By Jessica Freema and Nicole Moyen
Hydration is a balance between the fluid you consume from food and drinks, and the fluid you lose through sweating, breathing and urinating. Working in a hot environment already increases your risk for dehydration, which can have negative impacts on your performance, mood and cognition. So staying well hydrated is crucial to prevent increased cardiovascular (e.g., increased heart rate) and thermal (e.g., increased body temperature) strain especially during physical labor in a hot environment.
All bodily systems are affected by hydration: your body will not be able to efficiently function if you’re dehydrated. For instance, low body water (i.e., dehydration) can lead to reduced mental and physical capacity, which includes impairments in cognitive function and decision making, and cardiovascular functioning.
These systemic impairments throughout your body can lead to increased risk of developing severe illnesses, such as exertional heat stroke (which can lead to death if left untreated). Dehydration can also lead to impairments in decision making on the job site, which can increase your risk for injury. That being said, it’s important to know the signs that indicate whether you’re well hydrated so that you can avoid dehydration and minimize your risk of illnesses and injuries.
Are You Hydrated?
The most basic and easily accessible way to determine whether you are well hydrated or if you’re dehydrated is to 1) look at your urine color, or 2) assess your urine volume (how long you urinate for or how often you urinate during the day).
If your urine color is dark, this would be indicative of a dehydrated state. If your urine color is clear or a very light yellow, then you are well hydrated.
Body weight is another easy method to monitor hydration status because if measured before and after physical labor/activity, the weight you lost during the day will tell you how much water you should drink back to rehydrate. However, it may not always be possible to weigh yourself before and after work. This is why we recommend close monitoring of urine color or volume as the best options.
Biological sex is another risk factor that can change your susceptibility to heat injuries and illnesses. For example, dehydration may impact men and women differently. Current evidence shows that men may be more likely to get dehydrated during physical work in the heat compared to women. This is because men generally sweat more than women, as they are larger and therefore produce more body heat.
This is compounded by the fact that men tend to under drink even when fluids are available, meaning that due to their higher sweat rate and tendency to under drink, they could be at greater risk of dehydration compared to women.
By contrast, some indirect evidence suggests that women may drink more than they actually need, which can put them at greater risk of exercise-associated hyponatremia, which is when your body’s sodium levels are so low that it can cause muscle breakdown.
This risk of overdrinking may be a product of the fact that the occupational safety recommendations are typically tailored toward men, with women often being forced to follow the same recommendations that are not correct for their physiological needs. With this background, there is a need to improve work conditions for women by developing hydration recommendations that will protect the health and safety of women in the workplace.
Hydration needs should be tailored on an individual basis because the amount of fluid that works for one person may not lead to optimal hydration in another. This could be due to differences not only in sex, but body size, age, environment and intensity of the work.
That said, most recommendations indicate that laborers should drink one cup of cool fluid (8 oz.) every 15 to 20 minutes. This is a general rule of thumb and fluids should be regularly available in the workplace to encourage drinking on an “as needed” basis.
Water, opposed to an electrolyte-containing drink, is typically sufficient to stay well-hydrated during physical labor that lasts less than two hours. However, most occupational and athletic recommendations support consuming a sport drink with electrolytes (e.g., Gatorade or Powerade) for sustained physical activity lasting longer than two hours.
Electrolytes in sport drinks help to replace the electrolytes that you lose through sweating and also help to increase the amount of fluid you absorb. At the end of physical labor/activity, drinking to thirst is generally appropriate. It is also important to avoid alcohol or beverages containing large amounts of caffeine because they can increase your risk of dehydration. It is acceptable to consume these beverages only once the water you lost during the workday is replenished and you’re well hydrated again.
- Continually drink fluids through the workday to maintain productivity and avoid heat injuries and illnesses by avoiding becoming dehydrated. In general, you should drink 8 oz. of water and/or electrolyte-containing beverages every 15 to 20 minutes on very hot, humid days where you are sweating a lot.
- Make sure to assess the color of your urine and count how many times you urinate during the workday.
- Try to avoid starting your workday dehydrated. Throughout the workday, make sure you have regular access to water by stopping at rest stations or carrying water to your location.
- Note that your individual hydration needs may differ based on your own sex, body weight, and age. Avoid drinking more than six cups of water per hour during your physical activity to maintain electrolyte (e.g., sodium) balance.
- After work, drink to thirst, and avoid drinking alcohol and/or caffeine until your urine is a clear color again, indicating that you’re rehydrated.
Jessica Freemas, M.S, is currently a PhD candidate in Exercise Physiology at Indiana University under Dr. Zachary Schlader, a leading expert in environmental physiology. Her current dissertation work examines differences in fluid balance and hydration regulation during physical work in the heat between men and women.
Nicole Moyen leads R&D at Kenzen, the smart PPE innovator focused on physiological monitoring and the prevention of heat injury and death among workers. Kenzen’s real-time heat monitoring system is used by companies to keep workers safe from heat. Moyen has a decade of research experience in industry and academia related to human physiology and wearable devices, and advises companies on heat stress physiology and dehydration. Nicole has an M.S. in Exercise Physiology, and is currently finishing her PhD in Biology from Stanford University.