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GPS running watches: what to look for

A GPS watch records how far, how fast and how long you run. Basic models do this very well, so the real question is which of the many extra features you would use.

What a running watch does

The watch receives signals from navigation satellites and works out your position every second or so. From the change in position it calculates distance and pace. At the end of a run you get a map of the route, your time for each kilometre or mile, and usually heart rate and cadence as well. The data syncs to a phone app where you can see your training over weeks and months.

You do not need a watch to run. A phone app records the same basics. A watch is lighter, easier to read mid-run and has buttons that work with wet or gloved hands.

Features that matter most

  • Accurate positioning. Most current watches use more than one satellite system. Some add multi-band or dual-frequency reception, which improves accuracy among tall buildings, under trees and in steep valleys, at the cost of battery life.
  • Battery life in GPS mode. This is the figure to check, not the smartwatch figure. Ten hours is ample for anything up to a marathon. Ultra-distance runners and people who dislike charging should look for 20 hours or more.
  • A readable screen. Bright colour screens look sharp and are easy to read indoors. Reflective screens are duller but clear in direct sunlight and use less power. Check that you can show three or four data fields at a size you can read at a glance.
  • Physical buttons. Touchscreens are unreliable in rain and with gloves. Buttons for start, stop and lap are worth having.
  • Fit and weight. A watch that is too large for your wrist will bounce and give poor heart rate readings.

Heart rate

Most watches measure heart rate with optical sensors on the back of the case. Wrist readings are generally good for steady running and less reliable for short, hard intervals, in cold weather, or if the watch is loose. If you want to train by heart rate zones, a chest strap, or an optical band worn on the upper arm, is more accurate. Most watches will pair with either.

Training features

  • Structured workouts. You build a session such as six repetitions of 800 metres with recoveries, and the watch counts you through each part and alerts you if you drift off pace. Useful if you follow one of the training plans.
  • Pace and heart rate alerts. A beep or vibration if you go outside a range you have set. Handy for keeping easy runs easy.
  • Lap pace. Average pace for the current kilometre or mile. This is steadier and more useful than instant pace, which jumps about.
  • Race predictions and recovery estimates. These are estimates built from your recent runs. Treat them as a rough guide and compare them with the race time predictor, which works from actual race results.

Navigation

If you run trails or explore new areas, navigation is worth paying for. The simplest form is a breadcrumb trail: a line on a blank screen showing a route you have loaded, with an arrow for your position. More advanced watches show full maps with paths and contours and can reroute you. A barometric altimeter gives more reliable figures for ascent and descent than GPS alone. For road running on familiar routes, none of this is needed.

Smart features

Music storage, contactless payment, phone notifications and safety alerts that can share your location with a contact are common on mid-range watches and above. Decide which you would use. Music storage lets you leave the phone at home, and contactless payment is useful for a drink or a bus fare on a long run.

Using a watch in a race

Your watch and the official course will rarely agree exactly. Courses are measured along the shortest possible line, and almost nobody runs that line in a crowd, so a watch often shows a marathon as 26.4 or 26.5 miles. Your official time comes from the timing chip, as explained in how chip timing works.

A few habits make a watch more useful on race day:

  1. Charge it fully the night before, and wait for it to find a satellite fix before you enter the start pen.
  2. Start it as you cross the start line, not when the gun goes.
  3. Turn off auto-lap and press the lap button at each course marker, so your splits match the course and not the watch's own distance.
  4. Work out target splits in advance with the pace calculator and carry a pace band as a back-up.

How much watch do you need?

For most runners, an entry-level running watch with reliable GPS, wrist heart rate, lap pace and structured workouts covers everything. Step up if you need longer battery life, maps, or music without a phone. Buying more features than you will use adds weight and cost without making your training any better.