Donning flamboyant pink boxing gloves, competitive boxer SK, who requested to be known only by her initials, aimed rapid jabs at her male coach's focus mitts, her broad shoulders testament to the shift she puts in during training.
To most people, this is a typical training routine. But in Iran, women are not allowed to train with their male counterparts in closed spaces like gyms owing to the Islamic state's religious rules.
When training in open areas like public parks, women must be clothed from head to toe, and no physical or close contact between the genders is allowed.
Despite this being the case since the 1979 Islamic Revolution, the 22-year-old defies the authorities by training at an underground gym in Varamin, a city 50km south-east of the capital Teheran. She is the only woman who trains in that gym.
There, the 70kg, 1.73m-tall bodybuilding enthusiast spars with men and is trained by a male coach.
TWO SIDES OF THE COIN
Men, being competitive, will be more motivated to train harder because we don't want to lose to women.
SHAYAN MAZAHERI, male kickboxer, who feels that men will also benefit from training with women.
"There isn't any female boxer in my weight category (68kg) in Iran that has stepped up to spar with me. I am unable to challenge myself and have a suitable evaluation," she said. "I have no choice but to train with men."
SK started boxing when she was 19 to improve her "sense of fighting". She eventually traded her basketball sneakers for gloves, after an injury to her left leg forced her to focus on only one sport.
While the sports engineering undergraduate at Teheran's Islamic Azad University is "always up for a fight against female boxers", she sees nothing wrong with training with men.
"In my view, there are no problems training with men. Both my bodybuilding and boxing coaches are male, and training with male boxers has helped me progress in my career as a boxer," she said.
SK also hopes to attract sponsors, and plans to take part in international competitions against women abroad, starting with Dubai or Armenia. Despite training away from the public eye, she makes sure to cover up whenever she steps into the ring.
Said Khadem, who is also a fitness coach at Karen Fitness Club in Teheran and did not want to give her full name: "I always train with complete hijab like in a business meeting. It's hard to train with a hijab, but it is possible."
Women at other underground gyms have fewer qualms about how they dress. While SK dons her hijab to train, women at Akademi Razmi Armin, an underground gym in Teheran, have no such inhibition.
Kickboxers Leila and Mazanin, who requested to be known only by their first names, remove their veils and dress down to figure-hugging tights and tank tops when they train in the basement gym.
"It is much more comfortable to train without being impeded by hijab," said Mazanin, 27. "Nobody will intrude us or offend us unlike in the parks, where we have to tolerate the criticism of others."
Introduced to the sport by friends, the duo picked up kickboxing as a way to keep fit, and also as a method of self-defence.
They train every two days for two to three hours, usually at 10am in the morning. The workout includes exercises to increase their power like bar-bell lifts, striking punching bags, as well as sparring with men and women alike.
"Women usually have rivalry with other women, and we prefer not to exchange information (on how to improve as a kickboxer) with each other. With men there is more honesty and better feedback," said Mazanin.
Run by martial arts instructor Mohsen Talebi, the gym has 22 female students, the youngest being 18 and oldest, 45.
He has practised martial arts since the age of five and has run the gym for the past five years.
"There is no difference between women and men. Sport is regardless of gender," said Talebi, who set up the gym after friends asked him to start a place where both genders can train together.
Male kickboxer Shayan Mazaheri, who also trains at Talebi's gym, said that even men benefit from training with the opposite sex.
"Men, being competitive, will be more motivated to train harder because we don't want to lose to women," said the 25-year-old.
According to Talebi, there are other underground gyms that have been around for more than 20 years. The 47-year-old said: "The police have never caught us. For that to happen, someone must have complained about us… and we are a very friendly family. It is a very safe secret."
Leila, however, desires more than these clandestine workouts. She hopes to one day flaunt her dyed golden-brown locks during training without fear of reprisals. Women with dyed hair are expected to cover it up with a hijab.
"I have seen so many women who want to train like us. Being Muslim does not prohibit people from training like us," said the 29-year-old.
"There is no relationship between sports and religion, we are all human beings. Hopefully someday, men and women training together will become legal."