Your body generates a variety of hormonal responses to exercise, depending on both the volume and intensity of your training. Both cardiovascular exercise and resistance training have a profound effect on your metabolism, your endocrine system and even your pituitary gland. Getting the most out of exercise involves knowing how to get the most out of your body. Consult your physician before beginning any diet or exercise program.
Both men and women produce testosterone, but men produce far more. Testosterone is the most anabolic hormone and contributes to muscle growth. If your goal does not involve getting bigger and stronger, this hormone is still critically important. Testosterone contributes to the rebuilding and repair of your muscles following training. If you are not training hard enough for this to be a factor, you must train harder. Testosterone is stimulated through intense exercise, most notably by training with 75 percent or more of your maximum lifts in the gym.
Growth hormone is a polypeptide hormone, or a hormone comprised of a complex chain of amino acids. It is secreted by your anterior pituitary gland. This hormone is responsible for many things including muscle growth. Growth hormone also contributes to collagen turnover, and higher levels of growth hormone to joint health, immune system function and the health of your skin. Growth hormone is stimulated during exercise by intense training and short rest intervals. This would include heavy training in the gym with limited time in-between sets. When performing cardiovascular exercise, interval training with sprint-level intensity followed by short recovery periods fulfills the same function.
Your thyroid hormones are responsible for your metabolism and are produced by your thyroid gland. Thyroxine, or T4, increases the calories you burn while exercising by increasing the metabolic rate of many of your cells. While this is useful for disposing of excess sugar and burning fat, T4 does not discriminate and will assist in the conversion of amino acids for energy. The conversion of amino acids means in extended cardiovascular training sessions, if you lack sufficient sugar to burn, you may lose muscle. A solid nutrition program will help you avoid this. A decrease in lean muscle tissue does not just make you weaker, it lowers your metabolism.
The hormone primarily generated by your "fight-or-flight" response is adrenaline, or epinephrine. Epinephrine increases your metabolism quickly to allow for sudden increases in activity levels. This hormone scavenges fat and sugar for energy, but will also cause you to burn muscle in the absence of sufficient sugar and fat stores. Your production of this hormone is directly proportional to both your exercise intensity and duration. The longer you can maintain intense training, the greater the metabolic boost you will get from epinephrine. Epinephrine is a contributing factor in raising your metabolic rate secondary to heavy resistance training.
Insulin is a hormone secreted by your pancreas. This hormone regulates your blood sugar levels. High levels of insulin can cause a sudden decrease in your blood sugar as it works to metabolize available sugar. This is not always a bad thing, as high levels of insulin can also help shuttle sugar into your muscles following a workout. After an intense training session, your blood sugar is low and your insulin levels are high. You can take advantage of high insulin levels by quickly consuming a shake composed of simple sugars and simple proteins, such as dextrose and whey.
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- "European Journal of Endocrinology"; Free Leptin Index and Thyroid Function in Male Highly Trained Athletes; G. Perseghin, et al., December 2009
- "Obesity Research"; Effects of a Longitudinal Training Program on Responses to Exercise in Overweight Men; F. Crampes, et al., Februrary 2003
- "The Journals of Gerontology"; A Single Bout of Concentric Resistance Exercise Increases Basal Metabolic Rate 48 Hours After Exercise in Healthy 59–77-Year-Old Men; David L. Williamson, et al.; May 1997
- "Canadian Journal of Applied Physiology"; Gaining Weight: the Scientific Basis of Increasing Skeletal Muscle Mass; M. E. Houston; Aug. 1999