BSX Insight

The BSX Insight is the first wearable lactate threshold sensor and the result of the work of founders Dustin Freckleton and Nithin Rajan of BSX Athletics. The goal of BSX Athletics is to help athletes train smarter, not harder, through the use of lactate testing, which has typically been limited to professional/elite level athletes.

Without diving too deep into the science of lactate testing or how the BSX Insight works, blood lactate testing generally requires a laboratory, trained technician, lactate analyzer, and the taking of blood during the course of a ramp-up test. The BSX Insight is able to produce the same results minus the lab, finger pricks, technician, and lactate analyzer. The Insight uses a small device that is worn in a calf sleeve that uses near-infrared spectroscopy (NIRS) to sample and record data in the form of light as it passes through tissue and returns to the device. The distortions detected by the device from the original signal are processed, and through a series of algorithms it produces a result that corresponds with the results of blood lactate testing. For those of you with tattoos or other skin pigmentation differences, because of the intensity of the light and different wavelengths, the BSX Insight should not be affected by the problems reported with other optical sensor devices (e.g., Apple Watch).

There are three types of BSX devices available: a running version ($299), cycling version ($369), and multi-sport edition ($419). I opted for the multi-sport edition. For those of you who are curious, the major differences between the models is the degree of waterproofing and the algorithms used to calculate your lactate threshold.

Most endurance athletes currently use some sort of testing protocol in an effort to “guesstimate” their lactate threshold for cycling and running. These various testing protocols (e.g., 30 minute run, 20-minute FTP test) are often, but not always, an attempt to replicate blood lactate testing. The BSX Insight eliminates the guess work. This is not to devalue the performance evaluation benefit of such tests, but it is an improvement on their ability to determine training zones and lactate threshold.

The BSX Insight also allows the test to be conducted on a semi-regular basis, ideally in line with training phases (e.g., pre-season, build, race season, post season, etc.) in order to determine if one is improving based on training phases or if it is necessary to alter the training plan. This is where the BSX Insight thrives, allowing users to test on an as-needed basis, whereas most athletes are unable to have regular blood lactate testing.

Test Protocol

The BSX Insight test protocol for cycling and running is nearly identical to a standard blood lactate test. It is a ramp-up test based on your current/estimated lactate threshold. For running tests, users will need a treadmill, (ideally calibrated at 0.5-1% grade) and Ant+ heart rate sensor, and BSX Insight. For cycling tests, users replace the treadmill with an indoor trainer and Ant+ power meter. I found that a smart trainer is more effective for these tests as you can control the wattage during the ramp-up tests. For those who don’t have a smart trainer, BSX recommends you adjust your bike computer to 15- or 30-second smoothing to prevent chasing the wattage. I found this worked well for data-smoothing and produced similar results compared to tests I conducted on my smart trainer.

The recent updates to training software programs such as Wahoo and TrainerRoad, allowing for “PowerMatch” where your bike's power meter can control your smart trainer, become extremely useful in getting accurate results with smart trainers.

Prior to beginning the ramp-up test, users will begin by following the directions on the BSX Insight app (iOS and Android). The app requires users to answer a couple of basic questions to help establish a baseline level for the ramp-up test. A recent update to the app eliminated the need to repeat this step for subsequent tests. After answering these questions, the app displays the ramp-up test intervals and instructions on how to ensure a valid test. Finally, users are instructed to pair their BSX Insight to their mobile device, then pair either their power meter and/or heart rate monitor. This step is sometimes the cause of reported sensor dropouts with the BSX Insight.

Although the BSX Insight pairs to your mobile device and acts as a bridge for your Ant+ devices, your Ant+ sensors (power meter or heart rate monitor) pair with the BSX Insight, not your mobile device. I found that pairing any sensors with the BSX Insight first, and then putting on the BSX calf sleeve, nearly eliminated any pairing issues. I would be remiss not to mention sensor drop-outs. The most recent update greatly improved this problem and it remains a priority with BSX. I only noticed issues pairing my heart rate monitor during a cycling test, but I am aware that some users have reported problems pairing power meters with the device, which would be a much larger problem in terms of results.

The next step is the actual test. The BSX app begins the various stages with your goal power/pace displayed along with time remaining in the stage, heart rate, and real-time muscle oxygenation. Each stage is 3 minutes, and when 10 seconds remain in the stage a countdown timer appears on the user's mobile device. In the next software update, this timer will also have an audible warning which I think will be a nice addition. The test continues until the user hits stop on the app, which should be done when the prescribed pace or power can no longer be maintained.

One thing I noticed on the ramp-up tests, they were far less draining, both physically and mentally, than typical threshold tests I have done in the past. At the conclusion of the test, I did not feel exhausted, and in terms of training, I was able to do a quality session later in the day or the following day, unlike typical bike and running test protocols.

Another interesting feature I noted was the real-time muscle oxygenation. After running numerous tests, I learned what percentage corresponded to fresh legs or tired legs prior to a test. Understanding and being able to document these numbers was important in ensuring that any ramp-up tests I conducted were done when I was properly rested, if that was the goal. The real-time muscle oxygenation is a feature that users will be able to employ for daily training in the next major update to BSX software.

Having access to a tool like the BSX Insight also allowed for some creative testing. For example, conducting a run test after a bike ride or bike test after a swim to determine the progression from brick training, or to establish training zones for such training.


At the conclusion of a test, the BSX app produces a screen with a graph of your most recents tests, your lactate threshold, aerobic threshold, and corresponding heart rates. It also provides suggested training zones based on the results using either Coggan’s or Friel’s training zones, with the option to edit. Currently, the results of the test are presented in numeric format only but in the near future, as a result of user requests, BSX will also provide data in a graph format (raw data), as typically used with blood lactate testing.

In the past four months, I ran close to 30-40 tests under various conditions (e.g., rested, fatigued, outdoors, brick threshold tests, etc.), and the device functioned as described on each test and withstood the use. On one of these tests, I was able to confirm that my results from the BSX Insight corresponded with the results from a blood lactate test. BSX Athletics claims 95-97% accuracy when compared to blood lactate testing.

I also found that my results, particularly for cycling, were lower than I would have obtained using traditional "guesstimate" protocols in both running and cycling. In speaking with my coach and a test conductor for blood lactate tests, this is a common phenomenon.

By chance, I also had a test that failed to produce a result due to a dropped signal between my mobile device and the BSX server during the analysis stage. I was happy to learn that BSX was able to retrieve the data from my BSX Insight and the server, to obtain my results and push the data to my mobile device the following day.

In the event of a failed test, BSX can also pull the data to determine what caused the failure. Currently, if a there is a user error or other type of error during a test, users will not learn of the error until the ramp-up test is complete, even if it occurred in the first couple of stages. BSX will be releasing an update that will advise users of errors during the test. However I did not experience such an error over the course of numerous tests.

I also learned from conversations with BSX Athletics that as a user conducts more tests, the BSX Insight learns and can further refine its results.

Performance Improvement

Knowing your lactate or aerobic threshold will not make you a better athlete. Neither will your power meter or your heart rate monitor. It is all about how you use these tools. If the BSX Insight has any shortcoming, it is that it provides users with a great tool to improve performance, without the support to do so.

Anyone can buy a blood lactate analyzer and conduct tests, just as anyone can get certified to do a Retul bike fit. Just because a person is “qualified” and has the tool(s), doesn’t mean they are using properly or to its full advantage.

That being said, assuming you have the luxury of the likes of the Boulder Center for Sports Medicine, a qualified sport scientist will not only provide you with accurate and reliable blood lactate testing and results, they will also provide you with the appropriate training zones, and more importantly how to train to improve your performance based on the results. In other words, they have the ability to interpret your results and provide feedback to improve your performance, which is the ultimate goal of lactate testing. And if I had this luxury, and the financial resources ($150-$200 per test), this would be my preference. However, this is the very reason BSX Athletics developed their device, because most athletes don’t have the budget for this luxury.

I do have the luxury of having Coach Steve Brandes, who has experience in blood lactate testing, long term tracking, and training based on lactate testing. Having a coach with this experience, schooled in lactate testing, fills the current void with the BSX Insight. In fact, this is where I believe the BSX Insight is best suited: athletes with coaches who can take advantage of data provided by the Insight and modify training accordingly.

For example, I was able to discuss my test results with Coach Brandes prior to a recent 70.3 to develop my race plan. We also discussed his experiences with blood lactate testing versus traditional threshold testing (e.g., 2 x 20 minute FTP test), where he saw athletes produce results that were inflated based on the testing protocols. I am one of these athletes where the variance between a typical FTP test and BSX lactate test was 17 watts. After discussing the results with my Coach, we both agreed that the results of BSX Insight test were more realistic. This difference is significant when it comes to training in the appropriate zones, and personally I found it allowed me to go harder on hard days because my easy days were easier. The end result over the past four months was improvement in my aerobic and lactate thresholds.

Also, during base training when speed or FTP may decrease or remain constant, it was nice to see improvement in my aerobic threshold, which would have gone unnoticed without the use of the BSX Insight.

Examples such as these provide coaches and knowledgable athletes with key metrics that allow training phases and race plans to be evaluated for their effectiveness. My coach was also quick to note the potential value of a device that can monitor these metrics in real time, a feature BSX Insight users have also requested, and which BSX will be implementing in a future software update.

Individuals without a coach but with knowledge of lactate testing will benefit for the reasons listed above, but depending on their knowledge and experience, they may lack the ability to use the results to make necessary training adjustments. BSX Athletics recognizes that the education component (for athletes and coaches) is an area that needs attention, and it will be an integral part of their next phase of development.

Moving Forward

BSX Athletics has clearly stated their plans for moving forward. Users will be happy to know that the immediate objectives are improved sensor stabilization, speed of communications, and the use of the BSX insight for day-to-day training. No definitive timetable was provided, but based on our discussions, I wouldn’t be surprised to see a major update released before the end of 2015.

From here, I expect to see BSX push forward with the educational component for coaches and athletes, and that may close the gap between their device and services offered by sport scientists. I also expect to see the BSX Insight pair with Ant+ watches and provide real-time alerts based on data from the BSX Insight. And possibly direct import to training platforms, such as TrainingPeaks, and a BSX ramp-up test on TrainerRoad. For those of you with Bluetooth sensors, I don’t expect the BSX Insight to pair with such devices this year, although it has the hardware capabilities.

Final Thoughts

Are you at a point in your training where you need a hammer or a chisel? If you have reached a point where you are starting to fine tune your training and/or performance, the the BSX Insight is a great tool to add to the arsenal. It isn’t flashy carbon, but it does have the potential to improve your performance and help you train more efficiently.

The BSX Insight is another solid addition to the category of wearable technology, and it works as advertised. There are very few growing pains with the current model and with the ability to update the firmware, I look forward to taking advantage of upcoming features. This is not an entry level device, but if you have ever considered blood lactate testing and you have the ability to make the most of the results, this is a great tool for improved performance.