Thanks to technology, your heart rate, sweat rate, calories burned, stride length, and whether you’re wearing boxers or briefs can all be calculated in real time, wirelessly transmitted to a laptop, and posted to Twitter before you return home from your weekend jog. Engineers in Germany are hoping to add blood lactate levels to the abundance of fitness data using a miniature ear clip containing an electrochemical sensor.

Lactate levels quantify just how deep into anaerobic hell an athlete is. As exertion progresses, oxygen levels in the blood drop, starving tissues of the O2 they crave. At this point, pyruvic acid starts to be converted into lactic acid, thereby increasing the blood’s lactate level. Once the accumulation begins, the athlete’s performance is likely to slip. Understanding where and when an athlete reaches this threshold would be a valuable data point, allowing workouts to be optimized and focused, to increase endurance or sharpen a skill. But getting such data currently requires a costly instrument and a sample of blood from a pin prick. So only elite athletes undergo such analysis, and only do so in a lab setting.

Germans dislike a pin prick as much as the next country’s athletes, so researchers at the Fraunhofer Institute for Microelectronic Circuits and Systems have developed a prototype sensor to get athletes out of the lab and keep their fingers unscathed.

The sensor consists of multiple microchips, as shown in the photo, measuring just 2 by 3 mm. One contains an enzyme gel that triggers flow from the lactate. Additional chips with microelectrodes work to quantify the data from first chip. Apparently the electrode can be coated with various enzymes, allowing the quantification of other blood properties or electrolytes. The data can be transmitted from the ear clip to one’s chosen form of mobile data collection.

The researchers suggest it could be three to four years for commercialization. Till then, assume that burning in your legs on mile 13 is evidence enough that you’ve crossed the dreaded lactate threshold.