Unilateral training: advantages and who can benefit from it

Author: Mikhail Ziborov - author of the site makefitness.pro.
2022-05-14

Unilateral Training is when you perform an exercise starting with one arm or leg and then switch to the other. That is, you train each side of the body separately (left and right), hence the name – unilateral.

It is well-known that failure and pre-failure repetitions stimulate muscle tissue growth. But imagine this: you are training – bench pressing, pulling, squatting – yet your results are progressing very slowly. You might not be reaching those failure and pre-failure repetitions, thus not achieving the necessary volume for muscle growth (even if you have a personal training program).

Underworking is related to two points:

1. When we work with both limbs, fatigue is greater than when using one limb (particularly, there is more load on the nervous system).

2. There is a greater psychological load (perceived weight of the equipment or weights).

It is precisely for these two reasons that beginners often end their sets earlier than reaching failure. How can you help in this situation?

Unilateral Training for Strength and Mass Growth

A bit of theory. The concept of using one limb allows the brain to direct nerve impulses specifically to that limb. In simple terms, the brain focuses on the working limb, without being distracted by the other. You might be able to lift a 24 kg dumbbell with one hand for 12-15 reps comfortably. Now take that same 24 kg in the other hand (both will be 24 kg) and try to do those same 12-15 repetitions.

Your performance will decrease: the brain now has to manage two weights (arms) by sending equal-strength nerve impulses to both. The nervous system gets fatigued faster because it is responsible for muscle contraction. And the weaker the nerve impulses, the lesser the muscle's contraction capability. But what has changed? You simply took the same weight in the other hand that you were already lifting with the first.

In short! You can lift significantly more with one hand (do a greater volume of work and reach failure) than if you raised the same weight with both hands simultaneously. This is supported by a study (where BLD – bilateral deficit of strength of the limbs, i.e., a decrease in strength during bilateral contractions).

In Study 1, the activity of the deltoid muscles, oblique abdominal muscles, and lumbar muscles (spinal extensors) was measured. Twenty-one participants in the study worked with fitness ropes, creating waves first with one arm (one rope, i.e., a unilateral exercise) and then with both (two ropes, i.e., a bilateral exercise). The unilateral execution of the exercise showed significantly greater activity in the oblique abdominal muscles.

In Study 2, bilateral (classic) and unilateral squats (on one leg) were compared. The conclusion of the researchers states: “Unilateral squats with the same external load on the leg produce greater peak vertical reaction force than bilateral squats, as well as higher bar speed, which is related to strength development and the rate of strength development, respectively.”

Additionally: “Unilateral squats are performed with lighter loads (28 kg on one leg versus 135 kg on both with a barbell), but achieve comparable muscle activity in the hamstrings, calves, hip flexors, and abdominal muscles while placing less strain on the spine.”

In Study 3, greater muscle tissue damage was noted in unilateral lower extremity exercises compared to bilateral ones. Greater microtrauma in the muscles potentially leads to more significant muscle tissue gains after recovery. Therefore, we can assume that unilateral training may be more relevant for muscle mass gains.

Furthermore, unilateral exercises engage stabilizing muscles more effectively, which are responsible for maintaining balance during exercise. This can also contribute to:

- Overall muscle mass growth (stabilizing muscles will grow more actively);

- Training your functionality (balance and coordination).

Advantages of Unilateral Exercises over Bilateral (Classic) Exercises

1. Greater involvement of stabilizing muscles.

2. Ability to train with injuries (of the spine, one limb, etc.).

3. Increased muscle mass gain.

4. Better muscle engagement (in one study, Romanian deadlifts on one and two legs were compared; on one leg, the activity of the hamstring muscles was significantly higher).

On the downside, I would highlight that this type of training takes more time: first working one side, then the other – all of this requires more time.

How to Train One Side of the Body

There are different options. Some train both limbs in one session, but in turn: they press with one hand, rest, then press with the other (or work one side of the torso, then the other).

However, there is also a more advanced option (something like forbidden magic, I would say). Some people train, for example, the left tricep and right pectoral muscle in one session, and in the next training, they switch them. This approach can only be afforded by those who have enough time for the workouts and for recovery, as well as for appropriate nutrition.

Speaking of nutrition, you do understand that no training method will help you if you are simply not getting enough protein, right?

For clarity, I am by no means undermining the importance of bilateral exercises! On the contrary, they are the foundation without which you cannot progress. But if you periodically change your training program or incorporate unilateral exercises into it, you will achieve significantly better results, as studies show.

Who Can Benefit from Unilateral Training

1. People with Injuries. An injured shoulder, elbow, or other body area can still allow you to train using unilateral exercises. I have even heard a hypothesis that training one limb leads to strengthening the other, even if it was not trained. Obviously, the trained arm or leg will be stronger than the untrained one.

2. People with Long Limbs. Those with long arms need to lift weights to a greater height compared to people with shorter arms. The same applies to squats: taller individuals have to go lower. Considering that bilateral exercises are more taxing, it might be recommended for taller individuals to use unilateral exercises more often: the load remains the same or even higher, but overall fatigue is less.