My question is about leg position while using the horizontal leg press. Which is correct: feet externally rotated and hips off pad or feet pointed straight ahead? Also, is using the old vertical leg press a good idea?
In answer to your second question, yes, the vertical leg press may be the most effective form of leg press, superior to the 45 degree (“sled”) and any horizontal unit. That said, the vertical design is not readily available these days. If you use a vertical leg press, be sure to use the proper hip wedge and remain in a fixed position.
Your first question presents several concerns. First, I know of no reputable fitness professional who advocates a “hips off the pad” posture during a leg press. This is probably the number one injury-causing error in technique, regardless of the unit’s design. Don’t do it, period.
Secondly, while folk lore abounds relative to various limb or segmental orientation and how this may or may not activate certain muscle groups, there is very little hard data. A check of the Internet and numerous reputable texts produced no objective data relative to the effect of placing feet in a Plie position. All texts cautioned users to be sure to keep the feet securely flat on the platform area, with toes oriented slightly outward. This is true of the squat as well, although most novices attempt to squat with their toes pointed straight ahead. If we’re talking about the normal full range of motion squat, a straight-ahead foot orientation only succeeds with individuals who posses outstanding ankle flexibility (usually a fairly rare occurrence).
I’d err on the side of conventional wisdom and suggest you perform leg presses with feet flat and parallel to each other, toes pointed a few degrees outward. Attempt a full range of motion leg press, with your lower back “neutral” and fully supported throughout.
In reality, the leg press is a poor substitute for squatting, unless you are injured. Doing a leg press incorrectly may cause you to become injured. Then what?