Increased blood flow is associated with increases in muscle protein synthesis. Low capillarization in muscle is associated with poor nutrient delivery, reduced satellite cell activation, and less muscle growth. Both high intensity and low-intensity exercise stimulate increased capillaries, with the volume of exercise being the biggest driver. Combining aerobic exercise spaced out with resistance exercise may result in greater muscle growth thru increased capillarization with a greater source of blood flow to the muscle.
CARDIO FOR MUSCLE BUILDING SUMMARY
- Cardio for muscle building may have potential benefits.
- Increased blood flow is associated with increases in muscle protein synthesis
- Low capillarization in muscle is associated with poor nutrient delivery, reduced satellite cell activation, and less muscle growth.
- Both high-intensity and low-intensity exercise stimulate increased capillaries, with the volume of exercise being the biggest driver.
- Combining aerobic exercise spaced out with resistance exercise may result in greater muscle growth thru increased capillarization with a greater source of blood flow to the muscle.
CARDIO FOR MUSCLE BUILDING? IS CARDIO AND RESISTANCE EXERCISE BETTER THAN RESISTANCE EXERCISE ALONE
Satellite cells are essential for muscle growth and repair. Studies have shown that aging results in blunted activation of satellite cells, which can be related to age-related muscle loss.
Resistance training activates satellite cells. Satellite cells normally stay dormant; however, satellite cells proliferate (i.e., split) after resistance exercise and fuse into muscle tissue, resulting in muscle growth.
Previous studies have shown that people with greater satellite cell activation have greater increases in muscle growth. Hyper-responders rapidly increase muscle growth after resistance exercise and have greater satellite cell activation than those who make lesser gains in muscle growth.
Some suggest that cardio is counter-productive to muscle growth, but the newest research is shaking up the bodybuilding world. Thomas et al. recently reported that aerobic exercise combined with resistance exercise resulted in greater muscle growth than resistance exercise alone.
CARDIO FOR MUSCLE BUILDING THEORY
The theory is that aerobic exercise can increase satellite cell activation by increasing capillary blood flow to the muscle.
Increased capillary blood flow to muscle from aerobic exercise has enhanced satellite cell activation by increasing the concentration of growth factors and hormones for muscle growth. It makes sense that more blood flow and nutrients will allow for a greater anabolic response.
The study had 14 men and women perform either resistance exercise or a combination of resistance and aerobic exercise for 10 weeks.
The results were that the combination of aerobic and resistance exercise resulted in hypertrophy in type I and type II; however, resistance training alone experienced hypertrophy in only type II fibers. Satellite cell content was greater in the aerobic training + resistance training group compared to resistance training alone.
Before the study, the subjects with the greatest capillary-to-fiber perimeter exchange ratio (a measure of blood perfusion to the muscle) experienced the greatest muscle hypertrophy following the training intervention.(25)
This study shows that cardio is good for cardiovascular health and may enhance muscle growth in response to resistance exercise by enhancing blood flow and nutrients to satellite cells.
DOES CARDIO BUILD MUSCLE?
Who doesn’t like a great pump in the gym? A good pump feels great but can also lead to greater muscle growth. A previous study found that cell swelling post-exercise was correlated with muscle growth (1).
If you maximize muscle pumps while increasing muscle growth, ensure the weight is sufficiently heavy to stimulate muscle growth.
This was demonstrated in a 2018 study in which subjects trained with different intensities to complete muscular failure with a similar total workload for twelve weeks. Subjects trained with 20%, 40%, 60%, and 80% of their 1-repetition maximum. Training at 40, 60, or 80% of one-repetition maximum 1RM led to similar muscle growth, whereas the 20% of 1RM groups had less biceps and quad growth.
This suggests that lightweight (<20% of a 1RM) will produce suboptimal growth, and weights above 85% won’t further increase muscle growth (2). Thus, using a weight that you can use for more than 30-40 reps will be less conducive to muscle growth than reps in the 15-30 rep ranges.
BUILDING MUSCLE WITH CARDIO: INCREASING BLOOD SUPPLY TO MUSCLE FOR MORE MUSCLE GROWTH
Cardio for muscle building has been a myth for years in circles. Now, a new term called muscle-building cardio suggests cardio may enhance muscle growth beyond just doing resistance exercise.
SHOULD I DO CARDIO IF TRYING TO BUILD MUSCLE?
Muscles need a rich supply of blood flow to deliver nutrients, oxygen, etc. Capillaries supply the muscle with blood flow. Some studies have found that an increase in a capillary network of muscle leads to greater muscle growth.
CARDIO FOR MUSCLE BUILDING
Untrained subjects can have a 10–30 % increase in capillarization after 6–8 weeks of exercise training. In contrast, elite aerobic athletes with years of progressive exercise training express a capillary-to-muscle fiber ratio of more than 200 % of that of untrained individuals.(3)
Supplements that can increase muscle blood flow are nitrates (i.e., beet juice), cocoa, curcumin, green tea extract, and other polyphenols.(4-7) Studies suggest that increased blood flow has a positive effect on increasing muscle protein synthesis. (8) The nitric oxide-enhancing drug Viagra has also been shown to increase muscle protein synthesis after just one week. (9)
IS CARDIO BAD FOR MUSCLE GROWTH?
Aerobic exercise is well known to increase blood capillary supply, but resistance exercise can also increase muscle capillaries to muscle. Researchers had subjects perform a 12-week resistance exercise program.
During the first week of the training period, the workload was increased gradually from 70% (10–15 repetitions) of 1-repetition maximum (1RM) to 80% of 1RM (8–10 repetitions). After that, training was performed at 80% 1RM. Workload intensity was adjusted based on the outcome of the successive 1RM tests (performed at weeks 4 and 8).
After just 2 weeks of training, there was an increase in the capillary-to-fiber ratio in the muscle, which was matched by an increase in muscle growth.(10)
Another interesting observation is that older men have reduced capillary-to-fiber ratios and smaller increases in muscle growth compared to younger men. (11, 12)
One study found that men with the lowest capillary blood supply in muscle had the lowest increases in muscle growth, suggesting adequate blood flow to the muscle is essential for muscle growth.(13)
Another study found that those with greater muscle capillarization resulted in greater muscle satellite cell activation and accelerated recovery.(14) Others have found that those with the highest capillary-to-fiber ratio had higher muscle mass than those with the lowest capillary-to-fiber ratio.(15)