Research-based Exercise Prescription Part 3

Last issue, I summarized an article by Ogasawara et al. in the Journal of Applied Physiology. The authors studied rats performing either a single resistance exercise bout, 12 bouts on non-consecutive days, 18 bouts on non-consecutive days or the 12-bout protocol followed by 12 days of detraining and a single bout that resumed it. Results showed that muscle growth and strength gain were present after 12 and 18 sessions, but not after one, and each of these enhancements remained despite 12 days of detraining. However, signaling proteins thought to be responsible for muscle growth that were elevated after only one bout were less elevated after repeated exposure, although for the one bout after the detraining period, the initial most powerful response was restored. 

Upon first inspection, these findings imply that a one-day-on-12-days-off training regimen might provide the best approach! But a more logical conclusion is that when you train regularly, homeostasis (the body’s drive for internal constancy) wins out in the end and its triumph doesn’t take long. This explains why people who have been training with weights for many years have not grown to mammoth proportions. The fact is that just like not enough muscle can threaten survival of the species, too much also has its drawbacks. For example, an excessively-developed muscle could outstrip the ability of the cardiovascular system to adequately perfuse it. What is more, muscle growth in fibers with a “pennate” architecture (i.e., with angled fibers that attach to a central tendon; for example, the rectus femoris of the thigh) increases the angle of pennation. This means that the bigger muscle shortens less per given degree of fiber shortening. Apparently, this is not a problem up to a point (although it might decrease velocity of shortening a bit), but if the muscle ever became large enough such that the angle approached 90 degrees, we’d be in big trouble!

Down regulation of the adaptive response to resistance training after as few as 12 sessions supports the notion that we reach our genetic plateau for muscle growth in a relatively short period of time. How long? Well, that’s difficult to answer, but it might be better quantified in months as opposed to years! Now, one reaction to this is to be discouraged if you have been training long enough to know that you have gained as much muscle as you ever will. After all, it’s like starting a new job and having your pay cut after the first month despite doing all that was asked of you. But it’s a fact so the best bet is to accept it as reality and act accordingly.

Long-term muscle growth might not be possible due to the body’s drive for constancy, but it’s important to recognize that the increased level of development you do achieve when you reach your genetic potential must be maintained via quality training. Obviously, it’s human nature to always strive to get better, but when it comes to muscular development, I’ve come to appreciate that maintenance is a noble objective. And this is especially true as Father Time takes his toll.

Slowing the reduction in muscle that occurs with aging has many benefits in addition to those that are appearance related. For example, more muscle means greater strength, a higher basal metabolic rate, less cardiovascular activation (and, therefore, stress) for any given physical effort and better control of blood glucose. So, staying as close as possible to your genetic plateau for muscular development as the years pass is good for your health. This means that training simply to stay the same is a prudent game plan because muscle will leave if it is not regularly challenged. For example, although the study by Ogasawara et al. found no muscle or strength loss after 12 days of detraining, others that have assessed longer periods of inactivity have been more sobering. Case in point, a 2000 study by Hakkinen et al. in the European Journal of Applied Physiology that had middle-aged (37-45 years) and elderly (62-78 years) subjects perform a two-time-per-week strength training program for 24 weeks followed by either three weeks of detraining and 21 weeks of resumed training or 24 weeks of detraining. The good news was that both age groups achieved large increases in strength after the initial 24 weeks and during the period of resumed training, further strength gain occurred throughout in middle-aged subjects and until week 41 in the elderly. Muscle gain also occurred during the initial period in both groups, but not of the same magnitude as strength, which suggests that much of the strength enhancement was attributable to improved nervous-system function. This is also exemplified by the fact that no further muscle gain occurred during the second training period when strength continued to improve. More good news was that three weeks of detraining resulted in only minor decreases in strength and no change in muscle mass. This is similar to the findings of Ogasawara et al. detailed above. However, long-term detraining brings us to the bad news. Specifically, 24 weeks of detraining caused reductions in both strength and muscle size such that by week 48, muscle cross-sectional area was actually smaller than it was at the start of the experiment in both groups! The authors conclude by stressing the importance of on-going resistance training for increasing/maintaining muscle mass and strength.  






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