Almost two thirds of women are concerned about the risk of sexual harassment or intimidation when exercising outside in the darker evenings, according to a new poll.
The findings came as female runners gathered in central London as part of a campaign to draw attention to challenges they face in keeping up outdoor physical activity as winter draws in.
The Censuswide polling of 1,000 women across the UK last month for the This Girl Can campaign found that almost half (48%) said they do not like to get active outdoors after dark and 46% change their outdoor exercise routine or habits as a direct result of the darker months.
Six in 10 (60%) women are concerned about the risk of sexual harassment or intimidation when being active as the nights draw in, the survey found.
The run around Westminster on Monday evening, combined with the polling research, was intended to spark conversation around the issue, campaigners said.
Kate Dale, director of marketing at Sport England and This Girl Can, said: "As daylight hours diminish, many women are opting to stay indoors due to safety concerns, resulting in decreased physical activity levels. The impact of this on women's overall health and well-being is of massive concern and requires both attention and intervention.
"It's not right that for nearly half the year, we feel we have fewer options to be active in the ways that work for us. And even if we go out despite these fears, it's harder to get the joy, freedom and confidence that physical activity can bring if you're constantly looking over your shoulder or monitoring your surroundings.
"It's yet another emotional barrier, something else we have to manage if we want to build activity into our routines and lives.
"Helping women feel safe when getting active is not a singular responsibility; we need everyone to engage with the issue."
A parliamentary roundtable earlier this month, focussed on safety issues women face when getting active, identified key themes and action areas for making sport and physical activity safer for women.
They included better education around respect for and allyship with women, ensuring proper frameworks are in place to report misogynistic behaviour of all levels in a range of environments and planning environments such as sports and games areas in public outdoor spaces through a female lens.
Campaigners said their wider mission is to close the so-called "enjoyment gap" - saying that 2.4 million fewer women than men enjoy getting active - "by empowering society, including sport and physical activity providers, to make exercise safe, suitable, social and self-affirming for women".