This past June, WHOOP partnered with Major League Baseball to see how performance-enhancing data could provide a deeper look into players’ training and behavior, and potentially improve their fitness. Over the course of four months, WHOOP monitored the physiological data of 230 minor league athletes from 28 different teams, making it the largest performance study ever conducted by a pro sports team.  Armed with data that gave personalized daily Strain, Sleep, and Recovery, athletes were able to correlate specific metrics to their overall performance.

One of the most notable behavior modification stories comes from a player (this study is HIPAA compliant, therefore names are omitted) who quit drinking alcohol after seeing how it negatively affected his Recovery. Over time, this player subsequently saw a decrease in resting heart rate, an increase in heart rate variability, and an improvement in Sleep performance. Subjectively, he commented on how much better he felt during the time period after he quit.


WHOOP provides a daily Recovery score. The red zone indicates poor Recovery, while the green zone indicates a near full Recovery. This player’s average Recovery trend improves over several weeks.

In this case, because the player was more keenly aware of his choices and how it affected his performance on game day, he was motivated to modify behavior to gain an advantage. Modification, however, doesn’t only refer to negative behaviors that might affect performance. It goes both ways.

It’s one thing for an athlete to feel fitter, faster, and stronger, but it’s another to have data quantify his or her physiology. When athletes can digitally measure their fitness over weeks and months, it gives them a point of reference to go off of, and can motivate positive behaviors as they see the results.

Throughout the WHOOP MLB Performance Study, WHOOP measured the following metrics for all participating athletes:

Heart rate variability (HRV), which monitors the naturally occurring irregularity of your heartbeat, is one of the most useful metrics for tracking training and defining workout loads to optimize performance.  For the duration of the study, WHOOP measured the raw HRV data of a consistent segment of the athlete population. As displayed in the chart below, the raw data shows a positive trend over the course of the season, indicating greater cardiovascular fitness.


How receptive to the data were the players and coaches? According to Kristen Holmes-Winn, VP of Performance Optimization at WHOOP, who was an integral part of the study and recently attended MLB’s Winter Meetings, teams were enthusiastic about the long-term trajectory of having continuous access to this kind of data.

“For most of the athletes in this study, it was the first time they ever had visibility into their own physiological data. Initially, I think it was a little daunting because they could see very clearly how undesirable behaviors cost their performance,” said Holmes-Winn.

What was most exciting, however, was that the wisdom gained through WHOOP insight, which translated into behavior modification and ultimately led to significant physiological and performance improvements.”

If anything, our presentation at the Winter Meetings spurred new conversations surrounding the use of technological data, especially in a game as historic and traditional as baseball. For example, do players really need to be at the ballpark 8 hours before a game starts? What might help instead? By elevating awareness, WHOOP is giving coaches a platform to ask questions that otherwise might have never been brought up, and more importantly, empowering athletes to make the most of their season with the physiological data at hand.

Come back Monday for Part 4 of our Special Report on the The Locker detailing the findings of the WHOOP MLB Performance Study.

Introduction: WHOOP and MLB Conduct Largest Performance Study Ever in Pro Sports

Part 1: Effects of Travel

Part 2: Athletes in the Outfield