Bodybuilders and other athletes speak of growth hormone with hushed reverence. Many think that GH is what’s primarily responsible for the massive physiques that dominate professional bodybuilding today and that seem to dwarf those of a generation ago.
While it’s true that GH is one of three primary anabolic hormones in the body (the others being testosterone and insulin), it’s also true that GH is shrouded by myth. Take the notion that using a pharmaceutical form of GH enables you to eat as many as 10,000 calories a day yet lose appreciable levels of bodyfat simultaneously. Another idea is that GH promotes hyperplasia, or a splitting of muscle fibers into new fibers—a property that other anaboliic hormones don’t have.
The reality about GH is not quite so dramatic. The only drug-tested Mr. Olympia occurred in Chicago back in 1990. Several of the competitors told me, off the record, that they planned to circumvent that year’s drug prohibition by using large amounts of GH. Then, as now, there was no official test to show that an athlete was injecting GH. The competitors figured that GH provided little or no actual anabolic or muscle-building effects by itself but did pack a punch when used with anabolic steroids. When the steroids were eliminated a few weeks before the contest, GH froze the muscle size produced by the earlier drug cycles and kept delivering fat-loss benefits.
That makes a lot of sense because GH is a survival hormone. Among its many functions is that it preserves lean mass, mainly muscle, by promoting the use of bodyfat as fuel. GH also comes into play as a counter-regulatory hormone to insulin. When insulin lowers blood glucose, GH and other hormones prevent the levels from dropping too low. The antagonist effect of GH against insulin is so potent that many researchers believe that large doses of it promote insulin insensitivity, thus increasing the chance for diabetes. More recent studies, however, show that normal levels of GH, such as that induced by exercise, help prevent both metabolic syndrome and diabetes by cutting visceral, or deep-lying, abdominal fat.
The anabolic reputation of GH has also fostered a large response from the food supplement industry. Most GH supplements on the market are based on various combinations of amino acids. Whether aminos actually promote a GH response depends on how and when they’re used. Intravenous administration of the amino acid arginine in 30-gram doses promotes significant GH release unless you’re deficient in the hormone or have defective hormone release mechanisms.
When it’s taken orally, however, the scenario changes. Arginine goes to the liver, where it encounters the enzyme arginase, which degrades it. You could get around the formidable enzymatic barrier by increasing the oral dose, but then you’d probably have to deal with nausea. Besides, when you take arginine prior to weight training, it has the paradoxical effect of blunting GH release.
Several studies have shown that a drug form of GH combined with exercise offers no advantages over exercise alone. On the other hand, the GH release produced by exercise does offer several significant effects for bodybuilding purposes. An increase in GH, coupled with the rise in other anabolic hormones, improves muscle protein synthesis. That translates into increased muscle size and strength. The actual anabolic effector is insulinlike growth factor 1, which is produced in the liver under the stimulation of GH release.
The IGF-1 produced in the liver is used throughout the body. IGF-1 is also produced locally in trained muscle, often as a result of damage from intense exercise. That IGF-1 is used for muscle repair and promotes the activity of muscle stem cells, or satellite cells. Locally produced IGF-1 is further spliced into two variants in muscle, with one being the mechano growth factor, or MGF, probably the most anabolic substance of all because it directly controls the activity of muscle satellite cells. MGF is so potent that it can resuscitate dying satellite cells in older animals and people.
If providing GH alone doesn’t do much for muscle growth, and considering that IGF-1 and MGF are the primary anabolic growth factors in muscle, why be concerned about promoting GH release through exercise?
One reason is the size-and-strength synergy of GH, testosterone and insulin. Each hormone appears to potentiate the anabolic effects of the others. They’re synergistic in another sense too. A high level of GH offsets the possible side effects of other anabolic hormones. For example, by itself insulin is the greatest promoter of increased bodyfat synthesis. It also lowers blood glucose, leading to a loss of training energy and increased fatigue. GH and, to a lesser extent, testosterone counteract insulin’s bad side.
Of the three major anabolic hormones, GH provides the most potent fat mobilization, especially for people on low-carbohydrate diets who exercise. GH is secreted most substantially when blood glucose and fat levels are lower and amino levels are higher—conditions typical of people on low-carb diets.
One reason it’s so hard for people who have a lot of bodyfat to lose weight is that they usually have higher resting insulin levels. That opposes GH release. When they begin to exercise, their normal GH release response is also blunted, making fat loss an arduous process. The good news is research showing that losing bodyfat through regular diet and exercise normalizes the GH response to exercise.
Another reason you want to promote a GH response during exercise is that GH is uniquely useful for preserving and repairing connective tissue, such as ligaments and tendons. Anyone who’s lifted for any length of time knows well the training setbacks caused by connective-tissue injuries. Connective tissue, unlike muscle, has a poor blood supply, so healing injuries can take weeks or even months. GH strengthens and repairs connective tissue, accelerates its healing and prevents the damage from occurring in the first place.
That helps explain why so many world-class athletes use GH, even if they aren’t interested in building massive muscles. GH helps them recuperate from intense training and protects connective tissue from injury.
GH’s role in protecting connective tissue also applies to people as they age. Most forms of joint pain involve connective tissue and often appear when GH levels drop with aging. Paradoxically, injecting large doses of GH causes joint pain in many people through an overgrowth of tissue.
One interesting aspect of exercise and GH is that normally when large amounts of GH enter the blood, the brain’s feedback system blunts release of the hormone that releases GH. Yet with continued exercise, the body overcomes the feedback.
As to what precisely sets off GH release during exercise, scientists still aren’t sure. There are, however, several candidates.One theory is that exercise-induced muscle tension provides a neural effect, leading to a GH release. Another popular hypothesis is that nitric oxide stimulates GH release during exercise. Studies show that NO does potently promote GH release, but they involved isolated cells, and whether the effect occurs in a living human body is still speculative.The most popular explanation is that the hydrogen ions, or acid produced in muscle, relay a chemical message to the brain that results in a heightened GH response. When subjects take antacids, such as sodium bicarbonate, during exercise, the GH release is blunted.
That raises the question of whether using supplements that reduce muscle acidity, such as beta-alanine, would reduce GH release. The answer is no; supplements work in the muscle, and the acid feedback mechanism that stimulates GH release occurs in the blood.Thus, ingesting sodium bicarbonate, or baking soda, which has an alkalizing effect on blood acidity, would likely blunt GH release if ingested prior to physical activity.
So what type of exercise promotes the greatest GH release? The short answer is the kind that’s brief, hard and intense. Lifting weights would get more results than most aerobic workouts. To get a GH response from aerobics requires passing what exercise scientists refer to as the lactate threshold—when lactic acid appears in the muscle. That event signals a change from aerobic to anaerobic exercise metabolism. While doing high-intensity aerobics, such as interval training, promotes higher GH release, it also lowers the fat oxidation that occurs during lower-intensity aerobics. Interestingly, doing high-intensity aerobics increases resting pulse amplitude of GH release, meaning that you burn more fat at rest. That may help explain why interval training leads to greater fat loss than conventional steady-state aerobics.
Early studies suggested that you can achieve the greatest GH response from exercise that you do several times a day. More recent studies, however, demonstrate that you get the greatest effect from the initial workout, with workouts done later on the same day leading to blunted GH release. That’s because the workout stimulates higher blood lipids, which persist for several hours afterward. Higher blood fat blunts further GH release during exercise.1
The more muscle you use during an exercise, the greater the release of GH. So training larger muscle groups, such as the legs and back, produces a far greater GH release than training smaller muscle areas, such as arms or shoulders. Aerobic equipment that involves both upper- and lower-body muscles simultaneously stimulates higher GH levels than lower-body-only exercises or machines.
One reason exercise promotes GH release is that it usually raises core body temperature. GH regulates body temperature and helps prevent overheating during exercise. Conversely, exercising in the cold inhibits the release of GH.2 So, for example, rowers have higher levels of GH than swimmers, whose core temperature goes down because they’re in the water.
Eating a high-fat meal prior to training blunts GH release. So will eating carbs, but to a lesser extent.3 Some studies show that having a protein-and-carb drink before and after training leads to a greater GH release, though other studies haven’t substantiated that. Using asthma drugs in the category of beta-2 agonists also blunts GH release during exercise—that includes the drug clenbuterol. Researchers think that’s because the drugs increase the release of somatostatin, a protein that blocks GH. Even not drinking enough water during training blunts GH release.4
GH response is greater when you do multiple sets than when you do single sets. One study showed a greater GH response among exercisers doing four sets than those doing two, but doing six had no further effect. Another study showed that doing forced reps increased GH release.
Doing a high-rep set at the end of a series of heavier sets also produces a much greater GH release, as does resting one minute or less between sets. Lowering the weight (eccentric or negative reps) produces greater GH release than raising the weight.5
Since most scientists agree that GH and IGF-1 drop precipitously with age and that the lack of those hormones produces many symptoms associated with aging, continuing to engage in exercise known to elicit the greatest GH response can produce a reliable antiaging affect. It’s likely that the true advantages of weight training will manifest themselves in the realm of longevity and quality of life.
References
1 Stokes, K., et al. Human growth hormone
responses to repeated bouts of sprint exercise with different recovery
periods between bouts.J App Physiol. In press.2 Wheldon, A., et al. (2006). Exercising in the cold inhibits growth hormone secretion by reducing the rise in core temperature. Growth Hor IGF-1 Res.16:125-31.
3 Cappon, C.P., et al. (1993). Acute effects of high-fat and high-glucose meals on the growth hormone response to exercise. J Clin Endocrin Metabol. 76:1418-22.
4 Peyreigne, C., et al. (2001). Effect of hydration on exercise-induced growth hormone response. Eur J Endrocrin. 145:445-50.
5 Kraemer, W.J., et al. (2005). Hormonal responses and adaptations to resistance exercise and training.Sports Med. 35:339-61.
©,2012, Jerry Brainum.Any reprinting in any type of media, including electronic and foreign is expressly prohibited.
