of fluids, minerals and vitamins has been replenished, it is also possible to stretch slightly.

On a thermoregulatory basis, heat applications (hot water baths, hot air and steam baths, saunas) have so far been the focus of regenerative measures. After a marathon or a hard training session, lying in a bathtub with ice-cold water is the method of the marathon world record holder Paula Radcliffe to reduce tissue damage and to regenerate faster (Aderhold and Weigelt 2012). Stephane Franke also practiced this method during his active time. This type of regeneration (postcooling) certainly takes getting used to and is not for everyone. It is of course not a "must", but it is an interesting alternative. The experimental proof of the regenerative effect of cold water cooling is still low (Ückert 2012). Many runners, however, are familiar with the beneficial effects of a cold shower after a heat-breathing run in midsummer.

Of course, the time of year also plays a role. It's hard to imagine that after a hard training session in the cold season of the year, you can still lie in a tub of cold water. Perhaps one should then be less guided by considerations about performance physiological effects and rather follow one's body feeling (somatic intelligence). Especially in the cold season there is a great risk of catching a cold.

In 2009, the first cold chamber that is exclusively used for sport was put into operation in the federal performance center in Kienbaum. In Germany there are so far 70 cold chambers that are used in rheumatism and pain therapy.This leads to an improvement in mobility, a decongestion as well as a reduction in inflammation and pain. Short-term stays in the cold chamber at temperatures as low as -110ºC are intended to accelerate regeneration and improve performance, especially after intense exercise.

In this context, reducing muscle tone, increasing blood flow to muscles and reducing blood flow to the skin are important. The duration of stay in the cold chamber with a temperature of -110ºC is usually 3 minutes.

Cold or warm starts are therefore particularly a question of the type of sport and the conditions. In the case of endurance exercise under heat-stressing climatic conditions, pre-cooling has a clear preference over warming up.

The application of cold as a regenerative measure is an interesting starting point, especially in high-performance sport, which requires further research.


Dr. Dr. med. Lutz Aderhold 01/2012



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