Can Cardio Accelerate Muscle Growth?

When it comes to muscle growth, aerobic training (cardio) is usually discussed in only one way: how to combine it with strength training so that it does not get in the way. It is believed that cardio “steals” energy from the muscles, makes a person more tired, impairs recovery, and reduces strength (which it really can be).

A new study has found that cardio training can increase muscle growth under certain circumstances.

STUDY DESIGN

Fourteen people with training experience were randomly divided into two groups: one leg of each participant did cardio + strength, and the second strength only strength.

At first, participants cycled with one foot at moderate intensity for six weeks, three times a week, for 45 minutes. This was followed by ten weeks of strength training on both legs: squats, leg presses, calf extension and flexion in the machine, and toe raises, 10-12 reps per set, the last set to failure. Thus, it was possible to compare the results in one person on different legs.

WHAT DID YOU WATCH

The researchers took thigh muscle biopsies at the start of the study, after six cardio sessions, and after ten weeks of strength training, and looked at the following:

• muscle fiber size;
• number/density of capillaries;
• The number of satellite cells – those that are in their infancy and can become full-fledged muscle cells;
• The number of nuclei in a muscle cell (these are the only cells in the body that, due to their size/length, can have many nuclei).

Strength was measured at 1RM single rep max in squats and platform presses.

WHAT DID THEY FIND

Capillary density was higher in legs that did cardio before the strength phase.

After the completion of strength training, the cross-sectional area of ​​type I and II fibers and the average fiber area was greater in the legs, which also twisted the bike + power.

Also, more satellite cells and myonuclei were found in this group.

But the increase in lean leg mass did not generally differ across conditions, and all subjects significantly increased their 1RM in the squat and leg press.

The analysis showed that greater muscle hypertrophy was directly associated with a greater number of satellite cells and myonuclei, with a greater capillary density in principle and a greater one before the start of strength training.

Thus, people with good aerobic fitness can get more results from strength training due to increased muscle capillary density.

This is in line with previous research. For example, a 24-week study showed that the initial level of capillary density in the muscles at the beginning of strength training led to better muscle mass growth. And now it turned out that this effect extends to younger people.

WHY MIGHT THIS BE IMPORTANT?

We usually pay a lot of attention to what can increase muscle growth rather than too much to factors that limit muscle growth. And the number of capillaries in the muscles was one of these factors.

At the most basic level, the size of whole organisms and individual cells within an organism is directly related to energy requirements and the rate of energy production. Thus, the more capillaries that carry oxygen, energy, amino acids, and various signaling molecules and transport metabolic products from the cell, the higher the potential for growth, all other things being equal (adequate training program, progressive overload, enough protein in the diet, recovery, etc.). The whole organism and the individual cell have two options: either develop a better network of “roads” to provide themselves with everything they need or stop growing.

The study’s limitations tell us nothing about accelerating muscle growth in bodybuilders who have already “hit the wall”—reached a persistent plateau. But it can be assumed that capillaries’ density will also benefit them.

WHAT TO DO WITH IT?

We are in the uncomfortable position that aerobic training results help muscle hypertrophy. Still, aerobic training usually has a neutral or negative effect on muscle growth in those who do it along with strength training.

There are two possible exits:

1. You can try alternating periods of simultaneous strength + cardio training and periods when you do only strength. It’s okay if the rate of muscle growth slows down a bit when you combine strength with cardio because this phase aims to make the next training period consisting of only strength more effective. Ideally, it would help if you did both upper-body and lower-body cardio (rowing machine, swimming, ski machine ) so that all major muscle groups get the right stimulus.
2. Adding high reps to your training program also builds capillary density, a more traditional form of cardio. For example, if you’re doing up to 12 reps per exercise, then on one set, you’ll drop the weights to get 25-30 reps close to failure. Do it in various auxiliary simple exercises, not the “base.” After a heavy squat or chest press, doing another set of 30 times can be difficult and traumatic due to fatigue and deterioration in technique.

In conclusion, while cardiovascular exercise is an essential component of a well-rounded fitness routine and offers numerous health benefits, it is not typically considered a direct accelerator of muscle growth. Traditional cardio exercises such as running, swimming, or cycling primarily focus on improving cardiovascular endurance, burning calories, and promoting overall health. These activities primarily engage the cardiovascular system and can contribute to weight loss and improved cardiovascular fitness.

Muscle growth, on the other hand, is primarily stimulated through resistance training exercises that target specific muscle groups. Resistance training, such as weightlifting or bodyweight exercises, creates micro-tears in the muscle fibers, which then repair and rebuild, resulting in increased muscle size and strength. This process is known as muscle hypertrophy.

That being said, cardiovascular exercise can indirectly support muscle growth by improving blood flow, nutrient delivery, and recovery. Engaging in cardio exercises can enhance the efficiency of nutrient and oxygen transportation to the muscles, facilitating better recovery and overall performance during resistance training workouts. Furthermore, cardio exercises can help maintain a healthy body composition by reducing body fat, which can enhance the visibility and definition of the muscles.

To maximize muscle growth, it is crucial to prioritize resistance training exercises that specifically target the muscles you want to develop. Combining resistance training with appropriate nutrition, rest, and recovery is the most effective way to promote muscle growth.

In summary, while cardiovascular exercise does not directly accelerate muscle growth, it plays a supportive role in overall fitness and can indirectly contribute to muscle development by improving nutrient delivery, recovery, and body composition.