Sometimes if you can't get to the gym, you just have to make do with the equipment you have at home. Although some exercises are tricky to perform without specialized gym machines, you can manage most of them with a little improvisation. Case in point: the prone, or lying, leg curl. Although usually performed with a gym machine, you can also do prone leg curls at home with a single dumbbell.
Place a light dumbbell on the floor, standing on end. Choose a lighter dumbbell than you think you’ll need at first, until you’re comfortable with the exercise.
Lie down on the floor, on your stomach, with your legs straight and feet close to the dumbbell. Place your feet on either side of the dumbbell handle.
Squeeze the dumbbell between your feet and bend your knees to lift it off the floor. The top weight on the dumbbell will rest on the bottom of your feet.
Bend your knees slowly up toward your butt, keeping the bottoms of your feet facing the ceiling throughout the movement. Slowly lower the weight back down. Stop just before the dumbbell touches the floor; repeat.
Perform the exercise lying on a flat bench if you'd like more of a challenge at the bottom of the movement; the bench allows you to straighten your legs completely.