It is widely accepted that lifting heavy weight is absolutely required to effectively enhance muscular strength.
Yet, an alternative training method using considerably lighter weight, known as Kaatsu training, has been shown to potently increase muscle strength and size.
This unorthodox mode of training requires lifting lighter loads of roughly 20 to 30 percent of your one-repetition maximum (1RM) to muscle failure while restricting blood flow to the exercised muscle groups.
The remarkable capacity of Kaatsu training to enhance muscular development while using lighter weight partly stems from the preferential activation of fast-twitch muscle fiber, as this training technique depletes oxygen levels to the working muscles due to the moderate restriction of blood flow.
The reduction of available oxygen drives the muscle cell to produce energy without oxygen, or anaerobically, which preferentially activates fast-twitch muscle fibers instead of slow-twitch muscle fibers— as fast-twitch muscle fibers prefer anaerobic respiration, while slow-twitch muscle fibers favor aerobic respiration.
Since fast-twitch muscle has superior potential for strength, their preferential stimulation over slow-twitch muscle provides Kaatsu training with a greater capacity to develop strength.
A study by Takarada et al.1 showed that Kaatsu training produced considerable strength gains. In this study, some of the test subjects performed low-intensity (30% of 1RM) triceps extensions until failure with blood flow restriction, while a second group performed high-intensity resistance exercise (triceps extension at 80% of their 1RM) without blood flow restriction.
Related: Joe Donnelly Occlusion Training Tip
The group performing low-intensity Kaatsu training had similar increases in strength to the high-intensity group, revealing that Kaatsu training can improve strength to a similar degree as high-intensity resistance training.
Another study also revealed that low-intensity resistance training with blood flow restriction can also be good for healthy elderly people.
In this study, 20 subjects performed blood flow resistance training, while another 20 performed ordinary resistance training without blood flow restriction. Blood flow restriction improved vascular endothelial function and peripheral blood circulation.
Short-term low-intensity blood flow restricted interval training was also found to improve both aerobic fitness and muscle strength in another study. This study involved 37 subjects who were divided into four different groups that trained for four weeks.
It was found that muscle strength gains were observed only after blood flow restriction training, showing that short-term low-intensity blood flow restriction training can improve both aerobic fitness and strength.
Increasing Growth Hormone
Heavy weight training has also been shown to potently stimulate growth hormone secretion, promoting gains in muscle mass. Previous studies by Kraemer et al.2,3 have shown that high-intensity resistance exercise can actually increase growth hormone levels by more than a 100-fold.
On the contrary, light resistance training is not usually associated with muscular hypertrophy. Yet, the anaerobic environment caused by Kaatsu training likely triggers considerable muscle growth, as it relies primarily on anaerobic respiration, which generates large amounts of the metabolic byproduct lactic acid.
The increase in lactic acid then stimulates the release of generous amounts of growth hormone, ultimately enhancing muscle growth.
Kaatsu training’s key role in elevating growth hormone was demonstrated in a study by Takarada et al.4 In this study, six young male subjects performed five sets of leg extensions at 20 percent of their 1RM until failure, with a short rest period of 30 seconds, while restricting blood flow to the working muscles using the Kaatsu technique.
The concentration of growth hormone increased up to 290 times higher than before exercise. Interestingly, this level of growth hormone increase was almost twice as high as reported by Kraemer et al.2 in the aforementioned study that used high-intensity resistance exercise to boost muscle growth.
So, altogether, this finding shows that Kaatsu training can provoke a strong endocrine response, stimulating the production of more growth hormone that should support super muscle growth.
Less Pain, But Great Gains
The correct performance of Kaatsu training permits blood flow into the muscle with a slight amount of restriction. Adequate blood flow restriction is typically accomplished by wrapping either elbow or knee straps just above the muscle you want to train without wrapping too tightly, as you must not completely occlude blood flow for safety reasons.
For the standard approach to Kaatsu training, it is necessary to keep the wraps on for the entire exercise— providing ample time to trigger the biochemical and physiological effects that strongly augment muscle growth without occluding a muscle for more than 20 minutes in total.
Typically, four to five sets are performed at roughly 20 to 30 percent of your 1RM, with the first set consisting of around 30 repetitions, followed by three to four more sets of 15 repetitions with less than one minute rest between sets.
Overall, the standard approach to Kaatsu training described above is quite potent at generating strength and size. However, there is a downside to this style of training, as it can get rather painful. In fact, several studies— along with my own experience in the gym— have demonstrated that the standard Kaatsu approach elicits a high level of perceived exertion and pain.5,6,7.
Now, don't get me wrong, I actually value the discomfort caused by weight training, as it is a clear sign of strain on the muscle that will eventually cause the muscle tissue to adapt by getting larger and stronger.
However, all of the potential benefits of this form of training may be offset to some degree by the considerable discomfort brought on from the typical approach to Kaatsu training, ultimately resulting in poor adherence to training.
In view of the potential for training benefits to be compromised during standard Kaatsu training, a group of scientists from Indiana University and Purdue University8 investigated the muscle-building ability of a modified approach to Kaatsu training.
In the modified version, researchers cut the pressure of the pneumatic cuff used to restrict blood flow by roughly 50 percent relative to other studies1,6,7,9, while also removing the initial set of 30 repetitions that is usually performed during Kaatsu training.
Altogether, the modifications reduced the overall pain rating assessed during the study considerably, while still increasing muscle size and strength significantly, relative to the control group.
Notably, the gains in size and strength seen with modified Kaatsu training were not as large as earlier Kaatsu training studies showed1,6,7,9, likely because of the altered training protocol that apparently lowered both the training effect and pain experienced while training simultaneously.
Yet because there were still considerable gains in size and strength, this modified approach can still be used to increase muscle size and strength while mitigating pain, thus improving adherence to training for longer periods of time.
Proper Training Approach
While occlusion training is beneficial especially when combined with high-intensity training, it must be done correctly to avoid potential injury. The proper occlusion training involves tightly wrapping, with wrist or knee straps, just above the exercised muscle— making sure not to wrap too tightly, as this indicates complete blood flow restriction and could be dangerous.
In addition, it is critical to maintain blood flow restriction throughout all sets, but you should never occlude a muscle for more than 30 minutes at a time.10
As previously mentioned, typically four sets are performed right around 20 to 30 percent of your 1RM, with the first set consisting of 30 repetitions followed by three sets of 15 repetitions— with less than one minute rest between sets to produce the remarkable muscle-building effects from occlusion training.
What’s more, from what I’ve seen in the literature and in the gym, when occlusion training is performed along with heavy weight training, the occlusion work usually works best when it follows the high-intensity work— as the opposite order would likely preclude the effective use of heavy weights, because of the considerable muscle fatigue from occlusion training.
In summary, standard Kaatsu or occlusion training stimulates significant muscle growth and strength while using light weight, making it an attractive adjunct to high-intensity training. However, one potential limitation of standard Kaatsu training is the considerable discomfort generated when using this method.
Fortunately, a modified version of this training style has recently been shown to reduce pain perception considerably, while still having a positive influence on size and strength.
This makes the modified approach to Kaatsu training a more suitable exercise alternative for those looking for a low-intensity training style that yields size and strength gains, but with a little less pain.
- Takarada Y, Takazawa H (2000). Effects of resistance exercise combined with moderate vascular occlusion on muscular function in humans. J Appl Physiol 1985;88, 2097-2106.
- Kraemer WJ, Gordon SE, et al. Endogenous anabolic hormonal and growth factor responses to heavy resistance exercise in males and females. Int J Sports Med 1991;12, 228-235.
- Kraemer WJ, Marchitelli L, et al. (1990). Hormonal and growth factor responses to heavy resistance exercise protocols. J Appl Physiol 1985;69, 1442-1450
- Takarada Y, Nakamura Y, et al. (2000). Rapid increase in plasma growth hormone after low-intensity resistance exercise with vascular occlusion. J Appl Physiol 1985;88, 61-65.
- Hollander DB, Reeves GV, et al. Partial occlusion during resistance exercise alters effort sense and pain. J Strength Cond Res 2010;24, 235-243.
- Wernbom M, Augustsson J and Thomee R. Effects of vascular occlusion on muscular endurance in dynamic knee extension exercise at different submaximal loads. J Strength Cond Res 2006;20, 372-377.
- Wernbom M, Jarrebring R, et al. Acute effects of blood flow restriction on muscle activity and endurance during fatiguing dynamic knee extensions at low load. J Strength Cond Res 2009;23, 2389-2395
- Weatherholt A, Beekley M, et al. Modified Kaatsu training: adaptations and subject perceptions. Med Sci Sports Exerc 2012;45, 952-961.
- Yasuda T, Brechue WF, et al. Muscle activation during low-intensity muscle contractions with restricted blood flow. J Sports Sci 2009;27, 479-489.
- Loenneke JP, Wilson GJ and Wilson JM. Int J Sports Med 2010;31(1), 1-4.