The following comes from Stack.com in which Kyle Korver talks about the work ethic of Lebron James. You can see the entire article here which also includes some video of Lebron and the Cavs workout out on VersaClimbers.
Here is what Korver had to say:
"Behind the scenes, just how hard he works. He's a machine. You don't see guys this late in their careers, guys who've had this much success, be the first guy in the gym. He's still there," Korver said. "I was blown away." Korver would know—this is his 14th season in the NBA.
As an example of LeBron's unparalleled work ethic, Korver pointed to the morning after a regular-season game against the Utah Jazz. The night before, the Cavs had defeated the Jazz on the back of a Herculean 33-point, 10-rebound, 6-assist effort from LeBron. The next morning, LeBron was in the gym before anyone else.
"He played  minutes, he played hard. And the next morning, he was on the VersaClimber when everybody else got there, in full sweat doing a massive strength and cardio workout," Korver said. "He was like, 'The playoffs are coming! I've got to be ready! I've got to be able to play big minutes and play at a high level!'"