The Metabolic Stress Workout for Muscle Gains
For years, bodybuilders have been advocated to use short rest periods between sets to elicit metabolic stress and increase anabolic hormone responses. Although the newest research seems to suggest that the acute anabolic hormones response (i.e. acute GH and testosterone responses) to resistance exercise has little to do with increases in muscle mass, there is evidence to suggest that the direct metabolic stress can influence muscle hypertrophy. For example, numerous studies using resistance exercise training combined with blood flow restriction have shown to increase muscle hypertrophy with a training intensity as low as 20% 1RM. For instance, a low-intensity (~50% 1RM) resistance training performed with leg extensions caused a marked increase in muscular size [~12% gain in muscle size and strength (~20% gain) when combined with moderate vascular occlusion. These studies suggest that the muscle mass building effects of resistance exercise involves not only muscle tension (weight) but also metabolic factors.
Metabolic Stress Stimulates Protein Synthesis
One of the major determining factors for increases in muscle mass is increase in protein synthesis. Muscle protein synthesis has been shown to be elevated following acute blood flow restricted resistance exercise, further building a case for the accretion of muscle mass independent of external load. Metabolic stress may be more important than the external load for increasing muscle mass. For example, two different exercise regimens at the same external intensity (3–5 sets of 10 at 75% 1RM) resulted in different muscle adaptations. The only difference between groups is that one group rested for 30 seconds midway through each exercise set. The group that did not rest midway through each set which resulted in greater increases in metabolic stress, which resulted in greater gains in strength, endurance, and muscle mass compared to the group that rested during each set. The results of the study are that “metabolic stress” is essential for increases in muscle mass.
Caffeine and Lactate Supplements Increase Muscle Mass
The newest research published in the latest Journal of Applied Physiology seems to support that metabolic stress can increase muscle growth signaling factors. In the study, researchers examined whether a mixed lactate and caffeine compound could effectively elicit proliferation and differentiation of satellite cells or activate anabolic signals in skeletal muscles. Caffeine is a stimulant. It gives you extra stamina and increases your heart rate, improving blood flow from the heart to the rest of your body. At the cellular level, the major player causing muscle contraction is calcium.
Caffeine acts directly on the storage site for calcium in skeletal muscle, an area known as the sarcoplasmic reticulum. When caffeine interacts with the sarcoplasmic reticulum, increased amounts of calcium are pumped into the muscle, thus causing stronger muscle contractions. Lactic acid on the other hand is actually a fuel, not a caustic waste product as once previously thought. Muscles make it deliberately, producing it from glucose, and they burn it to obtain energy. The lactic acid is taken up and used as a fuel by mitochondria, the energy factories in muscle cells.
Researchers wanted to examine how when you combine both caffeine and lactic acid into a supplement how it would affect the anabolic pathways. The researchers hypothesized that, “a lactate-based supplement containing caffeine, an activator of intracellular calcium signals, could elicit proliferation and differentiation of satellite cells, activate anabolic signals in skeletal muscle, and thereby increase muscle mass when combined with low-intensity exercise training.“
Satellite cells are essential for muscle growth to take place; they lay dormant until activated to form new muscle fibers. The researchers looked at the impact of lactate and caffeine first in test tubes and then in animal studies (i.e. in vivo). First, the researchers found that when they mixed the lactate and caffeine in test tubes and mixed them with growth factors that lactate significantly increased myogenin and follistatin protein levels and phosphorylation of P70S6K (i.e. all three are growth promoters) while decreasing the levels of the muscle growth inhibitor myostatin relative to the control. Lactate and caffeine combination significantly increased the anabolic protein cellular pathways Pax7, MyoD and Ki67 in addition to myogenin, relative to controls. Lactate and caffeine combination also significantly increased anabolic signaling pathway follistatin expression relative to controls and stimulated the anabolic signaling pathway mTOR and P70S6K.
The really exciting aspect of this study seems to suggest that taking caffeine combined with the high intensity exercise which elicits high levels of lactic acid is a good combination for muscle growth and increases in anabolic pathways.
When the researchers examined the powerful combination when administered to male rats, they found similar increases in the anabolic signaling pathways. In an in vivo study, male rats were assigned to the control, exercise and lactate and caffeine supplementation groups. Lactate and caffeine was orally administered daily. The lactate and caffeine exercise group and exercise only groups were exercised on a treadmill, running for 30 minutes at low intensity every other day for 4 weeks.
The lactate and caffeine exercise group experienced a significant increase in the mass of the lower leg muscle groups gastrocnemius (GA) and tibialis anterior (TA) relative to both the sedentary and exercise only groups. The lactate and caffeine exercise group experienced a significant increase in myogenin and follistatin expression of GA relative to the exercise only group. These results suggest that administration of LC can effectively increase muscle mass concomitant with elevated numbers of myonuclei, even with low-intensity exercise training, via activated satellite cells and anabolic signals.
Takarada Y, Sato Y, Ishii N. Effects of resistance exercise combined with vascular occlusion on muscle function in athletes. Eur J Appl Physiol 2002;86:308–14.
Takarada Y, Takazawa H, Sato Y, Takebayashi S, Tanaka Y, Ishii N. Effects of resistance exercise combined with moderate vascular occlusion on muscular function in humans. J Appl Physiol 2000;88:2097–106.
Takarada Y, Tsuruta T, Ishii N. Cooperative effects of exercise and occlusive stimuli on muscular function in low-intensity resistance exercise with moderate vascular occlusion. Jpn J Physiol 2004;54:585–92.
Yoshimi Oishi , Hayato Tsukamoto , Takumi Yokokawa , Keisuke Hirotsu , Mariko Shimazu , Kenji Uchida , Hironori Tomi , Kazuhiko Higashida , Nobumasa Iwanaka , Takeshi Hashimoto Mixed lactate and caffeine compound increases satellite cell activity and anabolic signals for muscle hypertrophy. Journal of Applied Physiology January 2015
Fry CS, Glynn EL, Drummond MJ, Timmerman KL, Fujita S, Abe T, et al. Blood flow restriction exercise stimulates mTORC1 signaling and muscle protein synthesis in older men. J Appl Physiol 2010;108:1199–209.
Fujita S, Abe T, Drummond MJ, Cadenas JG, Dreyer HC, Sato Y, et al. Blood flow restriction during low-intensity resistance exercise increases S6K1 phosphorylation and muscle protein synthesis. J Appl Physiol 2007;103:903–10.
Goto K, Ishii N, Kizuka T, Takamatsu K. The impact of metabolic stress on hormonal responses and muscular adaptations. Med Sci Sports Exerc 2005;37:955–63.