The seated hamstring curl machine can develop good hamstring strength. To set the machine up, it is good to ask an instructor in the gym for help since the various makes of machines vary in what lever does what. As a general rule, the very bottom of leg sits over the leg roller and the back connects to the chair rather than floating in the air – ie no slumping about as if in front of the TV. It can be worked very simply as in the video clip. But more joy can be got from it by doing the same exercise but with one leg at a time. This balances out the strength of each leg. Always start with the weaker leg. The non-working leg just sticks out in the air.
The nature of the fibres of hamstrings mean they respond best to lower reps and heavier weights, so the maximum number of reps normally done when strengthening the hamstrings is 8. To strengthen the hamstrings effectively, curl the leg under more quickly than you let it straighten out again. This trains the eccentric part of the movement or the lowering phase (as the leg straightens, although the foot is going back up to the ceiling, if you look at the weight stack, you will see the weights themselves are going downwards), and most injuries occur in an eccentric, or braking, action.
Toe position makes a big difference. If the toes are pointed up as in the video,this engages the calves as well -the calves cross the back of the knee joint, so help lift the heel towards the bottom. To isolate the hamstrings more, then point the toes. At first, this may make the hamstrings cramp, if so then toes point up when curling under, and then point them down when straightening the leg.
In fact there are at least 18 variations on using the hamstring curl machine. So a machine that is rather less boring than most.
Hamstring strength can easily be ignored, especially by people who do a lot of cardio like running and cycling. These are quad dominant sports, so knee problems can develop if the hamstrings are neglected. Another important point about hamstrings is that they must be long enough – ideally when lying on the back, each leg can be lifted up, held straight, to a 90° angle. If sprinting is involved in the sport, then the hamstrings need to be longer than that or speed is compromised. I wrote a blog about stretching the hamstrings which is linked to. Get hamstring stretching wrong and you can tear the muscle which will weaken it and shorten it further. As a final remark, as I enter more and more Z Health, tight hamstrings are also a sign of dysfunction any where in the body, so, for example, mobilising the upper back can have a dramatic effect upon hamstring length.