The Credit Card Effect: Fact or Fiction?

By Bernie Clark

November 8, 2024

You just received your brand-new credit card in the mail. Now you get to destroy your old card. You could get out a pair of scissors, or you can destroy it manually. You bend the card back and forth, back and forth, over and over again until a thin white line appears in the middle of the card. Keep going, bending back and forth, and the line gets wider, thinner, until eventually the card breaks in two. That is the “credit card effect”. Repetitive stresses can weaken a material until it breaks. Now the thought occurs to you, “can this happen to me?” Every day you employ your amazing yoga flexibility and do drop-backs from standing into the wheel pose and come up again. You manage to do this 108 times each morning. Is this safe for your back? Are you at risk of the credit card effect damaging your back? Whenever I am asked a question like this, I offer the definitive answer, “Yes! No! Maybe? It depends….”

The credit card effect is real, relatively rare, and avoidable.

We can do too much of anything, and we can do too little as well. All living tissues require some level of stress to regain and maintain optimal health. If there is too little exercise, load or stress, the tissues atrophy and become weaker. However, if there is too much stress, the tissues wear out and degenerate. Unlike an inanimate object like a credit card, living organisms can heal and adapt to stress, provided, however, that the stress does not exceed the tissue’s tolerances and are given time to recover. Figure 2 shows the effect of cumulative stresses on tissues.¹ Every tissue is able to withstand a certain load, but with repetitive stress, this load tolerance decreases. If the load exceeds the tissue’s tolerance, damage develops. Microtrauma can accumulate until a significant injury occurs.

Notice the graph in figure 3. Here we see the recuperative effect of a refractory period (called “rest”). If we stress and then rest the tissue, the tissue’s tolerance level increases above what it was before. The key, then, is not simply to avoid over-stressing the tissue, but also to allow the tissue enough time to recover and grow stronger.

As noted above, all tissues need stress to regain and maintain optimal health. Let’s reemphasize that! All tissues. This includes our joints, our bones and cartilage, our fascia and muscles, our nerves and organs, and more. All tissues. This means that we cannot afford to ignore some areas of the body out of fear of injury. To say that we should never stress our sacroiliac joint is not helpful—no stress there will cause the joint to atrophy, tighten and lose range of motion. Yes, too much stress could lead to arthritis and hypermobility, but this does not mean that we should entirely avoid stressing the area.²

Chronic stress creates fragility; acute stress followed by rest builds antifragility. To quote Nassim Taleb, “Our antifragilities have conditions. The frequency of stressors matters a bit. Humans tend to do better with acute than with chronic stressors, particularly when the former are followed by ample time for recovery, which allows the stressors to do their job as messengers.”³ Stuart McGill observed that, “loading is necessary for optimal tissue health. When loading and the subsequent degradation of tolerance are followed by a period of rest, an adaptive tissue response increases tolerance…. Avoidance of loading altogether is undesirable.”⁴ Thus, exposure to load is necessary, but as microtraumas accumulate, the applied loads must be removed (with rest) to allow the healing and adaptation process to gradually increase the failure tolerance to a higher level.

In simpler terms, our tissues are subject to the credit card effect but, fortunately, because we are alive, our tissues can recover and become stronger, given enough time to rest. So, yes, the credit card is real, but if we exercise wisely, we don’t really need to be worried about it. But, do we all exercise wisely?

Examples of credit card effects

Clinicians do not use the term “credit card effect”. Instead, they use terms like “repetitive stress” and “microtrauma”. These are real effects. Overuse can come from many conditions and situations including bearing a load that is too high, having the load repeated too frequently, or not allowing sufficient time between loads for recovery. Even though we are living organisms and not machines, we can and do wear out. There are many examples we can look at. Certainly these conditions can arise in other ways, but here we are looking at the effects of repetitive stresses.

Tendons and Tendon Sheaths

• Repetitive stress can lead to tendinosis in tendons like the Achilles, patellar, or rotator cuff tendons. This condition involves degeneration due to chronic overuse rather than acute inflammation (which is called tendinitis).
• The tissue fibers in tendons break down and lose strength with repeated stress, similar to repetitively bending a credit card until it weakens.

Intervertebral Discs

• Repeated loading, especially with improper posture or heavy lifting, can cause the discs between vertebrae to degenerate or delaminate, potentially leading to conditions like disc herniation or spondylolisthesis. Over time, cumulative stress can weaken the disc structure, causing microtears or bulging.

Bone (Stress Fractures)

• Bones subjected to repetitive, low-level impact (like in runners) can develop stress fractures, where micro-damage accumulates faster than the bone can repair. This is especially common in the tibia, metatarsals, and other weight-bearing bones.

Bursae (Bursitis)

• Repetitive movement or pressure on joints can irritate bursae, the fluid-filled sacs that reduce friction between tissues. Chronic bursitis often develops in high-movement areas, such as the shoulder, elbow, and hip, due to repetitive microtrauma.

Nerve Compression (Peripheral Neuropathies):

• Repetitive stress on soft tissues can lead to nerve compression syndromes. For example, in thoracic outlet syndrome, repetitive arm movements can compress nerves passing through the shoulder, causing symptoms in the arm and hand.

Wherever you see the terms “repetitive” above, that is what I am calling the credit card effect. I have seen and heard many yoga teachers describe cases of this happening. Erich Schiffman told me about his practice of doing over one hundred drop-backs into Wheel pose until one day he hurt his back so much that he could not walk.⁵ Similarly, Paul Grilley said that he also hurt himself doing too many drop backs into Wheel. This repetitive movement caused him to compress nerves in his upper chest and neck region resulting in the loss of use of one arm for several days.

I have a friend who was a Cirque du Soleil performer. She has spondylolisthesis, which is an injury not uncommon among gymnasts. Spondylolisthesis is a condition where the bony structure of the vertebrae is weakened through, among other causes, repetitive stress. Eventually a part of the vertebra fractures causing the one above it to slide forward of the one below.⁶ Spondylolisthesis has been reported in almost half of all gymnasts, although more recent reports put the incidence much lower, closer to the rate found in the general population of about 6%.⁷ Six percent of the population is not rare! That is one person out of 14 who has some slippage of a vertebra, usually due to repetitive stress. In a yoga class of 20 students, there is a high probability that at least one student has spondylolisthesis.

Credit Card Critiques

I have mentioned the credit card effect in my book Your Body, Your Yoga.⁸ Some yoga teachers have taken issue with my concern that people may experience the credit card effect. Their objections are twofold:

1. Our tissues are not plastic and are not credit cards. Living tissues adapt and repair themselves, which credit cards cannot do;
2. The analogy creates fear which may prevent appropriate loading of the tissues. A spine will not break in two like a credit card!

I actually agree with these comments! Living tissues do adapt and credit cards do not. However, if we treat our living tissues improperly, they will not be able to adapt and they will suffer a similar fate as an inanimate credit card. As long as the loads we apply to our tissues are within their tolerance ranges and we provide the tissues time for recovery, the tissues we just used will become more usable. The credit card analogy is meant only as a metaphor. The metaphor is not meant to create a fear of movement or tissue loading. All tissues need exercise. The intention is to build an awareness that, just as we can do too little, we can also do too much. Overloading tissues and subjecting them to too much repetitive stress can be just as bad as not loading the tissues at all.

A Metaphor

As a metaphor, the credit card effect is not meant to be taken for truth or reality, but as a way to bring awareness to a possibility. Of course, our tissues are not plastic like a credit card. Our tissues are alive and can adapt. But this does not mean that our tissues cannot be affected similarly to a credit card under stress. If we overload our tissues and stress them too often or too heavily without allowing time for them to recover, they can wear out like a credit card. This does not mean that we should not exercise tissues. It does mean that we have to do so appropriately. Should you be afraid of movement or stress? No, definitely not. All tissues need exercise. Should you be afraid of the potential for the credit card effect happening in your body? “Yes! No! Maybe? It depends….” It depends upon how often and how much you stress your tissues and how much time you allow for recovery. The next obvious question is – how do we know when we are doing too much? That is a topic that will be addressed in the next article.

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¹ See Stuart McGill, Low Back Disorders: Evidence-Based Prevention and Rehabilitation, 2nd ed. (Champaign, IL: Human Kinetics, 2007), page 13. Also see McGill SM. The biomechanics of low back injury: implications on current practice in industry and the clinic. J Biomech. 1997 May;30(5):465-75. doi: 10.1016/s0021-9290(96)00172-8. PMID: 9109558.

² The Mayo Clinic on their web page lists several causes of osteoarthritis including, “repeated stress on the joint. If your job or a sport you play places repetitive stress on a joint, that joint might eventually develop osteoarthritis.” See https://www.mayoclinic.org/diseases-conditions/osteoarthritis/symptoms-causes/syc-20351925, accessed November 7, 2024. This claim is validated in several studies that show repetitive stresses either in the workplace or in sports can lead to OA.
• Wang X, Perry TA, Arden N, Chen L, Parsons CM, Cooper C, Gates L, Hunter DJ. Occupational Risk in Knee Osteoarthritis: A Systematic Review and Meta-Analysis of Observational Studies. Arthritis Care Res (Hoboken). 2020 Sep;72(9):1213-1223. doi: 10.1002/acr.24333. PMID: 32638548; PMCID: PMC7116019;
• Tran G, Smith TO, Grice A, Kingsbury SR, McCrory P, Conaghan PG. Does sports participation (including level of performance and previous injury) increase risk of osteoarthritis? A systematic review and meta-analysis. Br J Sports Med. 2016 Dec;50(23):1459-1466. doi: 10.1136/bjsports-2016-096142. Epub 2016 Sep 28. PMID: 27683348; PMCID: PMC5136708;
• Buckwalter JA. Sports, joint injury, and posttraumatic osteoarthritis. J Orthop Sports Phys Ther. 2003 Oct;33(10):578-88. doi: 10.2519/jospt.2003.33.10.578. PMID: 14620787;
• Perhaps my favourite study, which was done on cartilage is the following: Bleuel J, Zaucke F, Brüggemann GP, Niehoff A. Effects of cyclic tensile strain on chondrocyte metabolism: a systematic review. PLoS One. 2015 Mar 30;10(3):e0119816. doi: 10.1371/journal.pone.0119816. PMID: 25822615; PMCID: PMC4379081.

³ See Nassim Nicholas Taleb, Antifragile: Things that Gain from Disorder (New York: Random House, 2012), 58.

⁴ See McGill, Low Back Disorders, 14.

⁵ This was a personal anecdote Erich shared in a class. When he hobbled to B.K.S. Iyengar the next day, Iyengar asked him what he had been doing. Once Erich admitted to repeating deep backbends, Iyengar told him, “Don’t do that!”

⁶ Mechanically, spondylolisthesis disrupts spinal alignment, affecting the intervertebral discs, ligaments, and facet joints, and often compressing nearby nerve roots. Its causes range from repetitive stress and degenerative changes to congenital, traumatic, or pathological factors. In my friend’s case, she fractured her pars interarticularis (a bony structure between vertebral joints), leading to vertebral slippage.

⁷ Toueg CW, Mac-Thiong JM, Grimard G, Parent S, Poitras B, Labelle H. Prevalence of spondylolisthesis in a population of gymnasts. Stud Health Technol Inform. 2010;158:132-137. PMID: 20543413.

⁸ See Your Body, Your Yoga by Bernie Clark, pages 25 and 30.