Fatigue & Dehydration: Two sides of the same coin

By Kaitlyn Bruschi, Corporate Bodies International

Dehydration and fatigue are significant risks within the mining industry, both having considerable impacts on health and safety parameters within the workplace. Despite their similarities, education initiatives often address these risk factors separately.  By tackling these risk factors simultaneously, the individual gains a greater appreciation for a holistic approach to maintaining their health, while the company sees a reduction in lost time to injury and improved productivity.

Fatigue is characterised by a chronic decline in physical and cognitive function. Typically, fatigue presents as a change in personality, motivation, memory and concentration; as well as physical impairment, such as reduced immune function, poor coordination and reflexes, muscle weakness and pain. Sleep hygiene is often cited as the primary mechanism for improving an individual’s fatigue levels, often underestimating the potential positive impact lifestyle choices can have on an individual’s fatigue level. Maintaining adequate hydration is an integral component of this holistic fatigue prevention strategy.

Similar to fatigue, dehydration is also characterised by reductions in mental performance, mood, cognition and physical work rates. Impairment can be observed with as little as 1% dehydration by body weight (equivalent to 600 – 800mL); often before the thirst mechanism has a chance to kick in. At 2% dehydration, studies report a 6-7% reduction in physical work rates, with this decline climbing as high as 50% at 3-4% dehydration.

Mechanisms for association

It is clear that the signs and symptoms of fatigue and dehydration overlap considerably, but less clear is an understanding of the mechanism behind this association. One suggested explanation is that when dehydrated, your body produces hormones to help restore fluid balance. These hormones have a flow-on effect on other systems in the body that alter cognitive processing speed and lead to feelings of fatigue.

In Australia’s hot environment, heat stress is also always a concern, with fatigue a common side effect.  Humidity can also impact susceptibility to heat stress and subsequent dehydration. Hydration underlies some of the primary mechanisms for thermoregulation. Heat illness progression, from mild to more critical symptoms, has been found to occur in a relatively linear fashion, following that of hydration status. Above approximately 34 degrees Celcius the body relies on evaporation to dissipate heat. Through this process, heat is transferred from the organs to the skin via the circulatory system. The skin is then cooled through the evaporation of sweat. When dehydrated, we simply do not have the fluid required to maintain a sufficient sweat rate. As a result, our body temperature climbs. One study suggests the thermoregulatory impairment observed during dehydration to contribute to an increased core temperature of 0.1 to  0.4 degrees Celcius for every 1% decrease in body weight, with profound implications for the individual’s health. It is important to note that clothing can impact heat dissipation, dependant on its permeability, design, and the amount of clothing/ personal protective equipment required.

Leading to dehydration

The amount of sweat an individual produces per hour is extremely individual, determined by a combination of their acclimatisation, health status, environmental conditions, and work rate. In underground mines, workers have been estimated to sweat approximately 0.46L/hour. However, this can climb to over 1.5L/hour in very hot environments. This can equate to 5 to 12 litres of fluid lost over a 12-hour shift. A 2013 study found underground and surface mine workers to consume only 4.1L or 3.1L, respectively, per 12-hour shift. Workers were not consuming sufficient fluid to match that lost throughout their shift, resulting in dehydration. Excessive sweating is also associated with large losses of sodium, an electrolyte essential for maintaining fluid balance, and normal muscle and brain function. Both fluid and sodium need to be replaced continuously throughout the shift to maintain performance and avoid dehydration-associated fatigue.

It is important to recognise that although sweating is a significant contributor to dehydration for those working long periods in hot environments, dehydration can occur at any time when a fluid deficit is allowed to develop. This can include over long shifts in low-humidity airconditioned cabs, and even in winter, when hydration is often overlooked.

Strategies to improve both hydration and fatigue

1. Ensure adequate, structured rest breaks: Not only does this allow time for recovery, it also allows programmed drinking, whereby the individual consumes fluid consistently over their shift rather than in large doses at limited intervals.
2. Limit alcohol: Alcohol is a diuretic, a compound that switches off the body’s water conservation methods, telling your kidneys to excrete more water, thereby increasing urine output. Urine output has been found to increase by as much as 10mL for every 1g of alcohol consumed, potentially leading to negative water balance despite the fluid consumed with the alcohol. Alcohol can also alter fatigue levels by disrupting sleep patterns. Even at low levels – the equivalent of one or two standard drinks – alcohol can impair your brain’s ability to enter deep sleep required for full mental and physical recovery. This can result in the individual waking unrefreshed and be culminating in significant fatigue risk over time.
3. Limit caffeine: Caffeine also creates electrolyte disturbances by altering the processes by which electrolyte levels are controlled in the body. Excessive caffeine intake can also increase blood pressure. As the cardiovascular system is already under strain during dehydration, this additional pressure may increase the potential for adverse side effects. This is highly relevant to the mining industry where caffeine is often used as a stimulant to reduce fatigue. The introduction of energy drinks and pre-workout supplements deepens this health concern.
4. Consider a water bottle part of your personal protective equipment: Embed hydration in company culture, and part of safety management practices, just as fatigue would be.
5. Oral rehydration supplements: With the majority of workers not consuming sufficient fluid to match that lost through sweat, the importance of selecting the correct fluid replacement beverage is essential. It must have a composition to optimise water absorption, while also meeting electrolyte and energy requirements. The concentration of glucose and sodium in commercially available rehydration products can vary considerably but has a significant impact on their fluid replacement capacity. Hypotonic solutions, those with low carbohydrate contents, are absorbed the fastest. However, it is important not to eliminate glucose completely as it is required for efficient movement of water from the intestinal tract into the bloodstream. Excess carbohydrates can slow fluid absorption, while also leading to weight gain and subsequent health issues long term. They also negatively impact mood and fatigue. Education should be provided to ensure appropriate use of these products and optimise their rehydration capacity.

With both fatigue and dehydration posing significant risks within the mining industry, it is important to develop comprehensive education programs that address both, for the benefit of the individual and the workplace.