Hamstring/Calf Connection

Something has baffled me for years:

Why is it that I can generate more power during leg curls by contracting my calves? I can use considerably more weight by contracting my calves through the ROM, than by leaving them limp and focusing soley on my hamstrings to do the lift. Which way is better?

In my (limited) experience, hamstring curls are not the best exercises.

The hamstring can bend the knee, but in most sports, and everyday life situations, it’s more often used to extend the hip. So any hip extension exercises is superior to any knee bending exercises.

Deadlifts and squats for example.

[quote]Shane Colbert wrote:
Something has baffled me for years:

Why is it that I can generate more power during leg curls by contracting my calves? I can use considerably more weight by contracting my calves through the ROM, than by leaving them limp and focusing soley on my hamstrings to do the lift. Which way is better?
[/quote]

I believe the reason for this is the fact that the gastrocnemius assists the hamstrings with flexing the lower leg. When the gastrocnemius is inhibited to a certain degree in this function due to plantarflexion of the foot (foot pointing away), the hamstrings bear more of the load. The latter option would be more effective in isolating the hamstrings. If I’m not mistaken, Poliquin mentioned a way to reap the maximum benefits by plantarflexing the foot during the eccentric and dorsiflexing it during the concentric motion.