Starting Strength, 3rd Edition - Mark Rippetoe [195]
The single most important contributing factor to the successful heavy one-rep attempt is the ability of the muscles involved to produce force. The heavier the weight, the more force required to move it, as should be obvious. The one-rep set doesn’t take very long to do, so muscular endurance is not a factor, and neither is cardiovascular capacity, for the same reason. Even a bone-on-bone limit attempt doesn’t take more than a few seconds. The only thing the muscles must do is produce sufficient force to overcome the weight on the bar as it moves through the range of motion of the lift one time. So, in response to 1RM training, the body adapts by getting better at producing high amounts of force, one rep at a time. It does this by adjusting the components of the system that produce the force: the nervous system, the neuromuscular system, and the muscles themselves, specifically the components of the muscle that actually produce the contraction.
There are other adaptations that are secondary to the main ones, but they all involve helping the body perform a brief, intense effort. Psychological adaptations enable the lifter to overcome his fear of a heavy weight. The heart adapts by getting better at working with a huge load on the back, and the blood vessels adapt by becoming capable of responding to the demands of increased peak blood pressure. The tendons thicken to better transmit force, and the ligaments thicken and tighten to hold the joints together under the load. The skin under the bar gets thicker, the eyeballs get used to bugging out, and new words are learned that express the emotions accompanying success or failure with a new PR squat. But the primary adaptation is increased force production.
On the other hand, a heavy set of 20 reps is an entirely different experience, one of the most demanding in sports conditioning. A set of 20 squats can usually be done with a weight previously assumed to be a 10RM, given the correct mental preparation and a certain suicidal desire to either grow or die. The demands of a 20RM, and therefore the adaptation to it, are completely different. A 20RM is done with about 80% of the weight of a 1RM, and even the last rep is not really heavy, in terms of the amount of force necessary to squat it. The hard part of a set of 20 is that the last 5 reps are done in a state resembling a hellish nightmare: making yourself squat another rep with the pain from the falling muscle pH, an inability to catch your breath, and the inability of your heart to beat any faster than it already is. The demands of a 20RM involve continued muscle contraction under circumstances of increasing oxygen debt and metabolic depletion.
In response to this type of stress, the body gets better at responding to the high metabolic demand that is created. Systemic adaptations are primarily cardiovascular in nature, since the main source of stress involves managing blood flow and oxygen supply during and after the set. The heart gets better at pumping blood under a load, the vessels expand and become more numerous, and the lungs get better at oxygenating the blood – although not in the same way that a runner’s lungs do. The main muscular adaptations are those that support local metabolism during the effort. Glycolytic capacity increases. The contractile part of the muscle tissue gets better at working under the acidic conditions produced by the stress of the long work set. Psychologically, 20RM work is very hard, due to the pain, and lifters who are good at it develop the ability to displace themselves from the situation during the set. Or they just get very tough.
Figure 8-3. Sets of 5 reps are optimal for learning barbell exercises. It is apparent from electromyography (EMG, a recording of neuromuscular electrical activity, top) and force plate data (a measure of muscular force generated, bottom) that there is a progressive loss of motor coordination as reps increase. In reps 1–5, the muscle is firing in a coordinated manner, with tight, uniform EMG waves and consistent