Garmin 920XT and running Dynamics

Got new life insurance and the company i am with offers 50% off on garmin products and as I am such a gadget head i decided to buy the 920XT which is also useful for swimming besides my normal running and cycling.

Screenshot 2016-04-17 15.52.59

The watch itself maps other data that i was not familiar with so popped out this morning on a run just over 10km to explore what the running dynamics mean.

Screenshot 2016-04-17 15.39.25

Running dynamics give a summary

Screenshot 2016-04-17 15.46.35

Cadence i know is stride rate – quicker chi type running has always been my thing – i am not a long heavy impact strider … In general, more experienced runners tend to have higher cadence. An often-cited target for running cadence is 180 steps/min. So i am bang on target for this run.


First off is Vertical Oscillation

I was feeling stiff at first but loosened up after a km of running – this is where the data goes into blue – there are green spikes in sync with the downhill sections after that …

The colors show how your ground contact time compares to other runners. The color zones are based on percentiles.

Color Zone Percentile in Zone Ground Contact Time Range
Purple > 95 < 218 ms
Blue 70 – 95 218-248 ms
Green 30 – 69 249 – 277 ms
Orange 5 – 29 278 – 308 ms
Red < 5 > 308 ms

Garmin has researched many runners of all different levels. In general, more experienced runners tend to have shorter ground contact times. Elite runners often have ground contact times of less than 200 ms. Virtually all experienced runners studied have ground contact times of less than 300 ms. Higher cadence and faster paces are both associated with shorter ground contact times. Many running coaches believe that a short ground contact time is characteristic of a more economical running form. However, at a set cadence, decrease of ground contact time usually increases vertical oscillation.

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Screenshot 2014-08-02 13.47.13


there is no way my VO2 is 62 – my polar HRM used to say it was around 57-59


The Garmin 910xt – a user review

A review by John Sharp who will hopefully one day be writing more on this blog …. a review of the Garmin 910XT which was up there along with the newish Garmin Fenix a a possible Polar RCX5 replacement….


I used to love her. I used to stare at her, mesmerised within her Cyclopic trance. I would gently caress her cool smooth features. She would respond, teasing me with secrets, revealing ever more with each tap and stroke. I knew how to push her buttons and she knew how to respond. And she could read me: tuned into my palpating heart as I grew increasingly hot with her encouragement. It wasn’t to last. Passion this intense rarely does. She couldn’t live up to my expectations nor I hers. Her faults, invisible at first, soon became obvious and impossible to ignore. She became quick to fatigue; from her I demanded stamina which was beyond her. She needed attention and new energy almost daily. She was temperamental in anything other than perfect conditions. Sometimes unpredictable and chaotic; often stubborn and seized. Soon the cracks in our relationship (most metaphorical, some actual real cracks) became insurmountable and the first GPS watch I ever loved, my Garmin Forerunner 405, and I were to go our separate ways.

the queen is dead long live the queen

The limitations of the FR405 are well known but I had been able to tolerate the terrible battery and infuriating bezel for a couple of years before a broken strap served as the catalyst for indulging in a new toy. I’ve been wearing Garmin’s Forerunner 910XT since March this year, have used it whilst competing in a spring marathon and throughout the build-up for an autumn marathon effort. This article is less a technical review of the device and more a discussion of how I have used the device over the last six months or so.

publicity pic

Whilst Garmin have released and specifically marketed other watches (e.g., Forerunner 610) for runners, a reluctance not to endure an anticipated fractious ‘touchscreen’ and a shorter battery life led me to consider the FR910XT. Technically, the 910XT is a triathlon watch. In fact, it’s essentially an upgrade to the clunky Garmin FR310XT. This means that not only can it track every single data point imaginable whilst running, but it can also do the same thing whilst biking and swimming. It’ll track and display pace, elevation, distance, calories, pedal cadence, swim stroke, laps and much, much more. Any information you might want to know, the 910XT is probably able to provide it.

It would be easy to get bogged down in the wealth of data on offer. What is vital is to establish which information is most pertinent to your needs. When I started running regularly three years ago I focussed almost exclusively on pace, running every outing at or above a predefined speed which I believed I should be capable of. Nowadays I don’t care so much about pace for the vast majority of my running. Rather, most days comprise ‘easy’ running during which I will not exceed 75% of my maximum heart rate. One of the advantages of the larger case required to house a bigger battery is the opportunity to incorporate a massive display. This is excellent for allowing the presentation of multiple data fields simultaneously and users are able to choose how many ‘pages’ of data they would like to scroll through, how many data fields they prefer in any one display ‘page’, and what specific data that should be. My own preference is to have one single screen on which I can see my effort (%age of maximum HR), my average pace, distance, and time elapsed. Users can choose from a huge selection of options (e.g., some might prefer current pace rather than average). When racing I adopt a radically different approach and rely on only one data field, the time. Selecting just one data field permits a much larger size of font. No distractions with other information; just the bottom line. And even then I typically only switch to this screen in the final minutes of the race to see how close I am to any targets I’m aiming for. For the rest of the race, the forerunner is resolutely set to the ‘Virtual Partner’.

The ‘Virtual Partner’ (VP) was undoubtedly my favourite feature of the FR405. The VP allows you to monitor your current pace against a set speed or predefined pace. I use, nay depend on, this feature for tempo workouts and races. I will plug in the pace I want to achieve with the hope this somehow also ‘programs’ my legs. This mode displays a (poorly) illustrated running character who is either ahead, level with, or behind the target pace. It offers a quick and ready means of establishing whether you are ‘on’ or ‘off’ target in either direction and gives you a swift kick up the backside (comedy extending boot not included). It also indicates just how far ahead or behind you might be by both distance and, more usefully, time. Whilst for workouts I often find myself trying to ‘keep up’ with the VP, in races, at least when starting with fresh, tapered legs, this feature allows you to temper your enthusiasm and regulate your pace appropriately.

The VP has been embellished on the 910XT. The ‘Virtual Racer’ (VR) feature allows the user to race against existing courses and workouts. In essence it provides a ‘shadow’ of you, or someone else who has previously completed the same route, and allows you to monitor your progress against yourself or them. Whilst the VP maintains a constant speed regardless of the terrain and gradient, the VR allows for more realistic comparison. For example, when faced with a substantial climb, the VR adjusts to a much slower speed for the hill. A nice interactive feature allows users to download workouts from the Garmin Connect site onto their device. This would allow individuals to ‘race’ against friends who completed the same event in previous years. For example, if I had a friend who completed the Virgin London Marathon this year who I was desperate to beat, I would definitely consider inputting their effort to ensure I stayed ahead of them. It is exactly reasons like this that I have no friends. This feature can also be used when cycling and I understand the Team Garmin-Cervelo files from the Tour de France are available for you to ‘compete’ with David Millar et al. albeit without the EPO, closed roads, and full complement of domestics.

Numerous other features and settings are available. I can only imagine there are some people whose training life has been revolutionised by the ‘Intervals’ feature which enables users to setup a simple interval workout which the watch will then guide them through, barking (or vibrating and beeping at least) orders on cue. Setting up intervals allows the sessions to be designed and tailored for the individuals needs and permits the user to specifying how long the warm-up is, the number and distance/time of work intervals, the rest interval, and then the cool down. I suspect this mode would be useful for complex sessions and negates the athlete to carry and refer to pieces of paper or recall which number of 20 repetitions they happen to be on at any given time. Amazingly, there is the capacity for sessions to become infinitely more complex and any idiosyncratic routine can become designed in the ‘Workout’ mode, a feature with an endless array of ‘if/then’ type scenarios. In truth, I’ve never gone near it.
Whilst most of the features seem well designed to meet the needs of a competitive athletes, even the lame modes aimed at the novice can be adapted with a little imagination. For example, the Run/Walk function (essentially just an alert to prompt users to start running after a short pre-planned spell of walking) can instead be used as a fillip to get endurance athletes (e.g., ultra-runners) to eat regularly. I would guess the prohibitive pricing of the 910XT would discourage any entry-point purchasing. However, the battery and features will definitely appeal to seasoned ultra runners. Garmin should change this feature to an ‘Eat-a-gel’ alert.
The ultra-running boom has led to new performance demands for GPS devices. Training on predominantly flat surfaces altitude is rarely especially relevant for road racing. It’s data I neither seek nor need. However, my eventual hope is to turn to the trail and with those the hills. For years cyclists have managed to get barometric altimeters within their handlebar mounted computers. Runners have had to tolerate GPS-based altimeters. The FR910XT introduces an integrated a barometric altimeter. An old friend, Nicol Boyd, is a recent convert to running and, churning out miles on the mountainous trails of Hong Kong, accumulates thousands of feet of elevation. In a sport where elevation covered is arguably more important than distance is this a useful new addition? Unfortunately, Nicol is not convinced, “The barometric altimeter is highly temperamental and always spikes 100-200m at the start of every run. Even well into the run, when things should have settled down, the altimeter readings are pretty erratic and very often out by a noticeable margin. This sucks if you are one of the many people who like to run up hills.” Whilst firmware updates might help resolve such issues, it seems improvements are required.
It is not only the unreliable altimeter which takes the shine off the 910XT. The heart rate monitor frequently struggles to record accurate data. Most commonly this occurs at the outset of a run and can take a mile or so of spiking before settling down to accurate levels. This appears to be a long-standing problem for Garmin. Their previous HR monitor was inadequate and it appears their attempts to improve this, introducing a new design of strap and monitor, have failed. Some Garmin advocate transferring the Garmin transmitter into a Polar Wearlink+ strap.
Quibbles aside, there is much to be admired in this Garmin unit. The battery life is exceptional. Whereas my FR405 would regularly ‘die’ on me during runs, the FR910XT’s battery has never yet been fully depleted. Garmin estimates a 20-hour battery life and this seems accurate. The general build seems good. Being a triathletes watch requires the case to be waterproof and robust. Whilst the watch is most definitely ugly, it is functional. Besides, I’ve never understood people who want to be able to wear their GPS watch “as a watch”. Like all Garmin Forerunners, the watch syncs wirelessly to and ANT+ USB from which the information is upload to the online Garmin Connect software. This is becoming an ever expanding and accessible interface and includes optional synchronisation with iPhone apps and social media integration with easy sharing of routes and workouts. The interface is relatively attractive and easy to negotiate and generally very reliable.

So, with the six month honeymoon period over, are my new love and I for keeps? Lets wait and see whether she guides me to a new marathon PB in four weeks time.

Polar release integrated gps watch the RC3 GPS

For recreational runners and cyclists who want integrated GPS with smart guidance. This looks like a better made version of the Garmin 610 …. As some readers might know I have the Polar RCX5 with a separate G5 gps pod. I love the extra features of the RCX5 but think that for most athletes and the less tetchy and geeky this RC3 with integrated GPS makes more sense.

One thing polar need to look at in the future – well two things to really help Polar appeal to all the mass market is firstly to go ANT+ using the most common and useful protocol for sensors and the other is to enable polar personal trainer to export .tcx files so that users can upload into social exercise sites like Strava, Endomondo and MapMyRun to name a few. Or failing this to allow those websites to access the protocol for the polar communicator / uploaded.


  • Training Benefit gives you instant feedback after your session
  • Tracks your route, speed and distance using built-in GPS
  • Running Index scores your performance
  • Slim and lightweight design with rechargeable battery
  • Allows you to share your training with your friends


Body measurement features

  • Compatible with Mac (Intel-based) via USB cable
  • Compatible with PC via USB cable
  • Compatible with via USB cable
  • Back to start
  • Distance – training, lap, and total
  • Route mapping – opt. with web service
  • Running Index
  • Speed/Pace – current, average and maximum
  • Backlight
  • Date and weekday indicator
  • Display text in English, German, French, Spanish, Portuguese, Italian, Dutch, Danish, Finnish, Norwegian and Swedish
  • Dual time zone
  • KeyLock
  • Low battery indicator
  • Rechargeable battery
  • StopWatch
  • Time of day (12/24h) with alarm and snooze
  • Water resistant – IPX7

Ayr Duathlon – my first race – what a great day

5km run

28km cycle

5 km run

It hadn’t started out to well – I had pulled my calf last week doing hill repeats and it didn’t seem to clear up – it was niggling and I had avoided running for a whole week … did a slow 5km yesterday just to feel it and it was painful. I had doubts as to whether it might make me pull out of the race so it was weighing on my mind.

Last nights sleep was also pretty awful woke up 3 times with the kids and nightmares then the youngest stomped in a 6am in far from the best mood … so I did what any sensible person would do and I went downstairs for a leisurely porridge and honey breakfast.

Picked up Steven my brother in law at 7:40am then headed down to Ayr for the Duathlon … we arrived pretty early and registered looking out at the clear blue sky and the fact the air temp was only 6 degrees C. there was a fair share of TRI bike – saw at least 3 Cervelo P3’s and other TRI  bikes. Also glad to see another plain ti Racer like mine … (a van nicholas but any ti bride is good)

Duathlon prep - freebie shirt and deep heat applied

I decided to do the whole race wearing running tights (the compression i figured would help my calf) and a long sleeve cycling top. A pretty relaxed briefing then we were off …. a short run around the school where the run was based and then off to the coast road – a dirt track with its fair share of potholes. It is an out and back run so by the half way point the leaders were already 500m ahead.

Run 1

By transition I had my first attempt at doing transitions on my Polar RCX5 (which allows you to change sport in the same workout which is great and it also allows you to export separate gps .gpx files for each part) By the time I had my bike shoes on and was gulping down a gel Steven was also in transition. I left about 20 seconds in front of him and then looked down to see that i hadn’t restarted the watch – so add 30 sec and 300 metres to the time on this leg.

bike route and elevation

The ride was great – although I think the boys and girls on their all carbon TRI  bikes must have queried their decision as the road was pretty tatty and the route was quite hilly. You could definitely hear them as the carbon rattled over every bump and hole … I could see sense in an aero machine on a flat well surfaced road but South Ayrshire obviously hasn’t spent money on resurfacing in years and they must have flt every bump. There were a couple of uphills where I stood to climb as the lack of padding despite the lovely ti frame was very much felt.

There were great views and lovely sweep descents and the car drivers were passing very carefully which was great. At one stage I was getting a bit tired but sucked down another gel and then some water (they sure are gloopy) but then suddenly I was back at transition.

2nd transition was quick although my legs felt like they belonged to someone else.

2nd run

Second run was identical and after exiting I got to see the first person storming down the hill to the finish – so a 18min lead over what I would do. There is a little hill just in the first km and I was struggling … but after that first km I felt steady although my calf was pulling so just kept up with my pace. After the turn around i was heading back and saw Steven again about a km behind me. Had a mid road high 5 that nearly took me off my feet and then was aiming for the guy in front but could make no gain on him.

run comparison
Polar software breakdown

finished feeling good – just really happy that calf felt no worse … chatted briefly to chap in from then just waited for Steven … Watched a guy come in that was at least 60 and looked in better shape than I have ever been in my life and then another man just behind Steven that must have been at least 70 …. really inspiring.

So my first Duathlon finished and i loved it … big shout out to the Marshals who did a great job and the organisers …. I will be be back hopefully with a good calf and a better transition strategy.

Hill Running repeats but now a slightly sore calf

That was a bit horrible

Went to Alexander park to do some hill repeats tonight

amble to the park then started the repeats – 1st one was to scout the hill – then realised best option was the less steep longer ascent with a short drop down and then repeat repeat. The HR belt can’t have been sweaty enough as it showed a 109%HR effort …. but rest were fine showing me hit 92%of my MaxHR. It hurt a lot which I guess it is supposed to do ….

the hill repeated and my speed
polar HR (strange spike on 2nd hill)

then i started to feel my calf pulling so to prevent muscle damage i stopped and didn’t finish my 10 repeats ….. still a bit tender but should be fine.

Turbo Interval on the bike

yesterday was supposed to be a run day in light of the upcoming duathlon but I couldn’t face it (as opposed to today when I am forced to face the sleet and cold later)

So the plan was this:

10min warm up then

4 MIN at +85% MHR

4 MIN recovery at 65% MHR

Repeat 4 times

Then cool down for 10 min

But was watching the iPad – a doccie about the Yom Kippur war with John Snow daddy and son and kind of lost track of timings ….

Here is the Garmin read out showing speed

speed on the trainer

The intervals are not so easy to see on this graph – esp the 2nd interval where I went for nearly 7.5 minutes ….

Here is the polar Heart rate Graph from Polar Personal Trainer which shows the intervals clearer. Normally I program the RCX5 so that it beeps to remind me and beeps when HR is too high (rare) or too low ….. Think I should stick to that is it is less forgetful than me doing it manually.

Polar RCX5 HR graph clearly showing intervals

not working today so off to the cinema at lunchtime – how decadent ….

Duathlon Training starts in earnest today

my plan over the next 3 and a bit weeks and the training load as mapped out on my Polar software below

red - don't train
yellow - no hi intensity
green - go do something