January at Paragon:
Eccentric Load
Get ready goners, it’s time to lengthen and strengthen…
During any movement where muscle tissue is lengthening, if you are resisting a load, it’s an eccentric contraction. Most "down" motions are eccentric contractions working to oppose gravity: the down phase of a pushup, or the down phase of a squat, involve eccentric muscle contractions (so, no escaping that folks!) Eccentric load could also be contractions of surrounding muscles (so, yeah, like any active movement), or an externally applied load (like strength training). When you do a bicep curl with a dumbbell, as you curl the bell, your bicep is contracting concentrically (muscle is shortening). When you uncurl the bell to straighten your arm, you are eccentrically contracting your bicep (muscle is lengthening).
Eccentric contractions have been a bit of a mystery: for many years, we didn’t quite understand what was happening or how they worked (and really, they are still poorly understood). We all remember learning about the sliding filament (cross-bridge) theory, which states that the shortening of a muscle occurs as the myosin cross-bridges cyclically attach to actin and draw the actin across the myosin, creating force and shortening. Well, there are some shortcomings to that theory; namely, it does not explain how an eccentric contraction works.
So, in eccentric exercises, the muscle lengthens while still producing force. The number of possible cross-bridge formations is diminishing, yet the muscle is still capable of producing force. Muscles can even produce force in the absence of cross-bridge formations, when muscle is stretched beyond the thick and thin filament overlap.
What the heck is going on here? Titin, that’s what. Titin is a third filament, in addition to the thick filament (myosin) and the thin filament (actin). During an eccentric contraction, actin is pulled away from myosin and the distance between the Z-lines increases while titin binds to actin to contribute force in the absence of cross-bridge formations (Herzog 2014). This is how your muscle produces force as the cross-bridge formations diminish. When it comes to the way our crazy, intricate bodies work, there is so much we don’t know. But, here are a few things we do know about why eccentrics are so important.
Eccentric exercise results in less oxygen consumption, greater force production, and less energy expenditure than concentric exercise (Lindstedt et al. 2001). The energy requirements are typically 4-fold smaller than in concentric exercise of the same load (studies have shown that when a muscle is eccentrically lengthened, the energy requirement falls substantially in comparison to concentric contractions because ATP breakdown and heat production are both slowed). Applying eccentric load can also increase Type 1 collagen synthesis. This is really, really cool, and we will talk about this more in a bit.
Eccentric actions are so important because they often involve the control or deceleration of a movement. Muscles activated during lengthening movements function as shock absorbers, to decelerate during landing tasks or to precisely deal with high external loading in sports. So, when you are hiking down into the Grand Canyon...so many muscles need to eccentrically contract to control your body...and when you are downhill skiing at Snowbowl, eccentric activity of your quadriceps muscle is dominant through all of your turns. They happen all the time, during so many everyday movements. But not only are they an important part of our day to day activities, they are also an important tool in injury rehab and injury prevention.
Managing injuries:
Many studies recently have substantiated eccentric exercise as an effective treatment for tendinopathies. Eccentric work requires less oxygen consumption than concentric work, making it ideally suited for the rehabilitation of tendinopathies. Oxygen consumption is seven and a half times lower in tendons/ligaments than in skeletal muscle. Tendons have a low metabolic rate and anaerobic energy generating capacity, so that they can maintain tension for long periods of time. But, the low metabolic rate results in slow healing after tendon injury. We all know how nagging that achilles pain from running can be, or have felt that elbow pain after a long day of climbing. Because eccentric movements require less oxygen than concentric movements, they can be a good choice for managing those nagging injuries.
Studies have shown there are many injuries that have been shown to improve with eccentric load: ACL reconstructions, muscles strains, hamstring injuries, elbow tendinopathy, patellar tendinopathy, and achilles tendinopathy (Lorenz, Reiman 2011). Multiple studies have found that Type I collagen synthesis increased after eccentric training in athletes with unilateral achilles tendinosis.
Ok, in case you missed that, let me say it again. Eccentric load can increase Type 1 collagen synthesis. Do you know what is made of type 1 collagen? Ligaments and tendons are, that’s what! Let’s take a minute to talk about how cool this is….Type I collagen is amazing. It’s fibrils have enormous tensile strength; that is, such collagen can be stretched without being broken. These fibrils are packed side-by-side in parallel bundles, called collagen fibers, in tendons, where they connect muscles with bones and must withstand enormous forces. Gram for gram, type I collagen is stronger than steel.
When a tendon in injured, the collagen near the injury site becomes disrupted. Those neatly packed little bundles can become distorted. And then during the healing phase, the the collagen produced can also often be disorganized. But, adding eccentric load can help to remodel old tissue, aligning the collagen, at the same time increasing its synthesis (Galloway et al. 2013).
Preventing injuries:
So, if you don’t have an injury, eccentrics are just as important for you. We want you to climb, run, ski, bike, hike______(insert your awesome adventure of choice here), for a long, long time. Eccentrics are another important piece to add to the puzzle of keeping you healthy during your athletic endeavors. They are another way to make your body strong, and when your body is strong, it can better tolerate those many hours on the trail or the bike or the climbing wall. There is a lot of evidence that indicates eccentric strength training methods will encourage neuromuscular adaptations. So this can help with muscle coordination. (Eccentric compared with concentric muscle contractions require different activation strategies and programming processes by the central nervous system).
Eccentric training is a potent stimulus for enhancements in muscle mechanical function, and enhances the way the muscle and tendon work together. Including eccentric loads into your workout can improve your strength, power and speed performance (Douglas et al. 2016). Many studies suggest that increases in peak torque and strength-related performance parameters were greater following a program consisting of maximum concentric and eccentric muscle actions than resistance training using concentric muscle actions only (Colliander, Tesch 1990).
Improving range of motion:
Since tendons are mechanically responsible for transmitting muscle forces to bone as they connect bone to muscle belly at their ends, this is how motion is allowed and joint stability is enhanced. So, if your tendons, (are therefore the muscles attached to those tendons) are working as they should, then your joint will be more stable. And sometimes, the best way to gain mobility is to impart stability. One reason why joints lose mobility is because your body is locking them down in order to provide stability. The nervous system always wants to feel safe. So, by adding strength work to improve tendon and muscle performance will provide stability, ultimately leading to more mobility.
Ok Goners, time to put this knowledge into action:
There is no question that your exercise program should include periods of eccentric exercise, as this will provide protection from injury or reinjury, will help improve coordination and balance, and can increase strength in the full range of motion in your joints. Remember, you are stronger in a eccentric movement than a concentric. So, that means that you can you can handle more resistance or weight, so it is yet another way to boost your system and improve your athletic performance. It is another way to push beyond your perceived limits. And what a great way to start of the new year, by redefining your limits. So get ready to lengthen and strengthen, goners!
-Laurel Lippard
“If you always put limit on everything you do, physical or anything else. It will spread into your work and into your life. There are no limits. There are only plateaus, and you must not stay there, you must go beyond them.” Bruce Lee
References:
Colliander EB1, Tesch PA. Effects of eccentric and concentric muscle actions in resistance training. Acta Physiol Scand. 1990 Sep;140(1):31-9.
Daniel Lorenz, DPT, PT, ATC/L, CSCS, USAW1 and Michael Reiman, PT, DPT, OCS, SCS, ATC, FAAOMPT, CSCS2 The Role and implementation of eccentric trainging in athletic rehabilitation: tendinopathy, hamstring strains, and ACL reconstruction.. Int J Sports Phys Ther. 2011 Mar; 6(1): 27–44.
Debenham JR1,2, Gibson WI1, Travers MJ2, Campbell AC2, Allison GT2. Eccentric Loading of Triceps Surae Modulates Stretch Shortening Cycle Behaviour- A Possible Therapeutic Mechanism. J Sport Rehabil. 2016 Aug 24:1-22.
Douglas, J., Pearson, S., Ross, A., McGuigan, M. Chronic Adaptations to Eccentric Training: A Systematic Review. Sports Medicine Journal. 2016. Galloway, Marc T., Andrea L. Lalley, Jason T. Shearn. The Role of Mechanical Loading in Tendon Development, Maintenance, Injury, and Repair. J Bone Joint Surg Am. 2013 Sep 4; 95(17): 1620–1628. Published online 2013 Sep 4. doi: 10.2106/JBJS.L.01004Herzog W. The role of titin in eccentric muscle contraction. J Exp Biol. 2014 Aug 15;217(Pt 16):2825-33. doi: 10.1242/jeb.099127.
Langberg H1, Ellingsgaard H, Madsen T, Jansson J, Magnusson SP, Aagaard P, Kjaer M. Eccentric rehabilitation exercise increases peritendinous type I collagen synthesis in humans with Achilles tendinosis. Scand J Med Sci Sports. 2007 Feb;17(1):61-6. Epub 2006 Jun 19.
Lindstedt S.L., LaStayo P.C., Reich T.E. When Active Muscles Lengthen: Properties and Consequences of Eccentric Contractions. Physiology Published 1 December 2001 Vol. 16 no. 6, 256-261 DOI:
Mitchell, Jules. http://www.julesmitchell.com
Woodley, B., Newsham-West, R., Baxter, G. Chronic tendinopathy: effectiveness of eccentric exercise. Br J Sports Med 2007;41:188-198.