The sharp slap of pounding leather gloves attracts the attention of a few passers-by who peek through the barred windows of the community centre in one of the sprawling, impoverished Nairobi suburbs.
Inside the rundown building in Kariobangi-North, it's almost entirely women and girls, all training under the watchful eye of boxing coach Alfred Analo Anjere — founder of BoxGirls Kenya.
In 14 years, more than 3,000 girls and women have taken up the sport at the centre, where a faded picture of the cartoon character Asterix wielding boxing gloves adorns the decrepit walls.
All started out for the same reason — wanting to defend themselves in their gritty neighbourhoods, which are harsh worlds where poverty prevails and it is survival of the fittest.
"One day, when I was going jogging, a man came out of nowhere and slapped me. So I wanted to go back to the gym, get the skills and get revenge," says Sarah Achieng, a 34-year-old who turned pro.
For most at BoxGirls Kenya, the contact sport is a leisure activity, but some have made it their life, becoming professional pugilists.
Some have even made it to the Olympics such as Elizabeth Andiego, who took part in the London Games in 2012, and Christine Ongare, who will compete in Tokyo.
Anjere, nicknamed "Priest", says he doesn't want boxing to be about revenge: "Boxing is intended to be a tool... the means to empower girls, for them to have a voice."
A native of Kariobangi himself, he knows full well the problems encountered by women living in deprived areas of Nairobi including physical and mental abuse and rape. Often, girls are forced to drop out of school because of poverty, pregnancy or early marriage.
And women are also vulnerable because they are often not economically independent, he says.
So, after witnessing Kenya's bloody post-election violence that erupted in 2007, when women and girls were often the target of attacks, he decided to take action and created BoxGirls Kenya.
Anjere advocates a "holistic" vision of boxing, saying women can take from the sport the skills they need in daily life -- developing confidence, self-esteem, resilience, and learning "the importance of setting goals and striving to achieve them".
"Growing up in these neighbourhoods with no self-defence is a bit challenging," says Emily Juma, 22, an up-and-coming talent in the male-dominated sport.
"A lot of people... view girls as a sex object," she says, and easy prey for an attack.
Sarah Achieng agrees, but says what they learn at BoxGirls is more than just self-defence.
"Boxing also promotes leadership, self-discipline," as well as self-knowledge and learning to stand by your decisions.
The association conducts workshops on entrepreneurship, rights, sexuality, reproduction and child protection to raise awareness among both young women and men -- 225 of the 967 active members in 2021 are boys.
The goal, Anjere says, is to challenge stereotypes and "change mentalities".
At the Kariobangi community centre one day in May, 22-year-old Sophia Omari Amat is training in front of her six-year-old sister. But for a long time, she had to box in secret.
She says she discovered the sport at the age of 12, but her father refused to let her take it up. "He told me 'you are Muslim, I won't allow you'."
But she says her mother covered for her when she went off to train.
"Any time we had an event and maybe my mother wasn't around, I'd lie to my father, pretending to see a sick friend."
Omari Amat's perseverance finally convinced her father, who she says is now "proud" of his daughter.
"It's a hard sport, I'm not going to lie. But as long as you keep on... it's going through your veins, and you keep on loving it more and more."
Omari Amat now runs a branch of BoxGirls in western Kenya after learning "entrepreneurship" in one of the association's workshops.
The primary objective of BoxGirls Kenya is not to train champions, but a woman ready to face the outside world, says Anjere.
Nevertheless, he will be following the fortunes in Tokyo of Christine Ongare, whom he introduced to boxing in 2008.
"If girls succeed in boxing (we have) happiness and pride," he says.
"Most important is it is their choice. That's what they wanted to do in life and now they've met their goal."