Humon Hex Muscle Oxygen Monitor Review

The Humon Hex is a device for measuring Muscle Oxygen Saturation or SmO₂, similar to the more expensive Moxy. This is a brief review of the Humon, which I've been using from 2017-2020, alongside the Moxy which I used from 2015-2020.

1 Introduction

Humon works by shining infrared light through the skin and into the muscle to measure how much oxygen your blood is carrying to that muscle, called Muscle Oxygen Saturation or SmO₂. The idea is that a hard-working muscle will use a lot of oxygen so the blood in the muscle will have less oxygen remaining. The problem with SmO₂is that instead of varying directly with intensity, SmO₂is typically low at rest or low intensities, and rises with exercise intensity as more blood flows to the muscles, decreasing again at high intensity. The values can also vary widely from session to session, possibly due to slight changes in sensor position. The data can be displayed on recent Garmin watches and the Humon smartphone app. SmO₂sensors also provide an estimate of blood flow (tHb or Total Hemoglobin), allowing for the calculation of the amount of saturated and unsaturated blood, but this is rarely used in practice (Golden Cheetah being one of the few systems that perform the calculation.) While SmO₂ sensors are compared to measuring blood Lactate, I don't think this is valid.

2 Humon compared with Moxy

The only other SmO₂sensor on the market is Moxy. Having used the two side by side for some years, here's my thoughts.

• I don't think either offers valuable enough insights to warrant purchase.
• Both show similar patterns of SmO₂ change, though I have no way of knowing which one is "right". In all probability, the difference in reading is due to sensor placement. The Humon has more smoothing of the data than Moxy, and the smoothing is fixed, where Moxy has user selectable smoothing and sampling frequency.
• The Humon appears to have more IR receivers (4) compared with Moxy (2). It's unclear if this is a real world advantage.
• The blood flow measurement (tHb) seems to be more sensitive with Humon than Moxy, but it's unclear if this reflects actually changes or sensor artifacts.
• The Humon is far easier to use, with a strap that holds the sensor in place conveniently while the Moxy requires taping on.
• Humon has a smartphone app, though its guidance seems dubious. This reflects the difficulty in interpreting SmO₂ data as much as any flaws in the Humon app.
• The Humon has wireless charging and is waterproof to IP54, while the Moxy has a micro USB port for charging and is waterproof but without a stated rating.
• Humon is cheaper.

3 Images

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  The Humon, strapped to my quad.

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  The Humon top, in it's charging cable, with Moxy below

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  The post workout analysis in the iOS app.

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  The real time display of the iOS app. Note this is saying I'm reaching the limit, while I'm actually barely started my warm up.