BSX Insight: Getting your threshold heart rate (LTHR)

BSX Insight ReviewI had planned to write something a bit more in-depth about the BSX Insight’s approach to estimating your threshold efforts. However it was so straightforward that it just merits a quick nod in the right direction.

Before I start though here are three things to bear in mind.

  1. It seems pretty accurate based on ONE TEST (I will do more). So if you plan on doing a few lab tests every year it’s probably cheaper to buy a BSX. Just a thought.
  2. Why not get  your tri/bike/run club to buy one and share it round? You might need one of each sleeve size.
  3. The BSX and MOXY products do MORE than merely determining your threshold levels. I’ll be covering that separately.

With the multisport version of BSX there are options to just analyse your workout or to follow either a running or bike threshold test. Essentially they are ramp tests that take about 30 minutes. With the bike test you start at a very low level of watts (you’ll need a power meter) go for 3 minutes at a specified level and then increase by 20w and repeat multiple increments with no rest. You’ll probably be able to get a couple of levels higher than what you think your threshold power is. So if you think it’s about 300w (and it is about 300w) then you will probably go through the 320w, 340w and maybe 360w intervals.


So, you finish and you immediately get your LT1 and LT2 and your HR zones. Nice.

These are both Lactate Threshold Heart Rates. We normally refer to the second one LT2, the Anaerobic one, as the LTHR. The LT1 is the aerobic threshold.

One advantage of this method over Friel-type protocols is that you get LT1 andLT2. I’m assuming both are calculated by BSX. With Friel LT1 is just assumed to be at a certain level below the LT2.

Watt? Yes your get your power zones as well as your FTP at the same time. Simple.

Accuracy: Both the LTHR (-3bpm) and FTP (-5w) were a tad lower than I last had ‘measured’. I’d not done a lab test for over 6 months and not really cycled much for a couple of weeks, having just done a HM. So the results ARE quite plausible. Probably ‘about right’. Indeed the FTP was nearly identical to the mFTP recently calculated for my by Golden Cheetah (modelled FTP, -2w).

I suspect that the BSX will produce results whose accuracy lies between a sports lab test and a Friel CP20/CP30 type test. If that’s true it will be a move up in accuracy for most of us but not suitable for athletes who consider that they need absolute precision. You don’t get absolute precision from a lab test either, a lab test whose results could be different the following day.

Note: This is not claimed to represent a scientific test. Judge for yourself, if you think it’s accurate enough for you. If you read around various forums you will find many experiences of people happy with the accuracy for determining zones and thresholds. You will find others who have spent more time validating results but please note that many are based on the first iteration of the product. I am using the 2nd generation product. When I do more tests I will probably incorporate them into a more formal review rather than update this post.

Reader-Powered Content

This content is not sponsored. It’s mostly me behind the labour of love which is this site and I appreciate everyone who follows, subscribes or Buys Me A Coffee ❤️ Alternatively please buy the reviewed product from my partners. Thank you! FTC: Affiliate Disclosure: Links pay commission. As an Amazon Associate, I earn from qualifying purchases.

2 thoughts on “BSX Insight: Getting your threshold heart rate (LTHR)

Comments are closed.