|
|
|
Seated Leg Presses: Inject New Life into Your Thighs |
|
|
|
|
Written by Stephen E. Alway, PhD, FACSM
|
|
Monday, 23 April 2007 |
With most of your last New Year's resolutions well beyond broken, it's perhaps time to interject new life into those old training-centered promises. Sure, you had good intensions to pulverize your thighs with squats twice each week, but thigh work is plain hard to do. Furthermore, time is usually tight for each workout and somehow it made sense to drop the training that seems to be harder and harder to complete. The leg press is an exercise that can be done in most commercial or home gyms without the need for multiple training partners to spot you, or to slow your pace. Although it's not a perfect replacement for the squat, exercises like seated leg presses fit the category of activating a huge amount of thigh muscle mass. Leg presses allow you to use potentially heavy weights, yet your concentration can be even more intense than with squats because the problem with balancing heavy weights and the risk of injury is greatly reduced.
Muscle Structure and Function
The barbell squat places a much greater emphasis on the hip and buttock muscles than the leg press. Nevertheless, there is some activation of these muscles in the seated leg press. Obviously, the buttock or gluteal prominence is located on either side of the posterior portion of the hip bone. The gluteus maximus is the major hip extensor. It's most active during the push phase of the leg press because it helps straighten (extend) the hip joint. When the thigh is fixed (e.g., feet firmly planted on the floor) and the hip joint is free to move, the gluteus maximus muscle can extend the lower back. The fibers in the gluteus maximus are strong and large, even surpassing the muscles of the thigh and back. The leg press reduces the movement in the hips as compared to the barbell squat, so the effort becomes more concentrated in the thighs.
The gluteus maximus begins from the crest of the ilium of the hip bones and across the sacrum bone of the lower region of the vertebral column. It attaches posteriorly on the femur bone of the thigh at an area referred to as the gluteal line. The hamstring muscles include the semitendinosus, the semimembranous and the hamstring part of the biceps femoris muscles. (Note the biceps femoris also has a short head that does not cross the knee joint). Part of a fourth muscle, the hamstring portion of the adductor magnus, also crosses the hip and assists in hip extension. The hamstring muscles have two common features. In general, they attach to the hip bone structure posteriorly, and run to either cross the knee joint (semimembranous or semitendinosus, biceps femoris) or attach to the femur bone (adductor magnus). These muscles help to extend the hip joint during leg presses.
The leg press is primarily designed to activate the quadriceps femoris ("quads"), which, consists of four muscles attached on the anterior (front) portion of the thigh. The fibers of the rectus femoris muscle (rectus=straight) extend from the front of the hip joint, along the front of the thigh to join the quadriceps tendon above the kneecap (patella). The rectus femoris is functionally weaker in exercises with a flexed hip (e.g., seated position). Because the leg press is done in a seated position, the hip joint does not completely become extended, so the rectus femoris cannot make a substantial contribution to the lift.
The vastus medialis muscles cover the medial (inner) part of the thigh. This creates the "teardrop" area that's medial and superior to the patella. The vastus intermedius is positioned between the vastus lateralis and the vastus medialis muscle, but it is deep to the rectus femoris muscle (so you can't see it). The vastus lateralis is positioned on the lateral (outer) part of the thigh. The three vastus muscles begin on the femur bone of the thigh, and all attach to the upper border of the patella by the quadriceps tendon. The patella is attached to the tibia bone of the lower leg by the patellar ligament. As the muscles of the quadriceps shorten, they pull on the tibia by way of the quadriceps tendon and patellar ligament, so the leg becomes extended (straightened) at the knee joint. The three vastus muscles are not affected by hip angle, so they are active in a seated position and throughout the leg press.
Exercise Form: Leg Press
It's worthwhile to spend five minutes warming up your knees and thighs before heavy thigh exercises. Also, do a little stretching and ride a stationary bike for a few minutes at a low intensity before you get into position in the leg press. This is not intended to be an aerobic exercise, just something to warm up the knees, so you should not feel tired after the warm-ups. The warm-ups and stretching will increase the blood flow to the knee structure. You should also pyramid the first few sets, beginning with a lighter weight and working toward heavier weights in subsequent sets. The seated leg press station may be angled or positioned parallel to the floor. My preference is a unit with a press that's slightly inclined (30-45 degrees) because this decreases the hip angle somewhat and increases the activation of the rectus femoris muscle during the exercise.
1. After loading the weights, set the seat position so you won't let your knees flex to less than 90 degrees in the lowest position. Position your feet on the foot plate so they are approximately shoulder-width apart.
2. Grip the vertical uprights or hand grips firmly. Take a deep breath and press the foot plate upward with a controlled thrust as you straighten your knees, all the while expiring the air in your lungs. Don't hold your breath as you push the weight upward. Take about two seconds to push the first repetition upward.
3. Stop just short of your knees becoming straight. It's important to maintain some tension across the thigh musculature, and it does your knee joints no favors to forcibly "lock" your knees.
4. Slowly lower the resistance, taking about three or four seconds to resist the weight during its descent. Inhale as the weight is lowered and your knees come toward your chest. Don't let the weight bang into the bottom stops; control the weight, stop it under control, then thrust it upwards. Do not let the knee flex to less than 90 degrees in the lowest position. It's important to control the weight and not let the weight control you.
5. Start the next repetition upward, slowly at first; this will help protect your knees in a vulnerable position when the joint is flexed. After getting the weight moving upward, try to accelerate the weight towards the top, because this will be especially effective in recruiting the largest and fastest fibers of your thigh (the ones that also appear to grow fastest). Of course, the other fibers will be eventually recruited as you move closer and closer to the point of muscle failure, so it's important to push yourself hard as you complete the next repetitions. This acceleration should begin on the second repetition of each set. However, always try to slowly lower the weight on each repetition.
6. If your seated leg press is of the inclined variety, make sure the safety bars are in place before you terminate the set and move out from under the weight. People have been injured by attempting to leave the exercise unit only to find that the safety bars had not been properly engaged and that the weight has come crashing down on their legs. A little attention to this detail will prevent you from becoming an injury statistic.
Although arguably leg presses do not activate as much muscle mass as barbell squats, most of the differences are in the lower activation of hip and buttock musculature in the seated leg press. However, seated leg presses can be every bit as effective for the three vastus muscles, and is a better approach for building the thighs for persons with an injured back. This exercise also allows you to more fully focus on the quadriceps muscles without being concerned about balance or falling during a heavy set, as is often part of the distracting package associated with barbell squats. Perhaps leg presses may not solve all the neglected New Year's resolutions, but it will reverse the losses that have been accumulated from the missed thigh workouts, because you didn't have either the time or the drive for heavy barbell squats. Renewed thighs via seated leg presses will still take a lot of hard and persistent work, but press on, success is at hand.
References
Clemente, C.D. Anatomy, A regional Atlas of the Human Body. Third edition, Baltimore, Urban & Schwarzenberg Pub. Co., 1983, pp. 416-467.Akima, H., K. Kubo, H. Kanehisa, Y. Suzuki, A. Gunji, and
T. Fukunaga. Leg-press resistance training during 20 days of 6 degrees head-down- tilt bed rest prevents muscle deconditioning. Eur.J.Appl.Physiol, 82: 30-38, 2000.
Akima, H., S. Kuno, H. Takahashi, T. Fukunaga, and S. Katsuta. The use of magnetic resonance images to investigate the influence of recruitment on the relationship between torque and cross-sectional area in human muscle. Eur.J.Appl.Physiol, 83: 475-480, 2000.
Alkner, B. A., P. A. Tesch, and H. E. Berg. Quadriceps EMG/force relationship in knee extension and leg press. Med.Sci.Sports Exerc., 32: 459-463, 2000.
Escamilla, R. F. Knee biomechanics of the dynamic squat exercise. Med.Sci.Sports Exerc., 33: 127-141, 2001.
Escamilla, R. F., G. S. Fleisig, N. Zheng, J. E. Lander, S. W. Barrentine, J. R. Andrews, B. W. Bergemann, and C. T. Moorman, III. Effects of technique variations on knee biomechanics during the squat and leg press. Med.Sci.Sports Exerc., 33: 1552-1566, 2001.
Kubo, K., H. Kanehisa, and T. Fukunaga. Effects of different duration isometric contractions on tendon elasticity in human quadriceps muscles. J.Physiol, 536: 649-655, 2001.
Matheson, J. W., T. W. Kernozek, D. C. Fater, and G. J. Davies. Electromyographic activity and applied load during seated quadriceps exercises. Med.Sci.Sports Exerc. 33: 1713-1725, 2001.
Moore K.L. Clinically Orientated Anatomy. Third Edition. Williams & Willkins, Baltimore, 1995, pp 373-500.
|
|
Performance Nutrition 