Well, this article is for those of us in the latter group who could use a boost in muscle fullness.
Although we may never be able to match the genetically gifted freaks of fullness like current Mr. Olympia Phil Heath or former almost-Mr.-Olympia Flex Wheeler, we can all significantly, even dramatically, increase the fullness of our muscle bellies by using one or more of the following strategies.
1. Increase Time Under Tension
Time under tension (TUT) is about the amount of time the working muscle is under tension, as in contracting, during a given set.
Whether it’s concentric, eccentric, or isometric, muscle contraction increases the tension within a muscle. For purposes of filling out flat muscles, it’s the effects of a longer TUT, specifically the effect of blood vessel occlusion.
When a muscle is contracting, the blood vessels within it are squashed to the point of being occluded, dramatically reducing blood flow to that muscle.
The longer the muscle is contracting, the longer the blood flow is stopped. Your heart is still pumping blood during your set, so this occlusion results in more blood volume building up on the upstream side of the working muscle.
When your set is completed and the muscle relaxes, blood rushes into the muscle.
The longer the blood is occluded, the higher the volume of blood suddenly surging into the muscle. To literally feel this at work, do push-ups for five seconds and note the pump you get after. Now rest a couple minutes and then do push-ups for 30 seconds, again noting the subsequent influx of blood.
Whether you call it hyperaemic super-compensation or a pump, this sudden surge of blood flow and increased blood volume increases the pressure within the muscle. However, what we’re after is the increase in outward pressure, this increase in blood volume places on the tough, dense, fascia that surrounds the muscle.
Fascia isn’t easy to stretch, but over time it does respond to pressure by expanding and subsequently causing an increase in the volume and visual fullness of the muscle it surrounds.
Increasing TUT does, in fact, lead to an increase in muscle fullness. It takes time, no doubt, but it does occur. Using more resistance and a higher rep speed is advantageous in terms of motor unit recruitment (a.k.a. recruiting more muscle fibres).
Instead of prolonging TUT by doing reps more slowly with a lighter weight, it’s better to still move the weight quickly (at least concentrically) and to only lighten the weight as much as is needed to increase the TUT to around 45 seconds or so.
If a set takes less than 30 seconds, it’s not going to be optimal in terms of increasing intramuscular pressure. But, going longer than 60 seconds isn’t generally optimal either, because it requires using a weight that is too light. Performing a TUT of about 45 seconds is the target.
2 – Do More Volume
Our body is an amazingly adaptive biological 'machine' of sorts. It does its best to respond to everything we throw at it by adapting and coming back even more ready to tackle that particular task. Doing a high volume training session is no exception.
By volume we're talking the combination of sets and reps. In essence, it's the overall amount of work a muscle does during a workout. More work means more energy is needed to fuel that work. When we're talking fuel for muscle contraction, we're talking muscle glycogen...the stored carbs within a muscle.
Let's say you're going to apply the above fascial expansion rule-of-thumb and do sets of, for example, twelve reps during your chest workout. Doing 10 sets of 12 reps uses far more pectoral glycogen than does doing just two sets of 12. (Keep in mind that glycogen comes from the muscle being worked.)
A neat thing happens when we do a training session with enough volume to deplete muscle glycogen within a muscle. The body responds by trying to store more muscle glycogen in that muscle so that you're better able to handle the same workout the next time around.
The short-term increase in muscle glycogen is called glycogen supercompensation. This results in your muscles temporarily being able to store more glycogen than they could normally hold – say 120% vs. the normal 100%.
In the long run your body is still working to gradually build the capacity to store more glycogen, and it will if you keep taxing glycogen stores. So this increase in muscle glycogen is both a short-term and long-term strategy.
Although we're not arbitrarily concerned about more intramuscular glycogen storage, we are concerned about muscle fullness. And a muscle that stores more glycogen is a rounder, fuller, muscle.
3 – Optimize Rest Periods
Similar to the first strategy, optimizing rest periods between sets relates to maximizing blood volume and pressure within the muscle.
Imagine doing a killer set that really has you pumped to the max, feeling like your skin is going to tear at any moment. Now let's say you decide to rest 3 minutes in order for your body to remove lactic acid, buffer hydrogen ions, and replenish creatine phosphate (CP) stores as much as possible. In terms of performance on the upcoming set, this is a great idea.
But in terms of sustaining the increase in intramuscular blood volume, resting 3 minutes is not a good idea. You can probably feel your imaginary pump fading just thinking about resting 3 minutes.
Remember, fascia is a tough, dense type of tissue. It doesn't just expand because a little pressure is put on it for a few moments. Instead, it takes copious amounts of sustained pressure to eventually get it to expand.
So in order to maximize fascial expansion and muscle fullness, once you've got a muscle full of blood, you wanna keep it full of blood for as long as possible. Doing so provides more of a stimulus for fascial expansion.
As with every technique, there are pros and cons. If you resume your next set too soon, your performance on the following set will suffer. As mentioned above, it does take time to clear waste products and replenish CP stores, both of which are important if you plan to get a decent number of reps on the following set.
On the other hand, rest too long and you're going to release the outward pressure on the fascia.
This is certainly a time when paying close attention to your body will come in handy. By paying close attention to the tightness and fullness after a set and, especially, when that fullness begins to dissipate, you can finely tune your rest periods to optimize fascial stretch.
Also take note – as in literally in a notebook/training log – of your performance on the next set. If you get 15 reps on set one but only six reps on set two, then you didn't rest long enough.
If you combine your attentiveness to the dissipation of intramuscular pressure with your performance on subsequent sets, you can finely tune your rest periods for fascial expansion better than I could prescribe a specific rest interval.
With that being said, if you're like me and sometimes just wanna stick to a given rest period without occupying your mind with such details, then go with a rest period of about 45 seconds. Thirty to sixty seconds is a good range to stay within. Generally err toward the lower side on less taxing things like biceps curls, and toward the longer end on more taxing movements like squats...that is if you're ever feeling froggy enough to try squats with just 60 seconds of rest.
4. More Volume
By volume it’s the combination of sets and reps. In essence, it’s the overall amount of work a muscle does during a workout. More work means more energy is needed for that work. This is about muscle glycogen, the stored carbs within a muscle.
Let’s say you’re going to apply the above expansion and do sets of, for example, twelve reps during your chest workout. Doing 10 sets of 12 reps uses far more pectoral glycogen than does doing just two sets of 12. (Glycogen comes from the muscle being worked.)
When we do a training session with enough volume to deplete muscle glycogen within a muscle. The body responds by trying to store more muscle glycogen in that muscle so that you’re better able to handle the same workout the next time around.
The short-term increase in muscle glycogen is called glycogen super-compensation. This results in your muscles temporarily being able to store more glycogen than they could normally hold.
In the long run your body is still working to gradually build the capacity to store more glycogen and it will if you keep taxing glycogen stores. So this increase in muscle glycogen is both a short-term and long-term strategy.
Although we’re not arbitrarily concerned about more intramuscular glycogen storage, we are concerned about muscle fullness. A muscle that stores more glycogen is a rounder, fuller, muscle.
As with any training adaptation, this isn’t something you’ll necessarily see after a high volume workout, but it is something you’ll notice over time.
If you’ve already been using a relatively high volume of training, then you’re not growing experience, if any, adaptation, simply because you’ve already been doing it. The same applies to increasing TUT.
The other reason you may not see and experience the muscle fullness that you should isn’t training related, it’s diet related. If you don’t consume enough carbs, especially in the post-workout window of increased sensitivity to glycogen storage, then your body simply doesn’t have the fuel with which to fill your muscles up with glycogen.
Glycogen is simply stored carbs, not stored protein or fat. You have got to put ample carbs in your body to fully replenish muscle glycogen stores.
It’s worth pointing out that, if you’re chronically storing more glycogen within the muscle, the surrounding fascia is also receiving the pressure to stretch.
But you must keep in mind that volume and intensity simply must be inversely proportional to allow for complete muscular and nervous system recuperation. So, avoid the temptation to take every set of a high volume program to failure.