Hamburg/Cologne - In the old days, runners carried no more than a stopwatch showing how long they had been running. Nowadays, though, there are wrist-borne, mini-computers that measure things like elevation gains, too.

High-end running watches cost about 400 euros (532 dollars) and have up to 74 functions, noted Urs Weber, an editorial staffer at the Hamburg-based magazine Runner's World.

"In our experience, most runners use no more than 10, however," he said.

Models priced under 100 euros are adequate for most leisure runners, said Billy Sperlich, an assistant at the Cologne-based German Sport University's Institute of Training Science and Sport Informatics.

"I'd advise the average runner to wait until a running watch is for sale at a discount store," he remarked.

Cheaper watches may not look as classy as expensive ones, but they have what most runners need and use, Sperlich pointed out: They stop time and measure heart rate as accurately as an electrocardiogram. Everything else, he said, is just frills.

Sperlich added that healthy runners did not necessarily have to measure their heart rate because after a while they generally developed a feeling for their limits and the pace they were most comfortable with.

Most experts surveyed for this article, however, recommended a heart-rate monitor to help runners avoid undue strain and to optimize the benefits of training. "Heart rate is a reliable indicator of physical exertion," Weber noted.

He said a heart-rate monitor, a chest strap records heartbeat frequency and transmits it to the watch, helped all runners guard against overexertion. If the runner exceeds a certain rate, the watch beeps as a warning to slow down.

Checking a watch after a run to see the number of kilometres covered gives some runners extra motivation, Weber said. Running watches with pedometers measure distance either by counting steps or by using satellite data from the Global Positioning System. Some models also have an interface allowing data transmission to the runner's personal computer.

Many other functions are mere frills that in some cases provide inaccurate data, Weber warned. The amount of calories burned is calculated indirectly - based on heart rate and standard body types. So the actual number of calories that a runner burns can be quite different.

Rather than putting a premium on a watch with many functions, Weber said, runners should make sure it is easy to use and comfortable to wear. The display should be large and luminescent, and the numbers easy to read. And the watch should neither dangle from the runner's wrist nor pinch it and impair blood circulation.

This is why Patrizia Schiller, who works at the Recklinghausen branch of the Runners Point sporting goods chain, said that runners should always try on a running watch before buying it. Who knows? Maybe an old-fashioned stopwatch fits best.