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Do Muscles Actually GROW???

If you've ever wondered, just HOW muscles grow, then read on!

Have you ever wondered, just how do muscles actually grow?? Okay, we know they get bigger when we work out….but are we actually growing new muscle? Or maybe you’ve just thought “Why is resistance training (lifting heavy things) at all important? How does it help my general fitness?”. Can’t I just do cardio?? And just what is it with all those weight lifters eating gummy bears or bagels after their workout sessions - how does THAT make any sense?

Well, if any of these questions have crossed your mind, and you’re even remotely like me (an information geek), then read on! You might pick up some tips, or at least some inspiration, that all that hard work you do at the gym IS actually doing something!

Okay, put your geek hat on now:

Muscle growth occurs whenever the rate of muscle protein synthesis is greater than the rate of muscle protein breakdown. Both, the synthesis and breakdown of proteins are controlled by complimentary cellular mechanisms.

When muscles undergo intense exercise, as from a resistance training bout, there is trauma to the muscle fibers that is referred to as muscle injury or damage in scientific investigations. This disruption to muscle cell organelles activates satellite cells, which are located on the outside of the muscle fibers between the basal lamina (basement membrane) and the plasma membrane (sarcolemma) of muscle fibers to proliferate to the injury site (Charge and Rudnicki 2004). In essence, a biological effort to repair or replace damaged muscle fibers begins with the satellite cells fusing together and to the muscles fibers, often leading to increases in muscle fiber cross-sectional area or hypertrophy.

Resistance exercise can profoundly stimulate muscle cell hypertrophy and the resultant gain in strength. However, the time course for this hypertrophy is relatively slow, generally taking several weeks or months to be apparent (Rasmussen and Phillips, 2003). Interestingly, a single bout of exercise stimulates protein synthesis within 2-4 hours after the workout (which is why we try to have a post-workout snack as close to the end of our workout as we can) which may remain elevated for up to 24 hours (Rasmussen and Phillips, 2003).

Growth factors are hormones or hormone-like compounds that stimulate satellite cells to produce the gains in the muscle fiber size. These growth factors have been shown to affect muscle growth by regulating satellite cell activity.

Insulin also stimulates muscle growth by enhancing protein synthesis and facilitating the entry of glucose into cells. The satellite cells use glucose as a fuel substrate, thus enabling their cell growth activities. And, glucose is also used for intramuscular energy needs.

This is why having some sugar after a weight training session is beneficial. The sugar spike causes an Insulin hormone release in the body and the insulin then shuttles the glucose (sugar) into your muscle cells for muscle rebuilding and growth. So, eating a serving of a sweet, sugary treat will actually assist muscle growth instead of feeding fat cells! Timing when we indulge in treats can have a big impact on our body physique changes and goals.

Growth hormone is also highly recognized for its role in muscle growth. Resistance exercise stimulates the release of growth hormone from the anterior pituitary gland, with released levels being very dependent on exercise intensity. Growth hormone helps to trigger fat metabolism for energy use in the muscle growth process. As well, growth hormone stimulates the uptake and incorporation of amino acids into protein in skeletal muscle.

Aging also mediates cellular changes in muscle decreasing the actual muscle mass. This loss of muscle mass is referred to as sarcopenia. Happily, the detrimental effects of aging on muscle have been shown to be restrained or even reversed with regular resistance exercise. Importantly, resistance exercise also improves the connective tissue harness surrounding muscle, thus being most beneficial for injury prevention and in physical rehabilitation therapy. Resistance exercise also builds up bone mass, acting as a preventative bone loss in later years.

Resistance training leads to trauma or injury of the cellular proteins in muscle. This prompts cell-signaling messages to activate satellite cells to begin a cascade of events leading to muscle repair and growth. Several growth factors are involved that regulate the mechanisms of change in protein number and size within the muscle. The adaptation of muscle to the overload stress of resistance exercise begins immediately after each exercise bout, but often takes weeks or months for it to physically manifest itself. The most adaptable tissue in the human body is skeletal muscle, and it is remarkably remodeled after continuous, and carefully designed, resistance exercise training programs.

So folks, get on your stylish gym gear, grab that designer water bottle, and lace up those trainers. Have fun getting stronger, knowing that you ARE actually accomplishing something and creating some amazing health benefits within your body at the same time.

Go get it!!

Excerpts taken directly from the article: How do muscles grow?

Authors: Young sub Kwon, M.S. and Len Kravitz, Ph.D.

Article Reviewed: Charge, S. B. P., and Rudnicki, M.A. (2004). Cellular and molecular regulation of muscle regeneration. Physiological Reviews, Volume 84, 209-238.

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