Blood flow restriction has been demonstrated to be a powerful tool for improving strength, recovery, and endurance while utilizing lighter training loads and shorter sessions.
Exactly how hard should you push your sets under BFR though? Should you push until concentric failure, or can you stop a few reps shy and still catch the strength and hypertrophy benefits?
We’ll explore precisely that in this article, providing you with a clear analysis on what the existing literature tells us and how you can apply it for optimal performance.
Up until fairly recently, it was proposed that in order to gain maximum benefit from BFR training, you needed to train at a load anywhere from 20-40% of your 1 rep max until concentric failure during your sets.
This is an effective means of driving a muscle-building stimulus, but it’s worth digging a bit deeper to reveal whether or not this is absolutely necessary, because training to failure comes at a significant energy cost.
After all, a hallmark benefit of BFR training is that it enables you to achieve similar hypertrophy and strength adaptations as traditional resistance training at a fraction of the load, sparing your joints and overall systemic fatigue.
Sure, an easy argument can be made that all else equal, training to failure under BFR is less fatiguing than training to failure with traditional resistance training, but it’s still considerably more fatiguing than stopping 1-5 reps shy of failure.
If you’re training under BFR to maximize stimulus and minimize fatigue (perhaps during a deload), it would make logical sense to stop shy of failure if you can achieve similar results that way.
So can you?
Thankfully, there are some phenomenal exercise science researchers who’ve investigated this thoroughly - we’re going to break down their findings and provide you with well-grounded guidance based on what the literature tells us today.
Right out of the gate, it’s a bit of a misnomer that you’d need to train to failure with BFR to gain strength and muscle mass. Most of the research demonstrating BFR’s efficacy has not involved training the subjects to failure to begin with!
Some research has though, and it seems the appropriate question to ask (and probably the reason you’re reading this article) is “Can you get the SAME results without training to failure under BFR?”
BFR Training to Failure vs. Non-Failure Study
A recent study by Bjørnsen and colleagues explored this closely.
The researchers took 17 untrained men through two blocks of training and compared how each protocol worked. The interesting thing about this study is that it used a within-subject unilateral design, meaning each subject served as their own control.
In other words, each of the 17 men performed under BFR to failure on one leg during both blocks, while the other leg aimed to avoid failure (but still trained under BFR).
The study took place over two separate 5 day training blocks, separated by a 10 day rest period between blocks (5 days of training, 10 days of rest, 5 days of training).
During each block, the subjects performed one training session per day for days 1-3, and two training sessions per day on days 4 and 5, for a total of 7 sessions in 5 days.
Training session breakdown:
Leg # 1 (train to failure leg) - 4 sets of knee extensions to failure under BFR
Leg # 2 (non-train to failure leg) - 4 sets of knee extensions utilizing a popular 30-15-15-15 protocol (30 reps on set one, with the following 3 sets at 15 reps and 30 seconds rest between sets).
Let’s take a look at how it shook out.
Broadly, both protocols produced very similar outcomes in strength gain, muscle thickness and cross sectional area, and myonuclei and satellite cell responses.
There’s a caveat though.
The failure protocol resulted in greater perceived exertion during the sessions and greater soreness throughout the study.
Regarding the strength gains, we saw a common exercise science theme play out here called delayed supercompensation.
This just means that when you’re training for a characteristic like power, speed, or strength, the accumulated fatigue associated with that training can prevent you from expressing the improvements you’ve made in those qualities. Once you deload or rest we see a super compensation effect, where the adaptations you made during that phase come to fruition.
The subjects experienced this in both legs.
Immediately following the final block, maximum voluntary isometric contraction strength was below baseline! Max 1 rep max strength did not improve at all.
However, both measures continued to increase for 24 days after the final training block, resulting in significant strength improvements (6-11%) in each leg.
So what does this study tell us?
We can gather a pretty clear picture that you can achieve equal results with BFR whether you train to failure or you stop a few reps shy. However, these similar results come at a much lower energy cost when you’re not training to failure - less soreness, perceived exertion, and accumulated fatigue.
Before we get ahead of ourselves and call this the end of the story, it’s important to acknowledge some of the limitations of this study.
First and most obvious, these subjects were untrained. We can’t immediately assume that if a protocol works with untrained subjects, it will work to the same degree with someone who’s been training for years.
However, this is not the only study showing BFR’s efficacy - plenty have been conducted with trained subjects that showed favorable results as well. The within-subject unilateral design bolsters the credibility of this data as well since technically, both legs were equally as untrained from the onset.
The second limitation is time frame. The study took place over two separate 5 day blocks with a 10 day rest period between blocks. What does BFR training over the period of months or years look like? That’s something researchers will continue to investigate over time.
Lastly, it’s worth mentioning that some of the subjects in the non-failure group actually made it to failure on the 30-15-15-15 protocol.
Despite this, there was still a clear distinction between groups. Failure only occurred in about half the subjects and only on one set (the final set) in the first block of training.
It did not occur at all in the second block.
Ultimately, when weighing this study with the abundance of additional existing BFR literature, we can be confident that non-failure BFR training is not only effective, but likely just as effective as training to failure (at less of an energy cost).
As legendary sports scientist Greg Nuckols puts it, if you want to cover all your bases, the 30-15-15-15 protocol is a great place to start. Don’t worry about training to failure on every set - just pick a weight that brings you close to or all the way to failure on your last set.
If you apply that to your training you’ll not only drive incredible stimulus to the muscle, but also minimize fatigue, so you can keep pushing the boundaries of your performance.
If you’d like to take the guesswork out of your BFR training, SAGA’s bluetooth-enabled BFR cuffs calibrate to precision with a single tap and allow you to select your desired occlusion percentage.
That’s all for today, but we’ll see you in our next article in this blood flow restriction series.