Prana, life force energy or chi energy is the energy that keeps us alive. This is present in all living beings. It makes the plants grow, it keeps the heart beating. Life cannot sustain without this energy. This pranic energy, we get from the atmosphere around us as sunlight, the oxygen we breathe, the water we drink, the food we consume. Take one of these away and the body will not be able to sustain for long.
Prana energy is given recognition in eastern philosophies and yogic culture but not in modern science, due to its subtlety in operation even on a microscopic level. It is rather considered a field of energy present in every cell of the body. When a man ejaculates, around 100 million sperm cells (each capable of producing another human) are expelled, drawing prana from each cell of the body, leaving a person tired and weary. This energy loss is proven to be equivalent to 14 days of labor.
Similarly, unknown to us, pranic energy is expelled from the body on a cellular level, when people harbor negative emotions. Anger, lust, greed, grief, fear will disturb the ordinary vibration of these atoms of energy, giving them a frequency higher than the usual. This makes them leave the body. This outward pump prevents the pranic atoms of the atmosphere from entering the body to fill its inadequacies. This in the long run causes loss of health, strength and vigor.
Positive emotions increase life force energy. This is quite noticeable. On days we are happy, we experience less hunger whereas in times of distress a person may start binge eating. Likewise, lack of food or too much thereof, lack of sleep or too much thereof, lack of physical activity or too much thereof will compromise this energy balance. Prana promotes health and longevity. Absence of it depletes energy of a person making him sleepy, sickly, tired and purposeless.
As mentioned earlier, breath is the means by which prana present in the atmosphere is absorbed to the body thus life expectancy of a person could be determined by the intensity and the depth of his breath. A human is biologically programmed to take around 15 breathes per minute, more or less, depending on the lifestyle of the person. A tortoise lives up to 300 years. The reason of its longevity is 3 to 4 deep breathes per minute.
When the mind is quite, undisturbed and during higher meditative states the number of breathes one takes decreases significantly (as the body and mind are in an inactive state). Thus the body by itself will be refurbished, leaving the practitioner calm and collected after the practice. For the same reason, deep diaphragmatic breathing will make you calm in times of distress.
A light bulb will function, so long as the electricity supply is there. Once there is no electricity the bulb will stop emitting light, even if there is nothing wrong with the filament. Even though life cannot be prolonged, it could be lived till the filament lasts. The only plausible method (besides a healthy lifestyle) of regulating and conserving this prana energy is through pranayama or the exercise of breath itself (“prana” means “life force”, “ayama” means “extension” in Sanskrit), which supposedly could extend lifespan by 1 year if practiced daily for 15 minutes.