Inactivity results in immediate changes in the body. Being inactive for one week, one day and even one hour can lead to immediate changes. Some of these changes are natural and expected occurrences, regardless of an individual's fitness level. Ordinarily, the changes that occur due to inactivity of one hour cause no health problems. Health problems occur when an individual adopts a day-to-day inactive life-style.
Physical inactivity, even for a short time, can lead to weight gain. Of course, the potential for weight gain increases the longer you are inactive. Each individual must consume, on a daily basis, enough calories to maintain life-supporting biological functions. However, that level is relatively low compared to what is necessary to sustain physical activity. When fewer calories are expended (through inactivity), than taken in, weight gain is the result. Even if the consumption is higher than expenditure for only a day or two, weight gain results. Taking in 500 calories more than is expended each day, for 7 days, will result in a gain of 1 pound.
Pooling of Blood
Sitting in an inactive state for even a short while can cause the blood to pool in the lower extremities. Movement of the limbs helps to circulate blood. When an individual is still for a time, the blood slows, taking a longer time to return to the heart. The blood in the lower extremities must work against the force of gravity without any help from the movement of muscles. This immediate effect of inactivity, even in the short term, can lead of vascular problems in the lower extremities.
Decrease in Blood Pressure and Heart Rate
Inactivity also leads to a drop in blood pressure and heart rate. This is not necessarily a negative health factor, but rather a natural occurrence as a result of inactivity. Inactive muscles do not require the same amount of oxygen-rich blood as do working muscles. When an individual moves -- walking, running or just accomplishing daily tasks, the muscles are working and require a large blood supply. If the heart is not having to pump blood to working muscles, then the pressure in the veins is reduced. Over time, inactivity leads to an increase in both blood pressure and heart rate -- a sign of an unhealthy cardiovascular system.
Reduction of Respiration
During periods of inactivity, an individual's respiration is reduced. Respiration is the process of taking in oxygen and expelling carbon dioxide. Less oxygen is needed to support body functions during inactivity. Therefore, respiration decreases. An outward manifestation of this reduction can be seen in an individual who is seated for a long period of time. The individual may become sleepy due to the reduction of blood-rich oxygen to the brain, prompting him to yawn to take in more oxygen. Also, when the individual suddenly stands, he may feel light-headed or even faint, due to the lack of oxygen to the brain. Less oxygen is supplied if respiration is reduced. Over time, inactivity leads to an increase in respiration, due to the strain of supplying oxygen to addition body mass.
Reduction in Beta Endorphins
Exercise stimulates the production chemicals in the brain called beta endorphins. Beta endorphins are neurotransmitters that help to produce a feeling of well-being or euphoria. Scientists have determined that an absence or reduction of the secretion of beta endorphins is associated with depression. Individuals who are accustomed to regular exercise may note a decrease in a feeling of well-being when they abstain from physical activity for a few days.