The 4-Hour Body_ An Uncommon Guide to Ra - Timothy Ferriss [48]
On to one of the cooler aspects of this whole craziness: GLUT-4.
PRINCIPLE #3: ENGAGE IN BRIEF MUSCULAR CONTRACTION THROUGHOUT THE BINGE.
For muscular contractions, my default options are air squats, wall presses (tricep extensions against a wall), and chest pulls with an elastic band, as all three are portable and can be done without causing muscle trauma that screws up training. The latter two can be performed by anyone, even those who have difficulty walking.
But why the hell would you want to do 60–90 seconds of funny exercises a few minutes before you eat and, ideally, again about 90 minutes afterward?
Short answer: because it brings glucose transporter type 4 (GLUT-4) to the surface of muscle cells, opening more gates for the calories to flow into. The more muscular gates we have open before insulin triggers the same GLUT-4 on the surface of fat cells, the more we can put in muscle instead of fat.
Longer answer:
GLUT-4 has been studied most intensely for the last 15 years or so, as it became clear around 1995 that exercise and insulin appear to activate (translocate) GLUT-4 through different but overlapping signaling pathways. This was exciting to me, as it meant it might be possible to use exercise to beat meal-induced insulin release to the punch—to preemptively flip the switch on the biological train tracks so that food (glucose) is preferentially siphoned to muscle tissue.
But how much contraction is enough? It turns out, at least with animals, that much less is needed than was once thought. In one fascinating Japanese study with rats, high-intensity intermittent exercise (HIT) (20-second sprints × 14 sets, with 10 seconds of rest between sets) was compared to low-intensity prolonged exercise (LIT) (six hours of extended exercise) over eight days.
The surprising result? Bolding is mine:
In conclusion, the present investigation demonstrated that 8 days of HIT lasting only 280 seconds elevated both GLUT-4 content and maximal glucose transport activity in rat skeletal muscle to a level similar to that attained after LIT [“Low-Intensity Training” of six hours a session], which has been considered a tool to increase GLUT-4 content maximally.
Compared to a control, GLUT-4 content in the muscle was increased 83% with 280 seconds of HIT vs. 91% with six hours of LIT.
Now, of course, animal models don’t always have a direct transfer to humans. But I wondered: what if 280 seconds was all it took? This thought produced even more questions:
Do we have to get the 280 seconds all at once, or can they be spread out?
Is 280 seconds really the magic number, or could even fewer seconds trigger the same effect?
Is it even plausible that 60–90 seconds of moderate contractions could have a meaningful impact?
To attempt to answer these questions, I contacted researcher after researcher on three continents, including GLUT-4 specialists at the Muscle Biology Laboratory at the University of Michigan at Ann Arbor.
The short answer was: it did appear plausible.
The most important research insight came from Dr. Gregory D. Cartee and Katsuhiko Funai:
The insulin-independent effect of exercise begins to reverse minutes after exercise cessation with most or all of the increase lost within 1–4 hours. A much more persistent effect is improved insulin sensitivity that is often found approximately 2–4 hours and as long as 1–2 days after acute exercise.
I started with 60–120 seconds total of air squats and wall tricep extensions immediately prior to eating main courses. For additional effect, I later tested doing another 60–90 seconds approximately one and a half hours after finishing the main courses, when I expected blood glucose to be highest based on experiments with glucometers.9
Exercises are best done in a restroom stall and not at the table. If you can’t leave the table, get good at isometric (without moving) contraction of your legs.