Can we increase muscle strength with half the effort?
Improving someone’s muscular strength and size is extremely important and a key focus for physiotherapists as it is lost quickly due to inactivity but takes a very long time to come back. In my opinion one of life’s biggest discrepancies!
The current ACSM guidelines for increasing strength recommend lifting loads of over 60% of your one rep max (1RM) (1). For physically challenged populations, including the elderly, arthritis sufferers and those post surgery, this load is not possible, one reason is down to pain. We are therefore left with a bit of a dilemma?!
Everybody loves an easier option and fortunately a novel method of resistance training has become prominent in the research world over the last decade which utilises loads of 20-30% of 1RM that achieves similar, significant improvements in strength as lifting 60% of 1RM (2). It is called blood flow restriction training (BFRT) also known as occlusion or kaatsu training.
It basically involves decreasing blood flow from a muscle (occluding veins) by the application of a pneumatic wrapping device around the proximal part of the target muscle. In this way, blood goes into the muscle but can’t escape. It has been hypothesised that BFRT increases muscular strength and hypertrophy through a variety of mechanisms including metabolic accumulation, fast-twitch muscle fiber recruitment, increased protein synthesis and cell swelling (3,4). I wrote about this in more detail a couple of years ago here.
A big issue with this type of training is that using pneumatic wrapping devices (ie modified blood pressure cuffs) is expensive and not accessible or practical to use outside of a laboratory environment. The effectiveness of practical BFRT (PBFRT) using inexpensive elastic wraps has been researched over the last 3 years which introduces a new concept for rehabilitation for physiotherapists.
Yamanaka et al (5) and Luebbers et al (6) assessed the effectiveness of PBFRT (20% of 1RM) on muscular strength assessed by 1RM change in collegiate athletes (n=16 and n=62 respectively). Yamanaka et al (5) participants performed four sets of bench press and squat exercises and showed bench press 1RM (5.2kg; p60% of 1RM) was supplemented with PBFRT (20% of 1RM), 1RM squat measurement significantly increased compared to HIRT combined with supplementary training (20% of 1RM) without PBFRT (p
Wilson et al (7) assessed young males (n=12) performing leg press at 30% of 1RM for four sets using different PBFRT conditions. These were control= 0/10 or moderate pressure= 7/10 subjective perceived wrap tightness. The amount of PBFR was quantified by ultrasonography and at a moderate perceived wrap tightness (7/10) complete venous occlusion occurred but not arterial and at a perceived wrap tightness of 0/10 no BFR occurred. Their results showed that blood lactate, quadriceps cross-sectional area (MRI) and knee extensor muscle activity measured by EMG (mV) significantly increased in the moderate tightness (7/10) PBFRT group, with no change in the control group (0/10). This 7/10 perceived wrap tightness PBFRT application was also used by Lowery et al (8) who performed a crossover study (n=20) using PBFRT for the elbow flexors at 30% of 1RM for 30 repetitions (7/10 tightness) or 60% of 1RM for 15 repetitions (0/10 tightness) for four weeks, for a combined 8-week training duration. They showed that PBFRT and HIRT both led to significant increases in bicep hypertrophy (ultrasonography). Showing that PBFRT (30% of 1RM) resulted in the same hypertrophy gains as HIRT (60% of 1RM) without PBFR.
My critique of the above studies is that exercise technique, ie range of motion or contraction speed, was not described or standardised. This could effect some subjects having varied times under tension which in turn effect the strength gains observed. This frustrates me in a lot of intervention studies I read! Also, blinding of the outcome assessors only occurred in the Lowery study which could lead to added encouragement given to the PBFRT subjects especially during maximal strength testing, possibly effecting the results.
For my Masters I performed a study, which is currently awaiting acceptance for publishing . It looks at the effect of PBFRT during a bodyweight single leg squat exercise to fatigue on muscular strength assessed by dynamometry and attempted to improve upon the previous mentioned flaws in methodology. The exercise technique and speed was standardised and controlled and the outcome measure assessor were blinded to group allocation. One group performed the exercise with elastic wraps at a tightness of 7/10 with the controls performing the same exercise with wraps on at 0/10 tightness. The only difference we found between groups was a significant increase in quads concentric strength after 6 weeks of training in the PBFRT group but there was no difference between groups.
Place the elastic wrap as high above the target muscle as possible (eg thigh if training lower limb or arm for thr upper limb) a subjective tightness of 7/10 is the most evidence based and effective application at the moment.
The research to date that uses bodyweight exercise alone during BFRT in my opinion shows that it is not effective at increasing strength (although some papers say otherwise). However loads of 20-30% of 1RM, 15-30 reps with 30-60 sec rest between sets, has been supported by meta analytical data (2) and evidence based training guidelines (9) to significantly increase strength from the elderly to elite athletes.
The current research on PBFRT suggests that it could provide a similar benefit to using pneumatic expensive cuffs but is certainly not definitive yet (5-8). However it is still a possible option for elderly and also post surgical patients who cannot tolerate heavy loads to aid in increasing their strength and ultimately function due to it being implemented sooner in their rehab process and possibly speeding up their recovery.
‘Is it safe’ I hear you cry?
Well, when I first heard about this I thought that it can’t possibly be safe to cut off your blood supply! It goes against everything logical in anatomy and physiology. Quite rightly safety of BFRT has also been prevalent in the research community. A survey of over 1800 people performing BFRT reported the most common side effects to be subcutaneous haemorrhage and numbness, which were experienced by 13.1 and 1.3% of participants, respectively (10). However, these symptoms are often dissipate as the individual becomes more accustomed to this training modality. Reviews by Loenneke et al (11,12) have shown BFRT to be a safe and produce similar responses on blood pressure, blood coagulation, delayed onset of muscle soreness (DOMS) and oxidative stress that has been observed during regular resistance training. Contraindications include a history of deep-vein thrombosis, pregnancy, varicose veins, high blood pressure and cardiac disease (11,12).
Numerous studies on BFRT and the current research on PBFRT show substantial increases in muscle strength and growth when low-load lifting (20-30% 1RM) is combined with flow restriction (2,5-8). Gains are often on par with traditional heavy-load training and sometimes even greater. BFR research performed during bodyweight exercise only, suggests this load of exercise is insufficient to increase muscular strength.
Although future PBFRT research needs to perform rigorous and standardised methodologies to substantiate previous findings and a wrap tightness of 7/10 being the most effective. Clinical guidelines have been based on much less substantial evidence in the past! This method of training is easy and cheap to implement with the wraps bought for the study I performed costing £3 a pair on ebay!
It could prove to be a huge benefit for the elderly, arthritic and also post op patients to improve their strength and ultimately function in a faster way, and requiring less than half the effort of traditional resistance training methods.
I’d appreciate any feedback, comments and I’m very happy to answer any questions.
1, American College of Sports Medicine. Guidelines for Exercise Testing and Prescription (8th ed). Philadelphia, PA: Lippincott Williams & Wilkins, 2009. 65–66.
2, Loenneke JP, Wilson JM, Marín PJ, Zourdos MC, Bemben MG. Low intensity blood flow restriction training: a meta-analysis. Eur J Appl Physiol, 2012. 112(5): 1849-59.
3, Loenneke JP, Wilson GJ, Wilson JM. A mechanistic approach to blood flow occlusion. Int J Sports Med, 2010. 31:1–4.
4, Loenneke JP, Fahs CA, Rossow LM, Abe T, Bemben MG. The anabolic benefits of venous blood flow restriction training may be induced by muscle cell swelling. Medical Hypotheses, 2012. 78: 151–154.
5, Yamanaka T, Farley RS, Caputo JL. Occlusion training increases muscular strength in division IA football players.The Journal of Strength and Conditioning Research, 2012. 26: 2523-2529.
6, Luebbers PE, Fry AC, Kriley LM, Butler MS. The Effects of a Seven-week Practical Blood Flow Restriction Program on Well-trained Collegiate Athletes. J Strength Cond Res, 2014. 28(8): 2270–2280.
7, Wilson JM, Lowery RP, Joy JM, Loenneke JP, Walters JA, Amsden CE. Practical blood flow restriction training increases acute determinants of hypertrophy without increasing indices of muscle damage. J Strength Cond Res, 2013. 27(11): 3068–3075.
8, Lowery RP, Joy JM, Loenneke JP et al. Practical blood flow restriction training increases muscle hypertrophy during a periodized resistance training programme. Clin Physiol Funct Imaging, 2014. 34(4): 317-21.
9, Scott BR, Loenneke JP, Slattery KM, Dascombe BJ. Exercise with Blood Flow Restriction: An Updated Evidence-Based Approach for Enhanced Muscular Development. Sports Med, 2014 (epub ahead of print).
10, Nakajima T, Kurano M, Iida H. Use and safety of KAATSU training: results of a national survey. Int J KAATSU Train Res. 2006. 2 (1): 5–13.
11, Loenneke JP, Wilson JM, Wilson GJ, Pujol TJ, Bemben MG. Potential safety issues with blood flow restriction training. Scand J Med Sci Sports, 2011. 21: 510-518.
12, Loenneke JP, Thiebaud RS, Abe T. Does blood ﬂow restriction result in skeletal muscle damage? A critical review of available evidence. Scand J Med Sci Sports, 2014. 25(4): 521-534.