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Investigating the heat-inertia ratio

How to excuse the almost shameful lethargy that comes over us on summer days, writes Ami Dalal.

india Updated: Mar 31, 2006 14:33 IST

My heater has been unceremoniously chucked into a dusty corner of the closet when only a month ago I was yelping in alarm, clutching its grilled sides, when it stopped purring on a dreadfully cold winter night.

The temperature is quickly rising in Delhi and so, proportionally, is my inertia. When I woke up last Saturday, I mentally listed several ways cool to down and shake off my heat-kissed lethargy -- ranging from Mom's recipe for cold salty lassi to wearing filter-thin cotton kurtis to spritzing my face with bottled water every two hours. When afternoon swung around, I found myself still sprawled, panting, on the bed watching the fan spin slowly over my head.

Summer heat announces breeding season for germs and, deprived of my freedom to eat in roadside stalls because of my recent bout with amoebas, all I can do is stare longingly at the fresh fruit juice vendors lining my street and clutch a bottle of too-sweet soda in my sweaty fist. When I first arrived in Delhi, I would wake up with the sun and, within twenty minutes, be on my way to Humayun's Tomb, the Jama Masjid, or the Qutub Minar. Now if I walk to the local market and buy a slice of chocolate cake, I'm pretty pleased with myself. Am I getting lazy or can I really blame the heat?

The human body rids itself of excess heat by circulating blood closer to the surface of the skin so that excess internal heat can be lost to the cooler environment. When exposed to heat for a prolonged amount of time, the upper layers of the skin fill with more and more with blood. With so much blood going to an external surface of the body, relatively less goes to active muscles, the brain, and other internal organs.

Strength declines and fatigue occurs sooner than it would otherwise. Alertness and mental capacity may also be affected.

The range of health problems from overheating begins with the near-fatal heat stroke to the more temporary but still irritating heat rashes and heat cramps. Some people - like myself -- also suffer from transient heat fatigue, which is a temporary state of discomfort and mental strain from prolonged heat exposure. It takes 5 to 7 days to adjust to heat stress; but since the heat will keep rising, will my body always take one week to adjust to every upward swing in the temperature?

According to a study on worker productivity, there is a 15% loss in output and a 40% loss in accuracy when the temperature increases from 24 to 29C. In a laboratory experiment by the Banaras Hindu University with Drosophila flies -- the species popularized in genetics research -- it was found that females reared to adulthood in 18C showed a higher body weight and productivity when compared to those raised at 25C.

However, according to another popular ergonomics study by Cornell University, warm workers work better. In a month-long study, when temperatures were raised from 20 to 25C, typing errors fell by 44% and typing output rose by 150%. Clearly, colder temperatures negatively impact a person's productivity and concentration but, after a certain point, it probably gets too hot to concentrate on much at all.

Whatever it is, without air-conditioning, I doubt that I will ever shake this unrelenting summer slumber. Maybe it's because I'm not used to Delhi summers like the locals are, maybe it's because I complain too much and don't try all that hard to battle the heat, but I must say that that even the flies are moving rather sluggishly. They don't bother moving away from my swatting hand and, if they finally do get frightened, they launch off the wall like drunken sailors, wobble fatly on the hot unmoving air, and promptly fall down onto the nearest horizontal surface.

I'm embarrassed to admit that, well, they look a little like I did last Saturday.