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 Pains & Aches

June 2011
Effect of Heat on Joints
Dr. Maulik Patwa
 
As people around the world face global warming, we in India also face steady rise in temperature in summer. Temperature reaching 45 degrees Celsius is common during months of April to June throughout India. So we cannot think about life without air conditioning.

Now everyone has access to air conditioning at home as well as in the car, so it has become very common to feel changes in the temperature, as it is very hot (more than 40 degrees Celsius) outside and comfortable at home, office or in the car (20-30 degrees Celsius).

The healthy human body maintains its internal temperature around 37°C. Variations, usually of less than 1°C, occur with the time of the day, level of physical activity or emotional state. A change of body temperature exceeding 1°C occurs only during illness or when environmental conditions surpass the body's ability to cope with extreme temperatures.

Handling Heat
As the environment warms up, the body tends to warm up as well. The body's internal "thermostat" maintains a constant inner body temperature by pumping more blood to the skin and by increasing sweat production. In this way, the body increases the rate of heat loss to balance the heat burden created by the environment. In a very hot environment, the rate of "heat gain" exceeds the rate of "heat loss" and the body temperature begins to rise. A rise in the body temperature results in heat illnesses.

The main source of heat gain is the body's own internal heat. Called “metabolic heat”,it is generated within the body by the biochemical processes that keep us alive and by the energy we use in physical activity.

The body exchanges heat with its surroundings mainly through radiation, convection, and evaporation of sweat.
  • Radiation is the process by which the body gains heat from surrounding hot surfaces.
  • Convection is the process by which the body exchanges heat with the surrounding air. The body gains heat from hot air and loses heat to cold air that comes in contact with the skin.
  • Evaporation of sweat from the skin cools the body. Evaporation proceeds more quickly and the cooling effect is more pronounced with high wind speeds and low relative humidity.
We are very much aware of terms like heat stress, heat exhaustion and heat stroke which affect our body as a whole and cause symptoms varying from headaches, loss of concentration, syncope, fever, malaise, exhaustion and to even fatality.

Effect of Heat on Joints
Changes in the temperature also affect our joints, more so if they are already affected by diseases like Osteo-arthritis or Rheumatoid arthritis.

Heat and humidity, cold weather and changes in barometric pressure, affect a person’s joints and muscles and can result in aches and pains. Joints consist of sensory nerves called Baro-receptors. When the weather changes, these sensory nerves respond, primarily reacting to fluctuations in air pressure.

Warm weather typically does not cause joint inflammation; however, humidity can trigger an inflammatory reaction in joints. When the barometric pressure is stable and not too high or too low, you may find that you are feeling better. However, when wet weather is looming, the barometric pressure drops and your tendons, ligaments and muscles expand, and the nerves that are sensitized send out pain messages to the joint.

Sudden changes in the temperature do not affect normal healthy joints but arthritic joints do get more pain in cold atmosphere and humid climate, due to peripheral vaso-constriction and rise in barometric pressure in joint and surrounding structures. We might experience joint pains and weakness as a part of heat exhaustion, in such a case.

It is advisable to protect your diseased joints to extremes of temperature changes, keep exercising if you are exposed to cold to improve blood supply to joints, and keep yourself well hydrated and well covered during heat waves.

Dr. Maulik Patwa is Sr. Spine and Orthopaedic Surgeon in Apollo Hospitals Ahmedabad


    
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