the squat...
If you're going to go to the gym and do one movement only. Let that movement be the Squat.
- Bar is resting on traps
- hands are gripping as close as possible
- elbows tucked back
- back is arched, butt is back, hips are NOT forward
- feet are positioned around shoulder width apart, toes pointed out slightly.
- get full range of motion and come up fast.
here's an example: http://www.youtube.com/watch?v=zYddZUIzJ9g
weight on the bar = 325 #
The squat is the king of functional movement. Tight core, full body, full range of motion, etc etc.
There is NO other lower body based movement that comes close.
The leg extension, leg curl and... god forbid... the leg press are all great tools to rehab from injury and they all have a place.... in the physical therapy department.
for example, I hear all sorts of stuff like people trying to "save their back" or "not compress the spine" or whatever, what these people do not realise is that they are increasing their chances of future injury from using machines because for example, the leg press is designed so that the core does not have to remain tight in order to push up the weight (well not compared to the squat anyway) and you your legs may get stronger while your core remains weak, furthermore if you don't develop your body as a UNIT, you will never reach your athletic potential.
start squatting! with weight, without weight, with someone on your shoulders etc, your body will thank you for it.