Of all the bizarre fitness trends on TikTok, Blood Flow Restriction Training (or BFR training) may have caught your eye because it looks like it might actually be a terrible idea for your health.
The scene is usually this: an athlete strapping on what look like either large elastic bands, snipped seatbelts or a pair of blood pressure cuffs to their biceps or upper thighs, being sure to partially cut off the circulation to their limbs. Then they jump on the treadmill for a strenuous jog or grab a pair of dumbbells for a few curls.
This unorthodox workout hack has gained attention as a promising method to enhance sports performance, but does it work? And if so, what’s the science behind it? And, of course, is partially cutting of the circulation to stressed muscles even safe?
These questions led a group of researchers to go deep on science of BFR training, and the results are actually quite promising, particularly for runners looking to squeeze out some extra fitness gains without having to stress their entire bodies with yet another big interval workout.
The study, a meta-analysis published recently in the Journal of Sports Medicine and Physical Fitness, suggests that there are some real performance gains to be had, particularly for runners using BFR training, but there are also limitations.
But first, what the heck is blood flow restriction training, and why did anyone ever think this was a potentially game changing training tactic?
As it turns out, restricting blood flow to the limbs while exercising was not invented by some intrepid Instagram influencer. BFRT has actually been around as an ad hoc concept for many years. A basic version was originally developed in Japan during the 1960s, called KAATSU training. And despite its lengthy history and recent social media trendiness, its effectiveness was never definitively proven.
Various exercise physiologists have studied aspects of this training method over the years, but questions lingered about whether it truly works or is merely another fleeting social media fitness trend based on folk wisdom. Part of the problem was that each BFR training related study focused on one specific aspect of the regemin, leaving the bigger question of how or why it works unanswered. But this most recent study took a different approach, gathering all previously available research, providing scientists with a more nuanced understanding about how BFR training produce what are, at times, significant gains in certain athletes.
The Theory Behind Blood Flow Restriction Training For Runners
The aim of BFR training is to mimic the effects of high-intensity exercise by recreating an oxygen-depleted environment, but instead of, say, training at altitude or in heat, where the entire body is heavily stressed, BFR training targets only the constrained area of the body.
The training method is pretty straightforward: blood flow restriction training involves the application of a specialized tourniquet or cuff to either the upper or lower limb (depending on which sort of workout the athlete is targeting). With more advanced BFRT products, the cuff is then inflated to a specific pressure with the aim of temporarily limiting blood flow to specific muscles during exercise. This reduction in blood flow challenges the athlete’s muscles during the exercise, making them work harder. It’s not dissimilar to wearing a blood pressure cuff during a workout.
The restriction of blood flow caused by the cuff speeds up muscle fatigue, reducing the need for intense running or heavy lifting to achieve comparable gains. For runners, it would usually involve placing a specialized cuff around the upper thighs before a run. Then, the idea is to just carry on with the basic exercise — no need to attempt an intense workout, as the restricted limbs are already in a heavily taxed state.
To put it simply, you get a similar bang for your buck but with less stress imposed on the majority of the body.
The hack is that BFR training works by putting more stress on the body’s metabolic processes rather than the traditional emphasis on the intensity of muscle contractions.
As a result, it can lead to less breakdown of muscle fibers and subsequent soreness and fatigue, compared to conventional high-load training methods while still effectively engaging the metabolic system
Check out this video below for a visual guide to blood flow restriction training:
Three Key Findings From The Study
The reason why this study is so promising is because it’s actually a sort of “study of studies.” Meta-analyses take all available pre-existing studies on a subject and then pare them down to the most relevant ones in order to produce clear insights. The researchers looking at BFRT initially identified 249 studies, and then narrowed their focus to 93 eligible articles. Following a rigorous screening process, 18 studies were included in the final systematic review.
The meta-analysis highlighted three noteworthy insights into the effects of BFRT on athletic performance.
#1: Maximal Oxygen Uptake:
BFR training was found to have a substantial positive impact on maximal oxygen uptake.
This finding is particularly significant as increased oxygen uptake contributes to improved endurance, a key when running a marathon, particularly in the final 10 kilometers, which is statistically when the majority of runners lose the most amount of time in a race.
The researchers admit that they don’t entirely understand why BFRT has this seemingly magic effect on the body’s ability to more efficiently take in oxygen.
One theory is that the stress induced by blood flow restriction training can lead to increased production of metabolic byproducts, such as lactate and hydrogen ions. The body responds to this stress by increasing oxygen delivery to the muscles to support energy production.
Maximal oxygen uptake, essentially how efficiently your body uses oxygen during intense exercise, is like the powerhouse behind your endurance in running. The better this system functions, the longer you can keep pushing yourself without feeling completely drained.
So, when we talk about running performance, having a maximal oxygen uptake means you’ve got a better shot at maintaining a faster pace for an extended period.
Envision a 5K race, where the pace starts as challenging but manageable—often described by runners as “comfortably uncomfortable” for the initial kilometre or two.
Then, between the 3-4K mark, the pace becomes noticeably more demanding. Improved oxygen uptake becomes a game-changer in this scenario, allowing runners to navigate this challenging phase more effectively.
With enhanced endurance, they can sustain their goal pace for a longer duration, preventing premature fatigue and significantly contributing to improved overall performance.
#2: Vertical Jump Height:
The meta-analysis demonstrated a significant improvement in vertical jump height within the BFRT group compared to the control group.
BFR training may preferentially recruit fast-twitch muscle fibers, which are responsible for generating explosive force and power.
By stimulating these fast-twitch fibers through BFRT, runners have the potential to enhance their capacity to generate quick bursts of force and sustain performance during the demanding final stages of a longer effort, such as a marathon.
#3: Sprint Time:
And although BFR training appears to augment fast twitch muscle fibers and trigger big gains in explosive power, sprinters out there looking to shave a couple of seconds or milliseconds off their times, the study paradoxically did not reveal a significant improvement in sprint time.
So, what does the science say? Is BFR Training a magic bullet?
The researchers found significant improvements observed in vertical jump height and maximal oxygen uptake, meaning that there are potentially huge benefits to incorporating BFRT into a running training plan.
BFR training allows individuals to achieve muscle benefits similar to high-intensity workouts without putting excessive strain on the body.
This makes it especially beneficial for runners during periods of high training volume, offering a way to reduce muscle damage while still obtaining positive results.
For runners exploring blood flow restriction training, seeking expert advice to navigate its complexities and uncertainties is crucial.
When cutting blood flow to specific body parts, consulting with professionals specializing in BFRT will ensure safe and effective practice.
Start BFR training in a controlled environment, with short, low-intensity treadmill or stationary bike sessions to minimize adverse effects. Progress cautiously, incorporating faster intervals as you adapt while monitoring individual responses closely.
BFRT should be supplementary, not central, in a runner’s programming; it can serve as a valuable addition when used judiciously to enhance overall performance.
However, it is crucial to acknowledge the need for further analysis to fully understand the nuanced impact of BFR training on sports performance. Although the study’s analysis offers an overview, individual responses may vary.
Factors like age, health conditions, and differing athlete profiles can influence outcomes. It’s a reminder that while blood flow restriction training shows immense promise, it’s probably not a magic bullet for every runner.
