Whoop, a Boston-based wearable company working on a device for athletes, announced an additional $12 million in funding as it prepares to officially launch its Whoop Strap device and performance optimization system. Two Sigma Ventures led the round. Mousse Partners, Accomplice, Promus Ventures, Valley Oak Investments, and NextView Ventures also participated. This brings the company's total funding to $22 million.

The Whoop Strap, which is already in beta launch with a number of athletes and teams, is a 24-hour always-on wrist-worn wearable for athletes that tracks heart rate, heart rate variability, skin conductivity, ambient temperature, and movement, and can also deliver insights about an athlete's sleep quality. The device sends that data via Bluetooth to a smartphone or tablet app used by a coach or trainer.

Collecting continuous data allows coaches and trainers to get a complete picture of athletes both when they're active and in their off time, including evaluating their sleep quality. This can be especially helpful for athletes recovering from injuries. In order to facilitate 24-hour tracking, the device can be safely charged without removing it.

“At the elite level, it’s no longer just about outworking your opponents to get an edge,” Whoop advisor Mike Mancias, a long-time athletic trainer for LeBron James, said in a statement. “In fact, research shows that 30 percent of athletes are overtrained, which can lead to injury and poor performance. It’s only by balancing intensity with recovery that athletes can optimize performance. Whoop’s system and the data it provides helps me gain a better understanding of each of my individual athlete’s bodies, their capabilities, and their limitations, leading to better and safer athletic performance.”

The device is already in the hands of NFL, NBA, NHL, Major League Baseball, and Major League Soccer teams as well as some US Olympic teams and all the major collegiate conferences.

Whoop spun out of Harvard’s Innovation Lab, which likely helped it land some big name advisers, including MIT Media Lab Founder Nicholas Negroponte, former Puma Chief Marketing Officer Antonio Bertone, and UCSF Chief of Cardiology Dr. Jeffrey Olgin. The company raised a $6 million round in June 2014.

The new funding will be used to scale the company and continue to develop the next generation of the technology.