Tara Dunn, a cyclist and corporate lawyer in Denver says the coronavirus pandemic has turned her into a connoisseur of neck gaiters. The bandanna-like tubes of fabric that some outdoor enthusiasts wear against extreme sun or cold have become her mask of choice for workouts. “I’ve been testing out the different fabrics,” Ms. Dunn says. “Some are Lycra-esque, others are made from a heavier thermal material. None are easy to breathe in.” She wears the gaiter around her neck and pulls it above her mouth and nose when she sees people as far as 12 feet away.

Kinnier...