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In matters physiological, the process of occlusion has largely negative connotations. Occlusion, meaning to shut off or obstruct, of a major artery to the heart (as in coronary occlusion) or of a breathing passage if not detected early, can result in death. To restrict the safe passage of blood through the body is the last thing any health-conscious, fitness-minded person would want. Vital to supporting life and for the proper functioning of our many bodily systems, the efficient transportation of blood from the heart through the arterial network to various tissues and back via venous return is of key importance. This provides oxygen, nutrients and an array of additional life-sustaining molecules while allowing for waste product removal. For bodybuilders, those high-performance athletes for whom sustained blood flow promotes optimal performance and muscle growth, it would be safe to assume that any form of occlusion would negate the internal anabolic environment so conducive to positive training outcomes – or maybe not.

A seldom employed yet highly intriguing and amazingly effective training protocol, which actually encourages the occlusion of blood flow, is catching on among bodybuilders looking for new ways to stimulate the growth of lean muscle tissue: vascular occlusion training (or what scientists call Blood Flow Restriction training – BFR). Promising comparable results to standard high-load resistance training methods, occlusion training, highly intensive and extremely painful if done correctly, is performed with lighter weights (as little as 20% of our one repetition maximum – 1RM) and is designed to engorge the working muscles with as much blood as possible. Because occlusion training forces our muscles to respond to low level intensity lifting the same way they would to traditional bodybuilding training protocols (which may require up to 70% of 1RM), we can achieve the same muscle building benefits while using a fraction of the resistance, a strategy which provides several benefits (to be discussed soon).

How occlusion training works

To ensure that our muscles, through occlusion training, receive optimal blood flow and that this blood is pooled in the muscles, and not flushed out as would occur under normal conditions, we must restrict only the blood that has accumulated from returning to the heart. While arterial blood must be free to enter muscle tissue, once pooled, it must stay put, at least until the final set of an exercise has been completed. Many different aids have been used to occlude blood flow for training purposes. The best of these are knee wraps tightly secured around the top of the muscles that are to be worked (for example, when training the upper arms, secure the wraps as close to the shoulder joint as possible), with just enough pressure to occlude blood flow to the veins, not from the arteries.

The best way to do this is to tighten the wraps to such an extent that blood is able only to flow into the working muscles and not out through the veins. In a circular manner the wraps must be secured around the narrowest part of the limb; do not wrap a wide area (directly over a biceps muscle, for example) as this may occlude the arteries as well as the veins. A progressively more intensive muscle pump will signal continuous blood accumulation and confirm that the wraps have been applied properly. However, pain must not be experienced upon tightening the wraps; discomfort, yes, but not pain (which is suggestive of a complete blockage of both the arteries and veins).

Occlusion training benefits

Aside from, and in many ways linked to the massive muscle pumps produced via occlusion training are a number of anabolic benefits to be derived through the restriction of blood flow to our working muscles. Our muscles are comprised of two fiber types: type 1 (slow twitch) and type 2 (fast twitch). While the former are predominantly active during low intensity aerobic-based activities, it is the latter (which have the greatest growth potential and which are only recruited when we use heavy weights to go to failure) that bodybuilders seek to activate. Under normal training conditions (moderate/heavy weights and with blood freely flowing) our type 1 fibers (drawing from the oxygen supplied in blood) are engaged first, shortly followed by the type 2 fibers. However, when lighter loads are coupled with the occlusion of blood, the type 2 fibers are recruited much earlier in the set – due to the restricted blood flow, the type 1 fibers are pre-fatigued, thus prompting the fast twitch fibers to handle the resistance, even when much lighter weights are employed. This preferential activation of the type 2 fibers increases our potential for building greater muscle size and strength.

It is often suggested that the mechanical stress placed on our muscles during strength training is the primary impetus for the adaptive response which leads to muscle hypertrophy; that muscle contraction alone produces the anabolic signaling required to initiate protein synthesis and promote muscle growth. However, new research findings have shed greater light on the key role training-induced metabolic stress may have on fleshing out our physiques. Associated mechanisms of such metabolic stress include increased muscle fiber recruitment, elevated systemic hormonal production, alterations in local myokines (small cell-signaling proteins), and cell swelling, all of which combine to promote muscle hypertrophy. A further important metabolic by-product, lactic acid, is noted for its ability to enhance the production of growth hormone (GH) and insulin-like growth factor (IGF-1) and, when produced in abundance, enlist more muscle fibers.

Under normal training circumstances, all accumulated metabolites would be quickly flushed from the site of muscle activation. With occlusion training they are forced to accumulate near the muscles for a much longer period. The accretion of lactic acid through occlusion training alone has been shown to boost GH levels 290 times above baseline. The cell swelling and accumulation of metabolites in muscle tissue has also been shown to increase muscle protein synthesis, mTOR signaling (mTOR is an intracellular pathway which, as a key regulator of muscle protein synthesis, boosts muscle hypertrophy), and the production of NOS-1 (a messenger molecule associated with the neuronal regulation of muscle), which is thought to increase muscle growth through satellite cell activation.

For best results, perform occlusion training twice a week, with four sets per exercise and 30 seconds rest between sets. Complete all sets of an exercise before removing the wraps.

Is occlusion training for you?

Occlusion training is an advanced training method that is not recommended for beginners. Despite its benefits, occlusion training, even among experienced lifters, should be viewed as a way to augment regular moderate to high load hypertrophy-focused training protocols; it must be used to supplement, not replace, the heavy training to which most ardent iron pumpers have become accustomed.

More specifically, occlusion training can be used by those who are injured and can only manage lighter weights, but who wish to experience the benefits associated with heavy loads; athletes undergoing a de-loading phase; and for those wishing to incorporate a unique training stressor to further elicit maximal muscle building results. Occlusion training will provide tremendous benefits for all trainees seeking to pump their muscles to full capacity with lighter weights without forgoing the gains typically linked to the lifting of heavier iron. For seasoned hardcore lifters who would like to give their joints, tendons, ligaments and nervous system a break from back-bending poundages, there are few alternatives that work as well as occlusion training.

References
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Fujita, S., Abe, T., Drummond, M., Cadenas, J., Dreyer, H., Sato, Y., Volpi, E., & Rasmussen, B. blood flow restriction during low-intensity resistance exercise increases S6K1 phosphorylation and muscle protein synthesis. J Appl Physiol 103: 903-910, 2007.

Kawada, S., & Ishii, N. Skeletal muscle hypertrophy after chronic restriction of venous return blood flow in rats. Med Sci Sports Exerc 37: 1144-1150, 2005.

Kraemer, W., Marchitelli, L., Gordon, S., Dziados, J., Frykman, P., McCurry, D., & Fleck, S. Hormonal and growth factor responses to heavy resistance protocols. J Appl Physiol 69: 1442-1450, 1990.

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Loenneke, J.P., Abe, T., Wilson, J.M., Thiebaud, R.S., Fahs, C.A., Rossow, L.M., & Bemben, M. G. (2012) Blood flow restriction: an evidence-based progressive model. Acta Physiol Hung, 99(3), 235-250.

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Thiebaud, R. S., Yasuda, T., Loenneke, J.P., Abe, T. (2013). Effects of low-intensity concentric and eccentric exercise combined with blood flow restriction on indices of exercise-induced muscle damage. Interven Med Appl Sci, 5, 53-59.
Wilson, J. M., Lowery, R. P., Joy, J. M., Loenneke, J. P., & Naimo, M. A. (2013). Practical Blood Flow Restriction Training Increases Acute Determinants of Hypertrophy Without Increasing Indices of Muscle Damage. J Strength Cond Res, epub ahead of print.