It’s a fair question, one that’s asked often across sports and non-sports industries: shouldn’t equal work mean equal pay?

Claressa Shields, who fights on Friday against Marie-Eve Dicaire to unify all four super welterweight championship belts, believes that a big part of the reason why paydays for women in boxing lag so far behind the men is a simple one: time spent in the ring.

Women’s bouts are usually a maximum of 10 rounds, and just two minutes per round; men’s bouts are 12 rounds and three minutes each.

“I care about the sport and I know for a fact that [round and fight length] is why we don’t get paid like the men and also why women’s boxing is not considered on the same level as men’s boxing,” Shields told Yahoo Sports after a recent training session. “We don’t even go three minutes. Like, forget the 12 rounds, but we don’t even box three-minute rounds. A lot of fans have said to me that they feel like they’re being cheated out of our fights because they’re two minutes. … They want to see their favorite fighter get knockouts, they want to see their favorite fighter look smart and have enough time to execute, and two minutes is not enough time.”

Several elite women within the sport, including Shields and bantamweight Marlen Esparza, have been fighting for years to convince boxing’s governing bodies that they need to go to three minutes a round, not just to show that they can fight as long as the men and therefore deserve the same pay, but also for strategic and results reasons: two minutes just isn’t long enough to get a knockout.

WBC, which is influential in safety rules, has pointed to studies showing women get concussions at higher rates, and that’s why it insists on the shorter rounds. But Shields believes it’s antiquated science and Esparza told The Ringer in 2018 that when she’s asked to see the documented evidence she hasn’t gotten a response.

“It’s facts, women have smaller bones than men, and women have smaller necks than men. We know that that’s facts, but what does that have to do with boxing?” Shields said. “Like, we’re not in the ring fighting against a man for them to say ‘oh your necks are smaller.’ It’s a woman against a woman. You know, some men fight against other men some necks are smaller, what does that have to do with anything? If they’re saying our bodies are not capable to do three-minute rounds that’s absolutely incorrect. It’s false.”

Is it true that women are more susceptible to concussions?

“After this fight with Marie-Eve Dicaire, I will be fighting three-minute rounds for 10 rounds,” she said. “So any of my future opponents, they can jot that in their book and if they want to beat me they can start training for that now. But I’m not going to continue to fight two-minute rounds. I will be fighting three-minute fights for the rest of my fights.”