There is a great hormonal response to exercise. Hormones are substances secreted from a tissue that cause a biological response on itself or other cells. Hormones play a huge role in human functioning and play crucial roles in regulating growth, development, and reproduction. Hormones also increase the human body’s ability to withstand psychological and physical stress. The major function of hormones is to alter the time it takes for specific reactions of certain target cells to take place.
There are three categories of hormones. They are amine hormones, peptide hormones, and steroid hormones.
Amine hormones stem from amino acids. Amine hormones are water soluble and are transferred via the blood plasma (Marks and Kravits, n.d). Since amine hormones are water soluble, they are easily removed from circulation and thus, have only a short time to perform their role. Peptide hormones are structured by peptide bonds between multiple amino acids. Peptide hormones, like amine hormones, are water soluble and are transferred via the blood plasma. They are also easily removed from circulation and must perform their function quickly. Amine and peptide hormones are able to perform their purpose on objective cells by binding to the membrane’s specific receptors of the target tissue. After the initial hormone binding, a molecule called a “second messenger” is produced causing a cellular response. Steroid hormones, on the other hand, are not water-soluble and must bind to plasma proteins in order to be transported to their target tissue. The protein binding ability of steroid hormones causes a delay in the amount of time it takes for them to trigger a biological response (Marks and Kravits, n.d). Steroid hormones, unlike amine and peptide hormones, do not bind to the target tissue’s membrane. They instead pass through the membrane and connect to specific steroid receptors in the cell where they travel to the nucleus to allow for protein synthesis (Marks and Kravits, n.d).
The Hormonal Response to Heavy Exercise
A study on the hormonal responses to heavy resistance exercise on consecutive days with or without nutritional supplementation showed that a carbohydrate-protein supplement produces a positive effect on the metabolic and hormonal responses to consecutive days of lifting weights (Kraemer et al., 1998). During the study, 9 experienced weight trainers performed three days of consecutive weight training. They were split up into two groups. One group consumed a carbohydrate-protein beverage while the other group consumed a placebo. These drinks were consumed during recovery from the weight training sessions as well as two hours prior to their workout. The carbohydrate-protein drink resulted in a hormonal environment that could increase glycogen and protein synthesis more effectively than the placebo group (Kraemer et al., 1998).
The main hormones secreted during exercise are growth hormone, testosterone, insulin-like growth factors, cortisol, aceytlcholamines, and insulin. Growth hormone is a peptide hormone that stimulates growth, cell reproduction, and regeneration. Growth hormone plays a role in increasing calcium maintenance, increasing muscle mass, promoting lipolysis, stimulating the immune system, and increasing protein synthesis. Resting concentrations of growth hormones are higher in women than in men. Resistance exercise has been shown to elevate growth hormone concentrations in both men and women similarly 30 minutes after exercise. Factors that affect the growth hormone response are exercise selection, amount of muscle mass recruited, muscle actions used, intensity and volume of the workout, rest intervals between sets, and the total amount of sets completed. In a study on whether a single set of low intensity resistance exercise immediately following high intensity resistance exercise stimulates growth hormone secretion in men, the results showed that a high intensity, low volume training protocol resulted in the least amount of growth hormone (Takamatsu, Soto, and Goto, 2003). Growth hormone levels were increased, however, when an additional set of high repetitions at 50% of one-rep max was added to the end of the strength protocol. This study suggests that a strength workout may be maximized by adding a high volume set at the end of the workout (Takamatsu, Soto, and Goto, 2003). For the greatest growth hormone response from a strength training workout, high reps with low rest intervals should be used. The resting levels of growth hormone, however, do not seem to be affected by resistance training. Nutrition also seems to play a role on growth hormone levels as meals high in carbohydrates that increase blood glucose generally tend to decrease growth hormone levels (Volek, 2004).
Testosterone is a steroid hormone that is part of the androgen group and is secreted by the female ovaries, male testes, and adrenal glands. It is the main sex hormone of males and helps develop male reproductive tissues as well as increased muscle mass, bone mass, and body hair. Although both males and females produce testosterone, males produce substantially more of this hormone than women do. In response to resistance training, it has been shown that men have increased testosterone concentrations while women do not, which may explain the different responses that men and women have in response to resistance training.
Consistent resistance training has a higher effect on testosterone and in a study published in the Journal of Applied Physiology, higher concentrations of testosterone were reported in subjects who were previously resistance-trained versus subjects who were endurance trained following resistance exercise (Tremblay, 2003).
The testosterone response to exercise is dependent on many factors including the amount of muscle mass involved, intensity level of exercise, volume, nutrition intake, and training experience. One study showed that performing leg exercises before arm curls may have many advantages (Hansen et al., 2001). In the study, one group performed only arm curls for nine weeks consecutively, while the other group performed arm curls after lower body exercises. Testosterone was shown to be elevated when lower body exercises were performed first compared to only doing arm curls (Hansen et al., 2001).
Insulin-like growth factors are proteins that have a high similarity to insulin. Insulin-like growth factors are used by cells to communicate with their environment. They facilitate many of the growth hormones’ actions and they increase the synthesis of protein as well as boost muscle hypertrophy. In the Journal of Strength and Conditioning Research, the serum growth hormone response of 6 non-weight-trained and 6 weight-trained women was examined. Growth hormone increases protein synthesis and is responsible for stimulating insulin-like growth factor-1. The study predicted that women who weight train regularly would have a higher growth hormone response than women who do not weight train. All twelve subjects were healthy, normally menstruating, ovulatory women. The weight trained group consisted of women that had been regularly weight training for at least a year while the non-weight-trained women consisted of women who had not lifted weights at all for the 6 months prior to the study. The result of the study showed that both the weight trained and non-weight trained women had an acute rise in growth hormone levels following resistance training (Jane et al., 2000). However, the weight-trained women were able to sustain the elevated growth hormone levels for a longer amount of time (Jane et al., 2000). Since the protocol for both groups were the same, a possible explanation for the longer elevated growth hormone levels are that the weight-trained women had greater amounts of lean muscle mass and therefore, training allowed for greater recruitment of their motor unit. This caused more stress to be put on the sarcolemma of the muscle, resulting in increases in anabolic hormone levels.
Nutrition also has a profound impact on hormonal responses. Carbohydrate ingestion results in elevated insulin levels. Certain amino acids increase insulin secretion which is why carbohydrates and protein are often taken together. This allows for maximum insulin secretion with the hope of improving post-exercise glycogen re-synthesis and protein anabolism (Volek, 2004). According to a study regarding post-exercise muscle glycogen synthesis, there appears to be a benefit of consuming proteins and carbohydrates after intense exercise instead of just carbohydrates only (Loon et al., 2000). This may be due to greater insulin secretion after combined protein and carbohydrate intake. However, when carbohydrate intake is very high, increased protein intake dues not further improve the rate of glycogen re-synthesis (Loon et al., 2000). Increased levels of insulin from carbohydrate and protein intake could help protein ingestion because insulin is a stimulator of protein synthesis when sufficient amino acids are present (Volek, 2004).
Resistance training has been shown to stimulate an acute hormone response 15-30 minutes after exercise (Kraemer and Ratamess, 2005). This response, however, has not been shown to have much of an effect on resting hormonal concentrations in the body as it seems to be more for tissue growth and remodeling. The hormones shown to be elevated after resistance training are testosterone and growth hormones. The type of resistance training shown to have the greatest effect on hormonal levels increasing are workouts high in volume and moderate to high in intensity combined with short rest intervals compared against workouts using low volume, high intensity exercises with long rest intervals (Kraemer and Ratamess, 2005). Insulin-like growth factor-1 has also been shown to be elevated following resistance training. It is thought that the reason for the increase in insulin-like growth factor-1 is its response to the stimulated growth hormone (Kraemer and Ratamess, 2005).
Cortisol is a steroid hormone, also known as a glucocorticoid, which is produced by the adrenal glands. In response to stress and a low level of blood glucocorticoids, cortisol is released. Cortisol’s sole purposes are to increase blood sugar, suppress the immune system and aid in fat, protein, and carbohydrate metabolism. During exercise, glucocorticoids are released from the adrenal cortex.
Cortisol has been showed to be released in greater amounts in resistance programs that combine strength and endurance training. In a study on the effect of concurrent strength and endurance training on skeletal muscle properties and hormone concentrations in humans, a greater urinary cortisol was observed in women who were performing combined strength and endurance training than simply strength training alone (Bell et al., 2000).
In another study similar results were shown. The researchers of the study found that subjects whose workout consisted of a high volume, full body resistance training workout 4 days a week combined with 4 days a week of endurance training for 12 weeks showed an increase in exercise-induced cortisol concentrations (Kraemer et al., 1995). This was a result of combining resistance and endurance training.
Catecholamines include dopamine, epinephrine, and norepinephrine. They are derived from the amino acid tyrosine. Catecholamines are soluble in water and circulate in the blood stream. Factors that affect the catecholamine response include the force of the muscle contraction, amount of muscle stimulated, volume of resistance exercise, and rest intervals. Resistance training has been shown to increase the epinephrine, norepinephrine, and dopamine plasma concentrations. Many studies report a higher epinephrine response to exercise in endurance-trained subjects compared with untrained subjects after an intense exercise regimen equivalent to all out exercise (Zouhal et al., 2008).
Insulin plays a big role in regulating carbohydrate and fat metabolism in the body. Insulin triggers the liver, muscle, and fat tissue to intake glucose from the blood. The cells of the liver, muscle, and fat tissue store that glucose as glycogen in the liver and muscle. Insulin also directs amino acid uptake by the cells and has several anabolic effects in the body.
In conclusion, a workout high in volume and intensity with low rest intervals over a long period of time tend to have the most beneficial effects on hormones. Exercise’s effect on testosterone is mostly prevalent in men as it has little effect on women during exercise. According to research, testosterone is most beneficially affected during compound movements over isolation movements. Exercise has the greatest effect on growth hormone during workouts with at least one set of high reps. Workouts that that consist of all high rep exercises with low rest periods have the greatest effect on growth hormone. Cortisol’s response to exercise tends to be similar to growth hormone’s response, but it can be reduced with carbohydrate supplementation. Finally, insulin feeds the cells lots of nutrients and is most affected by carbohydrates so it would make sense to add carbohydrates to your protein after a workout. As shown, there is a great hormonal response to exercise and different types of exercise have different effects on the hormone response.
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