ANSWER: You're right - the hurdler's stretch is a high-risk exercise and contraindicated for the knee joint. It's done by sitting on the floor, bending one leg backward and extending the other leg out in front of your body. Then you stretch forward over the straight leg. This overstretches the bent knee's connective tissue.
A much safer and equally effective stretch is sometimes referred to as the "figure four" stretch. Sit on the floor and straighten out your right leg in front of you. Bend your left leg, placing the bottom of your foot against the inner right thigh. Slowly bend forward over your right leg and reach for your right ankle. Hold and breathe for 20 to 30 seconds. Repeat with the other leg.
Some other exercises that professionals consider unsafe are full sit-ups, double leg lifts,standing toe touches and full neck circles. Here are descriptions of each, with safer alternatives:
Full sit ups: coming all the way up to a sitting position with the legs straight. A better way: come only a fourth of the way up, shoulders about six inches off the floor, with the knees bent to take the strain off the lower back. Try not to bend your neck as you come up.
Another abdominal exercise you don't want to do any longer is the double leg lift with straight legs (done while lying on your back). This exercise doesn't even work the "abs." It works the thigh muscles that attach to and flex the hips (hip flexors). It also puts a terrible strain on the lower back.
Instead, do reverse trunk curls. Lie on your back with your thighs pointing toward the ceiling and your knees bent at about a 90-degree angle. Now contract the abdominal muscles and lift the tailbone up off the floor about three inches, allowing your legs to come in toward your chest. To make it harder, increase the knee angle (extend your legs more).
Standing toe touch: bending over to touch your toes in order to stretch your hamstrings and lower back, putting a strain on the back .
A safer way to stretch the hamstrings and lower back: Place your right heel on a step out in front of you and flex your right foot. Keep the right leg straight. Now bend slightly forward from the hips until you feel a tension (pull) in the back of your right leg. Support your body by placing your hands on your right thigh. Hold and breathe for 30 seconds. Repeat with the other leg.
Neck circles put a lot of strain on the vertebrae and disks in the neck -just the opposite of what you set out to do!
To relieve neck strain, slowly bend your head from side to side. Don't tilt the head forward as you do so. Follow this with a slow stretch forward, bringing your chin down toward your chest. Never bend your head backward.