Aug 30

Hot Weather – Humidity and Athletic Performance

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We all enjoy it – sun and lovely summer weather after miserable winter months! However, it is no longer just warm but temperatures are at sweltering levels. This plays havoc, especially in high humidity, and creates not only strain on the body, but also on circulation, skin, and the heart, no matter the age. 

Athletes have to take special precautions when exercising, training, and/or competing outdoors… and for that matter indoors due to potential increased humidity, dampness (pools), and other factors. Often, high school varsity, club soccer, and football teams hold regular pre-season workouts in the middle of the day (August), which has led to several deaths over the past years. Insane! 

Hydrating enough and properly is critical. The body is made up of 2/3 water inside and outside the cells and in the blood circulation. If the body dispenses more water than is taken in proper cell function is affected. Blood thickens and circulation deteriorates, blood pressure falls, and the brain does not receive enough oxygen. The most common result is fatigue/tiredness. 

According to several sources, consume 1.5-2 liter fluid (2.11 US cups). Some experts state that 2 liters are optimal although one has to consider the heat (degrees) and the amount of sweating.

1. Avoiding Heat Stroke

  • Signs of heatstroke: Red and hot head, body cool, head or neck pain, potential nausea
  • Move into the shade
  • Large hat or cap with a broad brim 
  • Airy clothes
  • Sunglasses – sunlight can impede vision

2. Balancing Sweating


Water with Herbs

(Apple Spritzer)
  • The higher the temperature – the more we sweat – the more fluid is lost – the more we have to drink (hydrate) – otherwise, headaches and issues with circulation occur
  • Suggestions: adding some herbs to water like rosemary and sage – they are said to slow down sweat production
  • Add several fresh mint leaves to a water bottle – mint treats dizziness, nausea, and headaches
  • Intake more citrus fruits to strengthen circulation
  • ‘Apfelschorle’ [Apple Spritzer] is a popular soft drink in Switzerland, Germany, and Austria – carbonated mineral water and apple juice
  • A broader category ‘Fruitschorle’ [Fruit Spritzer] – fruit juice mixed with carbonated water – contains fewer calories, and is less sweet than pure apple juice – also nearly isotonic, and popular in the summer among athletes in Europe – commercially available, generally contains between 55% and 60% juice

3. Sunscreen Protection and Plenty of Fruit and Veggies


Maracuja Fruit  

Variety of Fruits & Vegetables


  • Self-protection of light-skin coloured people only lasts about 10 minutes – therefore apply sun protection cream early – an adult needs about 4 fully filled tablespoons of cream for the entire body
  • The natural protection of the skin can also be aided from within with beta-carotene by eating carrots, maracuja fruit, mango, and apricots (some examples)  

4. Eating Vitamin-rich Food

  • Select vitamin-rich food to balance vitamin loss through sweating while working out, training and/or competing 
  • Magnesium is frequently lost through sweating, resulting in leg or calf cramping – loss of minerals like copper and zinc may occur

Exercising-Training-Competing in Hot Weather

Adapted from “Don’t sweat the weather – Adapt to it” by Jill Barker (2019, July 29) – with modification by M. Schloder

Athletes exercising, training, and/or competing in hot weather have to be extremely aware and conscious about ‘sweating it out’ during high-noon temperatures, which means being careful about- and not ignoring warnings between high outside temperature and humidity, and the body’s internal temperature (normal 37-degrees). The closer these two are to each other, the more difficult it is for the body to cool itself. When body core temperature rises, athletic performance declines, and the first signs of heat exhaustion appear. ‘Toughen it out’ during a heatwave has led to many hospital visits because of under-estimation the effects in 30 ̊C + weather. 

The struggle to keep cool is most acutely felt by endurance athletes because body heat accumulates over time. However, the most affected may not necessarily be elite athletes because they have most likely learned to manage hot conditions. It is the average exerciser or athlete such as runners, cyclists, or team sport athletes (football, soccer, etc.) who are most likely at risk of heat exhaustion. The body’s internal temperature starts to rise in as little as 15 minutes during hot weather workout or training, and especially if the intensity is high. While the challenge to exercise and train in temperatures near 30 ̊C has been the focus, researchers have also found that performance impairment can start as low as 21 ̊C (69.8 ̊F).

In cooler temperatures, the body functions well at dissipating the heat generated by exercise or training through the evaporation of sweat. However, in high humidity, evaporation does not occur, and heat loss is hindered. Sweat is induced when the body sends internal heat (blood) toward the surface of the skin to cool. As core temperatures rise, more and more blood used to supply working muscles is now diverted toward the outermost skin layers. Due to reduced oxygenated blood, muscles start to fatigue. In addition, the effect of less internal blood flow affects the heart, which has to pump harder to keep circulation flowing. These physiological changes obviously affect performance.

When sweat increases, fluid loss increases as well. This causes sweat production to taper off resulting in the rise of body temperature. Drinking enough water to replace lost fluids is highly recommended but it is not easy to do so, especially if athletes are ‘heavy’ sweaters. Moreover, athletes trying to increase their water intake frequently complain of an upset stomach, or water ‘bouncing’ around in their stomach, especially runners, who seem to experience that feeling with every foot contact on the ground. 

Heat Management Strategies

  • Keep workouts short or shorter 
  • Keep intensity moderate to reduce the accumulation of body heat
  • If possible – schedule early morning- or end of the day workouts when the heat is less intense
  • Maintain workout pattern for 5-10 days to get more efficient at managing the heat
  • As acclimatization improves the body’s cooling system; the body’s cooling mechanisms start working earlier in the workout (sweating sooner and in greater quantities), extending the time it takes for internal temperatures to build and heat-related fatigue to set in
  • When heading for workout or training, top off fluid to reduce the overall volume of water needed while exercising or training
  • Bring enough water/fluids or plan a route to access public water fountains, local corner stores, sprinklers, or hoses (if running or cycling) for a quick top-up on fluids
  • Overheated skin adds to discomfort – pouring water over the head creates a more comfortable feeling 
  • Maybe consider transferring exercise components to a pool (aqua exercise, kickboard swimming)

 Exercising/Training in Heat – Potential Mineral and Vitamin Loss

Adapted from “The Effect of Exercise and Heat on Mineral Metabolism and Requirements” by Carl L. Keen, 1993 – with modification by M. Schloder

Heat-exposed workout or training can lead to a large amount of sweat and thereby a loss of water-soluble vitamins and minerals, affects the level of micronutrients required and an increase of vitamins and minerals. In addition to water loss, the body also casts off electrolytes such as potassium, sodium, and minerals in the blood, urine, and bodily fluids that contain an electric charge.

There has been increasing interest in the idea that individuals engaged in strenuous exercise may have an increased need for several essential minerals. The idea resulted in a widespread perception that mineral supplements may be advantageous. This concept is based on two basic views: (a) individuals engaged in strenuous exercise have a higher requirement for some minerals compared to sedentary ones due to increased rates of urinary and sweat losses of select minerals, and (b) the perceived inadequate intake of some minerals results in a lowering of endurance capacity and ultimately leading to the development of some disease states. Although a significant number of athletes, coaches, and professionals in sports medicine believe in the beneficial effects of mineral supplements, few data support a positive effect of dietary mineral supplementation on athletic performance. Nevertheless, strenuous exercise does influence the metabolism of several minerals, and the number of minerals lost via sweat (due to either intense heat or exercise) can be significant.


Prolonged strenuous exertion can result in the reduction of plasma magnesium concentration, attributed in part to an increased rate of magnesium loss via sweat. Given that marginal magnesium deficiency can present a significant health risk to an athlete, more studies are needed to define the functional consequences of exercise-and heat-induced reductions in plasma magnesium concentrations.

Iodine – Chromium – Selenium

Effects of exercise and heat on Iodine, Chromium, and Selenium metabolism have been studied since 1966 through the 1980s, mostly in 38.5 temperatures during the day and 33.1 at night. According to research findings, sweat-associated iodine loss can be significant. Like iodine, limited literature on the influence of exercise and heat on selenium metabolism exists, although it has been suggested that athletes may benefit from selenium supplements due to its role in glutathione peroxidase synthesis. There is, however, no compelling evidence that selenium supplementation is necessary for individuals engaged in endurance activities (Lane, 1989; Lang, Gohil, Packer & Burk, 1987).

Chromium deficiency per se has not been accepted as a health problem in endurance athletes. However, it seems, given the above findings, chromium status of athletes engaged in strenuous activity for prolonged periods of time should be monitored, particularly if the activity is performed in a hot environment where chromium losses in sweat are predicted to be high. 


It is well recognized that iron-deficiency anemia can be associated with diminished performance in maximal and submaximal physical exercise (Andersen & Barkve, 1970; McDonald & Keen, 1988). However, there is considerable controversy about the extent to which exercise contributes to the development of iron deficiency. There is a common perception that athletes as a group tend to have a high incidence of anemia compared to the sedentary populations, but surveys of elite athletes have typically not supported this idea (Brotherhood, Brozovic, & Pugh, 1975; de Wijn, de Jongste, Mosterd, & Willebrand, 1971; Stewart, Steel, Toyme, & Stewart, 1972). Thus, overt iron-deficiency anemia does not appear to be a common complication of chronic intense exercise. 


Findings show that there are short-term effects of exercise on zinc metabolism. However, immediate physiological consequences are not known. Given frequent observation of exercise-induced hypozincemia, and the potentially high amounts of the element that can be lost via sweat, there may be a need for zinc supplementation in situations where prolonged exposure to exercise and heat is anticipated. Nevertheless, caution has to be used when advocating zinc supplements because this element at high levels can interfere with copper absorption due to the similar physiochemical properties of zinc and copper (Keen & Hackman, 1986). Chronic (more than 6 weeks) consumption of zinc supplements in excess of 50 mg per day has been linked to the induction of copper deficiency in humans (Fischer, Giroux, & L’Abbe, 1984; Fosmire, 1990; Prasad, Brewer, Shoomaker, & Rabbani, 1978; Samman & Roberts, 1988). 


Prolonged strenuous exercise can result in marked changes in chromium, copper, iron, magnesium, and zinc metabolism. Evidence of these changes can persist for several days after the exercise. Some of the observed changes in plasma mineral concentration may be attributed in part to an acute-phase response, which occurs as a result of tissue trauma or stress. Reductions in plasma mineral concentrations may also reflect in part an increased loss of these minerals from the body via urine and sweat. The increased rate of mineral loss that occurs in sweat with exercise is amplified by the simultaneous exposure to hot temperatures.

Hydration, Sodium, Potassium, and Exercise: What You Need to Know

The following is additional information on the topic. 

Adapted from “Hydration, Sodium, Potassium, and Exercise” by Perrin Braun (2018, January 4) – with modification by M. Schloder

Our bodies are mostly comprised of fluid, which means every cell, tissue, and organ needs enough water to function. While plain H20 is the most important part of hydration, athletes also need electrolytes like potassium and sodium to perform at their best. In addition to water, the body loses electrolytes through sweat. Chloride, potassium, and sodium are major electrolytes, minerals in the blood, urine, and bodily fluids that contain an electric charge. The body’s cells use electrolytes to carry electrical impulses that help the cells communicate with each other and provide the ability to taste, see, smell, touch, and hear.

Do Athletes Have Special Hydration Requirements?

How much water should athletes drink? This varies depending on the volume and intensity of the workout/exercise, and how much sweat is lost. However, there are ways to gauge whether the athlete has hydrated enough. One way is to monitor urine. Light-colored urine means probably adequately hydrated whereas dark, concentrated urine can indicate not consuming enough water. Athletes should weigh in before and after workouts – weight loss that occurs directly after a workout is likely to be caused by a fluid reduction.

During the first hour of exercise, athletes should rehydrate with water. Basic guidelines from the American College of Sports Medicine as a reference point are helpful, and then adjust water intake to fit hydration needs: 

  • At least 4 hours before exercise drink about 2-3 milliliters (mL) of water or a sports beverage per pound (lb.) of body weight. 
  • For instance, a 150-lb athlete needs to drink 300-450 mL, which equals about 10-15 ounces of liquid 
  • Consume approximately 8 oz. of fluid every 15 minutes after exercise; consume about 16-24 flu oz. of fluid for every pound of body weight lost during exercise.

Importance of Sodium

Many people associate sodium with high blood pressure, heart disease, and canned foods, but it serves important functions in keeping the body healthy:

  • Maintains fluid balance in the cells 
  • Helps to transmit nerve impulses throughout the body 
  • Helps muscles contract and relax

Since sodium is found in so many foods, it’s fairly uncommon to develop a deficiency unless one is having a bout of excessive vomiting or diarrhea. If a lot of water is lost, a lot of sodium is lost as well. Symptoms of a deficiency include muscle cramps, fatigue, dizziness, nausea, and the inability to concentrate. ‘Hyponatremia’ is a dangerous condition in which there is not enough sodium in the body fluids. Symptoms can be absent, mild or severe. Mild symptoms include a decreased ability to think, headaches, nausea, and poor balance. If the deficiency becomes very serious, the body can go into shock and the circulatory system can collapse. 

Conversely, if athletes’ diets contain too much sodium (Hamburger, French fries, etc.), the body tissues tend to retain water. The 2012 American Heart Association recommends that people consume no more than 1,500 milligrams of sodium a day – just a bit more than 1/2 teaspoon of salt. For comparison, a medium order of fast-food French fries contains about 260 milligrams of sodium. A recent study reported that Americans are consuming even more sodium – 8% more in 2010 than in 2001. Consuming too much salt can cause the kidneys to retain water, which may result in increased blood pressure, stroke, and heart disease. 

Importance of Potassium

In addition to helping to maintain a proper fluid balance in the body, potassium also performs the following functions:

  • Keeps the blood from clotting
  • Maintains the body’s pH balance
  • Carries nutrients to the cells
  • Protects the stomach lining from the damage that could be caused by stomach acids
  • Maintains healthy blood pressure
  • Promotes heart health
  • Preserves bone health

Athletes should be especially concerned with potassium intake as it plays a role in the storage of carbohydrates to fuel the muscles. In addition, the frequency and degree to which the muscles contract depends heavily on having the right amount of potassium in the body. If there is not enough potassium in the diet, or when the movement of potassium through the body is blocked, nervous and muscular systems can become compromised. The Adequate Intake (AI) for potassium is 4.7 grams per day, but most Americans don’t consume enough potassium in their diets.

One reason for our low potassium levels is that Americans generally don’t eat enough fruits and vegetables. Bananas are a great source of potassium which helps to promote muscle recovery. Fresh fruits, especially citrus and melons, and vegetables, especially leafy greens, and broccoli, are also rich in potassium. One can also find the mineral in fish, most meats, and milk. Sweet potatoes and legumes like Lima and Kidney beans are also high in potassium.

Since potassium is lost through sweat and urination, athletes need to consume daily potassium-rich foods because low potassium levels can reduce energy and endurance levels. A recent Australian study with highly trained athletes showed that drinking a caffeinated beverage immediately before exercise could help to maintain adequate potassium levels in the blood and delay fatigue during workout. The body definitely will indicate if one is not hydrated. If experiencing muscle cramping or high levels of thirst, get your potassium and sodium levels checked. 

Suggested Drink Plan: 2 Liters is Optimal 

Here are some suggestions from German Health and Fitness experts, cited from “Gesund und Fit” [Healthy and Fit], Freizeit Revue, No 29, 2019.

Athletes often complain that water is ‘just too bland’, and their intake may not be enough. For that reason, some flavour combinations like lemon or herbs or Apfelschorle (Apple Spritzer) is added. 

Breakfast1 glass water  1 cup of tea200 ml 200 ml
Morning2 glasses of water400 ml
Lunch1 large glass Apfelschorle300 ml
Afternoon2 glasses of water400 ml
Dinner2 cups of herbal tea300 ml
Before Bedtime1 glass water200 ml

Summer Olympics 2020 in Tokyo, Japan –Athlete Preparation and Humidity

The following was received from SIRC (Canadian Sports Information Centre), Ottawa, Canada. It looks like a vitamin, but it’s really a computer. This computerized pill is helping Canada’s high-performance athletes prepare for the heat at the upcoming Tokyo 2020 Olympics.

The “BodyCap” is an ingestible computer used to monitor athletes’ core temperatures

After tracking the temperature during warm-up. pre-race cool-down, and competition, data can be downloaded via BlueTooth for analysis

The technology is being used to help athletes prepare for the Tokyo Olympics where extreme heat conditions are expected

Check out the video featuring Evan Dunfee and the Canadian Sport Institute Pacific’s Trent Stellingwerff: https://www.cbc.ca/player/play/1310010435505/


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Barker, J. (2019, July 29). Don’t sweat the weather – adapt to it. The Calgary Herald. C2.

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SIRC (2019, August 1). ‘Sci-fi’ pill helps Canadian athletes prepare for extreme temperatures. SIRC News (Canadian Sport Resource Information Centre. Email. Retrieved August 4, 2019, from email and https://www.cbc.ca/player/play/1310010435505/

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