Introduction
When most people think of muscle they think of skeletal muscle. The biceps, pecs, delts, legs, and abs. This type of muscle, also referred to as striated muscle, is one of three types in the body. The others include cardiac muscle and smooth muscle. The former is found within the heart and generates force to propel blood throughout the body. The latter is found in several places within body, and is responsible for a variety of functions, such as aiding the bladder to release urine; aiding the digestive track to transport food; and providing blood vessels the ability to contract/relax to control blood pressure and flow.
Muscle consists of bundles of fibrous tissue with the ability to contract, using ATP energy, and produce force. Specific to skeletal muscle, these contractions typically produce movement—by pulling on bones—but sometimes involve no movement (referred to as an isometric contraction). Because muscle relies on ATP energy to function, providing the optimal nutrients can aid muscle contractions, especially if these are to be done repeatedly over time.
The actual contraction of muscle involves a series of events, including an intricate interaction between the brain, nerves, neurotransmitters, and the innervated muscle fibers. Muscle is very adaptable and can react to various stimuli to undergo hypertrophy (an increase in cell size) and sometimes hyperplasia (an increase in cell number). These are common adaptations to strenuous exercise and other physically demanding tasks. Muscle can also undergo a decrease in size, which is referred to as atrophy. This is commonly observed with a sedentary lifestyle and with aging.
In addition to muscle size, the strength of muscle can be altered considerably. In general, as a muscle gets bigger it will generate more force. Interestingly, although most people think of muscle size and strength more in terms of being purely cosmetic or functional, both are associated with all-cause mortality. Specifically, more muscle and greater strength = longer lifespan.
Exercise and Muscle
It is well accepted that regular, structured exercise is the best way to maintain muscle health. The evidence is clear that exercise can increase muscle size and strength, in addition to muscle endurance. With regards to the type of exercise, both aerobic (cardiovascular) and anaerobic (resistance) exercise should be included in a well-rounded regimen. While complex programs can be designed, in general and to keep things simple, exercise should be performed three or more days per week, for at least 30 minutes per session for aerobic exercise and at least 20 minutes per session for anaerobic exercise. More advanced trainees will exercise several days per week, often for 60 or more minutes per session for aerobic exercise and 60 minutes per session for resistance training. Beyond the frequency and duration, we know that the intensity of exercise must be sufficient in order to ensure adaptations in muscular strength, size, and endurance.
The amount of attention given to the different types of exercise will vary depending on the goals. For example, aerobic exercise (cardiovascular) is not responsible for much increase in size and strength but it does enhance the muscle fiber oxidative capacity, the mitochondrial density, muscle capillary density, and enzyme activity—all of which can aid multiple aspects of health. Anaerobic exercise, on the other hand, is best for increased muscle mass, strength, and power production. Of course, other health benefits are realized with both types of exercise.
Nutrition and Muscle
Aside from exercise, nutritional intake can make a significant contribution to muscle adaptations. This has been well described in the scientific literature but also seen anecdotally by those who seek muscular development through a combination of exercise and nutritional intake. For example, if interested in gaining muscle size and strength, consuming a diet rich in protein is important. This includes such foods as protein powders, chicken, turkey, beef, fish, eggs, cottage cheese, and milk. In addition, consuming nutrient dense carbohydrate-rich foods is important, such as beans, rice, vegetables, and fruits. Lastly, consuming high quality dietary fats can prove valuable, including items such as nuts and nut butters, seeds, and healthy oils.
Beyond the types of foods, we know that the timing of feeding may be important. Individuals seeking increased muscle mass may opt for frequent meals throughout the day (5-6). They may also focus on consuming a high quality meal shortly after their exercise session, inclusive of protein (for muscle repair) and carbohydrate (for replenishing lost glycogen stores). Providing nutrients every 2.5 - 3 hours throughout the day seems to work well for many who seek increased muscle mass and strength.
Beyond whole food nutrition, several dietary supplements have been reported to be helpful in terms of muscle size and strength gains. The most popular appear to be protein powders and essential amino acids. These can prove helpful in an effort to consume high quality sources that may aid muscle repair and growth. Consumption of healthy oils such as fish oil, flax oil, and borage seed oil is also of interest. When it comes to more isolated ingredients, creatine monohydrate (and other creatine forms) is likely the most well-researched and widely used supplement to aid muscle size and strength, as well as power. Other items such as vitamins and minerals (vitamin D and calcium), PQQ (may have an impact on stimulating mitochondrial biogenesis), and molecular hydrogen (may alleviate muscle degeneration) may prove useful.
Conclusion
There are three types of muscle: skeletal, cardiac, and smooth. Muscle has a variety of functions and is highly adaptable—it can both grow and become stronger, as well as shrink and become weaker. Exercise and nutritional intake are two highly influential variables as related to muscle growth and strength, with additional variables such as adequate nightly sleep and reduced stress also contributing to progress. Beyond exercise and whole food nutrition, select dietary supplements may be considered and have been reported to provide a significant benefit pertaining to muscle growth and strength. For optimal muscular development, a holistic lifestyle approach should always be considered, inclusive of exercise, food, supplements, sleep, and optimization of hormonal levels.
Disclaimer: Individuals should consult with their healthcare provider prior to beginning any new nutrition, exercise, or dietary supplementation program—in particular those who have medical conditions or who use medication.
