Forget about machines starting right now my friend.
If you want to develop some real leg power and are looking for a real leg strengthening exercise then you have got to use free weights, but more specifically the kettlebell to execute suitcase deadlifts.
Read and apply if you like getting results.
Leg muscle strength has got to come from you engaging in multi-joint lifts that stimulate and tension your body as a whole.
By doing this you initiate your core muscles to better support and stabilize your body, therefore increasing the amount of growth hormone production in your system.
Now don't freak out if you are not looking to increase the size of your legs because size is relevant to a number of variables.
You see growth hormone is great for increasing the amount of lean muscle mass, period.
The way you train, diet, and genetics can all have an effect on how big you want the muscle to be.
A great exercise for helping you to develop some serious leg strength and lean muscle mass in your lower extremities would be the kettlebell suitcase deadlift.
This exercise can be performed with either a single kettlebell or with a pair.
To execute this lift you will want to set the bell(s) on the ground just outside of your feet.
Perform the lift by properly squatting down and reaching down by your sides to pick the bell or bells up off of the ground.
Just make sure to stand up and lock out at the top of the movement.
When you lock out simply squat back down and place the bell back on the ground to stand up again.
The whole lift involves you picking the bell(s) up and setting them back down each time like a suitcase, hence the name.
When you lift the kettlebell(s) just make sure to not stagger or lean your body to one side if you are lifting off of one side.
Keep your hips and shoulders square throughout the movement.
The kettlebell suitcase deadlift is a great lower leg muscle exercise for you to perform to strengthen and develop your hips, glutes, and hamstrings.
This exercise is also a great core workout.
If you haven't implemented this lift then start today.
Remember that most anyone can train hard, but only the best train smart my friend.