You may not have really noticed, but the continuous-loop drawstring is typically center stage on sweats, athletic shorts and swim trunks. While the traditional two-end string seems natural, likely due to years of shoe-tying, the single loop can throw you for a loop. Going untied is rarely an option, as a snug fit is especially important in activewear to prevent any wardrobe malfunctions. Keep your pants snug by turning to the time-tested slip knot to hitch up with a continuous loop.
Pull the drawstring away from the waistband until the garment fits snugly and securely around your waist. Go a bit tighter than your instinct -- you'll likely introduce just a bit of slack when you tie the slip knot. If the drawstring comes out from the inside of the garment, turn the waistband inside-out before tying to make the process easier.
Place the thumb on your non-dominant hand right at the drawstring's outlet to hold it in place. Grasp the looped end of the drawstring between the thumb and forefingers of your dominant hand.
Wrap the drawstring around the index finger of your non-dominant hand, so it looks like a ring on your finger. Pull the looped end of the drawstring under the “ring” and remove your index finger. Continue pulling the drawstring until it makes a knot right near your thumb, then remove your thumb. If you flipped your waistband inside-out, return it to normal to help keep the knot in place.
If you'd rather tie your bottoms shoelace-style, cut the continuous loop drawstring into two strings by slicing it with scissors right in the center of its loop. If the drawstring is tied together at the end rather than looped, cut it just above the knot. This way, you can tie the string just like you tie your shoes, with a bow-style “granny knot” or wreath knot.