Occlusion training during low load resistance training is a new and novel way to increase both the strength and size of skeletal muscle (Takarada et al. 2000). It is also know as blood flow restriction (BFR) or Kaatsu training. Essentially, blood flow is restricted from the target muscle with the use of a blood pressure cuff or more practically with elastic wraps. The cuff or wrap is positioned at the proximal aspect of the limb e.g. if the target muscle is the quadriceps the cuff would be placed at the top (proximal aspect) of the femur. The idea for this type of training originated in Japan around 40 years ago and has developed into a commercialised training method (known as “Kaatsu”) that is used in many training centre’s. It works on the concept of metabolic accumulation and muscle fiber recruitment. This article will go through how Occlusion / BFR training works and its evidence based application to training and rehabilitation.
It has been established within the field of exercise physiology that a number of bi-products are produced as a result of skeletal muscle contraction. Under normal conditions blood flow would flush out these bi-products however with occlusion training these metabolic products stay local to the target muscle producing a concentration peak. These bi-products are anabolic and include Insulin-like Growth Factor (IGF-1) (Takarada et al, 2004). DeVol et al. (2009) concluded that the production of IGF-1 increases in response to skeletal muscle overload. Along with testosterone, IGF-1 is the main positive regulator of skeletal muscle mass in the human body. IGF-1 is a growth hormone (GH) that is predominantly produced locally at the skeletal muscle (as well as in the liver) and it’s role is to synthesize protein uptake. It does this via numerous methods including stimulating the proliferation satellite cells (which generate new muscle fibres) and inhibiting skeletal muscle atrophy – both of which are essential requirements for the up-regulation of skeletal muscle mass. The accumulation of metabolites can increase muscle fiber recruitment through the stimulation of group III and group IV afferents . It is postulated that this may increase fast-twitch fiber recruitment by inhibiting the alpha motor neuron, which ultimately supplies slow-twitch fibers. Takarada et al. (2000) found IGF-1 to be elevated 290 times above baseline levels following 5 sets of bilateral knee extensions at 20% 1-RM with BFR in a fully occluded state (pressure cuff pressure 214 mmHg). Similarly, Takano et al. (2005) reported that partial occlusion (1.3 times greater than systolic pressure) at 20% 1-RM elevated GH levels to 100 times baseline measures. Both these studies found that exercise at the same intensity without BFR failed to result in similar GH responses. It therefore works two-fold to up-regulate as well as preventing protein degradation.
Muscle Fiber Recruitment
As we know, skeletal muscles are made up of slow twitch (type I) and fast twitch fibers, of which two variations are present in humans (type IIa and IIx). Type I fibres are slow and oxidative in nature meaning that they utilise oxygen and therefore are fatigue resistant, however this comes at the cost of them only being able to produce low amounts of force. Type II fibres on the other hand can produce large amounts of force and are glycolytic in nature meaning they are activated via anaerobic metabolism and consequently fatigue easily. These fibres however have the greatest potential for growth. Research into skeletal muscle physiology has established that when muscle is recruited to perform work, the order of recruitment of these fibres is determined by axon size i.e. I → IIa → IIx. This means we prevent unnecessary fatigue. When oxygen is limited via blood flow restriction training, even though the load of the exercise is low (which will be discussed), the type I fibres aren’t able to cope with the demands of the work and as a consequence type II fibres are recruited quicker. Thus with BFR, fast twitch fibers are able to be trained with a low intensity workload. Electromyography (EMG) studies have been completed to confirm that there is an increase in motor unit firing with BFR. The EMG data also revealed no difference between low intensity BFR training and high intensity exercise (Takarada, Tsuruta & Ishii , 2004). This means that despite the light weight being lifted, the firing rate mimics that of heavy resistance training. If this method of training is utilized regularly these fibres adapt by growing in number and size resulting in muscular hypertrophy.
There is an abundance of research that has been performed on BFR / occlusion / Kaatsu training so I have hand picked a few articles showing its effects on male, female, young, older, active, sedentary and body builder adults.
A meta analysis performed by Loenneke et al. (2012) reviewed 11 randomised control trials (RCT) that looked at the effects of BFR with low intensity resistance training compared against the effects of low intensity endurance or resistance training alone. To be considered for the analysis, subject populations had to have similar baseline characteristics (e.g. both untrained and trained) so that valid outcome measures could be made. Finally, the outcome measures had to include at least one measure of muscle hypertrophy. This meta analysis found that BFR with low intensity resistance training significantly improved muscle strength and hypertrophy in the groups that utilized BFR training. Beneficial effects were found in untrained, recreationally active and athletic populations. Although greater benefits were seen in untrained individuals this is normal regarding any exercise, due to them having more scope for improvements. Here is the link to this Meta-analysis.
Since this meta analysis, a study by Manimmanakorn et al (2012) has looked at the effect of low intensity resistance training with BFR (cuff pressure 160 – 230 mmHg), breathing in hypoxic air through a mask with their O2 saturation maintained at 80% and control group performing the exercises in normal air conditions. They used 30 female netballers from the same team (20 ± 3.3 years). The intervention for all of the groups consisted of bilateral knee flexion and extension exercise using isotonic weight machines at 20% of their 1 rep max (1RM). They had 3 sessions a week for 5 weeks with 3 sets of flexion and extension exercises during each session. The outcomes for this study included MRI to measure muscle cross sectional area and sport specific skills for power, endurance, sprinting and agility. They found that both the BFR and hypoxic training group’s significantly improved muscles size and endurance compared to the control group. They also found the BFR group to be superior in significantly improving the netball sport specific skills including power, sprinting and agility compared to both the hypoxic and control groups.
A case study that looked at how a 22 year old body builder utilized BFR with low intensity resistance training after he got injured in the gym (Loenneke et al, 2013). The bodybuilder felt a snap and pain in his right knee during a weight training session. He had a competition in 10 days so did not want to stop training, he used BFR training with an elastic wrap and performed low load reps which made the exercises pain free. On MRI it showed a significant osteochondral defect on the medial femoral condyle. Surgery for this defect was indicated for him but it was postponed for after his competition due to him being to stand and make positions that were needed for the competition, pain free. He continued using BFR with low load whilst training for the competition. Once the competition had ended he had a second MRI which showed that the defect had gone back into position and had started to heal. He also showed no signs or symptoms with full range of motion of his knee and pain during movement so surgery was not required. With these beneficial results being contributed by fluid shifts are thought to be beneficial for bone formation with previous research using low load BFR exercise have found favourable changes in bone metabolic markers (Beekley et al., 2005; Bemben et al., 2007).
Effects of Occlusion / Blood Flow Restriction Training
The evidence shows that BFR training using low intensity resistance is effective at increasing muscular strength and hypertrophy to young, older, sedentary and active adults. It has also been shown to improve bone healing and can be performed safely when injured to continue training due to utilising lighter loads then traditionally used in weight training.
BFR can be applied without performing exercise, although it wont produce muscular hypertrophy it seems to maintain or slow down the loss in muscle mass and strength that is associated with immobilization and times of unloading (e.g. recovering from surgery). BFR can also be applied during slow walking or cycling. Although this type of exercise can produce muscular hypertrophy the greatest effects are seen when combining BFR with low intensity resistance training.
Possible applications for this training method could be post-operative patients / athletes and older adults who are unable to lift 70% 1RM which is traditionally used for strength training (ACSM). Heavy loading is an issue in athletes immediately post-op however with the stated benefits already mentioned when using low intensity BFR exercises – could we be missing out on a potential method of rehabilitating our athletes back to full function in a shorter time period? BFR can be performed for the thighs, calves, upper arms, and forearms using a blood pressure cuff or tightly wrapped knee wraps. To occlude the thighs and upper arms, wrap at approximately 70% of maximum tightness around the uppermost part of the muscles. Or Jeremy Loenneke recommends the elastic wraps to be ‘snug’ but NOT excessively tight.
The optimum guidelines for the use of BFR with low intensity resistance training according to the research are below:
2-3 days a week
3-5 sets a session
15-30 reps or to fatigue using 10-30% 1RM intensity
30-45 secs rest between sets
Cuff pressures 160 mmHg – 220 mmHg or more practically to use a 7/10 subjective elastic wrap tightness at the proximal part of the upper or lower limb
When performing BFR training, the research suggests it is essential to keep the occlusion device on throughout the exercise, to allow for the necessary physiological changes to occur leading to muscular growth and to keep sessions to 30 minutes in duration.
Practical application of wraps for Occlusion / BFR training.
Risks and Contraindications
Obviously there are risks to this method of training. Firstly, it will hurt! From my experience of utilising this the onset of DOMS is far above that experienced with conventional training. There is screening questions and risk factors which should be considered prior to the session.
Pre Training Screening Questionnaire
- Do you have a personal or family history of clotting disorders (eg SLE (lupus), haemophilia, high platelets)?
- Do you have a past history of DVT or pulmonary embolus?
- Do you smoke?
- Are you on any medication including the contraceptive pill?
- Do you have a history of injury to your arteries or veins?
- Do you have a histroy of injury to any of your nerves (including back or neck injury)?
- Do you have diabetes? Does anyone on your family have diabetes?
- Does your current or previous training include resistance training?
- Do you have any history of high blood pressure?
(Adapted from the British Olympic Association and English Institute of Sport)
If none of these contraindications or risk factors apply then it should be safe to perform BFR training to help improve muscular strength and hypertrophy.
Occlusion or BFR training using low intensity reistance training is a new and novel method of training that is effective at increasing muscular strength and hypertrophy. By using low intensity loads (10-30% 1RM) it is effective for increasing strength when the person is injured, post-op or with older adults who are unable to lift the traditional training loads of 70% of 1RM (ACSM). This training method could prove to be very effective at reducing rehabilitation times and reducing muscle wastage and sarcopenia that is associated with old age. The added benefits of BFR reducing muscle wastage during immobilization can help reduce rehabilitation times after surgery or fractures or when bed ridden. I personally believe that the benefits of this type of training need to be utilized in health care.
I would like to thank Paul Starrs @pstarrs89 for his input. Any comments regarding anyone’s experiences with using BFR training during their own training or rehabilitation of patients would be very welcome. Thanks for reading.
Loenneke, JP, Young, KC, Wilson, JM and Andersen, JC. (2013) Rehabilitation of an osteochondral fracture using blood flow restricted exercise: A case review. Journal of Bodywork and Movement Therapies (Vol. 17, Issue 1, Pages 42-45, DOI: 10.1016/j.jbmt.2012.04.006)
Loenneke, J. P., Wilson, J. M., Marin, P. J., Zourdos, M. C., and Bemben, M. G. (2012). Low intensity blood ﬂow restriction training: a meta-analysis. Eur. J. Appl. Physiol. 112, 1849–1859.
Loenneke JP and Pujol TJ. (2009). The Use of Occlusion Training to Produce Muscle Hypertrophy. Strength and Conditioning Journal 31: 77-84.
Manimmanakorn, A, Hamlin, MJ, Ross, JJ, Taylor, R, Manimmanakorn, N. (2012). Effects of low-load resistance training combined with blood flow restriction or hypoxia on muscle function and performance in netball athletes. J Sci Med Sport;16(4):337-42. doi: 10.1016/j.jsams.2012.08.009.
Takano H, Morita T, Iida H, Asada K, Kato M, Uno K, Hirose K, Matsumoto A, Takenaka K, Hirata Y, Eto F, Nagai R, Sato Y and Nakajima T (2005). Hemodynamic and hormonal responses to a short-term low-intensity resistance exercise with the reduction of muscle blood flow. European Journal of Applied Physiology, 95: 65–73
Takarada, Y., Takazawa, H., Sato, Y., Takebayashi, S., Tanaka, Y., & Ishii, N. (2000). Effects of resistance exercise combined with moderate vascular occlusion on muscular function in humans. J Appl Physiol 88, 2097–2106.
Takarada, Y., Tsuruta, T., & Ishii, N. (2004). Cooperative effects of exercise and occlusive stimuli on muscular function in low-intensity resistance exercise with moderate vascular occlusion. Jap J of Physiol , 54, 585-592.