GREEN BAY, Wis. -- The way Tony Horton explained it, every day the P90X founder trained Green Bay Packers running back Eddie Lacy this offseason was different.

“Some days it was a [plyometric] day. Some days it was shoulders, arms and core, or chest and back and core,” Horton said in an interview this week. “Or it was just a pure, sweat cardio day.”

Horton not only agreed to share what a day with Lacy was like but also broke down the specifics of their workouts:

Plyometric days

“There’s a Monday plyo day and a Friday plyo day,” Horton said of the practice, also called jump training, aimed at building explosive strength. “Endurance is everything. Glute strength, quad strength, ham[string] strength -- whenever you work the legs a lot, you’re working the heart and lungs too. For him that’s perfect as a football player.”

The Monday routine contained 20 sets of various exercises. Among them, per Horton: “deep squats; high jumps; left, right, center plyometric lunges; wall squats; squat jumps; and lateral high-knee jumps.”

“There’s 20 exercises, and the rep counts on them are 30 to 100 per,” Horton said. “I’ve had Olympic speedskaters come and do that routine, and then they can’t sit on the john for days.”

Friday was all core work.

“Deep core movement on stability balls, BOSU balls, and plyo boxes and lateral jumps,” Horton said. “We’re talking anywhere from 1-foot to 3½-foot plyo boxes. And the speed at which he improved in both of those was awesome to watch.”

Yoga days

“He hated the yoga,” said Horton, who participated in all the workouts alongside Lacy. “I hate yoga too, but I understand the benefits so I suck it up and go, and so did he. He’d look over at me in yoga class and go, ‘Are you kidding me?’ What was great about the guy was even when he was struggling, he had an awesome sense of humor about him.

“He’s a very private, very humble dude. He’s not like a lot of other athletes. He’s incredibly down-to-earth, which made it easy for me. I’ve dealt with egos for years, but I didn’t have to deal with one here. I think that’s why the relationship worked.”

Cardio days

Horton used a multi-apparatus plan to work Lacy’s cardiovascular system: a VersaClimber, jump-rope station, rowing machine, ski machine, treadmill, bike and slideboard.

“Seven stations, five minutes each,” Horton said. “We did that for one hour.”

Basketball and boxing

When the workout moved from Jackson Hole, Wyoming, to Los Angeles, Horton added two sports.

“He fell in love with the boxing,” Horton said. “He and I did some Box ’N Burn classes."

“By the end, he was playing hoops, and it was fun because he was just flying up and down the court and ripping down rebounds. He wouldn’t have been able to do that in early February, but by the end of our time frame, he was quicker, faster, stronger.”

Said Lacy: "Basketball is cool. Actually, I did boxing, too. That's tough."