Thursday, September 24, 2015

Blood Flow Restriction in Athletes: Did We Get it All Wrong? Must BFR-Cuffs be Worn After, not During Each Set?

If that's you. It's well possible that you've done it all wrong. Wearing the cuffs after the set may be the way to go!
You may have followed up on my recent suggested read in the SuppVersity Facebook News and read up on the recent scientific debate on the (non-)usefulness of training with cuffs (BFR-style). Well, after reading the full text of a recent study by Conor W. Taylor et al. (2015), I have to say: Maybe we have only done it wrong.

In their study, the researchers from the Loughborough University in Leicestershire had their subjects, 28 healthy trained males who were cycling 120 ± 66 km per week, all cuffed up after each set of a standardized sprint training. That's very dufferent from trying to sprint with cuffs on your legs (and usually reduced intensity) and appears to be - that's at least what the study results suggest - a potential game-changer.
You can learn more about BFR and Hypoxia Training at the SuppVersity

BFR, Cortisol & GH Responses

BFR - Where are we now?

Hypoxia + HIIT = Win?

BFR for Injured Athletes

Strength ⇧ | Size ⇩ w/ BFR

Training & Living in Hypoxia
Now, the good news is: The study involved both an acute and chronic exercise + BFR study of the effects of post-spring-training blood flow restriction.
  • In Study 1, a between groups design determined whether 4 weeks (2 d/wk) of SIT (repeated 30 s maximal sprint cycling) combined with post-exercise blood flow restriction (BFR) enhanced maximal oxygen uptake (VO2max) and 15km cycling time trial performance (15km-TT) compared to SIT alone (CON) in trained individuals.
  • In Study 2, using a repeated measures design, participants performed an acute bout of either BFR or CON. Muscle biopsies were taken before and after exercise to examine the activation of signalling pathways regulating angiogenesis and mitochondrial biogenesis.
As a science expert you'll know that study 2 probably wouldn't have been done if the results of Study 1 had not been encouraging.
Figure 1: Pre- to post-changes in VO2max (absolute, top-right), relative (top-left), MAP (bottom-left), 15k time trial (bottom-right) | I marked the individuals who saw positive and negative effects for you, the # on the buttons indicate the number of subjects who benefited (green) or saw no / detrimental effects (orange | original data from Taylor. 2015).
"Encouraging", in this case, means that the scientists observed a highly significant VO2max with post-workout BFR by 4.5% (P = 0.01) but was unchanged after CON.
So, does the increase in VO2 have anything to do with my gainz? Directly? No. But if there's an effect on hypertrophy it would - just as the effect on VO2 found in the study at hand - depend on increases in the stress response. Now, the more recent studies have shown that the necessary reduction in weight lifted when you do it with cuffs makes it practically useless for athletes. So, in conjunction with the study at hand, it's only logical to ASSUME that using the hypoxic stress after a set COULD provide an ADDITIVE stimulus (normal BFR training takes away from the regular stimulus, because it will.force athletes to refuce the weights and cannot fully compensate for that | see the results of this study.
The small advantage in the 15k time trial, on the other hand, did not reach statistical significance. That's "bad news", but the trend indicates that this might change with long(er) term studies.
Figure 2: Changes (%) in physiological and performance variables before and after CON and BFR training interventions (Taylor. 2015).
Whether that may change with a longer-term study will still have to be elucidated. What appears to be certain, though, is that the existing difference is not mediated by changes in PGC-1α, VEGF and VEGFR-2 mRNA expression between protocols. In fact, of all parameters the scientists tested to identify the underlying mechanism only the  mRNA levels of HIF-1α, the hypoxia-inducible factor 1-alpha, of which a recent paper by Lindholm and Rundquist (2015) highlights that it would be otherwise attenuated with long-term endurance exercise and thus lead to a blunted response to long-term exercise training (that's why rookies see fast results and pros only marginal results), differed significantly between groups (P = 0.04) 3 h after the cuffs were applied to the subject's legs.
Bottom line: While it is possible that the differences the scientists observed were triggered by BFR induced extra-stress (namely hypoxia, thus increases in Hypoxia-inducible factor 1-alpha), we will need additional (longer-term) studies to prove practically relevant improvements in time-trial performance and identify a definitive mechanism.

The benefits of blood flow restriction in healthy athletes may be less pronounced than the advocates would have it. If reversing the order of exercise and applying the cuff can solve that, this would be awesome!
With that being said, the results - although not fully convincing, yet - are quite exciting. After all, they really suggest that instead of training with cuffs, athletes who want to benefit from the additional low oxygen stress would have to copy the protocol of the study at hand and thus apply lower limb blood flow restriction within 15s of each sprint... or after each set of leg curls or squats? Well, that's a question we cannot answer based on the study at hand, but it would certainly be interesting to test what would happen if you applied the cuffs right after a set of biceps curls. Well, as you can see, there's still a lot of research to be done and as you know, the SuppVersity is going to be where you can learn about the results first ;-) | Comment on Facebook!
  • Lindholm & Rundqist, et al. "Skeletal muscle HIF-1 and exercise." Experimental Physiology (2015): Accepted Article.
  • Taylor, et al. "Acute and chronic effect of sprint interval training combined with post-exercise blood flow restriction in trained individuals." Experimental Physiology (2015): Accepted Article.