By Stephen E. Alway, PhD,
Lifters who construct their training around the idea that a well-constructed upper arm is only a rock-hard biceps really limit the potential of their upper arm. This is because the triceps has one-third more muscle fibers and has a greater genetic potential for overall growth and shape than the genetically smaller biceps. Many triceps exercises can preferentially activate the lateral or medial aspects of this three-headed muscle. Lying triceps extensions, or “skull crushers” as they are frequently called (for good reason), is an exercise that hits all of the regions of the triceps almost uniformly.
The main function of the triceps brachii muscle is to extend the forearm at the elbow joint. The triceps is a three-headed muscle (tri=three; ceps = heads). The fibers in all three muscle heads taper to attach to a common triceps tendon. The tendon crosses the elbow joint to anchor on the olecrenon on the ulna bone of the forearm. This position on the posterior (back) side of the elbow joint makes the triceps brachii muscle the primary extender of the forearm at the elbow (straightens the elbow joint).
The long head of the triceps brachii (often called the “inner head”) begins on the scapula (shoulder blade) just inferior to (below) the head of the humerus bone at the shoulder joint. Because this muscle belly crosses the shoulder joint posteriorly, the arm should be moved posteriorly into shoulder extension (i.e., arms and elbows back) to fully stretch and activate this muscle head.
The lateral head of triceps brachii creates the outside (lateral) boundary of the triceps. Its fibers run from a small section of bone on the posterior part of the humerus (upper arm bone) starting about two-thirds of the way toward the shoulder joint and stopping short of the shoulder joint.
The medial head of the triceps brachii is positioned deeper and between the other two heads of the triceps. It encompasses two-thirds of upper and posterior part of the humerus bone. This muscle becomes thicker as it approaches the shoulder.
THE EXERCISE: SKULL CRUSHERS (Lying Triceps Extensions)
1. Lay on your back on a flat bench. Straighten your elbows and hold a barbell over your chest, as if you were at the top part of a bench press. Move your hands close together so that there is about 3 inches between your thumbs. The palms of your hands should be facing in a pronated position (palms facing away from your face). Most people will prefer to use a thumbless grip rather than wrapping the thumbs around the bar. Instead of a straight bar, you can use an E-Z bar and take a close pronated grip on the bent part of the bar. The E-Z bar makes it a little easier on your wrists as you are lowering the weight.
2. Position the barbell so that it is now over your eyes (with your elbows still straight). Keep the elbows pointed toward your feet and the upper arm (i.e., humerus bone) should be perpendicular to the floor. Keep the upper arm in this position as you slowly bend the elbows and lower the bar toward your forehead. The elbow should point up toward the ceiling and not toward your feet as the bar is lowered toward your forehead. If you let your upper arm drop (so it is not longer perpendicular to the floor) this elbow position will not be correct.
3. Continue the slow, controlled descent of the bar, but stop just before the knuckles of your hands touch your forehead. Try to keep your elbows pointing toward the ceiling and do not let them drift out to the side as the hands approach your forehead.
4. Reverse the bar’s direction by pushing the weight upward with the triceps and straightening the elbows. The hands should be in a line that is directly over your eyes as the bar is moving upward. Stop the movement of the bar just short of completely locking out the elbow before returning the bar slowly toward your forehead.
As indicated earlier, you can choose to do this exercise with an E-Z curl bar instead of a straight barbell. Many people will find that the E-Z bar is more comfortable on the wrists. However, you need to be aware that this hand position will move the elbows more to the sides, and this tends to shift some of the emphasis toward the lateral head of the triceps and de-emphasize the long head of the triceps. Thus, you will need to evaluate your own triceps needs and determine the best bar for you in this exercise.
If you have always started your arm workout by training the biceps, perhaps it is time to mix things up a bit and begin your arm days with triceps training. The reason is that if you wait until you have already hit a few body parts, your energy and strength will wane just a bit (relative to starting fresh in the gym), so that your triceps will continue to lag and not quite ever reach their potential. That is not to say that you should always do the triceps early in a workout, but if you are specializing on this region, you should try to maximize your gains.
Alway SE, WH Grumbt, J. Stray-Gundersen and WJ Gonyea, Contrasts in muscle and myofibers of elite male and female bodybuilders. J Appl Physiol, 67:27-311, 1989.
Bottas R, Nicol C, Komi PV and Linnamo V. Adaptive changes in motor control of rhythmic movement after maximal eccentric actions. J Electromyogr Kinesiol, 2007.
Gentil P, Oliveira E, de Araujo RJ, V, do CJ and Bottaro M. Effects of exercise order on upper-body muscle activation and exercise performance. J Strength Cond Res, 21: 1082-1086, 2007.
Guazzelli FJ, Dias GA, Rodrigues JA, Goncalves M and Bull ML. Electromyographic analysis of the arm muscles in “back support” exercises. Electromyogr Clin Neurophysiol, 47: 337-340, 2007.
Jaskolski A, Andrzejewska R, Marusiak J, Kisiel-Sajewicz K and Jaskolska A. Similar response of agonist and antagonist muscles after eccentric exercise revealed by electromyography and mechanomyography. J Electromyogr Kinesiol, 17: 568-577, 2007.
Oliveira AD and Goncalves M. EMG amplitude and frequency parameters of muscular activity: Effect of resistance training based on electromyographic fatigue threshold. J Electromyogr Kinesiol, 2008.
Moore KL and AF Daley. Clinical Orientated Anatomy, 4th edition. Lippincott William s & Wilkins, Philadelphia, pp.665-724, 1999.
Rasch PJ. Kinesiology and Applied Anatomy, 7th edition. Philadelphia, London. Lea & Febiger, pp.117-120, 1989.