The hamstring muscles, semitendinosus, …semimembranosus, biceps femoris long & short cross the knee with all but the short head of the bicep femoris crossing and extending the hip. The short head crosses the knee. So instead of working hip extension and knee flexion in isolation, wasting time, you can work them all synergistically with one movement. Smart efficient training defined.
The entire length of the erector spinae muscles from the thoracic to lumbar are heavily recruited/worked as well as the gastroc and glutes.
So in the pictures of me performing a inverse leg curl and Brenna performing a swiss ball hip extension with knee flexion, the gastro(calves), hamstrings, glutes, lumbar and thoracic extensors are worked
Keep in mind….The kinetic chain is only as strong as its weakest link with that often being a weak back and hamstings. Women tend to be more quad dominate with female athletes suffering ACL injuries from weak hamstrings, certainly men do too with weak hams.
I don’t have a GHR or a inverse leg curl at my gym, I have a reverse hyper, so as an alternative we use a swiss ball in the pic, as well as rings which work great. The swiss ball still works very well for many people and weaker athletes.
A progression to the swiss supine hip extension with knee flexion is doing it with one leg. Once strength is built, You can also lay down a mat and have a partner )or they make benches/pads you can put your feet under to do this) hold your hands while you lower yourself to the floor and extend/flex up. You MUST first build strength to do this or you could injure/tear your hamstring. So be careful.
So integrate instead of isolating. Use one of these exercises or variations (GHR) to work both hip extension and knee flexion for bigger carry over in your training. You will prevent injury, run faster and lift more in compound movements like the squat, deadlift, and clean from using these exercises and strengthening what’s weak in the kinetic chain.
Train smart, get stronger to get a lot better!