07/16/2013 01:06 EDT | Updated 09/15/2013 05:12 EDT

New documentary shows all sides of tennis sisters Venus and Serena Williams

TORONTO - There's a scene in the new documentary about tennis stars Venus and Serena Williams where Serena is on a treadmill after a U.S. Open match ripping into her hitting partner. She's dressing him down for failing to give his best on the practice court and keep her on par with opponents.

And this is after a victory.

It's a rare glimpse into the ultra-competitive mindset of the world's current No. 1-ranked women's player and how she continues to stay atop that perch. It also shows the kind of access co-directors Michelle Major and Maiken Baird were permitted for their film "Venus and Serena: Icons, Rivals, Champions, Sisters," which opens Wednesday in select theatres across Canada.

After three years of attempting to convince the Williams sisters to agree to the project, Major and Baird were finally given the green light by Venus to follow them through the 2011 tennis season.

It turns out to be an emotionally eventful year as Serena battles back from blood clot surgery and plays in a U.S. Open final that will be remembered more for her outburst at a chair umpire — similar to her 2009 U.S. Open meltdown at a line judge — than Samantha Stosur's eventual victory.

It proves to be tough year for Venus also, as the older sister deals with the onset of an autoimmune disease that has slowed her career ever since.

Major says is wasn't strictly tennis accomplishments that drew her to the Williamses, but a desire to tell the story of how they got to the game's elite tier.

"Both of us thought it was a great American story and a great human story. We really didn't think of it as a tennis story, per se," she said.

"It just happened to be this story of two great women and how they overcome, and become something great, despite all odds. The elements of the story and the mythology surrounding how they got to that point was what really interested us."

The film digs up archival footage of the young sisters hitting balls with their father, Richard Williams, on the very non-luxury public courts in downtown Los Angeles. He later moved them to a tennis academy in West Palm Beach, Fla., where they live to this day, to work briefly with a coach named Rick Macci.

Macci comes off as jilted by the Williams family, and adds fuel to the common assumption that Richard Williams is a dictator and control freak who oversees all aspects of Venus and Serena's lives.

Major says this may have been the case in the past and he is certainly still involved in their training. But Venus, 33, and Serena, 31, didn't need his permission to get involved with the doc.

"Their father is a daily part of their lives, but they made the decision to do the film," she said. "We did not need his approval and he was willing to do whatever his daughters (wanted). He said: 'if they're into this, I'm into this.'"

While Richard Williams is often credited for having played a major role in developing his daughters' game, through tireless practise and unconventional training methods, the film shines an intriguing light on how much their mother, Oracene Price, factored in their success.

Price is shown on the practice court at tournaments like Wimbledon, giving her daughters calm suggestions and advice to counter-balance their father's ornery bluster.

"(Oracene) was the one who installed the mental toughness in them and courage," said Major. "And she is extremely protective as well, keeping them from a lot of things, and also (instilling) a pride in who they were as black young women."

"Venus and Serena" arrives in theatres at time when Serena is playing some of the best tennis in her career and is the hands-down favourite going into next month's Rogers Cup in Toronto.

She had a career-best 34-match winning streak, including her second French Open title, end at this year's Wimbledon with an upset loss to tournament finalist Sabine Lisicki of Germany.

She's also made headlines recently for a verbal spat with world No. 2-ranked rival Maria Sharapova, resulting from a Rolling Stone profile that also contained controversial comments about the Steubenville, Ohio, rape case. Williams has since apologized for both instances.

Major declined to comment on what she thought of the Rolling Stone profile, but did say the Williams sisters are rarely concerned about their own publicity, either positive or negative.

"They were raised not to read the press about themselves," she said. "They're not into reading newspapaers and watching television news, so they don't even see or know what's out there about themselves. That's how they were protected from the negativity or rumours because they don't pay attention to it."

Serena says in the film that she sometimes has an alter-ego named "Taquanda," who is the type of person that spits verbal darts at a line judge or tears a strip off her hitting partner. Major says she thankfully never crossed paths with "Taquanda."

"She's really not afraid of being who she is and letting people see it," said Major. "She has a focus and it's something you see in any great athlete. Their opponents are the enemies to be smashed and that's just the way they are. She's not playing around. That's her profession and she's the best at it. She's not out to make friends."