The topic we chose to investigate for this particular assignment was Growth Hormone responses to resistance training. It is believed that resistance training can result in an increased response of Growth hormone concentrations but it is unknown to what extent it does so and what specific factors could potentially effect this increase. Many studies associated with the effects of resistance training have been investigated over the years. This research has evolved over time to show us the effect of resistance training on hormonal responses. For the purpose of the topic of this assignment, we specifically chose to focus on the response of GH (Growth Hormone) concentrations to resistance training. The main purpose of this assignment was to carry out an in depth investigation into the earliest, more recent, and most recent research related to Growth hormone responses to resistance training in order to get a clear understanding of how this research topic began, developed over the years and in which direction this research is heading today. As this research topic develops over time, we can expect to see changes in the technology, equipment and methods used which will ultimately result in a change of our conclusions. Our main source of information was peer- reviewed journal articles that we found on the UP (University of Pretoria) online library. After reading the earliest, more recent and the latest articles, an integration of all the information was made which we drew our own conclusions from.
The earliest article that we could find based on the topic of Growth Hormone response to resistance training was published in 1989- Endogenous Hormonal and Growth Factor Responses to heavy resistance Exercise protocols. This article marked the beginning of all research based on the responses of the human Growth Hormone to resistance training. The Authors of this study were: W.J.Kraemer, L.Marchitelli, D.McCurry, R.Mello, J.E, Dziados, E. Harman Peter Frykman, A.Damokosh, C.Cruthids, S.Gordon, and S.J Fleck. All these authors form part of the USA Army Research Institute of Physiology Division (W.J.Kraemer, 1989). The main purpose of this study was to investigate the endogenous anabolic hormone and growth factor responses to a variety of different types of heavy resistance exercise protocols (HREPs). (W.J.Kraemer, 1989)
The population group used consisted of 9 male participants. It was ensured that all participants had recreational experience and that none of them were competitive lifters. A series of set methods were used in this study in order to obtain results. Written consent was obtained from all the individuals participating and it was ensured that none of the participants had a medical record of an endocrine disorder or on any medications or chemical therapy (this included the use of steroids). Strenuous exercise wasn’t allowed to be performed 48 hours prior to the experiment and no alcohol or caffeine could be consumed 24 hours prior to experiment. Two weeks of familiarization, descriptive testing and load verification for each experimental exercise protocol were carried out (W.J.Kraemer, 1989).
Blood samples were obtained 10 minutes before to the proceeding of exercise protocol – pre-exercise, mid-exercise (after 4 exercises) and at 0 (immediate-post), 5, 15, 30, 60, 90 and 120 minutes after each exercise protocol in seated position. The time of testing that were conducted was always consistent of every day (W.J.Kraemer, 1989). Exact Growth hormone concentrations were determined using radioimmunoassay procedures. Six different HREPs were performed in random order, with one being performed each week. The six different HREPs were namely Bench Press, Double Leg Extensions, Military Press, Bent Leg Inclined Sit-ups, Seated Rows, Lat Pull Down, Arm Curls, Leg Press (W.J.Kraemer, 1989). * There were two primary workouts out of the six different protocols, weight training protocol-1 (WTP-1) and weight training protocol-2 (WTP-2). WTP-1 consisted of a five-repetition maximum (5RM) workout with resting period of three minutes and a heavier weight (5RM). WTP-1 protocol is typically used for strength training. WTP-2 was based on 10RM with only one-minute rest intervals. WTP-2 protocol is typically used in bodybuilding in order to increase muscular hypertrophy. There were two exercise series which had the two primary workouts (WTP-1 or WTP-2), and a load control and resting control that were changed to match the total work being conducted (W.J.Kraemer, 1989).
Results of this experiment of (W.J.Kraemer, 1989) regarding growth hormone was as follows: (Figure 2) shows responses of human growth hormone (hGH). In series 1, WTP-1 resulted in an increase of serum hGH concentrations above rest at mid-exercise and at 0 post-exercise. When the load was altered to 10RM, but the total work and rest were kept constant, there were no significant increases in serum hGH. When the resting interval was reduced to one minute, there was a remarkable increase in serum hGH above the resting values measured at 0 and 5 minutes after exercise. (W.J.Kraemer, 1989) In series 2, the serum hGH concentrations showed a significant increase at mid-exercise and at 0,5,15 and 30 minutes following exercise. When the load (5RM) or the resting intervals were increased (3 minutes), the result showed that there were no significant increases above resting concentrations. The greatest (highest) increase in hGH concentration in this study was in response to Series 2, WTP-2 protocol (high work, 10RM, 1min rest). l. (W.J.Kraemer, 1989)
If we look at the total data collected throughout this investigation, it is clear that heavy resistance protocols result in increases in peripheral concentrations of anabolic hormones and growth factor and that various resistance exercise protocols produced different response outcomes. There may be a relationship or connection between certain hormonal responses and the characteristics of specific exercise protocols. Exercise variables of resistance training may play a major part in determining the type of responses in hGH (concentration). It has been proven (with substantial evidence) that hyperventilation and hypoxia stimulate significant increases in hGH during heavy resistance exercise, therefore hypoxia and other factors related to anaerobic HREP stimulate hGH responses. (W.J.Kraemer, 1989)
The final conclusion drawn from this study’s research findings is that growth factors such as growth hormones are responsive to resistance exercise, particularly when specific variables of resistance exercises such as resting periods and intensity are manipulated or altered. This manipulation within the protocols (such as decreasing the resting periods and increasing the RM or weight) can cause significant increases in hGH concentrations. (W.J.Kraemer, 1989)
One of the more recent studies we found was published in 1999 – Acute and chronic hormonal responses to Resistance Training designed to promote muscle hypertrophy by Gary E. McCall, William C. Byrnes, Steven J. Fleck, Arthur Dickson, and William J. Kraemer (Gary E. McCall, 1999). All of these authors form part of Department of Physiology in Los Angeles). The aim of this study was to determine the role of anabolic hormones in muscular hypertrophy associated with resistance training. The study investigates the effects of resistance training on resting hormone and acute exercise induced hormonal response concentrations (Gary E. McCall, 1999). For this assignment we chose to focus on the response of specifically the hGH (human Growth Hormone) to resistance training.
The main subgroup tested were resistance trainers (specifically males). Eleven college men (between 18-25 years old) with experience of recreational resistance training completed 12 weeks of training at a frequency of 3 sessions a week. All exercises were performed using free weights or weight machines (Gary E. McCall, 1999). Training sessions were held on a Monday, Wednesday, and Friday morning. Each session consisted of three 10 repetition maximum (10RM) sets for 8 exercises, with a 1-min rest between sets and exercises. Four of the exercises focused on the biceps brachii muscle while the rest of the exercises incorporated all major muscle groups of the upper and lower body. (Gary E. McCall, 1999)
Before and after their training session, the participants completed, strength, total muscle cross-sectional area and muscle fibre testing to evaluate muscular hypertrophy of the biceps brachii. Blood samples were also collected before and after the 12 week training period to determine and compare Growth hormone levels as well as the level of other hormones. Subjects remained in supine position during blood collection. At the 4th and 8th week of training multiple other blood samples were also obtained from the participants in order to regulate hormone responses throughout the training sessions, prior to the training session, mid training session (4 exercises completed) and post exercise. (Gary E. McCall, 1999)
The results of this study found that the difference in the magnitude of the acute exercise-induced responses of growth hormone (GH) were in fact dependent on the structure of the resistance training exercises. This investigation also found that the concentration of Growth Hormone increases at mid and post exercise and Cortisol remained elevated post as compared to mid training session (however our focus is specifically on the response of Growth Hormone).Due to the fact that there were no significant differences in Growth Hormone concentration found between the 10th and 20th sessions of resistance training, but there were significant increases of GH at mid (r = 0.81) and post (r = 0.86) exercise, the mean of both sessions was used as the measure of GH response. Results also showed that an increase in the concentration of GH resulted in an increase of muscle fibre (type) I and II also. (Gary E. McCall, 1999)
These relationships could be indicative of a role for repeated acute exercise-induced GH elevations on cellular adaptations in the trained muscle (Gary E. McCall, 1999)
Another study in Acute and Chronic hormonal responses to resistance exercises stated that anabolism in skeletal muscle are promoted and interactive when circulating GH and mechanical loading are combined. These studies have shown that acute GH administration increases net skeletal muscle protein anabolism by increasing protein synthesis rates (Fryburg.D.A, 1993). In agreement to the current study, other resistance training studies also found no changes in resting GH concentrations (Gary E. McCall, 1999). For example, (Kraemer, 1990) in (Gary E. McCall, 1999) found that a high volume training used by bodybuilding to enhance maximal muscle hypertrophy, resulted in a greater GH response compared to a high intensity training regimen typical of that used by competitive weightlifters to promote maximal muscle strength and/or power.
We immediately noticed that the more recent study by Gary E. McCall (1999) differed from the first (earliest) study we analysed in a number of ways. In the first study (1989) exercises were only performed once a week lasting for 4 weeks to complete the different protocols for one individual, whereas with the second study (more recent articles), exercises were performed 3 times a week for 12 weeks. The specific ages of the study groups (sub groups) utilized in each study also differed. The first study (W.J.Kraemer, 1989) only consisted of 9 older participants (fully developed), whereas the second study (Gary E. McCall, 1999) utilized 11 college men (still in developmental stages). The main focus of the study performed in 1989 was the effect of anabolic hormones on resistance training, whereas the second study (1999 etc.) focused on the effect of anabolic hormones as well as the effect of muscle hypertrophy with resistance training. The more recent article (Gary E. McCall, 1999) ultimately tried to observe the correlation between anabolic hormones and muscle bulking with the resistance exercise as one.
The specific exercises performed in the first (earliest) article/study focused more on exercises that incorporated muscles of the entire body, whereas the more recent studies placed more emphasis on specific parts (muscles) of the body (mainly the biceps branchii). The method in which blood was collected also differed between the earliest and more recent studies. In the earliest study blood was collected with the participants in a seated position, where as in the more recent studies blood was collected in supine position. This supine position ensures the safety of the participant and prevents them from fainting. It also ensures that the participant recovers faster after the blood test. There was definite correspondence between the results of the earliest and more recent studies. Both the early and more recent studies implied that GH levels stay constant at the beginning of the exercise but shows significant increases at mid and post- exercise. It was shown that high volume (resistance exercises) had a greater impact on GH than load variations. Resting periods also have a significant effect on the levels of GH. The shorter the resting period, the higher elevation there is of GH. The type of exercises conducted are also related to GH levels.
The most recent article we could find based on this topic was published in 2018 – The effect of changes is concentric-eccentric contraction time ration hormonal response to resistance exercise in trained men by (D. Sheikholeslami-Vatani, 2018). The main purpose of this study was to investigate the response of hormones (specifically Growth Hormone) in trained men when concentric and eccentric contraction time ratios were manipulated in a single session of resistance exercise when workload and volume level were kept the same (Sheikholeslami-Vatani D, 2018).
The subjects involved in this study included ten young males who volunteered (mean age 26.3 ± 1.2 years, mean weight 81.2 ± 4.25 kg, and mean height 178 ± 6 cm) (Sheikholeslami-Vatani D, 2018).Each subject had to have a history of at least one year of regular RE (Resistance Exercise) training in order to participate in this study (Sheikholeslami-Vatani D, 2018). When we compared the latest study to the earliest and more recent study, we realised that the population group that was used in the latest study also utilized individuals of the same age (approximately 6 years apart). We also noticed that this study (the most recent study) required the participants to have at least one year of RE training to participate whereas earlier studies just required that the participants have “experience” in RE training without any specific amount of experience required. Therefore, the more recent study is more controlled to ensure that the investigation is in fact valid and reliable. (Sheikholeslami-Vatani D, 2018)To, once again, ensure that the study remained reliable and valid, all subjects were asked to refrain from participating in any external (out of protocol) exercise programs. (Sheikholeslami-Vatani D, 2018)
———The article by (D. Sheikholeslami-Vatani, 2018) did followed the following systematic process: Subjects were clearly informed of the study’s objectives and all the potential risks that may be involved. A signed consent form and medical questionnaire with medical-sport records had to be completed by each subject. Exactly ten days prior to the first session of the investigation, a trial (trial-run) was done on a test group of 6 subjects that shared similar conditions to the individuals of the actual test group in order to determine the maximum applicable workload. The session resulted in 65% one Repetition maximum (1RM) applicable workloads for four different contraction TRs (time ratios) were determined. More workload in 1CON:1ECC protocol was not applicable (Sheikholeslami-Vatani D, 2018).
The individual 1RM’s in all the exercises were determined for all participants one week before commencing the program. This indicates a more controlled research study as opposed to the earlier studies where by the participants were all just given a set (constant) weight without taking any other personal factors of the individuals such as their conditions or characteristics into account. The participants were asked not to take any dietary supplements throughout the research process. The research process was conducted in four different sessions, separated by three days, making a total of ten days. Throughout the training sessions, participants learned how to perform exercises with different time ratios. The individuals had to start with a warm-up for ten minutes that included stretching and performing two sets of the first move being done with a 40%-50% 1RM, only after that they could continue with the main RE protocol. RE consisted of leg extension, bench press, hamstring curls and lat pull-down. Subjects had to perform three sets of eight repetitions at 65% of 1RM. Rest periods that occurred between sets and exercises were about 1 and 2 minutes long. The resting period between sets and exercises were one and two minutes, leading up to a total of 40 minutes for each session when all exercises were carried out at full range of motion (ROM). The sessions were conducted at 8am – 10am in the morning. We realized that the most recent study also controlled the specific time in which the sessions were carried out as opposed to earlier studies that did not really control this. (Sheikholeslami-Vatani D, 2018)
The focus of exercise was on the lower limb, this stands as a contrast to the 2de study that was conducted that had exercise mainly focusing on upper limb such as biceps brachii. The location, time of test and room temperature were controlled and kept constant. Blood examples were collected before (pre) and after exercises (post). Blood were collected in a seated position 1min after exercise and 15min before exercise. (Sheikholeslami-Vatani D, 2018)
Results showed that testosterone and GH showed a significant increase in Growth hormone that correspond with results from the first and second study that was conducted. It was proven that greater anabolic response would be achieved by slower contraction protocols (higher load), proving that load influences hormone levels. The types of contractions, intensity, duration and order influences the GH response to RE.** Matsuse et al. ** in (D. Sheikholeslami-Vatani, 2018, p. 3) reported that “combining a voluntary concentric muscle contraction and an electrically stimulated eccentric muscle contraction increased GH and lactate more than typical weight training”. **Simao, et al. 12** in (D. Sheikholeslami-Vatani, 2018, p. 3)reported that the sequence they use to exercise the larger muscle groups before the smaller muscle groups in an upper-body resistance-exercise session, ensures a greater GH production response. Serum concentrations of GH had a significantly increase after all the exercises in this study. Levels of GH is also in connection with the size of muscle group being used. The larger the muscle group, the higher the levels of GH. The duration of muscular contraction did not affect results. Concentric muscle actions had a greater GH response than eccentric muscle actions at absolute load. (Sheikholeslami-Vatani D, 2018).
Research studies on this particular topic of Growth Hormone responses to resistance training have developed to such a large degree in terms of the technology utilized ( for example we can now use electric stimulation to contract muscles and to obtain research data more accurately), the methods of testing which have become far more controlled and reliable etc.. This research topic has evolved from the earlier day’s where by scientists were merely trying to investigate whether resistance exercise even had an effect on GH concentrations. Today scientists are choosing to look even deeper and deeper into the specific factors of resistance exercise that causes responses in GH levels such as load, intensity resting, resting period, the type and amount of muscle fibres/muscle groups being used during exercise etc. This research is going to grow from here on. Results will increase in validity (more than ever before), methods of testing will become even more advanced with new technology and research being introduced every day and we will soon discover the precise mechanisms of resistance training and its influence of GH concentrations and use this better understanding of the relationship between the two to our advantage. We could manipulate more specific variables of resistance exercise in order to achieve a desired result.