a tam vegas walnij cos dluzszego, bo rownie dobrze mozemy sie przebijac badanimi i ciekawe kto bedzie mial wiecej tych przweciw hmb i tych za ;] ?
A dietary supplement used to increase the size and disease resistance of sheep, cattle, chickens and hogs can heighten muscle mass and strength in athletes who carry out regular resistance training, according to new research carried out at Iowa State University and the State University of New York at Stony Brook. The supplement may maintain muscle mass and improve recovery from strenuous exercise in endurance athletes as well.
Best of all, the exciting new supplement is not a hormone, appears to be safe. has no known side-effects, and has produced a variety of positive effects in a large number of scientific studies. The supplement is called HMB, a convenient abbreviation for the compound's rather difficult chemical name - beta-hydroxy-beta-methylbutyrate.
HMB is closely chemically related to an important branched-chain amino acid called leucine (see elsewhere in this issue), so we'll begin the HMB story by focusing on that for a moment. Leucine has been a major player in a scientific quest which has taken place over the past three decades. This scientific journey has actually had two key elements - an attempt to help patients suffering from major trauma (including victims of severe burns, those involved in serious car accidents, and patients recovering from extensive surgery), and an effort to make farm animals leaner and larger. While those two goals may seem somewhat unrelated, they both revolve around an activity which is absolutely essential for life: protein synthesis.
Basically, an individual suffering from major burns or physical trauma needs to rapidly manufacture new body tissues while making sure that any cells not affected by the injury remain healthy and viable. To quickly create the new tissues, the body must use basic chemical building blocks - amino acids - to assemble the mint-condition proteins which will be the foundation for the new muscles, tendons, ligaments, skin, and so on. Similarly, farmers raising livestock for market are hoping to accelerate the same processes in their animals. Like doctors working with traumatised patients, the farmers want to create as much new muscle as possible in their animals while preserving the muscle tissue that is already in place.
Leucine comes into the picture because it's one of the three so-called branched-chain amino acids (the other two are isoleucine and valine). These branched-chain fellows are important because some studies have shown that they have a special capacity to boost protein synthesis and inhibit protein breakdown. For example, when increased doses of the branched chains are given to hospital patients recovering from surgery, decreases in urinary nitrogen are sometimes noted, a sign that protein is being preserved more effectively (when proteins break down, they dump nitrogen into the blood). None of the other amino acids has as strong a protein-preserving effect as the branched chains.
Of the three branched chains, leucine has seemed the most potent. so a great deal of research time has been spent exploring its muscle-building potential. Unfortunately, the results of these efforts have been somewhat equivocal; sometimes the leucine seemed to work quite well, sometimes it didn't.
How HMB worked on farm animals
Fortunately, most scientists don't give up very easily and many of them continued fooling around with leucine and with some of its closely related metabolites (chemicals that are formed when leucine is partially broken down inside the body). One of those metabolites happened to be HMB, and weird things happened when Dr Steven Nissen and his colleagues at Iowa State University began feeding it to chickens. Basically, the chickens grew faster, died less often and ended up with bigger muscles when HMB was added to their chicken feed ('The Effects of Beta-Hydroxy-Beta Methylbutyrate on Growth, Mortality, and Carcass Qualities of Broiler Chickens', Poultry Science, vol. 73, pp. 137-155, 1994).
Nissen also obtained positive results with HMB when he branched out to experiment with lambs. In work completed quite recently, Nissen and his co-researchers were able to show that HMB improved 'feed efficiency' in growing lambs (the percentage of ingested food actually used to increase body mass). Interestingly enough, the HMB-fed animals also had a 56 per cent lower incidence and 63 per cent reduced severity of 'soremouth disease', a malady which is fairly common among lambs ('The Effects of the Leucine Catabolite, Beta-Hydroxy-Beta-Methylbutyrate, on the Growth and Health of Growing Lambs', Journal of Animal Science, vol. 72, Supp 1/J, p. 243, 1994). While it might seem surprising that HMB could control illness, bear in mind that protein synthesis and maintenance is absolutely critical for normal operation of the immune system, and HMB's bailiwick is protein protection.
Nissen also got pigs into the act. In research carried out with sows at the NOBL Laboratories at Sioux Center, Iowa, Nissen and several co-workers were able to show that female porkers taking HMB needed less feed to increase body mass, gained more weight, lost more backfat, and produced richer milk for their offspring, compared to pigs who did without HMB ('Colostral Milk Fat Percentage and Pig Performance are Enhanced by Feeding the Leucine Metabolite Beta-Hydroxy-Beta-Methylbutyrate to Sows', Journal of Animal Science, vol. 72, pp. 2331-2337, 1994).
Without going into endless detail concerning the extensive research done on HMB supplementation in animals, we can simply say that HMB has also increased 'carcase quality grades' in steers and reduced mortality in calves that were 'stressed out' by being shipped from one location to another. What does all this have to do with humans carrying out strength training or running 5Ks? Actually, quite a lot, as you'll see in a moment.
HMB in humans
You see, things looked so good in the animal world that the research group at Iowa State and Stony Brook decide to see what wold happen to humans who tried out HMB. The preliminary study took a group of 41 young men, many of them students at Iowa State University, and put them through three weeks of weight-training hell, the idea being to create as much muscle mayhem as possible. The notion was that if HMB really protected muscle cells by preventing protein breakdown, as many researchers theorised, it was bound to help individuals undergoing a very stressful programme ('The Effect of the Leucine Metabolite Beta-Hydroxy-Beta Methybutyrate on Muscle Metabolism during Resistance Exercise Training', just accepted by American Journal of Applied Physiology).
The subjects strength-trained three times a week for three and a third weeks, using both free weights and weight machines and alternating back and forth between upper-body and lower-body workouts (there were a total of five upper-body and five lower-body sessions during the overall programme). Seven exercises were used for the upper-body (weight machine exertions are designated with WM, while free-weight efforts are marked FW) - bench presses (FW), latissimus pull-downs (WM), seated rows (WM), the Cybex-Pec-Fly (WM), seated preacher curls (FW), inclined dumbbell curls FW), and triceps push-downs (WM). Seven exercises were also used during the lower-body workouts, including seated leg presses (WM), standing calf raises (WM), leg curls (WM), leg extensions (WM), 45-degree inclined sit-ups, inclined leg lifts and inverted sit-ups (back extensions).
Resistance was set at 90 per cent of one-repetition max (abbreviated as 90% 1-RM, which is 90 per cent of the heaviest weight which could be lifted no more than one time without resting). Subjects warmed up for each exercise by completing two sets of 10 repetitions of the exercise at only 30-60% 1-RM and then did the real work - three sets of three to five reps at 90% 1-RM for each exercise except for sit-ups, inclined leg lifts and back extensions, which were actually performed until complete exhaustion was reached. The principle of progression was applied to the training by increasing the average weight lifted on the last two sets of each exercise by 2 per cent for the subsequent workout.
Roughly one-third of the subjects took no HMB supplements during the three-week training period, another third ingested 1.5 grams of HMB every day, and the final third swallowed 3.0 grams daily. Of course, total caloric and protein intakes were tightly monitored in the three groups to make sure that one group's eventual edge in muscle mass or strength wasn't due to a higher-protein or more energetically rich diet.
How did HMB do?
The results were spectacular, to say the least. Individuals who took in no HMB lost about two pounds in weight during the study, while those who ingested HMB lost only from half-a-pound to a pound. Isn't that bad? Well, no, because the big difference was that the HMB people were building up their muscle tissue. You see, all three groups dropped about two to three pounds of fat over the three-week period. The really good news for those of you who are interested in improving your body composition was that strength trainees who took in no HMB boosted muscle tissue by slightly less than one pound, those who took 1.5 grams added 1.75 pounds of muscle, and the 3.0-gram people augmented sinew by 2.6 pounds!
Differences in muscle strength were also impressive. While non-HMB subjects increased abdominal strength by 14 per cent, both HMB groups upgraded ab-muscle fortitude by about 50 per cent after three weeks. Total strength (combined for upper and lower body) advanced by 8 per cent in the non-supplemented group but soared by 13 and 18.4 per cent in the 1.
5 gram and 3.0 gram lifters, respectively.
Why did HMB do such a good job of augmenting muscle mass and strength? Did it work on the protein synthesis part of the equation or did it simply protect against protein (muscle) breakdown during the strenuous weightlifting regime?
That dratted 3-methylhistidine
To get a better grip on what was going on, the researchers looked closely at the rate at which a chemical called 3-methylhistidine was lost in the subjects' urine. 3-methylhistidine is a marker of protein degradation: the more 3-methylhistidine that appears in the urine, the greater the rate at which muscles are breaking down. In this study, in which subjects without much weightlifting experience undertook a tough resistance programme, a fair amount of muscle damage and thus a lot of urinary 3-methylhistidine were expected.
The news was good for HMB fans. Basically, 3-methylhistidine levels soared by 94 per cent after one week in the subjects who were not taking HMB, a sign that their muscles were being broken down by the rugged training. However, 3-methylhistidine increased by only 50 per cent in individuals who were taking 3.0 grams of HMB per day.
By the second week, the subjects were adjusting to the training, so 3-methylhistidine was up by only 27 per cent in the non-HMB people. The really good news, though, was that 3-methylhistidine was actually down by 4 per cent in the 1.5 gram group and plummeted by 15 per cent in the 3-gram lifters. In other words, muscle breakdown was lower than it would have been if the subjects had been involved in a sedentary lifestyle, in spite of the fact that they were actually engaged in a very vigorous resistance-training programme.
Plasma levels of two key muscle enzymes which are often considered to the markers of muscle damage, CK and LDH , also were lower in the HMB groups. In addition, total blood amino-acid concentrations were 32 per cent higher in the athletes not receiving HMB, but 9 and 19 per cent lower than usual in the 1.5 gram and 3 gram groups. While that might seem bad, it probably reflected the lower muscle breakdown in the HMB subjects (when the proteins in muscles break down they deposit amino acids in the bloodstream). HMB just seemed to be doing a fine job of holding muscles together during training - allowing increases in mass to occur without simultaneous breakdowns.
Adding experienced athletes
Although this was a splendid study, carpers criticised it because it involved relatively untrained subjects. Their contention was that well-trained athletes might already have enough basic strength to protect their muscles from damage during training, and thus might not need HMB's muscle-coddling effect.
Well, the Iowa State researchers are a determined lot, so they quickly followed up their initial work with a piece of research that included both untrained individuals and also athletes with fairly extensive backgrounds in resistance training. Again, the groups were fairly large (23 trained and 17 untrained subjects), and a similar exercise programme was followed (four weeks in duration, 10 total exercises performed, three workouts per week, and three sets of 3-6 reps for each exercise per workout). The study was conducted in a double-blind manner (neither experimenters nor subjects knew which athletes were getting a placebo or 3 grams of daily HMB).
Again, the results were quite astounding. Basically, the increase in muscle mass was 61 per cent greater in the HMB group, compared to placebo. The decrease in fat mass was 232 per cent greater in the HMB group. The hike in bench-press strength was 55 per cent greater in HMB ingesters. And it mattered not one bit whether the HMB takers were experienced athletes or novice strength trainers: the results were essentially the same ('Effects of Beta-Hydroxy-Beta-Methylbutyrate Supplementation on Strength and Body Composition of Trained and Untrained Males Undergoing Intense Resistance Training', Federation of American Societies for Experimental Biology Journal, vol. 10, p. A287, 1996).
And endurance athletes?
So the evidence that HMB is good for strength athletes is strong, but what about endurance types? Is there any way that the supplement could help them produce greater performances?
Well, if you're just jogging 10-15 miles per week and you're not engaged in regular strength training, the answer is probably no: HMB is most effective during fairly strenuous training. Otherwise, the stuff might help you in several ways: first, by limiting protein breakdown, it could speed your recovery from tough workouts, allowing you to fit more quality training into your schedule. The idea is that since there's less muscle destruction after a workout, there's less that needs to be rebuilt, so recovery occurs more quickly.
Second, if you're engaged in endurance and strength training at the same time, HMB could be a real boon. As documented by scientific research, HMB might help you achieve better gains in muscle strength during your resistance programme, and this strength could eventually make you a more powerful (faster) athlete. In addition, a fair amount of research has indicated that there can be a basic conflict between endurance and strength training: it's hard for muscles to get bigger and more powerful and develop greater endurance simultaneously. Efforts to do so make muscles a bit schizophrenic (Bill Rodgers used to say that he knew he was ready for a great marathon when he couldn't jump more than a few inches off the ground). HMB, by limiting some of the protein catabolism and wear and tear produced when athletes bombard their muscles with both prolonged (endurance) and heavy-load (strength) work, might minimise this conflict and help athletes to become more fatigue-proof AND powerful.
Third, those endurance athletes who train really seriously often find themselves on the threshold of overtraining, in which there's too much muscle breakdown, too little muscle build-up. One key problem frequently associated with heavy training is that a hormone called cortisol increases its concentration. That's good in one sense because cortisol is a 'stress hormone' which helps the body withstand physically demanding situations. It's bad in another, because cortisol increases the rate of protein breakdown (this gives the body more energy to use since the proteins are used as metabolic fuel but it also means that muscle mass may dwindle). HMB may curtail cortisol's protein destruction and therefore may make overtraining less likely. The bottom line is that the compound might be especially helpful during periods when you're significantly raising the intensity or volume of your training.
Conclusions
HMB appears to be safe, should be of benefit during strenuous strength training, and may also help endurance athletes by accelerating recovery and/or preserving muscle mass during serious training. If you do decide to take the stuff, the 3-gram-per-day dose appears to be most effective, based on what we now know. Of course, HMB intakes should be coupled with adequate protein consumption of at least 1.6 grams of daily protein per kilogram of body weight.
Ćiastuś_
Krzysztof Piekarz
Anonim
DrMartens
_Future_
v3gas
chyba ze ja sie na angielskim nie znam 
Grasik
