Did you know that if you’re thirsty you are already dehydrated?
A study of Australian mine sites found that workers who rely on thirst to determine personal fluid requirements typically replace only half of the fluid they lose through sweat. Conversely, workers who engage in program drinking were found to maintain optimal hydration levels and do not become dehydrated.(1-3)
These results can be largely attributed to the failure of the thirst response. Scientists have found that the thirst sensation does not kick in until we are already 2% dehydrated (4) (which is about a 1.5L fluid deficit for an average 75kg adult male). At just 2% dehydration, workers suffer from reduced concentration and alertness, slowed reactions times, and physical work capacity decreases dramatically.[5-8]
Thirst – The Reactive Approach
Australian miners experience average sweat losses of 1L/hour.(1,9) If they wait until they feel thirsty to drink, they could be trying to bridge the gap on anywhere from a 1L – 2L fluid deficit. Drinking such large amounts in one go is difficult and can lead to many problems including nausea, headaches, and even vomiting if thermally heat stressed.
The human body’s maximum rate of fluid absorbtion is ~1.5L /hr. As such, we have difficulty retaining large amounts of fluid if consumed in a single sitting. In these circumstances, the body, unable to absorb such high volumes so quickly, will pass this excess fluid out through urination. This leads to difficulties rehydrating and leaves workers with an insatiable thirst, forced to consume copious amounts of fluid for minimal net gain.
Program Drinking – The Proactive Approach
With program drinking, workers focus on drinking small amounts frequently, over short intervals. Fluid intake requirements are calculated based on average sweat rates and guidelines are put in place to which all workers must adhere. For example, with average sweat rates of 1L/hr, it would be recommended that Australian miners aim to drink 250mls every 15mins. These smaller amounts are more easily absorbed, replacing fluids as they are lost and enabling workers to maintain optimal hydration levels throughout their shifts.
Implementing Program Drinking on Your Work Site
Legislative bodies such as the Occupational & Health Administration (OSHA) and the American Conference of Governmental Industrial Hygienists (ACGIH) recommend industrial workers consume 250mls every 20 minutes when working in warm environments(5). Whilst these recommendations are useful, it is important to note that actual fluid requirements vary based on a number of factors including the worker’s individual body type & physical fitness, the intensity of work involved, the type of clothing worn, the environmental conditions in which the work is taking place, and whether or not the worker has acclimatised to his or her environment.
Before implementing program drinking as part of your onsite hydration policy, it is recommended to first ascertain average worker sweat rates and then adjust your fluid intake guidelines accordingly. Workers in more physically demanding roles will experience higher sweat rates and have greater fluid requirements than their more sedentary counterparts. For example, while manual labourers sweating at average rates of 1L/hr would aim to drink 250mls every 15 mins, machine operators sweating at average rates of 600mls/hr would lower their intake to 200mls every 20mins.
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To be successful, program drinking needs to be part of a greater Heat Stress Management Strategy, the cornerstone of which is hydration education.
Studies show that over half of industrial workers in Australia report to work mildly dehydrated, many in a state unfit for working in warm environments. This condition is usually maintained or worsens throughout the work day. Workers who are educated on the importance of workplace hydration on the other hand were found to report to work hydrated and to maintain optimal levels throughout their shifts.(1-3)
Interested in implementing program drinking on your work site? Not sure where to begin? Our THORZT hydration experts can help.
. Brake, R & Bates GP. Fluid Losses and Hydration Status of Industrial Workers under Thermal
Stress Working Extended Shifts. QLD Mining Industry Safety & Health Conf. August
 Brake, R. Fluid consumption, sweat rates and hydration status of thermally stressed underground miners and the implications for heat illness and shortened shifts. In the proceedings of the Queensland Mining Industry Safety and Health Conference, 2001.
 Gazey, C, Bates, G and Matthew, B. Fluid loss and replacement in petroleum workers from the north west of Western Australia. J Occup Health Safety – Aust NZ 1996, 12(4): 457-461.
. Sawka M N & Montain, S J. Fluid and Electrolyte Supplementation for exercise heat stress. Am J Clin Nutr 2000;72(suppl):564S–72S
. Kenefick RW, PhD. Hydration at the Worksite. American College of Nutrition Vol.26 No.5, 597S-603S
. Wasterlund DS, Chaseling J, Burstrom L: The effect of fluid consumption on the forest workers’ performance strategy. Appl Ergon 35:29-36, 2004
. Ganio, MS & Armstrong, LE.Mild Dehydration impairs cognitive performance and mood of men. British Journal of Nutrition / Volume 106 / Issue 10 / November 2011, pp 1535-1543
. Armstrong LE, Ganio, MS. Mild Dehydration Affects Mood in Healthy Young Women. American Journal of Nutrition, Jan 1, 2012. jn.111.142000
. Sawka M N. Hydration Effects of thermoregulation and performance in the heat. In: Lau W M, ed. Proceedings of the International Conference on Physiological and Cognitive Performance in ExtremeEnvironments, Defence Scientific and Technology Organisation, Australian Department of Defense, Canberra. 2000:21-23