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Our muscles can contract in three different ways: 1) isometrically, where the muscle contracts but doesn’t make anything move - think wall sits and planks (a), 2) concentrically, where the muscle contracts to “shorten” while lifting a load - think of the bulge in your bicep when you lift weight to do a curl (b), and 3) eccentrically, where the muscle contracts to “lengthen” while lifting a load - think of your bicep lowering the weight during a curl, you can still see the muscle contracting (c). Without eccentric contractions, every time we lifted something it would crash uncontrollably to the ground. Our muscles still need to contract to control the weight while it returns to the starting position. It’s this eccentric contraction, or the “negative” portion of the lift, that has been shown to cause that debilitating post-exercise soreness and microscopic muscle damage that make it impossible to lift an empty laundry basket or walk down the stairs a day after hitting it heavy (4, 5, 9, 10). It’s also used to help heal severe muscle tears. But why? And how can it be used to do both?
The Power of Force
Eccentric contractions are valuable in quite a few ways. The body can tolerate much higher loads -- up to 1.75x more weight (1)-- during eccentric contractions than concentric contractions because muscle fibers can create a lot more tension when lengthening than with shortening (2, 6). It takes less energy and effort to do a lengthening eccentric contraction, so an athlete can move a much heavier weight eccentrically than concentrically (1, 4, 5, 6). This also opens the possibility of putting a lot more force on the muscles, tendons, and bones. We’ll come back to that in a minute.
Doing eccentric exercises, trying a new exercise or increasing weight on an old one, or doing an exercise outside the typical range of motion (stopping before or after the typical endpoint for example) are all asking the body to move in new, different, or unfamiliar ways, which is asking it to accept different loading forces than it’s used to. Until the body can adapt to, or learn, the new movement, doing it can cause natural microscopic tears leading to muscle soreness and inflammation (4, 9, 10). One of Brian’s favorite ways to switch up bicep curls is to change the degree of the starting and ending positions, so starting with the elbow bent at 45 degrees and ending at 135 degrees, or only doing half the range of motion instead of 0 deg to 180 deg. Learning a new boxing combo will make you sore for the same reason, the muscles are being asked to fire in a new pattern. This soreness and inflammation are caused by specific chemicals that the body releases when tears in the muscle happen - whether they’re microtears from exercise or larger tears from an injury. They make the body more sensitive to pain and attract white blood cells (the body’s “repair men”) to damaged tissue, or an injury (9). Most people know this discomfort, or pain, as delayed onset muscle soreness, or “DOMS” which usually starts 24-48 hours after one of these workouts (9, 10). When the body experiences an isolated, more aggressive eccentric force like doing a drop jump, stopping quickly after or cutting directions during a sprint, or even slowing down the arm too fast after spiking a volleyball or throwing a jab (5), more severe muscle damage can happen causing an actual temporary loss of the ability to fire the muscle and make a body part move (4, 6, 10).
In another article on our website, we talk about how the body adapts to the forces placed on it (4, 9). There’s tons of different ways to progress a strength training program depending on whether an athlete is looking for power versus aesthetics and physique because the variations in exercises and load progression will cause specific changes in the muscles. Runners’ bodies eventually begin to utilize oxygen more efficiently and are able to cut seconds from their mile times. Athletes will even travel to cities half a week in advance to acclimate to different altitudes or climate conditions before competition. Hessel, et. al stated that “the high forces produced by muscles during eccentric contractions, and the high forces consequently exerted on muscles, bones and tendons stimulate not only unique muscle hypertrophy and architectural adaptations, but also bone mineralization and tendon remodeling,” (4). So, eccentric exercises help heal, strengthen, and grow muscles, tendons, and bone, and it grows proportionately. Working out at a higher intensity and load will cause greater cardiovascular and strength adaptations(1). A great example of this is using slow eccentric exercise, or a slow negative, in a muscle hypertrophy program. But how does this happen?
How can eccentric exercises that cause these microtears be used to heal a muscle? It’s important to note that both eccentric and concentric exercises will cause tiny natural microtears to happen. Keep in mind that an athlete can move heavier loads with an eccentric contraction, so the microtears will be bigger and the post-exercise soreness more pronounced. “The high forces produced eccentrically seem to induce the remodeling response when applied chronically and progressively,” (2). Microtears happen naturally, but if progressed appropriately over time, high-force producing eccentric contractions actually cause muscle, bone, and tendon tissue to start what’s called the “remodeling response” all by themselves without causing an injury or further damage to an existing one (1, 2). It takes three stages to heal an injury: 1) inflammation, where the body pumps blood to the injury to flush out the damaged tissue and anything that could cause an infection, 2) proliferation, where new collagen tissue is made that will be the framework for either the new muscle, bone, or tendon, and 3) remodeling, where the new collagen fibers are lined up side-by-side with the other existing muscle, bone, or tendon fibers and the injury begins to heal (7, 10). So when the body performs repeated eccentric contractions against an adequate high-force load, it can actually stimulate itself to heal the natural microtears that happen (2, 3 4, 6, 9). This same process happens when a muscle is torn to the point of injury, and this cycle of breaking down and building back up is constant throughout the muscle, bone, and tendon tissue in the body (9).
Cold Laser Therapy, Microtears, and Muscle Tears
Muscle injuries are a huge problem for athletes. Even though muscles naturally repair themselves through the inflammation process, it’s a slow process, and a lot of times athletes continue to deal with weakness and risk of re-injury (7). “The exhausting physical exercises, drills, and games associated with insufficient recovery interval may cause athletes to enter a process called overtraining making them more susceptible to muscle and ligament injuries,” (8). The ability of cold laser therapy to heal all types of muscle, tendon, and bone injuries has been gaining a lot of attention because of it’s non-invasive, low-cost, quick and easy treatments (7). The best part is that unlike corticosteroid injections and over-the-counter, non-steroidal anti-inflammatories (NSAIDs) like ibuprofen, Advil, and naproxen sodium, there have been NO NEGATIVE SIDE EFFECTS found when using cold laser therapy (7).
A study in Lasers in Medical Science found that cold laser therapy reduced the inflammation process, initiated and sped up the proliferation phase (discussed above), and created new blood vessels around the injury (7, 8). When a muscle tears, the blood vessels tear along with it, causing bruising and swelling. This pooled blood can’t be used to heal the injury and needs to be moved out of the area (a part of the inflammation process), so new blood vessels need to be created to bring oxygen, white blood cells, and new collagen cells to the area so the tear can be repaired. Cold laser therapy works with the energy house of the cell to make this process happen faster (3, 7).
Cold Laser Therapy and Eccentric Exercises for Recovery
In the case of traumatic muscle tears, after the initial inflammatory phase, restoring range of motion and strength become the first goal. We discussed above that the body responds and adapts proportionately to the forces placed on it, and eccentric exercises present a safe and efficient way for the body to lift heavier loads resulting in a stronger remodeling response than would be triggered by concentric exercises (4).
The athlete should start an exercise program using loads that cause minimal to
no pain throughout the range of motion. I tell our clients that feeling anything at
or below a 3/10 pain level during exercise is safe and tolerable. When doing
eccentric exercises for rehabilitation, it’s suggested that the athlete do the
concentric part of the movement passively until it can be done pain-free (6).
Using heel raises as an example, the athlete should focus on lowering the heels
slowly and controlled, while using something like a handrail to help them get
back up on their toes using as little leg strength as possible (d). Once this happens,
the athlete can go through the concentric portion more actively, but this starting
point and method of progression allows the muscles, bone, or tendon to be stressed just enough to start the remodeling process without causing further damage.
We discussed above that cold laser therapy has been shown to decrease the length of the inflammation process, initiate and speed up the proliferation phase, and create new blood vessels around the injury. These all happen whether cold laser therapy is used or not. Since cold laser therapy makes this process happen faster and more efficiently, stacking this ability on top of the body’s natural healing ability to heal damaged tissue only serves to improve and speed up the process that much more.
Have You Torn a Muscle or Are Experiencing “DOMS”?
M&B Wellness Solutions offers multiple services to help relieve the deep ache from DOMS, and heal partial muscle tears. Whether it’s cold laser therapy, traditional, insurance-based physical therapy, or our PT Squared Program where our physical therapist works together with the highly qualified trainers at iThinkFit to design the perfect plan that will help athletes train through the recovery process, we have what it takes to help athletes recovery quickly and stay at the top of their game.
The best way to start your road to recovery is to see a healthcare professional specializing in movement and rehabilitation who can assess your range of motion, strength, and quality of movement to determine if your pain is due to chronic overuse, from strength and flexibility imbalances, or poor biomechanics. Stop by M&B Wellness Solutions located inside iThinkFit Gym for an evaluation with a licensed physical therapist so we can get you on your way to moving the best you possibly can.
Michaela Cantral, PT, DPT
(2) Camargo PR, Alburquerque-Sendin F, Salvini TF. Eccentric training as a new approach for rotator cuff tendinopathy: Review and perspectives. World Journal of Orthopedics. 2014;5(5):634-644. doi:10.5312/wjo.v5.i5.634. PMCID: PMC4133471
(3) Ferraresi C, Hamblin MR, Parizotto NA. Low-level laser (light) therapy (LLLT) on muscle tissue: performance, fatigue, and repair benefited by the power of light. Photonics and Lasers in Medicine. 2012;1(4):267-286. doi: 10.1515/plm-2012-0032. PMCID: PMC3635110
(4) Hessel AL, Lindstedt SL, Nishikawa KC. Physiological Mechanisms of Eccentric Contraction and Its Applications: A Role for the Giant Titin Protein. Frontiers in Physiology. 2017;8:1-14. doi:10.3389/fphys.2017.00070.PMID: 28232805. PMCID:
(6) Lorenz D, Reiman M. The Role and Implementation of Eccentric Training in Athletic Rehabilitation: Tendinopathy, Hamstring Strains, and ACL Reconstruction. International Journal of Sports Physical Therapy. 2011;6(1):27-44. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3105370/. Accessed March 15, 2017. PMCID: PMC3105370
(7) Neves Alves A, Porta Santos Fernandes K, Melo Deana A, Kalil Bussadori S, Agnelli Mesquita-Ferrari R. Effects of Low-Level Laser Therapy on Skeletal Muscle Repair: A Systematic Review. American Journal of Physical Medicine and Rehabilitation. 2014;93(12):1073-1085. doi:10.1097/PHM.0000000000000158. PMID: 25122099.
(8) dos Santos Maciel T, Solange Sepulveda Munoz I, Amadei Nicolau R, et al. Phototherapy effect on the muscular activity of regular physical activity practitioners. Lasers in Medical Science. 2013;29(3):1145-1152. doi:10.1007/s10103-013-1481-4. PMID: 24288083.