Are muscles that decrease easily with age easier to increase with strength training? Surprising differences revealed by the latest research

If you do strength training, your muscles will grow. However, not all muscles grow in the same way.

It is well known that muscles decrease as we age, but the way they decrease is not uniform throughout the body.

For example, it is estimated that the muscles in the front of the thigh decrease by up to 33% over about 50 years due to aging. On the other hand, the muscles deep in the calf decreased by only 6%.

Even though they are muscles in the same body, why are they so different?

And there is one more thing to be concerned about.

Are muscles that decrease easily with age also easier to increase with strength training?

If so, knowing which muscles are easily lost with age could be an important clue for planning future strength training.

This time, we will consider this question based on a review summarizing muscle loss due to aging and a review summarizing muscle changes due to exercise in the elderly.

◆ Some muscles decrease by 33% with age, while others decrease by only 6%

In 2023, Naruse et al. at Ball State University in the United States published a review that organized muscle loss due to aging by muscle.

The analysis included 47 studies comparing young and elderly people, summarizing data from 982 young people and 1,003 elderly people. The young people averaged about 25 years old, and the elderly averaged about 75 years old, and the changes over about 50 years were estimated from the differences in muscle size between the two groups.

As a result, it was found that there is a large difference in the rate of decrease depending on the muscle.

The largest rate of decrease was in the rectus femoris in the front of the thigh at 33%. This was followed by the vastus lateralis at 30%, and the psoas major deep in the hip joint at 29%.

On the other hand, the smallest rate of decrease was in the soleus muscle deep in the calf, at only 6%.

In other words, for the muscles examined this time, there was a more than fivefold difference in the rate of decline due to aging.

Why is there such a difference?

The review points out that factors such as muscle activity levels, muscle fiber types, gender, and the progression of aging may be involved.

For example, the soleus muscle is a muscle that works to maintain posture even when standing. On the other hand, the rectus femoris muscle has the function of bending the hip joint and extending the knee.

Such differences in function may be related to changes in muscles due to aging.

However, this study did not track the same individuals for 50 years. It compared people of different ages and estimated the changes over approximately 50 years.

Even so, it is clear that it is not appropriate to view muscle loss as a phenomenon where all muscles in the body decrease uniformly.

So, just as the way muscles decrease differs, does the response to strength training also differ for each muscle?

And if the ease of growth differs depending on the muscle, do we need to change how we train?

From here on, we will delve into the surprising differences revealed by strength training research in the elderly and the significance of increasing the number of training repetitions.