By Riva Preil Is totally going to be hot? Cold? Sunny? Stormy? Great question- these days, who knows! Considering the recent weather fluctuations, now is a good time to review the physiologic effects of hot temperature extremes on our bodies. Moist hot packs and cold packs are two of the most commonly utilized modalities by physical therapists to treat pain. Heat is often used to treat chronic pain as well as muscle stiffness and discomfort. Heat is a vasodilator (expands blood vessels to allow for improved circulation), and this brings oxygen and nutrients to the cells. In addition, increased blood flow allows toxic waste products and carbon dioxide to be removed from the cells. The recommended temperature for optimal most heat treatment is 104-113 degrees Fahrenheit for five to thirty minutes. However, heat should not be used over sprained or strained ankles or on body parts with decreased sensation for fear of inadvertent burning. Cryotherapy (cold therapy) is the other common modality often used for pain relief, especially for acute injuries. Cold has the opposite effect of heat- it is a vasoconstrictor (creates narrowing of blood vessels thereby decreasing the local blood flow). Cold decreases edema (swelling), pain, and inflammation, and it should be applied indirectly to the skin for less than fifteen minutes. The order of sensation when using cold are as follows: Cold, burning, aching, numb- so even if the initial cold, burn, and ache feel uncomfortable, the desired eventual numbness is worth the wait! The effects of cold therapy are longer lasting than heat therapy.