I was thinking back to a conference that took place some time ago on the theme of data capture, in particular to the presentations on wearable physical activity devices or trackers . These were still fairly new at the time and I quickly picked up that the people in the audience, most of whom were much younger than me, were quite sniffy about them. This contrasted with their enthusiasm for hearing more about music streaming. We talked about this over coffee and one participant mentioned his disappointment that his partner would only listen to the same songs again and again on Spotify rather than accessing their Daily Mix (a collection designed to extend your listening based on what you had already accessed). I sympathised. In contrast there was not much talk about activity trackers; they were not cool and they were not going to take off.
Well, I don’t think trackers have turned out to be cool but they have slowly taken off, at least among certain social groups, though nothing like to the same degree as social media . But it remains easier to see the limitations of the wearable devices than their advantages . An obvious constraint on take-up is that users have to invest in hardware (wearable devices) to get the full benefit and this costs money and is another piece of kit you need to look after. There are doubts too about the accuracy of trackers and concerns over privacy and sharing of data. Activity loggers can play into people’s anxiety about health and advertising can take the form of gender stereotyping. Ceaseless logging of physical activity can become an end in itself so that you end up gaming the system, e.g choosing your terrain carefully to increase step count. For that matter you can cheat outright – for example by attaching the device to a bike or dog! The key point, however, is that if you are comfortable about your fitness level the devices serve no real purpose; if you are naturally fairly active you just get on with it, you don’t need to measure what you are doing. This is even more the case when it comes to logging sleep activity. Those who sleep well don’t talk about it, record it or even think about it, they just do it. In fact were they to monitor sleep they might well become more self-conscious and disrupt what was working perfectly for them in the first place.
So why trackers? They can help users who have a special need to focus on physical activity and this seems to be particularly the case as you get older and are aware of becoming less active. The evidence is fairly slim, surprisingly these are still early days in research of activity logging , but as Ridgers et al. (2016) put it ‘there are some preliminary data to suggest these devices may have the potential to increase activity levels through self-monitoring and goal setting in the short term’. This is not a ringing endorsement but sounds about right to me.
Aside from large scale quantitative work, we also need to know more about the experiences of wearing these devices. Again there are some papers often based on what particular types of wearer get out of it, e.g. those recovering from serious illness, using activity as part of weight reduction programme, older people. The key point made by Jarrahi et al (2018) is an obvious one, but worth repeating: if you are disposed to see wearable devices as motivating then you will find them to be, if not forget it.
Noticing gaps in the literature I spoke to people I knew who used activity trackers and asked them for their opinions. They had found the devices generally useful as they helped with focusing on activity levels. Users had particular goals in terms of improving fitness or weight watching so that if they noticed their step count was falling they would deliberately do something about it, i.e. go for a run or walk. Some spoke of friendly competition with others. The devices were worthwhile though their usefulness was linked to the short term goals they had set themselves, future use was less clear.
I don’t wear an activity tracker. However, I did once have a Garmin watch which I used for a while for tracking runs. I got some satisfaction from knowing I was improving my speed and I liked to check that I was pacing myself evenly. I got out of the habit of using the device when, as age was catching up on me, my times were getting longer rather than shorter. Of course logging might be most useful when performance is dropping but I felt knowledge of my own tail-off was only go to depress me. I also found charging the device to be a faff and worried about the power running out. At one point I was disappointed about a run because the battery had discharged half-way through and I would not get a full reading to download. This was ridiculous. Why did I need to measure it to believe I had done it and enjoyed it? However, even if I no longer use my watch, I still line up with other runners after a weekly Park Run to get my time recorded . We clearly have no need to do this, so why do we do it? I found some comments by Engeström  useful here. Drawing on Vygotsky and Russian social constructivism, Engeström sees exercising agency (i.e. getting to do what we would know we want to do or must) as a two fold process: first design it and then do it (the execution phase). He gave the example of an alarm clock. Finding the will to get up earlier is not easy. The alarm clock helps reminds us that we must do it. However, an alarm set by someone else would not work, we need to have planned for its use, i.e. we calculate what time we need to get up and set the alarm accordingly. In fact very often the planning is enough and we wake up any way before or as the alarm goes off. I think tools to measure physical activity work in a similar way. We design the use of the tool, i.e. we personalise the device with our details, we look at captured data and we make judgments about what we need to do, and having designed it we feel encouraged to do it. We are using the device to put into effect an otherwise vague intention to take more exercise; the device is helping us do it. I don’t want to go out and buy a tracker or Smart watch but I am not as dismissive of them as my fellow conference participants once were. And I will still queue to log my time at Park Run even if the data are only pointing in one direction.
 Wearable devices will capture data on movement, including how far one has moved and how many steps completed. They will also do a calorie used count and may monitor heart rate, sleep length and sleep activity. Waterproof devices will do distance and strokes when swimming. Data can be shared by users. Probably the best known companies for producing wearable devices are Fitbit, Garmin, Huawei and Withings. A smart watch is not dedicated to physical activity but will include physical activity tracking. A smart phone App such as Map My Fitness can log runs, but does less than a wearable device.
 Estimates of numbers of users are in the tens of millions, e.g. 30 million estimated active Fitbit users and 55 millions Apple watch wearers, 20 million Map My Fitness users, These are large numbers but not in the same league as, say, numbers of Facebook users.
 There are several contributions on trackers and other devices to ‘The Conversation’ which are fairly sceptical of their value, e.g.:
Siek, K. (2020) Why fitness trackers may not give you all the ‘credit’ you hoped for [online]
Duus, R. and Cooray, M. (2015) How we discovered the dark side of wearable fitness trackers
Kerner, C., Quennerstedt, C. and Goodyear, V. (2017) Young people oppose Fitbits in schools [online]
 There are several systematic reviews, e.g. Ridgers et al. (2016) and Shin et al. (2019), with most concluding that there is not much to systematically review in the first place.
 Park run is a free 5km run held in many parks in UK [https://www.parkrun.org.uk] and now around the world.
 Engeström’s key example concerns ‘cheating slips’ used by students. These are notes which student might access during an exam but Engeström argues it is the making of the notes rather than the access to them that make them effective.
Engeström, Y. (2006). Development, movement and agency: Breaking away into mycorrhizae activities. In K. Yamazumi (Ed.) Building Activity Theory In Practice: Toward The Next Generation. Osaka: Center for Human Activity Theory, Kansai University. (CHAT Technical Reports #1).
Jarrahi, M., Gafinowitz, N. & Shin, G. (2018) Activity trackers, prior motivation, and perceived informational and motivational affordances. Personal and Ubiquitous Computing, 22, 433–448.
Ridgers, N., McNarry, M. and Mackintosh, K. (2016) Feasibility and effectiveness of using wearable activity trackers in youth: a systematic review. JMIR mhealth and uHealth 4, 4: e129.
Shin, G., Jarrahi, M.H., Fei, Y., Karami, A., Gafinowitz, N., Byun, A. and Lu, X. (2019) Wearable activity trackers, accuracy, adoption, acceptance and health impact: a systematic literature review. Journal of Biomedical Informatics, 93: p.103153.