Neural Adaptations During Strength Training

Most novices try to stimulate hypertrophy – an increase in the cross-sectional size of a muscle. They want to get big, but have only vague ideas about how this relates to increases in their levels of strength. When they work out for a while without noticeable results in the mirror, they think something’s wrong.

However, even with a perfect diet and weight lifting program, it can take up to six weeks before a new lifter notices any real increase in the size of his muscles. The short-term “pump” that fades away an hour or two after exercise is a tantalizing, but fleeting, glimpse of things to come, but it isn’t true hypertrophy; the pump is caused by fluid retention and it goes away quickly.

This can be confusing, because despite the fact that hypertrophy is mostly absent, strength increases rapidly in the first few weeks of a lifting program.

This initial strength gain comes from various neuromuscular adaptations rather than from hypertrophy.

These neural adaptation phenomena mean one very important thing: on a bulking program, novices will get a lot stronger before they begin to add muscle mass.

Five main mechanisms of neural adaptation are of interest to weight lifters

Bundles of motor units comprise a muscle.

  1. Motor Unit Synchronization is the most important neural adaptation for strength training. It is responsible for nearly all of the early strength gains experienced by a novice in the first few weeks of training. A motor unit consists of a neuron (motor nerve cell) and multiple muscle fibers. Each muscle fiber in a motor unit is functionally identical; that is, there is no mix of fast-twitch and slow-twitch fibers in a single motor unit. As a trainee makes progress, his ability to utilize multiple motor units increases markedly. This increased synchronization results in elevated levels of strength compared to those attainable in an untrained muscle.
  2. Enhanced Motor unit activation is another neural adaptation to training that rapidly increases the strength of a novice who hasn’t yet experienced hypertrophy. Training increases the frequency of motor unit firing and also increases the total number of motor units that effect a muscular contraction. In other words, more motor units work together, and they all fire more rapidly. Novices can only recruit a fraction of the motor units in a muscle during a voluntary contraction. Those with a few weeks of strength training under their belts are capable of recruiting a much higher percentage of the total motor units that make up a muscle.
  3. Skill acquisition and improved technique leads to increased strength. A novice unfamiliar with the weight lifting movements is unable to generate as much strength as a similarly-sized expert. This mechanism is especially important in movements that require the coordinated actions of several muscle groups.
  4. Specificity plays a huge part in early strength gains. Training one type of movement does not lead to strength gains in a seemingly-related movement. For example, increased strength on a leg-extension machine will not lead to an increase in the vertical leap. What the specificity principle means for novice weight lifters is that isolation exercises should be discarded in favor of general-purpose compound movements that develop strength which carries over to other techniques.
  5. Cross-education and increased involvement of the neural pathways contribute to strength gains too. For example, an untrained arm will gain significant strength in concert with a trained arm, because of interaction between the nerves of either arm at the spinal column. This cross-education is one of the clearest demonstrations of neural adaptation.


As strength increases, neural adaptation eventually gives way to hypertrophy

In the first six weeks of a strength training program, a novice will be able to increase the weight lifted. This steady rate of strength increase is almost wholly due to neural adaptation.

Later, after approximately six weeks, the novice’s neural adaptation markedly slows down and additional strength gains come mainly as a result of hypertrophy or increased muscle size. There is scientific evidence which shows that hypertrophy is only fully “switched on” when neural adaptations to strength training begin to tail off.
The relationship between neural adaptations, hypertrophy, and overall strength.

How does neural adaptation relate to strength training?

Novices have to pass through the neural adaptations stage before they experience significant hypertrophy. Until a novice learns the movements, significant hypertrophy won’t occur.

Isolation exercises violate the specificity principle which says that strength gains won’t transfer to other movements; use compound movements at least until neural adaptation seems to be complete and you feel like you’ve not only learned the movements, but your hypertrophy is slowing.

Don’t give up on a bulking program if hypertrophy doesn’t make itself apparent in a month. It takes longer than that for neural adaptation to reach its zenith.

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{ 4 comments… read them below or add one }

David September 19, 2011 at 1:49 am

best article ever in explaining this.


Philip January 13, 2012 at 7:33 pm

Really useful to know – now I won’t get disappointed when I’m still the same size after a month. But if I’m still not past the neural adaptation stage, does this mean Im not going to gain muscle weight for at least a few weeks – therefore will all weight gain during a bulking diet in this phase be fat?


elnino559 April 7, 2012 at 7:25 pm

This falls in line with the 5/3/1 program by Jim Wendler. I do a combination of strength and hypertrophy training (3 heavy days, 3 light days), increasing the intensity of strength training for the first three weeks of the month, then using the fourth week of the month as a “de-load” week (knocking down the weights on the strength training, cutting out all hypertrophy training, and only doing moderate-intensity cardio). I find that taking a “de-load” week will prevent the plateaus seen the graph, and when the weight gets too heavy knocking down the rep max to 90% will keep the progress going.


David November 12, 2012 at 3:44 pm

Interesting–now, to see what happens!


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