May 17, 2019

High repetitions or low repetitions for muscle growth: what science says

Hohe Wiederholungszahlen oder niedrige Wiederholungszahlen für ein Muskelwachstum: Was sagt die Wissenschaft

The general consensus is that training with high repetitions and light weights improves endurance but does little to increase muscle mass. Low reps and heavy weights, on the other hand, are the generally accepted "best way" to maximize muscle growth.

However, in 2010, Stuart Phillips, a kinesiology professor at McMaster University in Canada, began to challenge much of what was considered to be a commonly held view.

High repetition vs. low repetition: the scientific research

Phillips and his team found that muscle protein synthesis - a driving force behind muscle growth - was higher with lighter weights and higher repetitions (4 sets of 24 repetitions) than with heavier weights and lower repetitions (4 sets of 5 repetitions) (1).

At the time, these results led to a lot of controversy. They were ignored or considered irrelevant by many, mainly due to the fact that the study looked at short-term changes in protein synthesis rather than long-term gains in muscle mass.

For this reason, Phillips conducted another study. This time, he had a group of men train their legs on a leg extension machine three times a week for 10 weeks, using three different set and repetition configurations (2):

1 set of 10-12 repetitions to muscle failure
3 sets of 10-12 repetitions until muscle failure
3 sets of 30-40 repetitions to muscle failure

The result?

The amount of newly built muscle mass in the legs was almost identical. Training with lighter weights and higher repetitions stimulated just as much muscle growth as training with heavier weights and lower repetitions.

In addition, the average size of both fast and slow contracting muscle fibers increased to the same extent with heavy and light weights, indicating that both muscle fiber types were recruited and stimulated during training.

High repetitions vs. low repetitions for muscle growth

The second study also attracted criticism, mainly related to the fact that it used untrained beginners as subjects. Take someone who has never trained before and have them train with weights for a few months. They will tend to build muscle regardless of how they train.

Would you see the same results in someone who has been training for a few years?

To find out, Phillips recruited a group of 49 men who had an average of 4 years of training experience. These men were divided into two groups (3). One group performed 20 to 25 repetitions per set, while the other group performed 8 to 12 repetitions.

The result?

After 12 weeks, no statistically significant difference in the rate of muscle growth was observed between these two groups. As with the studies conducted with beginners, the average size of both fast and slow contracting muscle fibers had increased to a similar extent in both groups.

However, this does not mean that both training protocols produced identical results. The average muscle mass was one kilo in the group that used high repetitions, compared to 1.6 kilos in the group that trained with low repetitions.

If the study had lasted longer or the number of subjects had been higher, the difference in results between the two groups could have been large enough to cross the threshold of statistical significance.

Of course, these are only the results of a few studies and it is never a good idea to draw conclusions from a small number of studies. However, there is plenty more research showing numerous benefits of training with light weights and high repetitions:

Light training with slow speed of movement (55 to 60% of 1RM weight and 3 seconds to lift and lower the weight) can increase both muscle mass and maximal strength (4). The results are comparable to those achievable with heavy training at normal speed (80 to 90% of 1RM weight, 1 second for lifting and lowering the weight).
Both heavy (4 sets of 8 to 10 repetitions) and light training (4 sets of 18 to 20 repetitions) activate the expression of different genes involved in muscle growth (5).
Training the arms for eight weeks with light weights (20 RM weight) and short rest intervals (30 seconds) leads to increases in muscle mass that do not differ from the increases observed with heavier weights (8 RM weight) and longer rest intervals (3 minutes) (6).
Training with lighter weights and higher repetitions (not to muscle failure) stimulates protein synthesis in connective tissue just as well as heavy training, which means that such training can play a role in improving connective tissue recovery during rehabilitation after injury (7)
Eight weeks of training with high repetitions and light weights (30 to 40 repetitions per set) builds just as much muscle as training with lower repetitions (8 to 12 repetitions per set) and heavy weights (8). Using a mixed protocol, which included alternating between heavy and light weights, did not produce better results.

Training with super high repetitions: How light is too light?

Most of the studies we've looked at so far show similar rates of muscle growth at both low and high reps. But what happens when you start training with super high reps? And by super high, I mean something in the range of 60 to 70 reps per set.

That was the question posed by a Brazilian team of scientists who used a group of 30 untrained men as test subjects and had them train with weights twice a week for 12 weeks (9).

The test subjects were divided into three groups. All three groups trained biceps and quadriceps on one side of their body with very light weights and super high repetitions (20% of their 1RM weight and 60 to 70 repetitions per set).

On the other side of their body, the men used three different loading protocols, as has been done in other similar studies (10):

A protocol with high repetitions, where about 30 repetitions were performed with 40% of the 1RM weight.
A protocol with moderate repetitions, in which about 15 to 20 repetitions were performed with 60% of the 1RM weight.
A protocol with a low number of repetitions, in which around 10 to 15 repetitions were performed with 80% of the 1RM weight.

All three groups trained to muscle failure and performed two exercises: Bicep curls and leg presses.

At the end of the 12 weeks, training with low, moderate and high repetitions resulted in similar gains in muscle mass. Higher repetitions with lighter weights resulted in just as much muscle growth as heavier weights and lower repetitions.

However, things looked very different on the side of the body that was trained with super high repetitions. Here the muscles only grew at half the rate of the other training protocols.

In other words, this meant that even though 30 reps resulted in identical gains to sets of 10 to 15 reps, training with only 20% of 1RM weight appears to be below the stimulus threshold necessary to maximize gains in muscle mass.

High reps vs. low reps: two types of muscle growth

Some say that the type of muscle growth induced by training with lighter weights and higher repetitions is not "as good" as the type of muscle growth induced by heavier weights.

Here's what these people are talking about:

If you could take a closer look at a slice of muscle tissue, you'd see that it's made up of many smaller muscle fibers. Your muscles get bigger as these individual fibers get thicker - a process known as hypertrophy.

Within each muscle fiber are elongated structures called myofibrils that run parallel to each other. The myofibrils are the part of the muscle tissue that contributes to force production.

There is also a fluid part of the muscle fiber called the sarcoplasm in which the myofibrils are embedded. This sarcoplasm contains things like water, glycogen and myoglobin and does not directly contribute to the production of muscle strength.

The term myofibrillar hypertrophy refers to an increase in the volume of the myofibrils, while the term sarcoplasmic hypertrophy refers to an expansion of the plasma.

The idea is that training with lighter weights and higher repetitions mainly leads to so-called "non-functional" sarcoplasmic hypertrophy, which creates soft, inflated muscles that collapse relatively quickly.

Training with heavy weights and lower repetitions, on the other hand, should preferentially increase the rate of myofibrillar hypertrophy, leading to dense, strong and "functional" muscles.

At least that's the theory, but personally I'm not really convinced by it.

In one of the few studies that compared the effects of high vs. low repetition training on myofibrillar and sarcoplasmic protein synthesis, training with low weights and high repetitions increased the rate of sarcoplasmic protein synthesis to a greater extent than heavier training (1).

However, this training also increased the rate of myofibrillar protein synthesis. It is interesting to note that when measured 24 hours after training, training with high repetitions and light repetitions (4 sets of 24 repetitions) increased myofibrillar protein synthesis to a much greater extent than training with heavy weights and lower repetitions.

However, it should be noted that this study looked at the short-term changes in protein synthesis after training rather than the long-term changes in muscle tissue after several months of training. We cannot say with certainty that the former is completely reliable to predict the latter.

But nevertheless, this study challenges the idea that training with higher repetitions and lighter weights will preferentially increase sarcoplasmic hypertrophy rather than myofibrillar hypertrophy.

However, this does not mean that training programs based on the sarcoplasmic vs. myofibrillar hypertrophy concept cannot work. Only the way in which they are supposed to work probably does not correspond to reality.

The sarcoplasm exists and it can grow (11). However, there is no convincing evidence that gains in muscle mass resulting from training with lighter weights and higher repetitions are primarily based on "non-functional" sarcoplasmic hypertrophy, while the myofibrillar portion of the muscle remains the same, or grows to a much lesser extent.

High reps vs. low reps: final thoughts

What does all this mean in practice? It certainly doesn't mean that training with light weights and high reps is now the best way to build muscle. In fact, just because it's possible to build muscle using higher reps and lighter weights doesn't necessarily mean it's a good idea to do so.

Remember that, at least in terms of muscle growth, there were no discernible benefits to high repetition and light weight protocols. These protocols did not result in superior gains in strength or muscle mass, but each set took twice as long to complete.

Training to muscle failure in a higher repetition range is also very uncomfortable and extremely painful - and much harder than training to muscle failure with heavier weights and lower repetitions.

Doing longer, more painful workouts just to generate the same results doesn't sound like a great idea to me. In addition to this, lower reps with heavier weights are clearly superior when it comes to strength gains (12).

What all this means is that the repetition range you can use to build muscle is much wider than previously thought.

Most studies show quite similar gains in muscle mass across a wide range of repetition ranges. This gives you much more choice in the type of training you can do.

For example, joint problems or injuries can mean that training with heavy weights means pain in the shoulders, elbows, knees or wrists.

The solution to this problem is quite simple. If using heavy weights causes pain, then simply use lighter weights instead. You can switch from heavy weights and low repetitions to light weights and high repetitions without sacrificing any gains.

You may also prefer lighter weights for certain exercises and heavier weights for others. Even then, you can use the weights that suit you best without having to worry about your gains.

In short, you can grow your muscles with a wide range of repetition ranges and weights, from light to heavy, as long as you train hard and challenge yourself.

References:

Source: https://muscleevo.net/low-weight-high-reps/

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