When Collateral Damage is a Good Thing

The term “collateral damage” is typically a military term, one that denotes unintended damage to an area around a target. But as it applies to resistance training, collateral damage can be a good thing.


Collateral vascular damage inflicted by weight training occurs regardless of one’s specific intentions and to varying degrees based on training intensity, duration, frequency, and volume. By understanding its specific causes and effects, however, it is possible to optimize the benefits of this occurrence.

Muscle Tissue & Collateral Circulation

First, let us consider the location where this exercise-induced damage occurs. Collateral circulation perfuses the intramuscular areas in the form of microscopic capillaries and small veins. The capillaries transport oxygen and nutrient rich blood from the main arteries to the muscles, while the equally small and fragile system of veins (venules) works in conjunction with the lymphatic system to carry away muscle tissue wastes and oxygen deficient blood back to the main vascular tree. These small vessels facilitate the exchange of nutrients and oxygen on a cellular level.

This collateral vascular tissue is very delicate and branches extensively throughout the muscular areas. In general, the greater the volume of these intramuscular vessels, the better the health of the surrounding muscle cells. In fact, any body tissue cell that is sufficiently supplied with nutrient rich blood, by means of collateral circulation, receives the full benefit of what the cardiorespiratory system can supply (and remove), allowing it to perform more optimally and live longer than those not readily supplied by collateral blood vessels.

Adipose Tissue

Collateral circulation is also present, of course, in other types of body tissue, such as adipose and organs. It is thought by some researchers that the greater the volume of collateral blood provision to fatty tissue, the greater the conversion and storage of circulating calories (mostly over-abundant glucose, triglycerides, and fatty acids). This is obviously undesirable when it comes to weight maintenance and general health.

Effecting Collateral Damage

Capillary damage occurs when resistance exercise calls on the target muscle to maintain a sustained contraction for prolonged periods. The longer the duration and the greater the intensity of the sustained contraction, the greater the capillary damage. The greater the volume of high rep sets performed, the greater the damage, as well. During prolonged contraction, the girth of the working tissue increases enough to ‘pinch’ or block the flow of blood to the working muscles, much like the act of pinching a garden hose. With this ‘pinching’ comes a back-up of pressurized blood not able to enter the working intramuscular region. Upon relaxation, the blood quickly perfuses into the now relaxed musculature. This pressurized perfusion results in the bursting of already very fragile microscopic capillaries causing an ‘escape’ of blood in and around the working muscles.

The extent of the damage will be based on the variable factors of duration, intensity and volume. The repeated performance of high rep sets back to back (volume training) amplifies the rock hard pump that is the hallmark of high volume – or high rep – training. This so-called ‘pump’ occurs due to the collateral veins’ and the lymphatic system’s inability to capture and then return this exercise-induced increase in intramuscular fluid back to the main vascular tree. Not only are wastes removed more slowly while this ‘pump’ occurs, but cellular nutrient and oxygen provision is adversely affected, as well. In short, fluids remain in the intramuscular areas for longer periods when experiencing the pumped sensation. Since nutrient provision and waste removal are both limited during this time, it is directly prohibitive to size and strength training, if performed exclusively. In fact, it is possible to see burst capillaries (bruising) beneath the fascial layer covering a particular working muscle during high rep/volume training in some resistance trainees who have scant body fat.

Blood vessel damage can require a fairly long recovery period, about the same as that of muscle tissue. As with muscle tissue damage sustained during training, protein is needed to repair these tiny vessels. And, not unlike muscle tissue growth during recovery, when these small vessels are repaired, they in turn form new branches. This is the cardiovascular tissue’s way of preparing itself for the next exercise session, and it leads to a slight increase in muscle size. This usually is caused mainly by the temporary increase in fluid remaining in the musculature that has been involved in training. While the above would give one reason to think the ‘pump’ is something best avoided, it is important to keep in mind that these vessels will make a full recovery. Furthermore, the newly formed branches act to improve and make more efficient the movement of blood in the intramuscular regions. This increased proficiency will also lead to greater muscle growth in the long run, too. The muscle tissue in question becomes more efficient, which is the basis for defining improved health for all exercise participants, regardless of age, gender, or specific goals. The burning sensation associated with the ‘pump’ is a prime indicator of capillary extension.

The preceding information can be viewed as an argument in favor of phase training, holistic training, periodization, etc. In fact, anyone who performs resistance training can do so with a regular dose of high-rep training to enhance the exchange of nutrients and wastes on a cellular level. A weight training enthusiast looking for size and strength increase, specifically, might consider employing some high-rep training occasionally to optimize energy provision and improve cellular performance.


1. Byrne, Christopher, Craig Twist, and Roger Eston. “Neuromuscular function after exercise-induced muscle damage.” Sports medicine 34.1 (2004): 49-69.

2. Ivy, John L. “Regulation of muscle glycogen repletion, muscle protein synthesis and repair following exercise.” Journal of Sports Science & Medicine 3.3 (2004): 131.

3. Proske, U., and D. L. Morgan. “Muscle damage from eccentric exercise: mechanism, mechanical signs, adaptation and clinical applications.” The Journal of physiology 537.2 (2001): 333-345.


These resources are for the purpose of personal trainer growth and development through Continuing Education which advances the knowledge of fitness professionals. This article is written for NFPT Certified Personal Trainers to receive Continuing Education Credit (CEC). Please contact NFPT at 800.729.6378 or [email protected] with questions or for more information.
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