Coaches using heart monitors for better training.
Credit: Courtesy Polar USA

When University of Kentucky basketball coach John Calipari watches his players practice, he doesn't have to wonder who's working hard and who isn't. Thanks to the heart monitors he has each player strap around his chest, Calipari knows for sure. A quick glance at the data they pump to a courtside computer tells him players' exertion rates – requiring sprints for anyone who's been dogging it.

"They really don't know how to push themselves," he says of his freshmen-loaded but freakishly talented team, as it preps for another NCAA tourney. "In the past, whatever they've given has always been good enough."

Calipari is one of many coaches, both collegiate and pro, who are realizing the benefits of heart monitors in training. Whether using basic strap-on models or souped-up versions that incorporate GPS and other high-tech software (which can show how far a player has run on the court, how many calories he's burned, even how fatigued his muscles are), coaches can now work individual players to their maximum effort levels – and rest them when the data says they need it.

Since introducing the devices last season, Calipari has seen major transformations in seven-foot sophomore Willie Cauley-Stein (a first-round lock for June's NBA draft), sophomore Alex Poythress, and freshman Dakari Johnson. "If players want to be special, it's extremely hard," Calipari says. "We've got to break every barrier we can that holds them back."

Finnish cross-country skiers were the first to use portable heart rate monitors for training in the 1970s. Runners looking to build endurance took notice, as did European soccer teams. In 2002, Chris West, a strength and conditioning coach for the University of Connecticut's men's soccer team, pioneered the use of heart rate monitors in American collegiate athletics. (He discovered the head coach drilled players so hard that their exertion rates over four days were the equivalent of playing seven games.) West was the first to buy the now approximately $10,000 system made by Finnish manufacturer Polar; today, that company supplies around 330 clients, from Division III lacrosse to the NBA, NHL, NFL, and MLS.

The Phoenix Suns, known for their scientific approach to injury prevention and recovery (in 2012, the team purchased a cryo-chamber that cools the body post-workout with blasts of nitrogen), take the use of heart monitors one step further. Since last year, the team has had players practice in the Zephyr, a compression jersey with an Iron Man-like device embedded into the chest, designed to press against the heart to easily receive readings. The variety of data collected evaluates a player's physiological load (how hard the cardiovascular system is working), mechanical load (the number of jumps, starts, and stops made, and distance traveled), and training load (a complex algorithm that measures overall effort).

"These things cut out the guessing," says Suns forward Channing Frye. "Are guys out of shape? Do we need more days of actual hard work? And once we start getting in shape, Coach is able to see, 'OK, I've pushed them enough.' We know we're not being put in a position where our bodies are not feeling right and they're forcing us to go out there. They're fixing everything that's wrong with us, and we just have to go out there and hoop."

Trainers utilizing heart monitors predict that in 10 years, they will be commonplace in sports, even at the high school level. They envision a future where "performance management databases" will let them determine specific injury risks for individual athletes. "We're breaking new ground in performance and recovery," says Suns assistant athletic trainer Adam Annaccone. "We're on the cutting edge."