This study helped show the effect BFR has on growth hormone and protein synthesis

Key Takeaways

This study measures a ton of bio markers that aren’t measured in studies of its kind. It shows us that protein synthesis (your body rebuilding muscle tissue after exercises) is 46% higher in people that have performed blood flow restriction exercises. We see low-weight Blood Flow Restriction Training increasing muscle growth capabilities and growth hormone comparable to training with heavy weights.

Study Structure

This was a very small study containing only six individuals in their early 30’s. 4 sets of 75 total repetitions were performed on the leg extension exercise at a very low load, that being only 20% of 1-rep max. The subjects were only allowed to rest for 30 seconds between sets. They had a cuff inflated to 200 mmHG, which is comparable to a “moderate” level of tightness that we’ve seen in the previous studies we looked at (most studies from Japanese researchers set pressures around 240 mmHG).  This group was compared to a control group, who performed the same exact exercise routine and wore the same type of cuff, but the only difference in this group being the cuff was never inflated during the protocol. 

What makes this study very interesting in comparison to others of its kind is the vast array of markers that they tested for in its subjects. They analyzed growth hormone (GH), Insulin-Like Growth Factor 1 (IGF-1), testosterone, and cortisol (also known as the “stress hormone”). Particular antibodies were examined along with blood pH. Lactate is a waste product of vigorous exercise when the muscle can’t receive sufficient oxygen – people often improperly call this “lactic acid.” The analysis that sticks out the most here is the test for Muscle Fractional Synthetic Rate (FSR). Basically, this measurement is a direct measure of protein synthesis, which is what causes the repair and regeneration of muscle cells after intense exercise.

What They Found

The findings in the study greatly favored the blood flow restriction (BFR) group, as FSR increased by 46% in the 3 hours after the workout, compared to the control group, which didn’t see any increase in this factor. This is primarily due to the fact that BFR tends to enhance a pathway that is primarily responsible for muscle protein synthesis, which they refer to in the literature as mTor, or mTor signalling. 

Another benefit that was seen was that the increase in GH was comparable to traditional heavy-load resistance training. This works as a benefit for those who may have joint issues as a hack to GH increases without needing to lift heavy loads. 

Study Being Summarized

Fujita, Satoshi, et al. “Blood flow restriction during low-intensity resistance exercise increases S6K1 phosphorylation and muscle protein synthesis.” Journal of applied physiology 103.3 (2007): 903-910.

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