The first cellphones in widespread use were

The world’s first cell phone was launched in 1983. It was the Motorola DynaTAC 800x. It was priced at around $4,000 and lasted for 30 minutes of talk time before dying.

Explanation:

the more fit you are, the faster the recovery. your heart rate drops most sharply in the first minute after you stop exercising; it should then fall about 20 beats a minute—a drop of less than 12 beats a minute is considered abnormal. this “recovery heart rate” is measured as part of an exercise stress test.