I am curious about hearing some opinions about the role of knee flexion exercises in a sprint program. It seems that people (generally) oppose the use of knee flexion exercises stating that the step over phase is passive or that it doesn’t require much force or something of the sort. However, if hamstring size is of importance and weights and muscle size are general in nature then why wouldn’t maximizing hamstring size with the use of something such as a leg curl or glute-ham raise be of use?
I know that the short head of the biceps femoris only crosses the knee and therefore acts only on knee flexion, unlike the other muscles of the hamstrings- it may therefore be “unnecessarily” trained but I don’t think thats a big deal. Would the other hamstring muscles experience suboptimal development from knee flexion exercises? Does it really matter as long as their size is built up to the requisite levels?
No responses means I’m just fine building my hamstrings up with knee flexion exercises? Or does it mean I will wind up with the worlds best step over phase and little else to show for the hard work?
In all seriousness, I am having trouble understanding why people generally have something against using knee flexion exercises such as leg curls or GHRs to build up the hamstrings. If you get stronger at these movements and beef up the size of the hamstring muscles I don’t see why that wouldn’t allow you to produce more force in hip extension movements or why it would have a different effect on your sprints than building your hamstrings through deadlifts, hypers, etc would. Why not save some time, energy and recovery capacity for other aspects of training by doing some leg curls instead of more demanding hip extension movements (assuming other muscles are getting sufficient development otherwise)? Can anybody explain?
How heavy are we talking? Any ideas on why they would lead to injury?
If I recall you list leg curls as one of the lifts you used in the strength training videos. Have you since changed your position on their role in a sprint training program? Since weights are general, the hypertrophy gained from knee flexion exercises would be no different, with respect to sprinting, than the hypertrophy gained from hip extension exercises, correct?
I dropped most knee flexion exercises from my speed/power athletes programs esp in SPP and Comp because they lead to excessive tightness in the hamstrings vs. something like a hyper, rdl, or pull through would be more friendly in the SPP/Comp period.
I prefer exercises like rdls instead of curls because they lead to tightness like tamfb said. Heavy curls are also bad for your knees because a leg curl, like a lot of other machine exercises, is an open chain exercise and puts a lot of pressure on the knee joint.
In the past I have had several hamstring injuries all related to knee flexion and have since took training them very seriously. 3 main points that keep reoccurring through my reading:
At the end of swing phase the hams eccentrically contract powerfully at the knee which is a common site of injury, this area can be conditioned against injury by using the GHR especially the natural GHR which hits the outer range well. This exercise may not cause shortening like curls.
Strengthening at the knee crosses over to general strength of the hamstrings ie. at the hip also.
Restistance training for knee flexion can place the hams under greater stress when sprinting potentially leading to injury (as Charlie states); periodization is necessary, do not aim to strengthen in the gym and improve on sprint speed at the same time.
Since I have been using the GHR I can tolerate speed work better and have not yet had another injury, but I am also looking at other factors such as flexibility, stride length and gait.