The 35-year-old is still recovering from his torn Achilles that he suffered at the end of last season, and is now working on his conditioning.
"I've been pushing pretty hard, man," ESPN, quotes Bryant as saying.
"The hardest thing is the conditioning and getting back and playing at a high level. Being able to run and play at a high level for 48 minutes is tough, man. You really got to push yourself conditioning-wise to get in shape."
Bryant has yet to include basketball activity in his workouts and is expected to continue to work on his movement in the coming weeks.