How will it change my life?

Professional athletes sacrifice a lot for minimal gains, training every hour God sends, eating only what the nutritionists recommend and missing out on time with friends and family. Fortunately for us mere mortals the gains can be significant without the need to deny yourself the pleasures of a Sunday lie-in, occasional junk food and fun.

Even so, when you combine the novice with a skilled coach the rewards can be huge, with many runners doubling their total distance after just a few months. Sadly, with the chances of Mo Farah's coach Alberto Salazar offering up his services for free slim at best, the Garmin Forerunner 620 is the closest many of us will get to the magic of one-on-one running instruction, and on that front it does a magnificent job.

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The device can analyse your running technique in ways not seen from many gadgets before, being able to monitor not only vertical oscillation - how bouncy you are - but also ground contact time. The dynamics of running are pretty straightforward, but doing it well involves several elements to come together in harmony like instruments in an orchestra. In this case, the Forerunner 620 is the conductor.

The science bit I've watched Rocky many times, marvelling at his tenacity, but each time I question the effectiveness of his training regime, which simply seems to entail working out until he drops.

For a start, it's at odds with the training needed for distance events and a key factor in why many runners fail to break their personal barriers. It all comes down to the heart and conditioning it for the copious demands required. Long-distance events require a slow, steady pace so the muscles don't fatigue too quickly, enabling the heart to pump enough oxygen to maintain them and the lungs to expel enough carbon dioxide before the burn sets in.

The training to control these processes is called "zoning" and encourages you to train in the heart rate zone you'll spend most of your time in during your event. Knowing these zones requires a heart rate monitor and a bit of time doing exercise.

Good points The heart rate monitor which comes with the bundle is top notch and simple to set up and use. The Forerunner 620 provides a plethora of data for analysis such as running cadence, speed, HR (heart rate) zone, calories burned and VO2 Max (a measure of aerobic capacity).

Bad points Scrolling through the many data fields can be irritating on the watch-size screen.

Best for Anyone training for a running event, from a 5k to your first marathon.

Avoid if Quitting is your mantra. Buying a Forerunner 620 would be an expensive mistake.

Score 9/10.

l Garmin Forerunner 620, £359 (