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Now I got your attention, right?
The subjects were a group of 18 male highly trained young swimmers (age: 14.9 ± 0.4 years, BMI: 20.8 ± 0.4 kg/m²) who regularly accomplished a total training distance of 12.3 km/day (think of the Chinese girl at the Olympics in London, last year ;-). While 8 of them remained within their regular training environment in Singapore, the 10 subjects who had been randomized to the active group were transfered to Kunming. Contrary to Singapore, of which all of you probably know that it's a metropolis at sea level, Kunming is located at an altitude of 2,300m and thus an ideal and in fact highly frequented high altitude training camp.
|Figure 1: Changes in BMI, lean and fat mass in the two study groups (Chia. 2013)|
Now, all that is actually not new and wouldn't be SuppVersity news-worthy, if the Chinese and US researchers had not observed a profound and rapid (3 weeks) reduction in body fat levels in the subjects who trained in the high altitude training camp in Kunming (it should be mentioned that in animal studies similar effects have already been observed; Chen. 2010). As the data in figure 1 goes to show you, these changes were not just statistically significant (even the increase in lean mass was), but also much more pronounced than the fat loss effects of the epigallocatechin gallate (EGCG), capsaicins, piperine & carnitine stack that was in the news yesterday (cf. "EGCG, Capsaicin, Pipreine & Carnitine: Rather a Health Than a Fat Loss Stack?") -- and that despite the fact that the subjects already had a comparably low body fat level to begin with and did not restrict their total energy intake or make any other changes to their dietary or traning regimen.
"So what's that? Dark magic?"
To further elucidate the underlying mechanisms, by which the altitude training induced hypoxia (shortage of oxygen supply) triggered this body recomposition effect (in fact, all ten swimmers demonstrated reciprocal decreases in fat mass and increases in lean mass after the 3-week altitude exposure), Chia et al. conducted a second experiment in the course of which the
"effects of hypoxia (at 16% oxygen) on blood distribution to the skeletal muscle were assessed under glucose-ingested condition (i.e. insulin-stimulated condition) after training at sea level. Skeletal muscle blood distributions were measured using near infrared spectroscopy (NIRS) to detect changes in hemoglobin concentrations under hypoxic (16% oxygen) and normoxic conditions for 90 min after oral glucose ingestion." (Chia. 2013)Aside from the expected change in oxygen saturation and more constant hemoglobin levels during the hypoxia condition, the scientists also observed an increase in lactate production and a decreased glucose clearance from the blood, which was compensated by an increased insulin response.
|Figure 2: Low frequency to high frequency ratio as a measure of sympathetic activity (left) and glucose and insulin response (right) in the follow up experiment at sea level during normal (normoxia) and low oxygen (hypoxia) conditions (Chia. 2013)|
On the other hand, you could probably also make a point that the decreased glucose uptake in the follow-up study must have caused a shift towards fatty acid oxidation during the workout. Aside from the PGC1a and AMPK activity Chen et al. obversed in the aforementioned rodent study (Chen. 2010), another, or rather an additional mechanism, which may explain the profound body recompositioning effects, could be mediated by a hypoxia induced increase in PDK-4 and a subsequent decrease in PDC mediated feeding of the TCA cycle with pyruvate (cf. Kelly. 2008). In order to get enough energy, the mitochondria would consequently have to ramp up their fatty acid uptake and beta-oxidation, which would require a greater release of fatty acids from the storage tissue. The latter shouldn't be a problem with the increase in autonomic nervous system activity (by the way something classic stimulant based fat burners do as well). In this context, it would have been interesting to see whether there was a major difference in the respiratory exchange ratio (RER). With the latter being an indicator of the ratio of carbs vs. fats being used as fuel, this could help clarify, whether my hypothesis is correct or not.
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That said, I know that your next question is, whether this does have any implications for your training? Well, as of now, probably not. It would however be interesting to see if non-altitude induced hypoxia could have similar beneficial effects. I know that the second experiment in the study at hand would suggest it does, but Ii probably don't have to tell you that it is one thing to have a reduced oxygen supply for a couple of minutes vs. 24/7, as it is the case in a high altitude training camp.
- Chen CY, Tsai YL, Kao CL, Lee SD, Wu MC, Mallikarjuna K, Liao YH, Ivy JL, Kuo
CH. Effect of mild intermittent hypoxia on glucose tolerance, muscle morphology
and AMPK-PGC-1alpha signaling. Chin J Physiol. 2010 Feb 28;53(1):62-71.
- Chia M, Liao CA, Huang CY, Lee WC, Hou CW, Yu SH, Harris MB, Hsu TS, Lee SD, Kuo CH. Reducing Body Fat with Altitude Hypoxia Training in Swimmers: Role of Blood Perfusion to Skeletal Muscles. Chinese Journal of Physiology. 2013 [Epub ahead of print]
- Kelly DP. Hypoxic reprogramming. Nat Genet. 2008 Feb;40(2):132-4.