A wearable device appears to be just as good at measuring lactate thresholds for endurance runners as older, more complicated methods, according to a new study.

The lactate threshold is when the blood concentration of lactate or lactic acid exponentially increases during exercise, when muscles can't make enough energy using available oxygen anymore and start to make energy anaerobically, without oxygen. Endurance athletes want to exercise as close to this point as possible without exceeding it.

Older methods of measuring these thresholds require blood samples to be taken during exercise tests, or analysis of the air inhaled and exhaled during exercise. Both approaches require costly equipment and experts. The wearable device sleeve fits on the lower leg and is non-invasive.

Higher lactate thresholds help endurance athletes perform at high levels for extended periods. "Additionally, an athlete's lactate threshold can be utilized to dictate training practices as training zones specific to the athlete's lactate threshold can be made," said lead author Nattai Borges of Central Queensland University in Rockhampton, Australia, by email.

"This would allow a coach or athlete to construct a training program with workloads that are specific to the athlete and allow better monitoring of training loads over time," Borges added.

Lactate threshold is not a key performance predictor for sprinters or shorter event athletes, Borges told Reuters Health.

The BSXinsight multi sport edition used in this study uses near infrared spectroscopy to monitor muscle tissue oxygenation via the absorption of the near infrared light as it passes through muscle tissue.

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It is the first commercially available and self-administered method to predict lactate threshold and costs $419.99. The manufacturers did not respond to a request for comment.

"Near infrared spectroscopy is an accepted and non-invasive method to measure tissues oxygenation and has been utilized extensively in previous research," Borges said. "Further, the device sits in a compression sleeve that fits over the calf muscle of the user which is similar to commercially available compression garments."

None of the participants in the study reported any irritation or pain from the device, he said.

The researchers, who are not affiliated with the device manufacturer, studied seven male and seven female adult athletes, from recreational to highly-trained, who performed exercise tests to exhaustion on a treadmill. They wore the calf-sleeve devices and had their blood lactate levels measured by finger pricks at the end of each exercise stage.

Lactate thresholds predicted by the wearable device were similar to the ones predicted by actual blood samples, the authors reported in the Journal of Strength and Conditioning Research.

The devices were also reliable in repeated tests and tested against each other, the authors wrote.

The self-administered exercise test prescribed by the BSX insight would also allow coaches to remotely monitor athletes, useful for when coaches and athletes are not located in the same city, Borges said.