BFR GUIDE · SAFETY
Is blood flow restriction safe? Side effects, clot risk, and who should not do it.
BFR is safe for screened people under supervision. Here are the measured numbers, the side effects, and who needs a closer check first.
THE SHORT ANSWER
Is blood flow restriction training safe?
In screened people, under a physiotherapist, with pressure set from occlusion pressure, the measured rates of serious harm are low. A 2006 Japanese survey of 12,642 people reported venous thrombosis in 0.055 percent and pulmonary embolism in 0.008 percent. A 2020 review of 19 clinical studies found people doing BFR were no more likely to have an adverse event than people doing exercise alone. Bruising under the cuff, in 13.1 percent, and short-lived soreness are the common effects.
Slowing blood flow in a limb is one of the things that can cause a clot, so the question deserves a straight answer from the data: the largest survey, the pooled clinical trials, and the blood tests researchers ran to look for clotting changes. Then the screen your physiotherapist runs before the cuff goes on.
AT A GLANCE
- Largest survey
- 12,642 people, 105 facilities, Japan, 2006
- Venous thrombosis
- 0.055 percent; pulmonary embolism 0.008 percent
- Clinical trials
- 19 studies, 322 people: no more adverse events than exercise alone
- Common effects
- Bruising under the cuff 13.1 percent; numbness 1.297 percent; soreness
THE BIG QUESTION
Does the cuff cause blood clots?
Rarely, in the data. The 2006 survey by Nakajima and colleagues covered 12,642 people and reported venous thrombus in 0.055 percent and pulmonary embolism in 0.008 percent. The 2019 position stand reports no rise in D-dimer, a blood marker of clotting, after BFR exercise, and an increase in the protein the body uses to dissolve clots. The 2020 review by Minniti and colleagues pooled 19 studies, 322 people: rare events occurred in 3 of 168 BFR participants and 0 of 154 controls, one of them a deep vein thrombosis in an arm, with no excess of adverse events overall. Low is not zero, and the screen is why it stays low.
COMMON EFFECTS
What you are likely to notice
In the Japanese survey the most common effect was bruising under the cuff, at 13.1 percent, then numbness at 1.297 percent and feeling faint at 0.277 percent. The position stand adds muscle swelling that settles within 24 to 48 hours and soreness that is short-lived, and links numbness to pressures set outside the guidelines.
Bruising: 13.1 percent
Marks where the cuff sat. Fades over days. More likely on blood thinners.
Numbness: 1.297 percent
Not expected. Report it at once; the pressure is lowered or the cuff removed.
Feeling faint: 0.277 percent
Usually on standing after a hard set. Sit, let it pass, and say so.
Soreness and swelling
Expected for a day or two. Swelling back to baseline within 24 to 48 hours.
THE SCREEN
Who should not do BFR, and who needs a closer look
The position stand names the risk factors that matter most: a prior clot, major surgery, immobility and cancer. Our screen builds on those and repeats at every visit.
BFR is not applied while
You have an untreated or recent deep vein thrombosis or pulmonary embolism; an active infection or wound in the limb; an unstable heart condition; or a condition your physician has said rules out restricted blood flow.
A closer screen or physician clearance first
A history of clots or a clotting disorder; blood thinners; blood pressure that is not well controlled; vascular disease or varicose veins in the limb; cancer under treatment; pregnancy; sickle cell disease; recent major surgery with restricted mobility.
Also raised at the screen
Diabetes with nerve or circulation changes; lymphedema or lymph node removal in the limb; a vascular access such as a fistula; nerve injury in the limb; any medication that affects bleeding or clotting.
General information only. BFR is applied by a physiotherapist after a health screen. Do not buy a cuff and copy a protocol from this page.
WHEN TO STOP
Warning signs during and after
During a session: numbness, pins and needles, a cold or pale hand or foot, chest pain, shortness of breath, or faintness that does not pass when the cuff is released. Afterwards: a calf or limb that is swollen, warm, red or tender in one area and stays that way is a same-day medical question, and chest pain, shortness of breath or coughing blood is a 911 call. Ordinary soreness and cuff marks are expected and settle.
BOOK OR ASK
Tell your physiotherapist before BFR if you have
- Any history of a blood clot, or a family history of clotting disorders
- Blood thinners or any medication that affects clotting
- A heart or blood vessel condition, or uncontrolled blood pressure
- Surgery, a hospital stay or a period of immobility in the last few months
- Pregnancy, cancer treatment, or an infection or wound in the limb
BFR AT LAUNCH REHAB · NEW WESTMINSTER ONLY
Blood flow restriction is used inside a physiotherapy visit at our New Westminster studio, by Alex Carrod, registered physiotherapist. Book a physiotherapy initial assessment and mention BFR, or call the studio and describe the injury. There is no separate BFR appointment type and no separate BFR fee.
New Westminster
219-800 Carnarvon St, New Westminster, BC V3M 0G3
Inside Shops at New West, above New Westminster SkyTrain station
About this studioFAQ
Common questions.
Rarely, in the data. The 2006 survey of 12,642 people reported venous thrombosis in 0.055 percent. The 2020 Minniti review found one deep vein thrombosis among 168 BFR participants and no excess of adverse events over exercise alone.
SOURCES
Where the facts on this page come from.
- Nakajima T, et al. Use and safety of KAATSU training: Results of a national survey · International Journal of KAATSU Training Research, 2006;2:5-13, via J-STAGE · Published 2006. Accessed 22 September 2026
- Minniti MC, et al. The Safety of Blood Flow Restriction Training as a Therapeutic Intervention for Patients With Musculoskeletal Disorders: A Systematic Review · American Journal of Sports Medicine, 2020;48(7):1773-1785, via PubMed · Published June 2020. Accessed 22 September 2026
- Patterson SD, et al. Blood Flow Restriction Exercise: Considerations of Methodology, Application, and Safety · Frontiers in Physiology, 2019;10:533 · Published 15 May 2019. Accessed 22 September 2026
- Lin Q, et al. Effects of Low-Load Blood Flow Restriction Training on Muscle Volume After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis · Orthopaedic Journal of Sports Medicine, 2024;12(12), via PubMed · Published December 2024. Accessed 22 September 2026
- College of Health and Care Professionals of BC (physiotherapist regulator) · CHCPBC · Accessed 22 September 2026
KEEP READING
More from the BFR guides.
- Booking, cost and safety
Your first BFR session
The screen, the calibration, the first set of thirty, and how your leg feels afterwards.
READ - Start here
How BFR works
A cuff, a light weight, and why the muscle responds as if you lifted heavy.
READ - Knees, surgery and tendons
BFR after ACL surgery
The strongest evidence: protecting the quad in the weeks when the graft cannot take heavy load.
READ
FROM THE JOURNAL
Related reading from our clinicians.
READY?
Book blood flow restriction physiotherapy in New Westminster.
Applied by a registered physiotherapist inside a physiotherapy visit at our New Westminster studio, after a health screen. Not sure BFR fits your injury? Call 604-519-0777 and describe what heavy loading does to the joint.