MOSCOW • Maria Sharapova revealed she refused to feel sorry for herself during her doping ban, occupying her time by studying at Harvard, writing a book and even learning how to box.

The former world No. 1 and five-time Grand Slam singles champion told a Russian chat show on Wednesday that she particularly enjoyed lacing up a pair of boxing gloves as part of her fitness regimen.

"I tried boxing as I needed to keep myself in good form. It was great as I could imagine some particular people whom I wanted to hit," she said.

She was banned from the sport after testing positive for meldonium at last year's Australian Open. However, she will return to action at the Stuttgart clay court tournament on April 26 after her initial two-year ban was cut to 15 months.

"I found out that I'm very good in resting," added Sharapova when she was asked what lessons she had learned during her enforced absence from the circuit.

"Formerly I couldn't imagine what to do during such a huge period of free time. I had almost 12 months to think, read books, etc.

"I also had a vacation in Croatia, I celebrated the new year in Hawaii. I've never been in London as a tourist before. I've seen almost nothing there while playing at Wimbledon."

Sharapova, who studied at Harvard Business School to help expand her candy business, added she has written a book about her life. It will be out in September.

She said it was too early to discuss the possibility of playing at the 2020 Olympics at Tokyo.

"Now I'm focused on my comeback," the London Olympics silver medallist and 2008 Fed Cup winner told Russia's Tass news agency, saying it was "still unclear" if she would play in Tokyo.

"I would really love to play (in the Tokyo Games). It was hard to watch people competing at (Rio) Olympics, while I was unable to play there."

AGENCE FRANCE-PRESSE