Wednesday, December 5, 2018

Humon Hex sensor review - part 2


Some time ago I reviewed the Humon Hex muscle O2 sensor.  There were several major issues making it a very poor choice for interested athletes.  Recently I purchased another unit (Black Friday sale) and decided to give it another chance.  Perhaps the most glaring problem in the original one I used was the extraordinarily weak Ant+ signal making it almost not usable.  
The tracings below are some preliminary results from just 2 rides, with more to follow.  I will be looking at 2 major parameters, signal strength (drop outs) and O2 saturation patterns.

The following figures were from an interval of 360 watts for 90 seconds then 240 watts for 45 seconds.  A BSX sensor was on my L costal and the Hex was on the R costal area.  I am sure they were not over the exact corresponding mirror areas, but were close.  In addition, the Hex still needs a calibration step (according to tech support this is used to adjust the led brightness for different skin pigmentation).  I picked the costal area because it is a great non locomotor site to follow, and the Moxy, in most hands does not work there.  If the Hex does, that would be a major advantage.

O2 saturation
Humon Hex on R costal
Power in red, Yellow is O2


BSX on the L costal
Power in red, Yellow is O2  

Observations:
  • Both signals are solid with no drop outs.
  • The nadir is lower with the BSX (10 vs 30%), but the baseline and recovery are very similar (within 3%).
  • The overall pattern is similar but there are subtle differences (the green arrows)
  • At this point I do not know why the desaturation patterns were different.



Total hemoglobin:
Humon Hex
Red is power, purple is THb

BSX
Red is power, purple is THb  
Observations:
  • As with the O2 data, there are no drop outs or loss of signal.
  • The general pattern is similar, with the start of cycling power there is a drop in THb.
  • However, the Humon Hex has a gradual drop at the interval start, whereas the BSX abruptly declines then stays level until power declines (green vs purple arrows).


Deltoid (no BSX data, this is Humon Hex only)

This was shown on the last post, but from the standpoint of signal strength, expected data I show it again.  In addition, no light shielding was used.  The BSX would not have provided data without shielding:
Red is power, yellow is O2

Observations:
  • Good signal strength.  The watch was on my R wrist but the sensor on my L deltoid.  The signal needed to pass through a fair amount of tissue.  Lack of light shield was not an issue.
  • Consistent, reproducible results.  Both nadir values were similar with intervals reaching VO2 peak.
Same ride as above, but I simply elevated my arm (lateral raise) holding an empty water bottle:
Red is power, yellow is O2, purple is total Hb
  • As expected the total Hb drops (external muscle compression) along with the O2.
  • No signal loss. 
Final thoughts:
  • The Humon Hex now has excellent signal strength.  No drop outs were seen!
  • The Deltoid tracing was internally consistent, similar baseline and nadir values seen with VO2 peak intervals.  A simple lateral raise shows the expected drop on O2 and total Hb.
  • An unexpected bonus is the tolerance for outside light.  No other shielding is needed.  This is not a trivial point.  Veteran muscle O2 users know all to well the problems with getting a good clean tracing free from light contamination.  
  • Usage for monitoring Costal O2 and THb is possible.  Fit and stability were fine.  Signal was free of drop outs.  The overall curve shapes were similar to the BSX but not exactly so.  I will continue to explore the Humon Hex as a costal O2 monitor but it seems very promising.
  • Cost is much lower than Moxy.  I was able to get one for just over $200 during the sale. 



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