MILITARY TRAINING: WHEN TO OBSERVE CAUTION DURING HOT WEATHER?

Dear Editor,

It is common knowledge that both increased environmental temperature and high relative humidity increase likelihood of ill effects of heat such as heat stroke/exhaustion. Though all medical officers are aware that the interaction of temperature and humidity is more important than either of the two per se, no objective guidelines are easily available in standard textbooks or for that matter even the Manual of Health for the Armed Forces (popularly known as the ‘Red Book’), to objectively advise the regimental officers whether or not to carry out strenuous training activities such as BPET, cross country, etc.

Reproduced below is a chart (Fig-1), from a military training pamphlet [1], which serves the above purpose. It gives details of determining the risk of exercising in the heat, once we know the outdoor temperature and relative humidity. With these weather data, one can use the chart to predict whether it is safe to exercise. In the “safe zone” of the chart one can exercise without risk. In the “caution zone” it is safe to exercise lightly if one takes adequate fluids before, during and after training sessions. When the temperature-humidity combination is in the “danger zone” it is unsafe to exercise at all.

Fig. 1.

Humidity – temperature chart to determine heat risk

To determine the risk of exercising in the heat, find the temperature at the left of the chart, and read from it across the right and stop at vertical line that represents relative humidity. For e.g. on a 90°F day, if relative humidity is less than 30%, the weather is in the “safe zone”.

It is proposed that this chart should be available readily with all medical officers particularly during summer months, and they should also keep a note of temperature and relative humidity daily to properly advise on military training in hot weather. Metereological data are maintained at the station health organizations which can also advise the station authorities to appropriately issue necessary station orders.