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This is a series of emails on the Moxy Data Update Rate that I wanted to post so everyone could follow along.
Initial Question from Andrew Sellars A question to Roger from the group from the BPR Testing Team:
What is the rate of data sampling of the Moxy? By this we mean, how often are samples analyzed through the device? Or, is it a continuous flow of information, with the digital read out simply giving an average digital value over the contraction/relaxation phase of the muscle being examined?
Sincerely, Andrew Reply from Roger Hello Andrew,
The Moxy cycles through the LED sequence 80 times and averages the data. It uses the averaged data to calculate a new SmO2 reading every 2 seconds.
On the commercial version of the Moxy, we talked about having a "high speed" mode where the device calculates a new reading 5 or 10 times per second. It would be more data than you might normally want, but you could see SmO2 changes on much smaller time scales. I would appreciate feedback on if this mode would be a useful feature.
Roger Reply from Juerg Roger, it is a question of change of price as well. If there is no or only minimal cost involved to improve sampling size it is always beneficial and I can show later in our ongoing discussion why and how it can or could be used for. For the "road model" but even for the coach out there one nice option would be to have an option to average the data's so we can choose averaging for 30 sec or I min easy so we can easy fill it in an excel sheet coaches may have developed for their own purposes. So having the current out put with an excel option of a 30 or 1 min averaging would be nice certainly once we go to the IPAHD version of the small center ( UrPahd ) Even on the display on the watch an averaging of 15 seconds would be much better , than the steady restless jump on numbers. We will show you end of the week , when going through the first part of the assessments we do here in Quesnel. Cheers Juerg
Reply from Neal Henderson
It might be nicer for an even faster data rate capture for the MOXY, as many training devices (cycling powermeter head units, GPS units, heart rate monitors, etc.) allow 1-second sampling, it would be nice to sync the data with 1-second MOXY data as well. Also, since the MO2 values are far more dynamic than some other physiologic values, having the faster sampling rate would be nic to have. From what I’ve been told about the ANT+ protocol, I believe that there are 4-samples per second of data averaged for the 1-second ANT+ information displayed/captured. My .02, Neal Reply from Rober Pickels I agree with Neal in regard to reporting raw data. A 1 second report would be significantly easier to sync with existing data.
I will say that the speed with which the Moxy unit responds is impressive. We tested myself today and saw that my value at max (16) began to rise immediately at the cessation of workload and was 51% at 30s and 60ish by 1 minute which is where it stabilized.
Both a good and bad trait is that we discovered if I sat up to drink water, my values dropped ~8% with the increased vastus load. This could be very useful for our bike fitting (instead of EMG go right to oxygen utilization), but may benefit from selectable averaging at the display for training. Robert Pickels, M.S. Reply from Roger Thanks for all of the feedback on the update rate.
I can provide a bit of technical background on some of these issues.
Right now, the fundamental "speed limit" for Moxy is determined by how fast the microprocessor can execute the algorithm to calculate a new reading. I haven't checked this on our newest microprocessor yet, but I'm thinking that we should be able to do at least 8 readings per second, maybe faster.
It is true that ANT+ typically updates at 4 readings per second, but we could overcome this several ways: ANT+ has options to go faster Moxy could send multiple data points in each transmission Moxy could store data with finer time resolution than it transmits In my own experience, one of the biggest drawbacks of faster sampled data is just that there's so much more data to deal with so it takes longer to download, makes bigger files, fills up the sensor faster, etc. It seems like having several options would be useful. We'll work on it. Reply from Juerg Here an add on from the practical side. I think first priority is to have a NIRS system , which is cost efficient and practical. Meaning we have to have the ability to store longer workouts. One of the problem is batteries life and with it as well the storage ability. The second part is what is practical usable. We have with the Portamon a tool for research with an incredible data collection information and it is so overwhelming , that for practical use we move to ab average of 15 seconds to have some decent practical information. The advantage from MOXY is exactly that no overwhelming information but practical information. Take it like a HR monitor versus a 12 lead ECG. both are great at the right place. I think the main part is to have NIRS for real practical use first over all other great ideas. As long we can't make a break through resp. changes in the traditional way we look at intensity control we do not even have to think to compete with Portamon. I think that the target group is the coaches , centers and person on the street. and once we have this target reached, than there is a smile on all peoples face and enough other options will show up with further and smarter development. First goal should be a fast recovery opf data's for coaches with an average of 15 - 30 or 1 min options so we have a clear trend in SmO2 and tHb . I will sent you once graphs with data collection in high rate and even when taking the MOXY it is too much to see where you like to go. Summary : Research tool versus simple step for the public. Main goal battery life span for longer events . 2. Easy to retract information in a average rate 3. Big question and open still for solutions . How to fix the moxy on an muscle without creating a compression ( circular which comes up as a incomplete occlusion. Thanks for the great feedbacks and yes it is great to internally discuss open and =clear where we can go. BUT. We have to get to a practical tool to be able to make more steps forward. It is fun to discuss till the sun goes under but at the end MOXY has to survive to get to the different ideas we can discuss. So guys , work hard and let's go out and show , what we can do with small but practical steps to change assessment ideas. Let's jump over our own shadow sometimes and accept changes. Hmmm should have been a priest
Reply from Andrew Sellars
I am not sure if this should be posted to the Forum, so will write it here, and let Juerg post it if it is warranted:
This is an interesting discussion that came about from a simple first question. The background behind the question was actually based on a much more practical aspect of assessment. The question we had was whether the MOXY was sampling often enough to pick up the differences in SmO2 values between contraction phase and relaxation phase during a single cycle rotation, and whether the number represented the AVERAGE SmO2 of the time period being tested, or some other value.
Roger has stated the digital value is an average of 80 cycles over a two-second period, which is much faster sampling rate than I was expecting. Clearly, with 40 readings each second, the unit goes far beyond any human motion we would be looking at in sports, so the answer for me is very satisfactory.
Having the data averaged over 15-30 seconds would be absolutely fine, with the exception of VERY SHORT intervals, where we may be interested to see how quickly the recovery phase happens, but otherwise, the slower display rate would be easy to justify for the end user.
We continue to have some interesting results here. First field test subject was unable to clearly affect SmO2 results at intensity of HR=152. Second subject at slightly lower intensity able to CLEARLY affect SmO2 with breathing pattern changes.
One PROBLEM we have been able to identify. Deliberately slowing cadence, while maintaining power leads to a dramatic drop in SmO2 in every rider we have tested so far (this was another reason for our original question on sampling rate). The implication, is that while respiratory changes CAN affect SmO2 data, which could have profound implications for both training and racing, this data might be obscured by the more "normal" response of some athletes to change cadence under varying loads.
I would like to suggest to Andri, that for the purposes of the study, that the cadence for each test subject is recorded, and held stable throughout the test. Without accurately and aggressively maintaining cadence, I feel the test results could be called into question. Reply from Andri Hi everyone
I just wanted to give my opinion on some of the topics begin discussed.
In regard to the sampling rate. A new averaged SmO2 reading every two seconds in my opinion is sufficient for almost all users, with exception of maybe some researching groups.