WIMBLEDON, England — Serena Williams attended a Green Day concert over the weekend and worked on her curtsy.

That's her way of getting ready for Wimbledon.

Tennis traditionalists have long derided the Williams sisters' unorthodox preparation for Grand Slam events, but hey, it works. At Wimbledon, Serena and Venus have combined to win eight of the past 10 titles, and they're seeded 1-2 in the tournament beginning Monday.

Serena tweaked her practice regimen by polishing her curtsy in anticipation of a visit Thursday from Queen Elizabeth II. With Green Day in town for a concert Saturday night at Wembley Stadium, she — Serena, not the monarch — also made time to take in the show.

It was like a workout, Serena joked.

"Did a little cardio there, jumping around a little bit," she said. "It was amazing. Everyone knows I'm a massive Green Day fan. They were so close; no chance I could have missed it."

Williams has time to catch her breath before her opening match Tuesday as defending champion against Michelle Larcher de Brito of Portugal. Venus was to play Monday against Rossana de los Rios of Paraguay.

As in the past, the sisters skipped the grass-court warmup tournaments and haven't played since the French Open.