While pro athletes turn to many of the other apps on this list for amusement, WHOOP plays a key role in athletic performance.
That's because the WHOOP app pairs with the WHOOP band, which has become the go-to wearable of elite athletes.
What makes WHOOP so beneficial is the way it tracks metrics like sleep, heart rate variability, resting heart rate and skin temperature to produce both a daily "strain score" and a daily "recovery score."
By monitoring these numbers, athletes can see how both hard they pushed themselves and how well they recovered each and every day. The sleep tracking, in particular, seems to be of great benefit to pros.
A couple years ago, NBA players like DeAndre Jordan (who can be seen wearing a WHOOP in the above photo), Chris Paul and Matthew Dellavedova started vocalizing their support of the device.
Since then, the NFL Players Association announced a five-year partnership with WHOOP in which every active player will be provided with a device, and the WHOOP has also been approved for in-game use by Major League Baseball.
Kevin Durant also recently invested in the company.
A rider in the 2018 Tour De France wore a WHOOP during the entire competition, producing a fascinating look at the data behind one of sport's toughest tests.
For more info on the WHOOP wearable and app, read our "5 Things I Learned From Using the Wearable Design for Profession Athletes" article.
Photo Credit: WHOOP