Bryton Cardio 40 intro image

Bryton makes a range of wrist worn and handlebar mounted systems for running, cycling and multisport fitness. Its Cardio range comprises two products – the Cardio 40 and Cardio 60, the latter of which is a multisport watch perfect for triathletes. I’m looking at the Cardio 40, designed specifically for runners here.

This is a really beautifully designed sports watch. It is thin to the point where it is difficult to believe there’s a GPS unit tucked inside it. Yet it has a big face that’s capable of displaying plenty of information in large, bold figures that are easy to see at a glance when you are on the move.

Bryton Cardio 40 easy to see

The shiny plastic fascia and green highlights tip a nod to good design that’s welcome. They’re appealing to look at and mean you probably wouldn’t feel like too much of a nerd if you wore the Cardio 40 as your everyday watch. A couple of words of warning though. This is a large beast. I’ve got smallish wrists and I like to wear a big chunky watch, but even I found it a little bit big to wear.

Bryton Cardio 40 on wrist

It’s worth being aware of battery life too. Bryton says the battery will give you 14 days in ‘clock mode’ and 8 hours in training mode. That’s good going for a GPS watch, but means if you do wear it as an everyday watch you’ll be advised to set a regular weekly battery top up schedule. Given that you’ll be using it regularly for running that’s probably not a big deal – it’s the regime I used during the testing period and it wasn’t a bother. But it is worth noting that like other sports watches of a similar grade it uses a proprietary charging clip that you’ll have to have on hand when the juice runs low.

Bryton Cardio 40 charge clip

As well as offering a wide range of on-board features and coming with a heart rate monitor the Cardio 40 synchronises with a web based service that can help you analyse performance, so you get just about everything you need out of the box – there are no extras you need to get hold of to get full value.

Setting up the Bryton Cardio 40 is an easy job. The first few steps have you selecting a language and putting in your sex, age, weight and height as well as selecting a maximum heart rate.

Bryton Cardio 40 setup

The Heart rate monitor clips easily onto a fully elasticated chest strap that I found comfortable to wear. Pairing it with the watch for the first time is a bit tedious as you have to enter an ID code – found on the HRM packaging. But it is a once only job and it does mean the watch can’t get confused by any rogue equipment.

Bryton Cardio 40 hrm

You don’t get quite as much viewing area on the Cardio 40 as you might at first think. As I noted earlier on the screen is quite large, but the viewing area has a narrow bezel all around. Still, at 1.4-inches across there’s enough room for up to four fields of information to be shown. You can customise what you see selecting from a huge array of options. The standard fare is all here including time, speed, distance, pace and calories burned. You can also tap into the heart rate monitor and display actual, max or average heart rate and a couple of other heart related stats.

Bryton Cardio 40 viewing area

In addition you can display your stride rate, average and maximum strides. I rather like this option. Many runners can overstride, shortening the stride can help them move faster and more efficiently. If you are on the road to a shortened stride then keeping an eye on stride length could be really useful.

The full list of metrics you can display is too long to recount here, but I’d like to note that you can even show sunrise and sunset times, which I guess is handy if you are on a long trek or run and want to be back before dark. You can configure up to four of display screens, and even auto scroll between them so there’s a huge potential for personalising things.Bryton Cardio 40 screensYou can set up workouts. Under the ‘simple’ heading you can set the watch to let you know when you have gone a certain distance, spent a certain time on a workout, or burned a required amount of calories.  There are also interval training workouts and custom workouts to play with.

Like any sports watch worth its salt the Cardio 40 will record your performance against specific intervals – km or mile based laps. But you can also set your own laps and you can do this either for a set distance or using a specific location a starting point.

This is all very flexible, but one thing that really irks me is the lack of vibrating alert for lap completion. The beeps the Cardio 40 gives off are high pitched, short and very quiet. They’re truly the weakest part of the whole setup. You’ll struggle to hear them in all but the quietest environments. A vibrating alert is really important for any sports watch and it is a shame it is missing here.  I’d also say that the watch is ever so slightly slow to respond to button presses, something that annoyed when I was going through menus.

Bryton Cardio 40 buttons

Another gripe is the side buttons. They’re large enough, but quite spongy and I found them a little tricky to use with sweaty fingers. I often grumble about this on watches, though, so maybe it’s just me. The front button, for OK and lap marking, is, by contrast, easy to use. Shining out like a green jewel in the surrounding black space you can see it readily, and it protrudes a bit too so it’s easy to find by touch.

Bryton Cardio 40 green button

If you want to make use of the online features you also need to download the Bryton Bridge application which connects to the Cardio 40 via the USB wired charge cable to upload activity data and download firmware updates. Using this you can upload to the web or to your computer for later uploading if you don’t have the internet. You might want to do this for backup purposes, but the Cardio 40 has plenty of internal capacity – its limits are 82 hours of activity and 1,500 laps of data.

Once your data is uploaded you can view workouts on a calendar that summarises what you’ve done when for a macro level view, or drill right in and take a look at today’s data giving you a dashboard view of calories burned, distance travelled, altitude gained, cadence and a range of heart rate statistics. This dashboard view actually means the Cardio 40 could double up to offer you all the stuff a Fitbit does, with the added accuracy on distances measurements that a GPS can – as long as you have a signal, of course.

What you are most likely to want to do, though, is analyse and track your activities, and this you can do to the nth degree. You can see summary charts of how much activity you’ve done over any timeframe and look at distance, heart rate, speed, intensity and all manner of other stats. There are loads of dynamic elements. For example the graph below your mapped route is linked to the map so that if you pass the cursor along it you can see where you were each statistic was recorded. Where did that peak in activity come? Where did I slow down so much? It can all be revealed.

Bryton Cardio 40 online

As if that weren’t enough you can create workouts giving you even more control over how you train.  The interface is suitable for all three triathlon sports as well as for walking and ‘other’ making it flexible if you change disciplines and as your levels of activity grow over time. To schedule workouts you just drag them from the list onto the calendar.

Bryton Cardio 40 calendar

It’s actually difficult to think of an analysis metric that isn’t offered here, and if I have a criticism it is that for the newcomer things might be a bit tricky to get to grips with. Serious athletes, though – by which I mean anyone looking to work hard and develop even from a standing start – will find everything they could wish for here.


The Bryton Cardio 40 is a smashing piece of kit. The watch is superb, its main failing being the lack of a vibrating alert and a slightly sluggish response to button presses. The range of metrics gathered is vast, battery life good, on board storage likewise.

The online software offers so much functionality that I’ve not actually covered it all in the review. Suffice it to say that walkers and marathoners ought to find it has plenty to offer. Some watches are designed for people at particular levels – for experienced athletes, or ‘serious’ ones, others better for beginners. The Bryton Cardio 40 really could be all things to all runners. Start with it as a couch potato whose goal is to walk five miles quickly, and it will see you through your first marathon and beyond.



  • Comprehensive metrics
  • Good battery life
  • Good on board features
  • Stylish design
  • Great online features


  • Proprietary charge and sync connector
  • No vibrating alert
  • Very quiet audio alert

  Score: 9/10

Manufacturer:  Bryton

SRP: £150