To build a balanced, strong, injury-proof physique you need to do some unilateral training. Unilateral training is when you train one limb at a time—examples could be the pistol or Bulgarian split squats. Unilateral training helps you to maintain even strength levels from one side to the other to help avoid one side becoming disproportionately developed.
For the upper body, training unilaterally is relatively simple. Dumbbell versions of rows, presses, curls, and extensions do the job very effectively. As I’ve already mentioned, unilateral work for the legs is often done with pistol squats and split squats. Lunges and step-ups are other common free-weight choices.
You can of course use machines for single limb work. Machines are used more commonly for the lower body than upper body when performing unilateral work. This is largely because balance can be an issue on single leg lower body work. If you are worried about stability and trying to stay upright then you are unlikely to be able to really challenge the target muscle to its full capacity.
Leg Extensions and Leg Curls
As a result, single leg extensions and leg curls are popular choices to work the quadriceps and hamstrings unilaterally—neither exercise requires you to balance. You can lock yourself into position and focus purely on working the muscles as hard as possible.
While this may not have a great deal of carryover to sporting performance, it is extremely useful for increasing size and strength within the specific muscles. If your goal is muscle size then this is very useful.
Leg curls work the hamstrings in knee flexion (think bending your knee to kick your heel to your butt). The problem with relying on single leg curls for your unilateral hamstring work is that the hamstrings actually have two functions (the other one is a hip extension).
If you only do single leg curls to work the hamstrings unilaterally you are missing out on half of its capabilities. For full development, you need to also train the hamstrings unilaterally as hip extensors (e.g. hinging at the hips and then driving them forward).
This is where the problems come in. Many hip extension exercises are done standing. Doing these on one leg means balance rather than the muscle’s strength is the limiting factor. Consider is the Romanian deadlift. This is the most popular hip hinge movement.
Done on one leg the load used has to be so light to allow you to balance that very little training effect for the hamstring is achieved. Another popular choice to train hip extension is the barbell good morning. Doing this on one leg could very quickly turn your good morning into a bad morning at A & E!
So, I have established it is important to train the hamstrings one leg at a time in hip extension. I’ve also shown why you can’t just switch your favorite hip hinge movements from two legs to one.
What Is the Solution?
Answer: the single leg 45-degree hip extension.
Firstly, the 45-degree hip extension I a phenomenal exercise for working hip extension. The position of your body during this movement means that you can challenge the muscles through a greater portion of the entire range of motion (ROM) than on either a horizontal back extension or RDL.
With an RDL the tension is high at the bottom but minimal at the top. A horizontal back extension is just the opposite. The 45-degree angle, however, means that you create a relatively long lever arm throughout the entire range. As such, it should be considered a staple movement for developing a strong, muscular, injury-proof backside.
It trains the hip hinge pattern meaning your hamstrings are trained in hip extension. Balance is not a limiting factor. The machine provides a very stable base to train the hamstrings one leg at a time so, you can load it up and create incredibly strong hamstrings which are evenly developed.
To see this exercise in action, watch the video above.