BFR Shown to Increase Strength and Growth Hormone in as Little as One Week

This is the study we’re summarizing

Abe, T., Yasudu, T., Sato, Y., Kearns, C., Inoue, K., Koizumi, K., & Ishii, N. (2005). Skeletal muscle size and circulating IGF-1 are increased after two weeks of twice daily ‘‘KAATSU’’ resistance training. International Journal of KAATSU Training Research,1, 6-12.

Key Takeaways

  • 7% of the growth experienced by the BFR group occurred in week 1 (topping out at 9% after two weeks)
  • BFR participants saw a strength increase of 16.8% in their squat and a 22.6% increase in their leg curl  (while lifting low loads)
  • Participants using BFR saw a 3X increase in growth hormone (GH) over what we typically see in typical strength training. 

Study Structure

In a 2005 study, researchers investigated the effects of training twice daily with very low loads (20% of the individuals 1-repetition maximum), with 9 of them utilizing traditional blood flow restriction (BFR) while the other 7 performed this low-load training in isolation without BFR. These individuals were recreationally active, but hadn’t participated in a weight training regimen in the 6 months prior. This training took place over the course of 2 weeks.

This study primarily concerned the lower body – squats and leg curls were the exercises performed. Three sets of 15 repetitions were done by both groups, with 30 seconds of rest being provided between sets and exercises. The researchers chose to use a pressure of approximately 240 mmHg for the cuff on the thighs, as this is what is suggested by Takarada and colleagues, who are other well-respected researcher in the field of BFR. 

Summary of the Findings

The results illustrated that cross-sectional area (a measurement used to estimate strength and power of the muscle) increased by not only 7% by the end of the first week, but by a total of 9% by the end of the 2-week study. Compare this to 2% for the low-load only group by the end of the study. Also, strength was shown to increase at a greater rate in the BFR group in both the squat and leg curl exercises (16.8% and 22.6% respectively) as compared to the low load group (8.9% and 1.3% respectively).

So, what is notable about this study is that the increases of strength that were seen here are comparable to traditional high-intensity strength training. Interestingly enough as well, increases in growth hormone were seen 3x higher than traditional strength training. This is what appears to cause these substantial results in comparison to simply training with light weights by themselves.

This study makes it clear that BFR training is effective almost immediately (i.e. in one week these participants saw 7% of their growth) but it’s comparing light weight to light weight not light weight with BFR to traditional heavier strength training loads.  This was one of the first studies that made it clear that if you need to lift light weight during injury, recovery, or during any high volume accessory work you should really be doing it occluded or your sort of missing out on a lot of growth and strength as the control group here did.  

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