Gear Review: Garmin Forerunner 405CX (Part Two)

fig 1.

fig 1.

Having given the new Garmin 405CX rave reviews a couple of weeks ago when it arrived, I thought it would be a good idea to write a follow-up review now that I’ve got a bunch of training runs under my belt with it.

I’m pleased to say that my opinion hasn’t changed: this is an incredibly clever piece of kit. But more important than the clever design and ease of use,  it really has made my training more effective.

Training smarter with the 405CX

Now, as the Garmin website itself give comprehensive details of all the many, many clever things that this thing can do, I won’t waste your time trying to regurgitate them here. Instead, I’m going to focus on just three screens that I’ve been using on the Garmin 405CX, by way of illustrating how even I, of all people, can finally make the claim that I’m ‘training smarter.’

Figure 1, shown at top left is the screen that I now use most on training runs. As previously noted, the little chap at the top is your ‘virtual training partner’, the little chap at the bottom is you, and the ‘you are ahead by’ numbers relate to exactly how you’re doing in relation to the pace you’ve set for yourself, which is shown in figure 2.

fig 2.

fig 2.

Here, I’ve set it for 8 minute mile pace, but you can easily adjust that by simply stroking the bezel either up or down. Then, once you press the start button, the screen changes to show your virtual partner.

Should you wish to change to a simple stopwatch mode, you simply tap the bezel once. And if you want to see what your heart rate is doing, just tap it again, to go to the screen shown in figure 3.

(Could I also point out at this juncture that as a finely honed athlete in my mid 40s, my resting heart rate is a healthy 60 beats per minute. The somewhat higher reading on this shot seems to be due to the cafetiére of Columbian Roast I had imbibed just before taking these pictures.)

(And while we’re talking in brackets for a moment, I might also add that if, like me, you always struggle to run in the heat, the heart rate function on this thing has proven to me how big an effect the heat has on you, as my heart rate is a staggering 15% higher when running in 24 degrees than it is in 18 degrees of heat when moving at exactly the same pace.)

Training smarter by running slower

As you may know, training at full pelt all the time isn’t the cleverest way to go about it. So for some years now, I have attempted to mix ‘slow’ runs with tempo runs, and fartlek sessions. Yet running slowly all the way through a run (as opposed to just in the last mile or so when I’m knackered) is a skill that has always eluded me.

But with the Garmin, you can tell it just how fast or slow you want to go, and even a total incompetent can run at exactly the right pace to get the most from their training runs.

fig 3.

fig 3.

Listen to your heart…

Another fancy training technique that has always seemed like far too much trouble is ‘running at 75% of maximum heart rate’ which is, by all accounts, the optimum fat burning zone. Yes, I know. Seems like an incredibly nerdy thing to aim for, doesn’t it? But not if you’ve got a Garmin 405CX.

I used it to establish my maximum heart rate by the simple expedient of running up and down sand dunes until I felt sick, before dividing the resulting heart rate by 75%. So now when I go for a slow run, I simply use the heart rate screen shown in figure 3 to make sure that I’m burning fat rather than rubber.

The upshot of all this is that in just three weeks of using the Garmin in this way, I’ve dropped two pounds in weight, I feel fitter than I have in a long time, and I’m performing dramatically better on my tempo runs.

So while I’d love to return to the ‘jumpers for goalposts’ simplicity of my youth, I have to say that if you’re at all serious about improving your fitness through running, you really do need to have a Garmin 405CX.


12 thoughts on “Gear Review: Garmin Forerunner 405CX (Part Two)

  1. Great blog. I, like you, have found the 405cx to be a revelation.

    I came across your blog searching for an explanation for the “you are ahead by” numbers. I still don’t know what they mean. I’m assuming (using your fig.1 above) that 0.15 is 150m (assuming you’ve selected metric) and 1:24 is, well, I dunno! Is it 1:24 seconds per lap? Is it 1minute 24 seconds for the whole distance to that point? I’d very much appreciate your thoughts!

    Keep up the good work and don’t forget to stick to your pace on your slow runs!

    Take it easy

    • Hi Leesie,

      thanks for your comment. Unfortunately, I’m not sure what the 0.15 is – I’ve assumed it’s a percentage of the target pace. But I think that the 1:24 shows how far ahead you are of target cumulatively. ie, if you’d set the watch for a 10 minute mile pace, but actually ran the first mile in 8:36, you’d be 1:24 ahead of target pace.

      And yes, sticking to a slow pace on long runs is essential – it’s just a pity it took me so many years to realise that.

      All the best,


  2. Thank you for both of your reviews on this gadget. I have been on the fence about whether or not to purchase something like this to help me. Your first and second reviews have given me the answers to my concerns!

    Thanks and happy running…

    Houston, TX

    • Hi Stacy, thanks for your kind comments. Hope you like the Garmin as much as I do. And congratulations on being fit enough to run in the heat of Texas…



  3. Thank you so much for your very helpful review on the 405. If you don’t mind, I have 2 questions: Do you think this would be helpful for a newbie runner like me (been running for only 5 months)? Also, what’s the difference between the 405 and the 405CX?

    Thanks again!

    • Thanks for your comments Aya. Not 100% sure of the difference between the two, but I think the 405 comes without HRM and adjustable wrist straps.

  4. Hey,

    Thanks for your review and tips – very helpful. Just got my Garmin 405CX yesterday – SO EXCITED! Will take it to my first run tonight and 10k on Friday:). Good times all around!

  5. I have been using a 405 for about three years now and honestly don’t know what I would do without one! I have tried out a few of the other Garmin models but keep going back to the 405 for the advanced workouts and the virtual training partner. Best bit of running kit I own by far!

    My Garmin 405 Review

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