According to a report by the Women's Sport and Fitness Foundation (WSF), published last week, fewer than one in five women do enough exercise to stay healthy. And among many ethnic minority groups exercise rates for women were found to be lower still, with only 13.2% of Muslim women managing the recommended 30 minutes of daily moderate activity five days a week. According to the study, the situation is worsening, which, says the WSF chief executive, Sue Tibballs, "points to a real crisis".

Certainly, religious and cultural beliefs can present a barrier. Muslim societies, in general, do allow women to exercise; in fact, Islam positively encourages physical activity for both sexes. But, in some Muslim communities, female participation in sport and fitness is permitted only on the condition that women adhere to their religion's code of modesty. And for many Muslim women, outside of school PE lessons, there is little opportunity to exercise. For some women, swimming in public pools is not an option, and neither is any activity where men will be present.

Rimla Akhtar, chairwoman of the Muslim Women's Sports Foundation (MWSF), based in Harrow, says: "Religiously, there is still concern that sport is wrong but there are definite signs that this is being overturned with the younger generation." Every week, the MWSF runs two-hour training sessions in north London, which attract budding female footballers from as far afield as Leicester and Leeds. And at the East London Mosque, the Hayaa Fitness Centre holds yoga, kickboxing and other similar sessions. Zaynab Shirji, 23, who works out regularly there, says that the difficulties of finding a suitable fitness venue "mean that in the past many Muslim girls ended up doing nothing. There are still relatively few places Muslim women can get fit."

In Birmingham, the Sisters Games initiative, launched last year, provides Muslim women with single-sex sporting opportunities and exercise classes that allow them to adhere to Islamic values. Akhtar says a huge breakthrough was made when Britain became the first non-Muslim country to take part in the Muslim Women's Games, a four-yearly championship run like a mini-Olympics. Many of those who took part in the 2001 and 2004 competitions, including Akhtar, say they were inspired to take up sport by the emergence of elite Muslim women athletes from other countries. High-profile role models include Nawal el Moutawakel of Morocco and Hassiba Boulmerka of Algeria, both Muslims who have won Olympic track golds. Boulmerka was often forced to train outside her country after being criticised there for training in athletic vest and shorts.

At the Athens Olympics in 2004, women from Iraq, Afghanistan, Bahrain, Kuwait and Somalia were present; most notable was the appearance of 18-year-old Rakia al Gassra from Bahrain who ran in the Olympic 100 metres with only her face uncovered.

For further evidence that a cultural shift is imminent, look to the £160bn-a-year global sportswear industry, which has started to turn its attention to the spending power of the 650 million women who practise Islam. Manufacturers are preparing to launch cover-up ranges of fitness wear, and last year, a partnership between Nike and the United Nations saw the development of a volleyball uniform for Somalian women that allowed them to play with their heads and bodies covered. At the Asian Games in Doha, Qatar, last year, the Bahraini runner Rugaya al Ghasara won gold in the 200 metres. She wore tracksuit pants, a long-sleeved top and a headscarf emblazoned with a prominent Nike swoosh.

Meanwhile, an Australian designer, Aheda Zanetti, has come up with the so-called burqini - a two-piece bathing suit. Struggling to cope with demand for the outfit, Zanetti says it has been adopted by Australia's new Muslim women lifeguards and some swimmers with Olympic potential.

Zanetti has also developed what she calls a "hijood" - a hijab shaped like a hood. She explains: "As an active young Muslim girl I found it difficult to participate in most sports because of all the excess clothes I had to wear" ·