by Chad Kerksick PhD April 27, 2012 4 min read
Resistance training is the best form of exercise to build strength and muscle mass. Many variables are key factors to consider as you build and follow a resistance training program. A number of theories exist as to why and how our bodies build stronger muscles. The answer to the “why?” question is more straight-forward as it most simply is because your body is responding to the new and foreign level of overload you place against the muscles and bone when you perform heavy resistance training. The “how?” question is much more debated and complicated. It is currently accepted that muscle growth occurs primarily through a coordinated increase in muscle protein synthesis and a number of anabolic or body building hormones. While some scientists have recently debated against the impact of hormones and their role in muscle growth, additional research needs to be completed to fully determine the role in which they play. A number of hormones are closely linked to muscle growth and they are testosterone, cortisol, leutinizing hormone, and follicle-stimulating hormone. Before this conversation continues too far, a hormone is basically a substance that your body produces and releases into the blood where it then travels somewhere else inside the body and cause some type of change. The signal for this process oftentimes starts in the brain and progresses to other body parts where the hormone is actually produced.
Testosterone is one of the most important hormones regarding growth of cells like muscle cells. Resistance training is widely known to increase the production of testosterone. With more testosterone circulating throughout the body, the greater chance it will bind to important cells and stimulate any number of positive changes. Key variables must be utilized in your favor to maximize the hormonal change which occurs after resistance training. As mentioned before, resistance training is responsible for much greater changes in testosterone as opposed to endurance exercise. In fact, endurance exercise has been shown to result in the suppression or decreases in testosterone. When deciding to do resistance training to stimulate large changes in testosterone, the complexity of the exercise must be considered. The easiest way to determine if an exercise is simple or complex is to count the number of joints in which movement has to occur when the exercise is performed with perfect technique. For example, performing leg extensions involves primarily one joint in the body, the knee. On the other hand, when performing squats or leg press, the body has to move the ankles, knees and hips to perform these exercises correctly. Same goes when comparing the chest fly to the bench press or a dumbbell curl to a pulldown. When more joints are involved, more muscle is involved. When more muscle is involved, greater changes in testosterone will likely occur. Rule #1 is thus to have at least one exercise for each body part you intend to train that involves multiple joints in the body. A 2nd reason exists why this rule works. When more weight is lifted, more muscle is recruited. If more muscle is recruited, more testosterone is likely produced. The more joints you use, oftentimes the more weight you can use which means more muscle is recruited which means more testosterone will be produced.
Other variables can also be considered and manipulated in your favor. For example, changing the amount of rest you take between sets of each exercise can greatly impact hormonal changes. Less rest results in more fatigue which can stimulate certain hormones to be released. This is a catch-22, however, because if you rest more completely your muscles will be more recovered and thus more likely to be able to lift more weight. Remember rule #1 more weight = more muscle recruited. All in all rule #2 says to grow bigger, lower rest is needed. Rule #3 relates to intensity; the single most important variable to consider. The bottom line is if you don’t train with enough intensity, the amount of rest or number of joints being used won’t matter nearly as much. To best stimulate changes in hormones, you need to commit yourself to train with intensities that will result in muscular failure between eight and twelve repetitions. When the word “fail” is used, it is meant literally. You physically cannot lift the weight anymore; that is true muscular failure. Not, “I’m tired, my muscles are getting uncomfortable and I am going to stop”. Big difference!
In response to a heavy bout of resistance exercise, testosterone will rapidly increase during the workout and reach peak levels within several minutes after you complete the exercise bout. These values will then slowly decline back to normal levels. However, people who regularly resistance train will maintain higher levels of testosterone overall and this can go on to positively impact many other things besides just your strength. In summary, testosterone is a key hormone that needs to be maximized through heavy resistance training. For years, studies have shown an association between increases in testosterone and positive improvements in strength and muscle mass, but it is also related to general positive feelings of mood and self-esteem. Certainly, the saying, “Go Heavy or Go Home!” has some application, particularly for those people serious about their training and gaining muscle mass.