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Development Team Member
Posts: 45
This was my first day using a BSX sensor on the VL, left leg.  Test conditions, subject age 60, male, riding 150 miles a week x 15 yrs, Powercranks x 12 yrs, Powertap P1 pedals, ipbike android software recording to a Note 4, compression Skins full length and black bike shorts, estimated 30 min TT power 240 watts, recent best 3 min power 380 watts, best 1 min power 550 watts.  Temp about 70.

First 3 min interval at about 330 watts, hit close to my max HR.
Note the slow rise in smO2/thb after the fast dip(fast dip caused by muscle compression).  Quick O2 rise after stopping.
Type 2 muscle phenotype with acidosis(relative poor capillary density, mitochondrial activity)  vs other muscles taking over?

3min interval 330.jpg 

Second interval 2.5 min near 330 watts, followed by just L leg pedaling (170 watts/leg--see shaded) for about 1 min (simple to do with powercranks)
Cardiac supply should have been fine for one leg (HR not too bad) but O2 drop pretty significant.

2.5 min 320_then L leg.jpg 
Last 2 data points are from a second ride a few hours later (legs were pretty tired).

4 min interval about 300 watts.
smO2 also dips then climbs a tiny bit.  Very tired and winded at the end, but fast O2 rise.


5 min at 215 watts (just under CP?)
Pretty flat smO2 and thb-very good overshoot of O2, thb.

215_5 min tired.jpg 



Development Team Member
Posts: 178
Hi bjrmd
Since you are using a BSX I presume it was on your calf. When we use moxy's we usually place them on our quads. Typically the VL but sometimes the RF. It seems to me that you are not desaturating that much. This could mean that A) your calf is not doing much of the work, B) that your mitochondrial density is low so you cannot use much oxygen, C) you have mainly slow twitch fibres with a high myoglobin content that does not desaturate so readily. 

Others may different ideas or better explanations. 

I would suggest that you try some short sprints of no more than 30 seconds to see how far you desaturate. This may give more insight.

Posts: 265
You need to be a bit careful with assessing the BSX data the same way as Moxy data with respect to the magnitude of desaturation.  In my experience, the BSX reading sometimes doesn't have as much dynamic range as the Moxy and there is not a consistent relationship. It's one of the limitations of the measurement algorithm they use.  So a 50% on a BSX might be close to 0% or it might not be close to 0%.

You might need to get more creative in your assessment protocol to be able to infer the things that Craig was describing when you are using a BSX.


Development Team Member
Posts: 1,501

Since you are using a BSX I presume it was on your calf.

He  actually  fixed it   on the VL  as  explained  at the start so  no problem there.
 The  SmO2  amplitude  is  not  that    high so BSX  or  the athlete's   leg reaction

I have  many  BSX  MOXY  data  comparison  so   no comments  just   a  few  pics  here  sent to me  from  readers  who  have both .

 Below placement  at the same  muscle

Ture    some  small difference  due to placement always

calf  VL  bsx  MOXY.jpg 

 Below  repetition of a  test   2  times   so one after the other  and no  change in  sensor  placement

moxy bsx.jpg

o  different equipment  and one is  sold as a  bloodless no prick  lactate analyser. The other one  is a  simple   NIRS  equipment.
Below a  similar idea but we used Portamon and MOXY, Very old comparison I did  many years back  with a first generation MOXY  as it was hard  for me to believe  that my super great portamon  for  15'000  $    would show  the same  as   the MOXY

portamon  an dmoxy super  overlpa.jpg  Purple  is  Portamons  Hb diff.  which is  the MOXYs  SmO2  and  red and blue  2 MOXY's and above  purple  blue  and red   is  1 portamon  and 2 MOXY's  overlap in an assessment.

Now  it  the great  datas.  Every   picture is a  workout on its own  with its own limitation  and  information. Problem  it is  to long  for  a  local  feedback limitation  and too short  for  a  more  towards delivery  limitation  options.
 basically the  question   we often show on here.

Ipahr and ipahd end.jpg 

The  first hint  you always  can look is  at  HR in the different loads. This  gives  you a  simple  feedback on   the  indirect  reactions  of  CO (  true no SV  feedback )

Than  just a  short    question   it looks  like some   small intervals  at  the end  see circle as  Watt  shows  this  and tHb  interval but he was  able  to maintain  SmO2  so no visual   interval in SmO2  how    was he able to do this. Very nice  work here  and great ability to manipulate  SmO2.



Development Team Member
Posts: 1
Well as everybody is so very polite and careful in their words, allthough quite devastating with the graphs, my few cents. As an original  kickstart supporter of BSX and now enthusiastic user of Moxy I would like to say that in my experience the BSX is a useless toy that shows hardly any variation in its data, works with a black box approach on its algorithm, gives no advice on how to actually improve your training with smo2 data on their site, and I could go on. I regret every cent I paid for the original and the update BSX.
However now I am very happy with the Moxy which is real and great tool and is supported by a very knowledgeable and positive thinking group of developers and trainers.

Development Team Member
Posts: 45
Many thanks for all the comments.

I need to digest carefully but wanted to respond to the issue of the BSX dynamic range. I saw that posted elsewhere so did the following 2 tests.
The first graph is the sensor on my bicep and the 3 smo2 dips are caused by a bp cuff at 200 then 100 then 50 mm mercury (yes the old fashioned mercury, I am a physician and have it in my office)

The second is the sensor on my biceps in the gym.
I did 3 sets of curls using about 45 percent 1rm(25 lbs) , 45 sec for 8 reps, 45 second rest then repeat.

As you can see, oxygen dropped quite well and rebounds after. Sorry but the bsx app and website won't show thb.

I originally became interested in nirs after 10 yrs of worsening bilateral shoulder impingement and getting very close to needing surgery.
I am a long fan of bfr, kaatsu but after doing a reread of the literature, it seemed that documenting muscle ischemia is very important.
The moxy, or bsx is an ideal way to follow this.

Yes, the bsx software is horrible. I could not record thb as noted above. But I could have used an ant + watch or phone(which I will do next).

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Development Team Member
Posts: 45
In regards to the question on if I did intervals in the above circled picture, no,I was just trying to pedal to cool off.

Also just some more personal physiological guesses.
 I am not a natural endurance athlete, and have really worked hard (powercranks) to become decent. I am(was) a good sprinter, type 2 muscle person, and relatively very strong for my age at the gym.

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