Kobe explains why he continues work out at 4 a.m.

Even in retirement, Kobe Bryant is still hitting the gym before sunrise.

Bryant recently sat down with best-selling author Lewis Howes for a wide-ranging interview, and explained why he continues to maintain a strict workout schedule.

"There's several factors for that, like when I first retired, I let myself go a little a bit ... and then the challenge was, can I get back in shape?" Bryant said. "And it's really hard because there's no end goal; I'm not training for anything. So how do you motivate yourself to do it? For me, it was, okay, I have to aim for something. I said I want to aim for size, I want to aim for bulk. So that's a tangible thing, I'm gonna go for that."

Bryant added that he's also motivated by his three daughters, 15-year-old Natalia, 12-year-old Giana, and 1-year-old Bianka.

"Your kids can't see how hard you work. You go to the office, I come to the studio. They don't really see the effort," Kobe said. "So how can we teach our children what it means to work hard? You do it through training."

Natalia has even started joining her father for the early workouts.

"When I get up in the morning, my daughter goes with me. 4 a.m. My 15-year-old goes with me," Kobe said. "She goes with me before school and it becomes a daddy-daughter thing."