It is common in "big" marathons for the fastest runners to have pacers with them who help establish and keep a pace. They could be male or female, but the faste

It is common in "big" marathons for the fastest runners to have pacers with them who help establish and keep a pace. They could be male or female, but the fastest marathon runners are generally male, so they tend to be male. "Female-only-pacer" means that only female pacers are used.