rates. Recycles are tracked by the class they start with, and affect only that class's graduation rate. Physical effects Following the completion of Ranger School, a student will usually find himself "in the worst shape of his life". Military folk wisdom has it that Ranger School's physical toll is like years of natural aging; high levels of fight-or-flight stress hormones (epinephrine, norepinephrine, cortisol), along with standard sleep deprivation and continual physical strain, inhibit full physical and mental recovery throughout the course. Common maladies during the course include weight loss, dehydration, trench foot, heatstroke, frostbite, chilblains, fractures, tissue tears (ligaments, tendons, muscles), swollen hands, feet, knees, nerve damage, loss of limb sensitivity, cellulitis, contact dermatitis, cuts, and insect, spider, bee, and wildlife bites. Because of the physical and psychological effect of low calorie intake over an extended period of time, it is not uncommon for many Ranger School graduates to encounter weight problems as they return to their units and their bodies and minds slowly adjust to routine again. A drastically lowered metabolic rate, combined with a nearly insatiable appetite (the result of food deprivation and the ensuing survivalist mentality) can cause quick weight gain, as the body is already in energy (fat) storing mode. Food and sleep deprivation A Ranger student's diet and sleep are strictly controlled by the Ranger Instructors. During time in garrison students are given one to three meals a day, but forced to eat extremely quickly and without any talking. During field exercises Ranger students are given two MREs (Meal, Ready-to-eat) per day, but not allowed to eat them until given permission. This is enforced most harshly in Darby and Mountain phases. Since food and sleep are at the bottom of the priorities of those in the infantry behind security, weapons maintenance, and personal hygiene, it is generally the last thing Ranger students are allowed to do. As such, the two MREs are generally eaten within three hours of each other, one post mission, and the other prior to the planning portion of the mission. Though the Ranger student's daily caloric intake of 2200 calories would be more than enough for the average person, Ranger students are under such physical stress that this amount is insufficient. The Ranger Training Brigade does not maintain weight information in the 21st century, but in the 1980s, Ranger students lost an average of 25–30 pounds during the Ranger course. Ranger