The impact of repetition count on muscle strength

Author: Timko Ilya - master of the whole project and fitness trainer.
2012-02-20

Recently, I was asked, “What is strength training?” And I found myself pondering that. What exactly is it? Well, it’s logical to assume that strength training is primarily focused on developing muscle strength.

Okay, then another question arises: what should a training regimen look like to maximize strength development? Well (I told myself), it’s commonly accepted and scientifically proven that the heavier the weight a person lifts, and consequently the fewer repetitions they perform, the greater their muscle strength develops. So, it seems that the ideal strength training session should consist entirely of sets with one repetition?

Something doesn't quite add up, does it? The thing is, many factors influence muscle strength. Some are beyond our control (the muscle's attachment site, the arrangement of fibers in relation to one another, the percentage of fast-twitch and slow-twitch fibers...), while others are within our control (the amount of ATP and creatine phosphate in the muscles, muscle volume...). Of the factors we can influence, muscle volume is the most significant. One doesn’t need to be a physiologist to know that: the bigger the muscle, the stronger it is (assuming other conditions are equal).

Alright (I told myself again), it’s widely known and beyond dispute that to increase muscle volume, one must perform repetitions in the range of 6 to 20 per set. Then the volume increases, and consequently, muscle strength does as well. It’s also known that in a sport like powerlifting, athletes include sets with a low number of repetitions (down to one). And they are very strong. Stronger than bodybuilders, despite the fact that bodybuilders tend to have larger muscle volume. So, it's not just about volume? There must be another factor that influences muscle strength and is amenable to development. And once again, knowledge of human physiology helps us here.

The thing is, hypertrophy (increase in the volume and mass of an organ) of muscles comes in two types.

Sarcoplasmic hypertrophy occurs when there is an increase in sarcoplasm within muscle fibers, which allows the muscle to gain volume. This type of hypertrophy leads to an increase in glycogen and creatine phosphate stores in the muscles. Sarcoplasmic hypertrophy is prominently manifested during work in the moderate power zone. In other words, when a light weight is lifted many times.

The other opposite type of hypertrophy – myofibrillar hypertrophy – is associated with an increase in the contractile apparatus of muscle fibers (myofibrils). In this case, muscle volume either does not increase at all or increases only slightly. However, muscle strength noticeably rises due to the enhanced capacity to contract. This hypertrophy is most prominently manifested during maximal muscle contractions with a low number of repetitions.

I hope this is clear. So, in nature, these two types of hypertrophy hardly ever occur in isolation. Simply performing either a certain number of repetitions will shift the effect toward one type or the other. The effect of bodybuilders' training is more tilted towards sarcoplasmic hypertrophy. That’s why they are so big. The effect of powerlifters' training is more tilted towards myofibrillar hypertrophy – which is why they are so strong.

Conclusion

To achieve maximum strength performance, it is necessary to train not only for strength but also for volume. Of course, you could focus solely on strength training, but then, your strength gains will plateau relatively quickly due to a lack of volume growth. In other words, it is essential to alternate mass training (where you perform 6 to 20 repetitions) with pure strength training (where you perform 6 or fewer repetitions). Only by simultaneously developing myofibrillar and sarcoplasmic hypertrophy can your muscles become maximally strong.

As you can see, there is no ready-made formula. It’s essential to try, combine, and experiment. If you believe you have already reached your desired volumes – focus on training strength. If not – start with volume training. But that’s a completely different story...