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Muscle Science
The biology of muscle isn't, in fact, rocket science. At its most basic level is the SAID principle, an acronym for "specific adaptation to imposed demand." "When a muscle contracts against a large amount of resistance, it adapts by getting bigger and stronger," says Caiozzo. Likewise, if it's regularly forced to contract for long periods of time, it becomes more resistant to fatigue. These adaptations occur to reduce stress on the body, which is why you can per-form everyday functions -- like walking up stairs or picking up a light object -- with little effort.
Now let's apply the SAID principle to your workout. When you lift weights, you cause tiny tears in your muscle fibers. This accelerates a process called muscle-protein synthesis, which uses amino acids to repair and reinforce the fibers, making them resistant to future damage. And although this happens at a microscopic level, the effect becomes visible over time -- in the form of bigger arms, broader shoulders, and a thicker chest.
Understanding this process provides you with a logical rationale for how often you should train your muscles. In multiple studies, researchers at the University of Texas Medical Branch in Galveston have reported that muscle-protein synthesis is elevated for up to 48 hours after a resistance-training session. So if you work out on Monday at 7 p.m., your body is in muscle-growth mode until Wednesday at 7 p.m. After 48 hours, though, the biological stimulus for your body to build new muscle returns to normal.
On paper, this supports Cosgrove's first assertion: "Performing total-body workouts three times a week is the most effective way to gain muscle." Unfortunately, that advice directly contradicts what most guys actually do. That's because almost everyone subscribes to a leftover from the Stay Hungry days of weight lifting: what Cosgrove calls "body-part training."
The idea is to divide the body into specific muscle groups, or body parts, and dedicate an entire session to working each individually. For example, you might perform exercises for your chest on Monday, your back on Tuesday, your shoulders on Wednesday, and so on. Even though you're training daily, each muscle group is targeted only once a week. So, in essence, those muscles grow for just 2 days out of every 7. With total-body workouts, though, you work each muscle more often. "When you train a muscle three times a week, it spends more total time growing," says Cosgrove.
Connections
Anatomically speaking, you can't isolate muscle groups in the first place -- which is Cosgrove's other beef with body-part training. Imagine, for a moment, that you could strip the skin away from your muscles. You'd see clearly that they're interconnected, surrounding the body like a unified web. This is because all of your muscles are enclosed in a tough connective tissue called fascia. And since fascia attaches to bone and other muscles, it creates "functional" relationships between seemingly separate muscle groups.
"Even a small movement of your upper arm triggers a complicated network of muscles from your shoulder down to your hip," says Bill Hartman, P.T., C.S.C.S., a physical therapist in Indianapolis. Here's why: The latissimus dorsi (or lat), the largest muscle of the back, attaches to the upper-arm bone, shoulder blade, spine, and thoracolumbar fascia--a strong layer of connective tissue that attaches muscles to the spine and pelvis. The glutes, or rear hip muscles, attach to the pelvis. See the connections?
Don't misunderstand: There's no doubt you can emphasize a muscle group by choosing the appropriate exercise; just don't confuse targeting with isolating. To illustrate this point, Cosgrove uses the example of a popular exercise known as the bent-over row. If you subscribe to body-part training, it's a back exercise, since that's the area of your body it emphasizes. But, because of the interconnection between the muscles and connective tissues of the hips and back, your hamstrings and glutes are contracted for the entire exercise. So you're not only working your back, you're challenging your legs as well. And don't forget the involvement of your forearms and biceps in pulling the bar to your chest. "Separating your workouts by body parts is illogical," says Cosgrove. "You're not actually separating anything."
Also, since body-part training is generally performed intensely on consecutive days, it impedes the recovery process. "The nutrients your body needs to repair muscle damage from the previous day are allocated toward providing energy for your workout instead," says Jeff Volek, Ph.D., R.D., an exercise-and-nutrition researcher at the University of Connecticut. "Your muscles grow best when your body is resting, not working." This isn't an issue with Cosgrove's total-body recommendation, since there's a built-in recovery day after each session.
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A New Prescription
Bodybuilders argue that total-body training doesn't allow you to work muscle groups hard enough. For instance, they claim that if a typical chest workout takes 30 minutes or more to complete, you'd have to spend hours in the gym to adequately train your entire body. "That's based on the assumption that a chest workout needs to take 30 minutes," says Cosgrove. He goes on to explain that a typical chest day might consist of three sets of four exercises, for a total of 12 sets every 7 days. But Cosgrove says you could do the same amount of work -- 12 total sets -- in the same time period by performing four sets 3 days a week. "I've found that training works like a prescription," says Cosgrove. "You wouldn't take an entire bottle of Advil on Monday to relieve pain all week; you'd take smaller doses at regular intervals."
A study at the University of Alabama supports this notion. The researchers had one group of men train each muscle group once a week for 3 months; another group performed the same number of total sets weekly but split them equally among three total-body workouts. The result? The men who worked each muscle more frequently gained 9 pounds of muscle -- 5 more than those who trained each muscle only once a week.
But, to save even more time, Cosgrove employs another strategy: alternating sets. When possible, he pairs exercises that work opposite muscle groups and cuts the rest period between sets in half.
It's a concept based on the scientific work of Sir Charles Scott Sherrington, who won the Nobel Prize in 1932 for his contributions in physiology and neuroscience. Sherring-ton's law of reciprocal innervation states that "for every neural activation of a muscle, there is a corresponding inhibition of the opposing muscle." This means when you work your chest muscles, the opposite back muscles are forced to relax, thereby resting.
So, instead of waiting 2 minutes between sets of bench presses, you can perform one set of the bench press, rest for just 1 minute, and then do a bent-over row. After you finish, you'll rest again, then repeat the entire process until you complete all sets of both exercises. "In an average workout, this technique saves at least 8 to 10 minutes," says Cosgrove, "without sacrificing performance."
There's another piece to this puzzle, though. In analyzing thousands of work-out logs, Cosgrove developed a volume-threshold theory. "It seems that growth occurs once a muscle has been exposed to 90 to 120 seconds of total tension," he says.
For example, let's say it takes 5 seconds to complete one repetition. This means one set of eight repetitions would place your muscles under tension for 40 seconds. So, using Cosgrove's theory, you'd need to do only three sets -- for a total of 120 seconds -- to perform enough exercise to stimulate muscle growth. Likewise with four sets of five repetitions or two sets of 12 repetitions.
However, even Cosgrove admits that this is more theory than fact, primarily for one reason: Human studies simply haven't compared a wide variety of set and repetition ranges or even controlled for the duration of muscle tension. So there's simply no data to draw from. At least not until you look elsewhere in the animal kingdom.
Researching Muscle Growth
Some men simply gain muscle faster, easier, and to a greater degree than others, which is why we study rats," says Caiozzo. Compared with humans, rats are a much more homogeneous species, meaning there's little variation from one to another. This allows scientists to more accurately study the enzymes, metabolic pathways, and genes that regulate muscle growth.
Of course, actual lab rats aren't gym rats by nature. So, in 1992, Caiozzo developed a rat-size resistance-training apparatus -- a device that looks like a high-tech leg-curl machine. However, since they couldn't simply ask a group of rats to lift weights, there was another step involved.
The researchers permanently implanted a stainless-steel wire in the gastrocnemius muscle of each rat's hind limb and ran the wire under the skin to the skull, where two small screws had been inserted using a handheld drill. By connecting a wire to the outside of the screws, the scientists were then able to stimulate the muscle manually with an electric current, causing it to contract with maximal force. This allowed them to mimic a human weight-lifting workout.
To test the device, the rats were "encouraged" to perform four sets of 10 repetitions, with each repetition lasting 2 seconds -- a total tension time of 80 seconds. The result: The group didn't increase muscle size in an 8-week period. This meant that either the machine didn't work or the volume of exercise was too low. So the researchers tweaked the workout. When the contractions were increased to 4 seconds in duration, doubling the total tension time, the rats gained a significant amount of muscle mass -- and in just 4 weeks, not 8.
Of course, this doesn't authoritatively validate Cosgrove's volume-threshold theory in humans, but it does provide a biological precedent that supports it. And it just may be that some of his data is simply ahead of its time.
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Repetition Ranges
"Go heavy or go home" is a common saying among bodybuilders. But, while it's crucial that you use a weight that provides a challenging load, the mantra is flawed. That's because muscle fibers can grow in two ways. The first is when the myofibrils -- the parts of the fiber that contain the contracting proteins -- increase in number and density. This type of growth leads to strength gains and can be accomplished by using heavy weights that allow only one to seven repetitions.
The second type of growth, however, occurs when your muscles are forced to contract for longer periods of time. Typically, this means using lighter loads that allow you to complete 12 to 15 repetitions. This increases the number of energy-producing structures within the fiber. So you don't get significantly stronger, but you do get bigger.
Using a repetition range that falls between the two causes a combination of both types of growth, but each to a lesser degree. And that's why Cosgrove uses all three repetition ranges. For instance, he might prescribe five repetitions of each exercise on Monday, 15 on Wednesday, and 10 on Friday. "It not only leads to better growth but also helps keep you from hitting plateaus," he says.
And indeed, in a 2002 study, Arizona State University researchers discovered that men who alternated their repetition ranges in each of three weekly training sessions gained twice as much strength as men who didn't vary their repetitions. To Cosgrove, it's just another case of a logical approach generating a logical result.
