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From Fellrnr.com, Running tips
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TUNE consists of two insoles and attached pods, connected by a cable as shown in the image below. This allows it to potentially gather the metrics typically associated with a Footpod, plus have data from pressure sensors in the insoles. I've not tested the TUNE, but what I can gather suggests it provides less data than you might expect. There is obviously Cadence, and they have Ground Contact Time which is shown as Swing Time and Stance Time (these are just simple calculations from and GCT.) The only metrics from the insoles appears to be the percentage of footfalls that are heel strikes (Rear Foot Strike, RFS), and something called "Stance Dynamics." It's not entirely clear what "Stance Dynamics" is except for the text "the time in propulsion during the Stance Phase." This suggests that perhaps the insole can measure sharing forces to determine how much of the Ground Contact Time is spent with the foot pushing backwards to generate propulsion. Having one device for each foot provides some insight into your symmetry which is likely to be a significant factor in injuries, but obviously that's limited to the metrics that TUNE is gathering. It looks like TUNE will provide audio coaching, but it's unclear if there will be any real-time audio feedback. They have created the option of sharing data with your coach, which is a nice option for those who work with a coach. Their website suggests that they might be adding and iWatch in the future, something I wish more running sensors would do. I'm not seeing enough data being gathered to make this device worthwhile. There are a couple of concerning caveats, the main one being that the TUNE is not waterproof. The other possible concern is that the insoles cannot be cut to size, but in practice these insoles go under your existing insoles rather than replacing them, so this might not be an issue. Overall, I'm a little underwhelmed by the amount of data that TUNE is providing, and I'm not planning on testing it at this point.
[[File:KinematixTUNE.png|none|thumb|300px|The TUNE sensor.]]
=Testing Approach=
Where possible, I like to verify the metrics that these running sensors are providing. In some cases, this is a fairly trivial, such as [[Cadence]] which you can measure by simply counting your steps. Some other metrics I've verified by using High Speed Video (HSV.) This requires a little bit of time and effort, and a lot of attention to detail but it can be quite an effective approach.
* '''Ground Contact Time'''. I've used HSV to verify Ground Contact Time, and found more variation than I expected. Using HSV to measure Ground Contact Time you can see the very earliest and latest stages of contact as well as estimating the pressure changes from the compression of the foam midsole. Examining the video makes it clear that some devices are including time where the shoe is completely airborne, which is a little surprising.
* '''Vertical Oscillation'''. I've evaluated the accuracy of Vertical Oscillation by looking at the movement of my torso using HSV and lasers. This proved to be rather more tedious and time-consuming than I'd anticipated, but the results were worthwhile (to me at least.)
* '''Foot Strike'''. I've done some simplistic testing of sensors that measure [[Foot Strike]]. I've run with these sensors in my usual heel strike, plus running forefoot both with and without my heel touching down. I've used HSV to verify that my foot strike pattern is what I think it is, as it's easy to be mistaken. I didn't include midfoot strike as this is tricky to get exactly right, and tricky to verify using HSV. This approach to measuring Foot Strike is based around the point of first contact, not the point of highest force. Personally, I believe that the latter approach is far more relevant, but harder to measure.
* '''Power'''. It's tricky to measure running power without access to VO<sub>2</sub> equipment, so I've resorted to some simple tests. An incremental treadmill test should show an increase in power with an increase in pace; if it doesn't pass that test, then it's probably not much use.
=Ideas For The Future =
This section documents a few ideas I've had for running sensors, partly to inspire manufacturers, and partly to disclose these ideas so that they cannot be patented in the future.
==Proportional Audio Feedback ==
Many running sensors will provide information on your biomechanics using an audio message. Typically, this is a spoken message such as "you're landing on your heel" or "your braking is 1.31 feet per second." I generally find these audio messages far more annoying than they are useful. The messages tend to occur too infrequently for me to get a sense of how any modifications in my form are changing the metric being measured. The spoken word means it's a little tricky to combine this with music or radio. A better approach is to have a simple signal like a beep when your metric is outside the desired level. For example, [[TgForce]] will beep when your [[Impact]] is too high, and you can combine this simple audio signal with music for the spoken word from a in audiobook or the radio. I believe that a superior approach is to have a variable audio signal that indicates how well you're doing. So instead of having a simple threshold such as 7g you'd have a range such as 5-9g. Then, when your [[Impact]] is above the lower threshold you would get an audio signal, but the audio signal would vary in one or more of volume/pitch/duration depending on where you are in the range. So a 5g [[Impact]] would produce a quiet, short, deep beep, and 9G [[Impact]] would produce a loud, longer, high-pitched beep. This way you'd get quantitive feedback on how well you're doing against your chosen metric.
==Deriving Practial Practical Impact From Acceleration==
Often running sensors will provide a value for impact based on the acceleration measured at the foot or leg. However, the bulk of the stresses on the lower limbs comes from the acceleration of the overall body mass during landing. Therefore, I believe it would be more effective to measure the acceleration of the torso on landing to provide an estimate of the stresses on the lower limbs. I suspect that both peak acceleration and the area under the acceleration curve would provide insight into the stresses of running. Peak acceleration is fairly obvious, and I suspect is more useful than a jerk. However, it may be useful to evaluate the area under the acceleration curve, as the time spent under stress could also be a significant factor on injury rates.
==Foot Strike==
Several running sensors will measure [[Foot Strike]], though so far, I've only found RunScribe and SHFT to provide useful data. However, even these devices tend to measure the foot angle on initial contact, and I suspect that it would be far more useful to measure foot and call at the time of maximum deceleration of the torso.
