You train several times a week and you hang more and more weight on the bar. So you become stronger. Yet you do not or hardly become more muscular, while that is precisely your goal. What’s going wrong?

Key points:

1. In general, you can become stronger through adjustments in muscles (especially muscle growth) or in the central nervous system (especially the more efficient use of existing muscle mass).

2. How you get stronger (especially muscle growth or especially neural and other adaptations) depends on your training style (bodybuilding or powerlifting) and on your diet.

3. If you mainly train for maximum strength, i.e. with a lot of weight and few repetitions, you train powerlifting style and strength gains are accompanied by relatively little muscle growth. If muscle growth is your goal, train with lower weights and more reps. Also do enough sets and put enough effort into your sets (i.e. train until or close to muscle failure).

4. If you can gradually use higher weights (progressive overload), that is usually an indication of muscle growth. So you don’t grow because you get stronger, but you get stronger because you grow.

5. Even if your training is in order, muscle growth may not occur, namely if you eat too little. In most cases, muscle growth requires a calorie surplus (100-400 kcal on top of the maintenance level). In addition, you should eat enough protein (1.6-2 g/kg body weight/day).

6. But perhaps there is also muscle growth without resulting in strength gain, namely pure sarcoplasmic hypertrophy. This would result from low-intensity strength training (both absolute and relative), where primarily metabolic stress provides the growth stimulus.

THE RELATIONSHIP BETWEEN STRENGTH AND MUSCLE SIZE

It’s hard to deny that there’s a relationship between strength and muscle size. In the average gym, the biggest guys are often the strongest. However, that is not necessarily always the case.

HOW TO GET STRONGER

There are several factors that can make you stronger. They are described in an article by scientific author Chris Beardsley. To keep it simple, we limit ourselves here to the two main ways:

The first way is adjustments in the muscle (muscle growth). Muscle growth (or hypertrophy) in most cases means that the cross-sectional area of the muscle cross-section (the muscle fiber diameter) increases, with the result that individual fibers (and thus the entire muscle) can exert more force ^[ i ] .
The second way is adjustments in the central nervous system (neural adjustments): your body becomes more efficient at using the muscle mass it already has. Through strength training, your body learns to better control the muscle fibers from the brain, so that you move more efficiently ^{[ ii ] [ iii ]} . To this end, adaptations take place in the central nervous system, which is why one also speaks of CNS adaptation (Central Nervous System adaptation).

We want to emphasize that strength gains are a result of processes in the body and not a cause of those processes. It is often said that you have to get stronger to build muscle mass. But it is actually the other way around: if you have become stronger, that may be an indicator of muscle growth. Coach and author Eric Helms:

Increased strength, especially when quantified using a low skill isolation movement and which persists over longer time periods, indicates hypertrophy has likely occurred ^[ vi ] .

The ‘possibly’ and ‘probably’ indicate that you may also have become stronger due to factors other than pure muscle growth, most likely neural adaptations.

THE IMPORTANCE OF NEURAL ADAPTATION

Although we usually immediately think of bigger muscles when we get stronger, we should not underestimate the importance of the neural adaptations.

For example, neural adaptation means that training with one arm leads to better strength performance in both arms – while the other arm is not actively trained ^[ iv ] . They are also the reason that beginners often gain strength faster than they increase in muscle size: when you start with strength training, the neural adaptation is greatest. A similar effect is there when you do a completely new exercise. The fact that you initially quickly become stronger in that exercise is due to the adjustments in the nervous system. Which by the way does not mean that as a beginner or if you do a new exercise you do not also achieve some muscle growth ^[ v ] – it is just that the adaptation in the nervous system is then more dominant than that in the muscle cells.

Over time, the importance of neural adaptation diminishes in favor of muscle growth. But to what extent that happens depends on how you train. If you train purely for maximum strength, as powerlifters do, muscle growth plays a lesser role in getting stronger than if you train more on strength endurance, as bodybuilders do, according to Chris Beardsley (see also below). So by training for maximum strength, we mean that you can lift as heavy a weight as possible, even if you can’t do reps with it. In this form of strength training, the body relies more on neural adaptations and reinforcements other than muscle growth, such as increasing tendon stiffness. In the bodybuilding style of strength training (lighter weights and more reps), muscle growth plays a greater role in getting stronger,

The extent to which strength gains are accompanied by neural adaptation on the one hand and muscle growth on the other also depends on genetic factors. So you don’t have it completely in your own hands.

TWO TYPES OF MUSCLE GROWTH

It gets a little more complicated, because when a muscle has grown, it probably doesn’t always mean you’ve gotten stronger. There are two types of hypertrophy (muscle growth): myofibrillar and sarcoplasmic hypertrophy.

In myofibrillar hypertrophy, the muscle grows because the number of myofibrils increases. Myofibrils are supposedly the building blocks of muscle fibers. An increase in the number of myofibrils therefore causes a muscle fiber to grow larger. Myofibrils, in turn, are made up of contractile elements (sarcomeres), which allow the muscle to contract. An increase in the number of contractile elements is mainly associated with an increase in maximal strength and training intensity .

Sarcoplasmic hypertrophy is muscle growth due to an increase in the sarcoplasm, the sheath of the muscle fibers. This form of muscle growth is mainly associated with an increase in strength endurance and training volume. The sarcoplasm contains energy stores, in the form of glycogen, which increase with sarcoplasmic hypertrophy. The sarcoplasm contains so-called non-contractile proteins, which means that they do not directly contribute to force production. So sarcoplasmic hypertrophy doesn’t make you stronger in terms of absolute weight.

Sarcoplasmic and myofibrillar hypertrophy. The third, most common possibility is missing from this image, namely the growth of both the sarcoplasm and the number of myofibrils. (Source: Zatsiorky/Science and Practice of Strength training via Lyle McDonald)

There is still a lot of uncertainty and therefore controversy about these two forms of muscle growth. It is often thought that they occur simultaneously and that you cannot train specifically for one type of muscle growth. The sarcoplasmic hypertrophy would then be mainly intended to create space for larger muscle fibers, as a result of the myofibrillar hypertrophy. Others claim that you can train specifically for a certain type of muscle growth. Myofibrillar hypertrophy would mainly occur with a lot of mechanical tension (high absolute weights, few reps, long rest times), sarcoplasmic hypertrophy especially with high metabolic stress (low weights, many reps, short rest times).

The latter theory is gaining more and more scientific support. For example, there is a (not yet officially published) study by Haun et al., which implies this ^[ x ] . The scientists examined the effects on muscle growth of a six-week training program with a relatively high volume and low intensity on young, experienced strength athletes. To be precise: many reps with fairly low weights (60%1RM) and low relative intensity (average 4 RIR, or sets of up to four reps of muscle failure). After the six weeks of training, a muscle biopsy was taken to determine exactly how the muscle growth had taken place. What turned out? The size of the muscles had increased, but not due to the growth of muscle fibers! Thus, the training regimen did not result in myofibrillar, but only sarcoplasmic hypertrophy. Due to the low intensity, the muscle fibers were apparently not stimulated enough to let them grow, but the great metabolic stress still resulted in muscle growth due to the increase in the sarcoplasm.

Quite a revolutionary discovery, according to hypertrophy scientist Brad Schoenfeld. He tweeted in response to the investigation:

If you had asked me several months ago, I would have dismissed that “sarcoplasmic hypertrophy” occurred to any meaningful extent in the absence of contractile growth. This study has me reconsidering my opinion. ^[ xi ]

The study was also fodder for author Lyle McDonald, who devoted a hefty piece on his site . His tentative conclusion is that for maximum muscle growth, bodybuilders should also adopt a more metabolic training style, in addition to the traditional, more mechanically oriented style. This can be done by combining these styles in one training program, or by alternating them in blocks (meso cycles).

CONCLUSIONS

There is a strong relationship between muscle growth and strength gain, but these two processes are not inextricably linked.

In the first place, you do not only get stronger through muscle growth, but also through neural adaptations. The importance of neural adaptations increases the more you train for maximum strength. The importance of muscle growth increases the longer you put a muscle under tension, more precisely, the more stimulating repetitions you apply to a muscle during a workout. Volume is therefore at least as important as intensity for muscle growth.

Second, muscle growth does not always lead to strength gains. Muscles grow not only because muscle fibers get bigger, but also because the plasma around them increases. Certain, more metabolic styles of strength training seem to lead primarily or only to growth of that plasma and not that of the muscle fibers. As a result, the muscle grows and perhaps also your strength endurance, but not your ‘normal’ strength.

So in fact we can say:

To a certain extent, you can get stronger without your muscles growing. Conversely, you can also achieve muscle growth without getting stronger, albeit to a small extent.

TRAINING FOR MUSCLE GROWTH VERSUS TRAINING FOR PURE STRENGTH

If you put a powerlifter next to a bodybuilder, you will usually notice that the bodybuilder is (much) more muscular. The powerlifter, on the other hand, can lift much heavier weights. Undoubtedly, both athletes have become stronger in recent years, but in one this has led to significantly more muscle growth than in the other, in whom other factors, especially the neural one, have apparently led to an increase in strength.

Let’s put theory into practice. In other words: how should you train specifically if you mainly want to become stronger (powerlifting) or if you mainly want to become more muscular (bodybuilding)? It is obvious that you will eventually become both more muscular and stronger.

BODYBUILDING TRAINING

There are many paths to muscle growth, but which is the fastest? Although subject to ongoing debate, science has revealed the following guidelines for hypertrophy training:

For significant muscle gains, your training weight should be at least 30%1RM (30% of your one-rep max, the weight that allows you to do a maximum of one rep) ^[ vii ] . So you can never achieve optimal muscle growth with baby weights.
In theory you can achieve optimal muscle growth with all weights above 30%1RM, provided you train with the weight of your choice to or close to muscle failure ^[ viii ] . Muscle growth is therefore not about the absolute weight, but about the weight in relation to the number of repetitions you do with it. This means that you can actually train in all rep ranges, as long as you put enough effort into the set, i.e. train to or near muscle failure (0-4 RIR), also called the relative intensity. The last few repetitions before muscle failure determine the actual mechanical tension. For practical reasons, 6-15 reps for muscle growth is the most ideal.
If you want to get stronger in addition to being more muscular, you will have to train with heavy weights, in the range of 4-8 repetitions. Low weights are not optimal for strength gain.
In order to grow, you must gradually and consistently increase the training load (progressive overload). But you don’t necessarily have to go higher in weight for that. For example, you can also do more reps, or manipulate other training variables, such as RIR (Reps In Reserve – the number of repetitions you stay away from muscle failure), training pace and rest time between sets.
Increasing weights and/or number of reps is only possible when you get stronger (ie more strength and strength endurance). Getting stronger for a bodybuilder is primarily a matter of muscle growth. And muscles only grow if you do enough volume (so if you do enough sets per muscle group, on a weekly basis). Volume is thus the actual driver of muscle growth. Muscle growth requires significantly more volume than when you train purely for strength ^[ ix ] .
In principle the following applies to volume: the more, the better. But volume is limited by your recovery capacity. And your recovery capacity is partly determined by your training intensity, or the aforementioned effort. If you train each set to muscle failure or even further (for example by means of dropsets ) your volume will have to be a lot more limited than if you keep two repetitions in the barrel for example (2 RIR). The higher the intensity (the extent to which you train to muscle failure), the lower the volume. Average bodybuilders need about 10-15 sets per week per muscle group (assuming average heavy weights and 1-3 RIR).
Landing on a strength plateau often means that your body has become accustomed to your current volume. In that case, add sets, if your recovery capacity allows.
For optimal muscle growth, it’s probably also advisable to focus on creating metabolic stress rather than mechanical stress in a small portion of the workout. Because you may be stimulating sarcoplasmic hypertrophy through metabolic stress.

THE DIFFERENCES WITH POWERLIFTING TRAINING

From the above, it appears that weight plays an important role in hypertrophy training, but in a different way than in pure strength training, such as powerlifting training. After all, with bodybuilding training

maximal strength is not the goal: you have to use a lighter weight and be able to do several repetitions with it;
you have to exhaust a muscle (ie train to close and sometimes even to complete muscle failure), regardless of the weight you use. In short, it is not the absolute, but the relative intensity that counts;
your muscles have to do enough work in terms of exercises and sets;
you may also need to do some metabolically grafted training to achieve optimal results.

This immediately makes the differences with pure strength training or powerlifting clear. In addition, you train for maximum strength, with very few repetitions (sometimes even just ‘sets’ of one) and relatively few sets ^[ ix ] . In fact, in powerlifting only one training variable counts, the absolute intensity, while in bodybuilding relative intensity and volume are important.

	bodybuilding	powerlifting
# reps	many (6-15)	little (< 5)
# sets	quite a lot (≥ 10/muscle group/week)	few (8-12/muscle group/week)
rest time between sets	short (1-4 min.)	long (3-6 min.)
weight	anything from 30%1RM, but mostly medium to heavy (60-85%1RM)	very heavy (85-95%1RM)
training to muscle failure	sometimes (usually 1-3 RIR)	rarely or never
pace	controlled	fast
exercises	composite and insulating	composite and Olympic
main goal	aesthetic (muscle growth)	functional/performance (strength)

BODYBUILDING TRAINING IS OPTIMAL FOR MUSCLE GROWTH

Although powerlifters are often quite muscular, they usually lose out to bodybuilders in that respect. This is because when training for maximum strength, in addition to muscle growth, other factors also make you stronger – especially the aforementioned neural adaptations, but also, for example, increasing tendon stiffness. If you’re training with lower weights and more reps, like bodybuilders do, it’s mostly muscle gains that cause the strength gains, except for absolute beginners or if you’re doing a brand new exercise.

THE ROLE OF NUTRITION

In addition to your training style – bodybuilding or powerlifting – there is another aspect that determines the extent to which you become stronger through muscle growth: nutrition. After all, to grow muscles you have to provide them with sufficient calories and proteins.

If you eat too little or do not consume enough protein, your muscles cannot grow (optimally). You can still get stronger, but your body will only have to rely on neural adaptations for that.

Usually only absolute beginners and/or overweight people can grow muscle with a calorie deficit (body recomposition).

CONCLUSIONS AND ADVICE

If you get stronger, but you don’t see that translated into an increase in muscle mass, it can have two causes. Sometimes it is a combination of the two.

1. YOU DON’T TRAIN (WELL) ENOUGH

You may not be training enough bodybuilding style. The most important training principles for muscle growth once again:

train with weights that allow you to do 6-15 reps (50-85%1RM);
put enough effort into your sets, but don’t train too much to complete muscle failure (unless you have adjusted your volume accordingly). In general, go for 1-3 RIR;
maintain sufficient volume (for average bodybuilders 10-15 sets per muscle group per week) and increase the volume if you end up on a strength plateau, if your recovery capacity allows it;
spread the volume per muscle group over 2 or 3 sessions per week;
wait at least 48 hours before retraining a muscle group;
make progress in your overload, by adding weight and/or reps.

2. YOU DON’T EAT (WELL) ENOUGH

To grow muscle, you must:

manage a calorie surplus: aim for 100-400 kcal above your maintenance level;
use the correct amounts of macronutrients, ie proteins (1.6-2 g/kg body weight/day), fats (approx. 1 g/kg body weight/day) and carbohydrates (the rest).

IN SUMMARY

1. In general terms, you can become stronger through adjustments in muscles (especially muscle growth) or in the central nervous system (especially the more efficient use of existing muscle mass).