For adults, a normal resting rate is 60 to 100 beats per minute. Athletes may have a rate as low as 40 bpm because their hearts are trained to efficiently pump blood. If your heart rate is consistently below 60 or above 100, you may have a heart condition, such as arrhythmia.
Integrating Factor. An integrating factor is a function by which an ordinary differential equation can be multiplied in order to make it integrable. For example, a linear first-order ordinary differential equation of type.
Limiting factor. A limiting factor of a system, is an input or variable such that a small change in it from the present value would cause a non-negligible change in an output or other measure of the system.