מקבילים וצורת חזה (ליאו?)

[amir harduf]

The Triceps Brachii
I’m sure most of us have been told that a narrow grip hits more triceps than the wide grip. The close grip bench is widely used by powerlifters to develop strength in the triceps to accomplish those massive bench press attempts. According to the EMG study this is very true. The narrow grip when done in a flat position, produced more electrical energy than the incline or decline positions. It should be noted though, that the decline position was pretty close. Cutler explains, "While the decline may be close, I prefer to target the triceps using the flat bench with a narrow grip." Professional bodybuilder Mike Francois agrees, "The flat bench with a narrow grip is a great mass builder." "A narrow grip means your hands should be at your body’s width," Dr. Arria warns, "If you want to create a permanent wrist injury, go with a extremely narrow grip."
The Anterior Deltoid
Since the front deltoids are used for flexion of the arm, it makes since that the incline bench would activate the deltoids much more than the flat or decline positions. Once again our EMG study agrees. The incline bench press with a wide grip produced more electrical energy than the narrow grip. Francois remarks, "I agree! The greater the incline of the bench the more the front delts will be activated." Dr. Arria adds: "While the narrow grip is a stronger position, the wider grip produces more stress to the muscle."
The Latissimus Dorsi
Many of us were probably unaware that the lats were even involved in the bench press. However, EMG studies do show that the lats are activated for a short period of time just prior to the start of the bottom phase of the lift. Robinson states, "There is no doubt in my mind that the lats are used to help get the weight moving off the chest." However, while the lats are activated briefly in the pressing movement, it should be noted that this activity is considered to be very small when compared to that of the other muscles used in the bench press. In any case, the decline bench seemed to activate the lats much more that either the flat of incline positions. Also the wider the grip the greater the activation of the lats. "While the lats are not so much directly related to the push motion of the bench press, they are directly related to the stabilization of the torso," says Dr. Arria. "This is very important because greater trunk stabilization means that the dynamic load on the muscle is more specific."
While the lats appear to help get the bench moving off the chest and provide stabilization, no variation of the bench press should ever be considered to be a good exercise for developing the lats. But that in no way means that good lat development is not important for optimal chest development. Francois agrees and says, "The lats are definitely a factor in the movement and stabilization of the bench press, but there are certainly much better ways to develop good lats."
Don’t Forget the Dumbbells!

Does the use of dumbbells in chest training change any of the rules? Absolutely not! "The rules we have discussed absolutely do not change when dumbbells are used, but what the use of dumbbell in training does is enable the lifter to have a much greater range of movement," claims Dr. Arria. "Further growth can be stimulated from these deep ranges of movement." Cutler agrees and says, "I think you should expect the about the same results with the use of dumbbells except it is much easier to isolate the pecs."
"Another important factor to be considered," says Dr. Arria, " Is because you are using the arms independently dumbbells will require a little more stabilization. This means more activation of the synergistic muscles in the shoulder used to stabilize the load." Francois adds: "I like using the flat dumbbells to isolate the chest and build more mass. I feel that dumbbells allow me to get a better stretch at the bottom and more of a contraction at the top."
Partial Movements

Do partial movements stimulate particular muscles better than full range movements? Perhaps some of the prime movers are used more during different phases of the lift. Elliot et al (1989) used an EMG to answer this question and reported that prime movers of the bench press (pectoralis major, anterior deltoid, triceps brachii) achieved maximal activation at the start of the concentric phase of the lift and maintained this level throughout the upward movement of the bar. So while many still use partials to selectively target specific muscles Hatfield contends, "Overloading the upper ranges of the movement may work, but training partial movements is for those who haven’t learned the secret of compensatory acceleration. "I agree with Hatfield," says Robinson. "I don’t use partial movements at all, I feel they increase you chances for injury."
While partials may not be so great for targeting specific muscles, they do seem to be useful for exhausting the muscle. Cutler states, "I use partial movements at the end of a set only to further exhaust the muscle." Francois agrees and says, "Partial ranges of movement are great for further fatiguing the muscle after your full range of movement has failed." However, Dr. Arria again cautions: "While partials do further exhaust the muscle, you have to remember that chances of injury to the muscle are much greater as you reach the point of fatigue." So the use of partial movements should be done with discretion.
In conclusion, most of could benefit greatly by just depending on the flat bench to gain mass in the upper and lower pecs. However, you must custom tailor your training to meet specific goals. If you have a particular body part that needs further development you must find an exercise or angle that will stress that particular area even more. Therefore, variations in the angle of the bench and the grip are important to optimal development of muscles of the pecs, shoulders and triceps.
References:
Barnett, C., Kippers, V., and Turner, P. (1995). Effects of variations of the bench press exercise on the EMG activity of five shoulder muscles. Journal of Strength and Conditioning Research. 9(4): 222-227.
Elliot, B.C., Wilson, G.J., and Kerr, G.K. (1989). A biomechanical analysis of the sticking region in the bench press. Medicine, Science, Sports and Exercise. 21(4): 450-462.
Lockhardt, R.D. (1974). Living Anatomy: A Photographic Atlas of Muscles in Action and Surface Contours, 7th ed. London: Farber & Farber.
McCaw, S.T. and Friday, J.J. (1994). A comparison of muscle activity between a free weight and machine bench press. Journal of Strength and Conditioning Research. 8(4):259-264.
Thompson, C.E. and Floyd, R.T. (1994). The shoulder joint. In: Manual of Structural Kinesiology, 12th ed. Smith, J.M. Ed. St. Louis, MS: Mosby-Year Book.