scratch

BSX Validity

I have a number of concerns with the validity of the results of the BSX.

• No independent validation. There is no independent validation of the results of BSX, which doesn't mean that the device it doesn't work, but it is a concern.
• Black Box. The BSX algorithm is proprietary and not clearly documented. This means it's hard to know if there is any scientific basis for their approach. BSX states that their algorithm is patented, but nowhere do they indicate want to their patent number is. Patent US20130096403 A1 (Apparatus and method for improving training threshold) looks like it could be for BSX, but I could not verify this.
• BSX Validation. BSX has performed their own validation but to the results are not formally published. There are various articles online describing this validation that BSX performed, but they did not use the gold standard of MLSS for Lactate Threshold. Instead they used an incremental treadmill test with lactate measurement from a blood draw, and relied on the Carmichael Training Systems determination of lactate threshold. I believe that this indicates that BSX has performed their internal validation against a seriously flawed baseline. (See Lactate Threshold for details.)
• 3 minute stages. The BSX protocol uses an incremental test with three minute stages, which does not appear to be a valid approach for measuring blood lactate directly. This is because blood lactate takes 20-30 minutes to stabilize for a given intensity. However, it is possible that muscle oxygenation would not be subject to this limitation as it is measuring a very different physiological parameter.
• %O2 Display. In my testing the BSX application showed a stable oxygen saturation regardless of exercise intensity, typically 86 to 87%. This is in contrast to Moxy that showed a decline in oxygen saturation with increasing exercise intensity, roughly in line with the published literature. BSX has suggested that future versions of their software will present a more realistic estimate of oxygen saturation, and this problem should not indicate an issue with their validity. Personally, I find this a lack of even a relative change in oxygen saturation rather troubling.
• Invalid results. In my personal testing, the results of the BSX did not seem valid, but seemed to be based on what I told the application was my 10K pace, and at the pace at which I terminated the test. The BSX indicated I had a Lactate Threshold pace of between 6:10 and 8:50 depending on what 10K pace I input and what pace I terminated the test.
• Exercise ignored. A bigger concern is I get the same indicated LT if I tell the BSX I'm performing a test, but don't actually do any exercise. Just sitting still and terminating at the same point gives pretty much the same result.