Here's what you need to know...

Your body doesn't really want to build a lot of muscle. You have to force it to adapt with the right kind of training. One of the most important factors is mechanical tension. Tension is created when you lift heavy weights and your muscles contract against it. The more mTOR is stimulated, the more protein synthesis occurs, and there's a direct relationship between mTOR and mechanical tension. The more tension a muscle is put under, the greater the mTOR stimulation. Load and time under tension (TUT) are key and they must be balanced. Use a heavy enough weight and keep the tension up for almost a minute. Drops sets and unilateral assistance exercises are great hypertrophy tools, and machine variations have advantages when it comes to bodybuilding.

The Best Way to Get Bigger?

Ask a hundred coaches or bodybuilders for the best way to increase muscle mass and you'll get about a hundred different answers.

Unfortunately, much of the advice will border on ridiculous. The volume in typical bodybuilding programs is often so high that the only way to recover is through serious chemical enhancement.

But if you prefer a more natural approach to getting bigger, you need to understand the science behind hypertrophy, and how to take advantage of it.

The Science of Hypertrophy

Hypertrophy is the end result of increased protein synthesis within our muscles following training and proper nutrition. Our body adds protein to muscle fibers, which thickens them. Ideally, this thickening continues and slowly builds, making our muscles bigger and stronger.

But this doesn't just happen. Our body doesn't want to change. We have to force it to adapt, and the way we train is very important.

A review of the literature on hypertrophy reveals that the most important factor in training is mechanical tension. Tension is created when we lift heavy stuff and our muscles contract against it. The actin and myosin strands in our muscle fibers working against the tension triggers a series of reactions in our body.

Brad Schoenfeld, one of the leading experts on the science of hypertrophy, wrote, "It is believed that mechanical tension disturbs the integrity of skeletal muscle, causing mechanochemically transduced molecular and cellular responses in myofibers and satellite cells."

What this means is that tension on your muscles increases protein synthesis in the fibers. If you're trying to get big, that's good.

More recently, Dr. Keith Baar was researching the p70S6K relationship to hypertrophy. He discovered that the key regulator of muscle protein synthesis is something called the mTOR pathway.

He also found that the more mTOR is stimulated, the more protein synthesis occurs, and that there's a direct relationship between mTOR and mechanical tension. The more tension a muscle is put under, the greater the mTOR stimulation.

Tension

There are two parts to tension that are important to stimulating mTOR:

Load Time Under Tension (TUT)

As the load increases so does tension, which stimulates mTOR, thereby increasing protein synthesis, which is what makes our muscles bigger.

So, all we have to do is lift really heavy weights, right? Not exactly.

We can't forget about time under tension. TUT also stimulates increases in mTOR, so the longer our muscles are under tension, the more we ultimately increase protein synthesis.

Okay, what we need to do is lift lighter weights for more reps, right? Again, not exactly.

mTOR actually starts to be inhibited after about 60 seconds of tension, and if the load is too light, we reduce tension. So, the trick is to find the right balance of load and TUT.

Doing one, really heavy rep will produce a lot of tension, but a very short TUT. We need to find the heaviest weights that we can move for a little under 60 seconds.

If one rep takes 4-5 seconds (1 second up, 1 second hold, 2-3 seconds down), then shoot for between 6-12 reps to maximize both load and TUT.

You can argue about whether 6 or 12 reps are better, but it's anyone's guess. In fact, it might not even matter because the two factors (load and TUT) probably combine equally at either end of the range.

Metabolic Demands

Dr. Baar also found that mTOR is actually turned off by too much work or metabolic demand.

We know that testosterone drops significantly in workouts lasting more than one hour, which isn't good for muscular growth. It seems that mTOR acts the same way.

It was also discovered that workouts using a great deal of ATP also lower mTOR, which means we want to use as little energy as possible during maximal tension workouts if the goal is hypertrophy.

In short, we need to fully recover between sets and avoid doing too much metabolically demanding activity during the workout, otherwise mTOR will start to shut down, limiting the hypertrophic effect of the workout.

This is why workouts like P90X or CrossFit get people ripped and lean, but not very big. They're so metabolically demanding that mTOR shuts off, limiting protein synthesis.

This is great if you want to lose weight and look lean, but bad if you want to move up a shirt size or two.

So when using any hypertrophy training routine, the research indicates that full recovery should take place between sets so that:

Maximal effort can be given on each set.

Your heart rate can return to normal levels to reduce the overall metabolic demand.

Now if all this rest almost sounds like you'll be wasting time farting around, look at how many of the top bodybuilders train. They take a long time between sets talking, posing, cracking jokes, and preparing for the next set.

Does Ronnie Coleman seem in a hurry when he's yelling "Yeah buddy!" from across the gym? And he was definitely on to something when he said, "Everybody wants to be a bodybuilder, but ain't nobody want to lift these heavy-ass weights."

As juiced and genetically gifted as Big Ronnie may be, he understood mechanical tension.

Negatives: Another Layer of Hypertrophy

Doing sets of 6-12 reps is a good start, and limiting the metabolic demand is even better, but let's take advantage of all the science we have available.

Numerous studies have clearly shown that eccentric contractions (negatives) are very important to hypertrophy. This has been demonstrated in MRI studies that reveal how much more muscle is stimulated during eccentrics compared to concentric-only training.

Eccentrics have been shown to create greater motor unit fatigue and increase protein synthesis and p70S6K more than concentric or isometrics. We can also handle greater weights (about 120% of our max concentric ability) eccentrically, which means larger loads may be used, creating greater tension.

Heavy eccentrics also cause greater localized muscle trauma, which has been shown to activate even more tissue repair and protein synthesis. They also provoke Type II fibers to a greater degree, and these fast-twitch fibers have greater hypertrophic potential than Type I fibers.

Eccentrics are demanding, however, so you can't do a ton of them or do them too frequently without running the risk of injury or overtraining. Make sure to recover fully between workouts.

There are a few other problems with heavy eccentrics. One is that they often require a partner. The other is that the greatest tension-producing eccentrics are done at fast speeds.

Fast eccentrics also create tremendous tendon trauma – which we definitely don't want – and can be dangerous. Tendon trauma also takes significantly longer to repair than muscle tissue trauma, which means you must rest longer between workouts.

Machines for Growth?

To safely and practically take advantage of eccentrics, plan one day every week or two for eccentric training, and get ready to use some machines.

Machines obviously aren't as "functional" as free weights but they're a great way to incorporate eccentric training. Remember, our muscles don't care where the tension comes from, they simply respond to it. So go ahead and use free weights and other functional methods most of the time, but take advantage of machines for this one specific purpose.

Two great ways to blend science and machines for hypertrophy are drop sets and unilateral assistance.

Drop Sets

Machines, especially with a weight stack, are perfect for drop sets because you don't need a partner – you can easily change weights very quickly, and they're safer than free weights because you can't drop anything on yourself as you fatigue.

We want to create maximal tension and keep the TUT under 60 seconds. This requires starting quite heavy for more tension and only performing 1-2 drops. You also want to drop the weight as quickly as possible so your muscles aren't going without tension for very long.

Drop sets work because you're always using the heaviest load possible at that moment. You're creating maximal tension on every rep, especially at the beginning of the set when you're fresh.

Start with a weight you can only get 2-4 reps with (allowing for huge amounts of tension), then drop the weight once you get tired to lengthen the TUT.

You're also stimulating a maximal number of motor units. As some motor units fatigue during the first set, other fatigue-resistant motor units are still fresh. Dropping the weight and continuing forces these fresh motor units to work without the help of the already-fatigued motor units that have already "crapped out."

This means we can stimulate muscle fibers that would otherwise not be touched in a standard set, creating a bigger effect on the muscle.

Unilateral Assistance

The basic idea is to focus on one limb/side at a time, using maximal weight for that side. Use both limbs to lift the weight, but only one to lower. Only use the "assistance limb" as much as required to raise the weight.

Let's use a biceps curl machine as an example. Suppose you can curl 100 pounds for one rep using your right arm. That would create maximum mechanical tension, but the TUT would be very short.

Here's what to do: put 100 pounds on the machine and curl up with both arms, but only use the left arm just enough to get the weight up. At the top, hold the weight for one second and slowly release your left hand from the bar. Lower the weight smoothly (2-3 seconds) with the right arm only. At the bottom, use your left arm again, raise the weight and repeat.

You'll reach a point where you can't control the negative, usually in the critical 6-12 rep range. Don't go past 60 seconds or let it get out of control – use your assistance arm if necessary so it doesn't get dangerously fast. The assistance arm will "assist" a little more on each rep as fatigue sets in.

Great machines for this kind of training include:

Leg curl variations

Biceps curl machine

Triceps extension machine

Seated dip machines

Chest press

Row with chest pad

Unilateral pulldown

Leg extension

Calf raise

Back extension on glute ham raise

Leg press with limiter that stops the carriage at the bottom

Unilateral assistance works best on machines where both sides are connected (meaning both sides move even if you push on only one side), but you can make it work on any exercise with a little creativity.

On unilateral machines like the Hammer Strength chest press or pulldown, you can put your assistance hand on the same side as your working hand for the concentric, then release it and use only one hand for the eccentric.

One of the best applications is on a leg press with a range limiter. It's one of the few ways to safely use high load eccentrics on a compound lower body movement. It's not safe to load up a bar heavy and do eccentric squats or deadlifts, so this is a safer alternative.

Amino Acids

Without getting too much into the nutrition side of hypertrophy, it's important to note that Dr. Baar's investigation into mTOR also revealed that increased concentrations of amino acids in the blood directly after a workout also stimulated mTOR production.

This means that workout nutrition makes a big difference in your ability to grow. Skimp out on the muscle-building proteins during the workout window and you risk sabotaging the whole process.

What To Do

If you've been looking for a practical and natural way to maximize your gains, science has the answer. Use the research on mTOR and hypertrophy to your advantage by:

Concentrating on the 6-12 rep range.

Using the heaviest weights possible to increase tension.

Keeping maximum tension on the muscles for up to 60 seconds.

Taking advantage of eccentrics and breakdowns.

Reducing the metabolic demand of your hypertrophy workouts by recovering fully between sets.

Making sure you've got amino acids in the form of sound workout nutrition flowing through your veins to maximize the effects of mTOR.

If you're used to following some muscle magazine workout, this type of training will feel very different. You won't necessarily get the same "pump" as with other routines, and you'll feel kind of fresh because of the long rest periods between sets.

Don't be fooled. The eccentric work will leave you extremely sore the next day, so be sure to give yourself sufficient rest before hitting it again.

Size training deserves a scientific approach just like strength training. Apply these principles and get growing.