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From Fellrnr.com, Running tips
Moxy
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Moxy is a device for indirectly measuring exercise intensity, and could be considered an alternative to measuring blood Lactate. I believe it's most useful as a way of evaluating the effectiveness of an athlete's [[High Intensity Interval Training]].
=Introduction=
Moxy 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 SmO<sub>2</sub>). 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. Moxy provides a figure for the percentage of oxygenated blood compared with the overall total. (For the technically minded, Moxy is looking at the differential infrared absorption from saturated and desaturated hemoglobin.) This technique has been used in laboratories for a while, but Moxy is the first device that is practical for regular use. Moxy is a small device that is taped above the muscle, and provides real-time information to a variety of devices including many recent Garmin watches. In many ways Moxy is a similar to a heart rate monitor, measuring something that is a proxy for exercise intensity. The Moxy approach is a little different to many others because it measures a specific muscle, and while that is influenced by overall exercise intensity it does provide some uniquely muscle specific insights. The Moxy has the characteristics of a research device rather than a consumer product. It's rather expensive, and some aspects of it are a little crude, but the flip side is that a lot more effort has gone into the underlying functionality. It's not a trivial device to get the best out of, and I think it will appeal more to coaches and serious athletes than it will to the recreational runner. While measuring [[Muscle Oxygen Saturation| SmO<sub>2</sub> ]] is not equivalent to measuring blood Lactate, I think it can provide a similar type of insight.
=Moxy Placement=
Where [[BSX]] has a nice calf compression sleeve that it slots into, Moxy requires taping onto your skin. This is far from ideal, but in practice is works well enough. Moxy provides some specific tape that has a hole cut out and a ring of adhesive on the outside to hold the Moxy in place. I've typically put the Moxy on my calf to mirror the positioning of the BSX so I can compare the two, but when I want to use the Moxy on its own I tape it over my quad. The company claims the Moxy will read the muscle through up to 12mm/0.5" of fat, which may be a factor in placing the Moxy for some athletes. The Moxy is fairly immune to movement as long as it's well attached, unlike Pulse Oximeters which won't tolerate even slight movement. (Pulse Oximeters measure superficial blood flow which includes venous and arterial blood flow, so they have to detect the pulsing arterial blood and ignore the deoxygenated venous flow. The Moxy is reading the blood far deeper so this is not an issue. It's also why Moxy won't tell you your heart rate.) Moxy should be waterproof enough for running or cycling in the rain, but they recommend putting it in a small sealed bag for use underwater. Ambient light can cause a problem for Moxy, and they sell a small plastic "Light Shield" that blocks the light. I didn't buy the light Shield and simply cover my Moxy with a piece of light proof fabric. While my approach works, I'd recommend getting the light Shield, as you need something you're confident will block infrared light and normal materials will be effective.
