Since we have a young (seems like most are younger than us) friend who has personally been involved in a study on DMG I asked her to write something on the subject. Since she`s not on the *list* yet I`m posting it for her -- yep, trying to get her on the list but since extra time is at a premium due to studies she is afraid to get caught up in it. This is a grad student that has ridden endurance for about 10 or 12 years so she KNOWS what is involved with this sport. As far as using it ourselves we do so and find that the 2nd day after a ride we don`t have those terrible muscle aches -- in other words we can sit down without falling the 2nd half of the way and don`t have to go down stairs backwards.
Hope this helps.
Jim & Karen Clanin
OK, here`s another two cents regarding the use of DMG in endurance horses, and specifically in answer to Dr. Lynn Taylor`s statements that research has not demonstrated its benefits. If anyone`s comparing initials, my BS and pending MS are both in Animal Science with an emphasis in equine exercise physiology. DMG also happens to be very near and dear to my heart, the subject of a study we did here at Cal Poly last year and the subject of lots of heated debates around here. (I`m also engaged to a guy whose initals are DMG, so you can imagine the comments I got to hear that I really do need to try drinking decaf and maybe even get a life.)
Anyway, on to the debate---I think I may have an explanation for the differnce between research and anecdotal evidence regarding DMG. Dr. Taylor is absolutely correct that there is no research that clearly demonstrates any benefits to performance horses performing maximal or submaximal exercise. There was one study conducted on Standardbreds that supposedly showed some "improvement in recovery" but the methodology in its statistical design was so poor that any alleged results really must be totally disregarded. Several other studies by Rose, Snow, as well as a study a year or so ago conducted at Texas A & M, were all done with excellent attention to detail and none of them showed any decrease in lactates while exercising.
HOWEVER---if the research literature is read carefully, there are several important points to consider before you totally write off DMG. In all of the previous studies, except for Cal Poly`s, lactate levels were only measured actually during the exercise bout itself, but not during the subsequent recovery period. This is probably because the funding was coming from the Thoroughbred racing industry, which very much wanted to know if DMG would help a horse go faster during the race itself, but weren`t particularly interested with how stiff the horse felt the next day. The Cal Poly project measured lactates not only during the exercise bout but ALSO during the recovery period following the exercise test. This is because we hypothesized that if DMG did provide any benefit, possibly it was during the recovery period, rather than during the exercise period. That is, maybe the horse still accumulated as many lactates, but DMG helped to clear it out faster, which is almost as good. obviously, this would not benefit horses such as Thoroughbreds which compete in a single, maximum effort event, but would definitely benefit endurance horses which exercise for a time, rest for a time and then exercise again. The second difference in Cal Poly`s study is that DMG was fed to the horses via syringe two to three hours before data was collected. ALL of the prevous studies fed DMG to the horses from eight to 24 hours before exercise. This is possibly a major factor because DMG is a relatively small molecule---basically just a glycine (an amino acid) molecule with two methyl groups tacked on. It`s NOT going to take very long for the equine system to get DMG into the system, broken down, metabolized and waved goodbye to. It`s a reasonable possibility that in previous studies, by the time they got around to pulling blood and measuring lactates, any benefits from the DMG fed yesterday had already been and gone. It`s the same thing as saying that aspirin doesn`t work because you took some last week and this week you have a headache again.
SO, when we did our study at Cal Poly, we fed the DMG at a time so that it would be in the blood system while lactates were accumulating during the treadmill exercise bout. We did a random, Latin square design so that every horse did the test at three different levels of DMG dosage---zero, 2 mg/kg and 4 mg/kg. At all three dosage levels, lactate accumulation was exactly the same and oxygen utilization was the same. This confirms all the earlier data that DMG is of NO benefit during an exercise test that was sufficient to produce significant blood lactate levels. Also,in the zero and low dosage group, there were no differences in lactate levels during the 90 minute recovery period. OK, here`s the part where you pound your head and think about going to work at Burger King like everyone else. We had problems with lameness in a number of our test horses and by the time we were done, the "high dosage" group had to be removed from the study because they were no longer a statistically viable group. However, in the two high dosage horses that did get measured, we did see a distinct and significant drop in lactate levels during the thirty minutes immediately after the exercise bout. When these two horses had previously done the same exercise test twice before, once having been fed no DMG and once having been fed a low dose of DMG, they did NOT show this drop in recovery lactates. This is a SUGGESTION, AND A SUGGESTION ONLY, that MAYBE feeding DMG at 4 mg/kg or higher provides some benefit during recovery. However, there is no way that you can make any sort of broad statements after observing results in only two horses. That would be the same thing as going into your backyard, seeing two gray Arabs and therefore concluding that all horses are gray. Therefore, the article that resulted from Cal Poly`s study could only mention the two statistically viable groups that showed no benefits from DMG.
So, to make a long story shorter, I think the only truly accurate statement that could be made about DMG is that no research has YET proven any benefits, however, the same research has also failed to completely DISPROVE any benefits. To do so, someone is going to need to do another study in which DMG is fed at high doses, fed within a few hours of the exercise bout, and in which lactates are measured throughout the recovery period. And if anyone cares to fund such a project, by all means let me know. Until then, NO ONE can make any authoritative statements either for or against DMG`s usage.
Susan Evans, MS (in progress)
Uppity Grad Student
Equine Research Center
Calif. State Polytechnic University, Pomona
OK, 2 more cent`s worth...not to be fussy, BUT...until I see published results in a peer-reviewed journal, I am not convinced of anything. Numbers of horses, statistics, methodology are all difficult to assess, and the professional community demands that academics regulate themselves by reviewing each other`s work. Some points to consider:
1. How do studies come uo with dosages? Has anyone done a toxicity study on DMG?
2. Blood lactate and plasma lactate are 2 different things. Which is measured? When was it sampled? What type of anti-coagulant was used? How was it stored after collection? How long before it was assayed? Blood lactate is always lower than plasma lactate because the red cell contents dilute the concentration - there is not an equilibrium of lactate distribution across the red cell and plasma.
3. What if the timing of DMG feeding is still incorrect? How many timing regimens were initially tested?
4. Why would endurance horses need lower lactate? The levels during an endurance ride are fairly low - nothing even close to racing, polo, cutting, reining, junping, cross-country, etc.
5. What is really going on during recovery? What are horses doing at this time? Walking? Standing? Turned out? In stalls? Massaged? Fed differently? All these things can affect recovery varaibles.
6. Are there interactions in studies with training effects? maybe all groups of horses are fitter.
7. What are the possible detrimental effects of DMG?
So anyway, not to be too uppity, but there are lots of research projects out there. They need to be carefully planned out, and subjected to rigorous statistical analysis. If they pass the grade, great, I will read it and ponder it myself. If it only ends up in a meeting proceedings book, or The Equine Athlete etc., then I begin to wonder why it was possibly rejected from a quality journal. Well, there is my pompous and supicious 2 more cents...PLEASE nobody sned me hate mail, we all have to be careful about believing everything we read!!!
Lynn E. Taylor, MS, PhD
Dept. of Equine Science
Westerville, Oh 43081
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