As early as I can remember doing weight bearing exercise, I nearly always emphasized the “pushing” or contractive part of the movement. If I was doing a push-up, my effort was on pushing myself off the floor. Then I quickly lowered myself and began the next one. If I was doing a sit-up, my effort was on sitting up; then I’d drop back to the floor. If I was doing curls with dumbbells, I was focused on raising the weight, bringing by hand toward my shoulder. After each curl, I’d let my arm drop without much restraint, and then start the next rep. This type of exercise focuses on what’s called the concentric aspect of muscle work – the part where muscle fibers are shortening.
There’s another kind of work that our muscles do in exercise, which is to restrain the re-lengthening of the muscle after a contraction. This is called eccentric (“ek-sentrik,”) exercise, and it has unique benefits and even some advantages over concentric exercise. In the three examples in the previous paragraph – pushups, sit-ups, and curls – the part of the exercise I wasn’t paying attention to (lowering my body in the push-ups and sit-ups, and lowering my forearm in the curls) was the eccentric phase.
In studies comparing strength and muscle mass gains between concentric-only and eccentric-only exercise, the two forms produced about equal results.  The main difference was that participants found eccentric exercise easier to do. One study, published in January 2011, found that women who did 30 minutes of eccentric exercise per week experienced an improvement in their Resting Energy Expenditure – a measure of how many calories the body burns in a 24 hour period while resting – and their fat oxidation – the breakdown of fat into energy. 
Because it’s so much easier to do eccentric exercise versus concentric, many studies utilized considerably more weight for the eccentric phase than the participants could possibly lift concentrically. For example, if a 100 pound barbell is the most weight you could press off your chest, it’s likely that you could (eccentrically) lower 120 pounds or more to your chest.
However, because of the heavier loading and high number of reps certain studies have employed, some researchers have concluded that eccentric exercise has a greater potential for muscle damage than concentric exercise. In a small percentage of cases, the muscle damage resulting from very intense, high-force eccentric exercise has been severe enough to flood the blood stream with muscle tissue particles that are toxic to the kidneys (a dangerous condition called rhabdomyolysis). These studies also demonstrated the potential for prolonged muscle weakness and severe swelling.  However, this is quite unusual, and not to be expected with regular exercise programs.
Intense eccentric exercise tends to produce significant muscle soreness, and possibly weakness and reduced range of motion, beginning about 24 hours later. However, in a paper by Priscilla Clarkson, PhD, of the Department of Exercise Science at my alma mater, the University of Massachusetts at Amherst, she states, “The damage that is induced by these exercises is completely repairable in a short amount of time.” Clarkson states that even after high-force eccentric exercise, within 7 to 10 days, muscle function is fully recovered. Furthermore, “ the damage also results in an adaptation in the muscle making it more resistant to damage from subsequent strenuous exercise.” In subsequent bouts of high-force eccentric exercise, study participants experienced better performance, quicker recovery, less muscle damage, and less soreness afterwards. 
Luckily, even if you stay on the safe side, and engage only in moderate eccentric exercise that produces little muscle damage, this “training effect” still occurs. No such adaptation occurs with concentric training. 
So, what do you do with this information? The simplest and most immediate way to apply this research to your fitness regimen is to start placing equal emphasis on the concentric and eccentric phases of the exercises you do. Don’t switch to only eccentric training, because eccentric and concentric exercises benefit us in slightly different ways. A balance is best. Spend just as much time on the eccentric phase as you do on the concentric. As a starting point, I recommend 3 seconds on each phase for each rep. For example, if you’re doing a pushup, that means it should take you 3 seconds to go up and 3 seconds to go down.
Later I’ll write more about how to increase the weight for the eccentric phase and some of the interesting uses of eccentric contraction to treat injuries.
In my last article on eccentric exercise, I covered the basics of what it is, how it differs from concentric exercise, and its unique benefits. In a nutshell, the concentric phase of an exercise is where you are working to shorten (contract) a muscle. An example is, when doing a curl with a dumbbell, you start with your arm hanging down and then you bend at the elbow, bringing the weight toward your shoulder. This is concentric contraction – the phase, in nearly all exercise, that we tend to focus on. When you let the weight down again, this is the eccentric phase. The exercise part of eccentric exercise occurs by resisting allowing the muscle to lengthen. Rather than letting your arm and the weight come crashing down, you work in this phase to slow down the lengthening of the muscle, and the more emphasis you put on this, the greater your eccentric workout. The eccentric phase is often neglected, yet it’s just as important as the concentric phase.
Now, let’s look at some of the ways to make eccentric exercise work for you.
The easiest way to emphasize the eccentric phase of an exercise is to simply perform this part of the exercise slowly. If you want to focus on eccentric contraction of the chest, for instance, you could raise yourself into a pushup and then lower yourself back to the floor over a nice slow period of about 8 seconds. If that’s very easy for you, work up to 20 – 30 seconds. If you’re doing sit-ups, instead of focusing entirely on the sitting up part, and dropping back down quickly, you can spend 8 seconds on the lowering phase of each sit-up. Likewise, if that’s too easy, lengthen it to 20 – 30 seconds.
You can lower more weight through eccentric contraction than you can lift with concentric contraction, but you usually need to do a concentric contraction to set yourself up for an eccentric contraction. If, for instance, you want to emphasize the eccentric phase of a pushup (that is, lowering your body), how do you lower more weight than you lift? The easiest way is to use both arms to push yourself up, and then transfer all the weight one arm and lower yourself. However, it’s only safe if you can lower the weight (your body, in this case) in a controlled manner. Only those in great shape can lower their body from a pushup with just one arm in a slow and controlled manner. So, an easier modification would be to do the pushup against a wall, stepping far enough away from the wall to make it difficult to lower yourself slowly with one arm, but not so far away that you can’t lower yourself slowly and with good form.
Another upper body exercise well suited to emphasizing the eccentric phase is pull-ups. Even if you can’t pull yourself up to the bar, you can use a stool to get yourself up and then let yourself drop very slowly. Again, you can start at around 6 – 8 seconds, and make it longer over time if you’re able to do more than about 10 in a row. You can also strap weights around your waist to make it even more difficult. If you go to a gym that has an assisted pull-up machine, you can use it to help you up to the bar (if you’re not strong enough to do the concentric phase) and then flip the footpad out of the way so you can lower yourself without assistance.
Squats can be a great lower body eccentric exercise. Just lower yourself as slowly as you can. If you have friends to help you, you can add weight on your waist or shoulders and they can help you stand up each time (if it’s more weight than you can lift concentrically). Another way to do this is to have a grab bar or rope to help you straighten up. But even without extra weight, you can just slow down the eccentric phase, so that it eventually takes you 20 seconds or more to drop to a squat.
Eccentric workouts are best done using compound exercises as opposed to isolation exercises. Isolation exercises involve just one joint and isolate a single muscle group. Examples include biceps curls (especially on a machine), leg extensions on a machine, and triceps presses (“kickbacks”). Compound exercises involve multiple muscles and joints. Examples include push-ups / bench presses, overhead presses (lifting a weight up above the head), dead lifts, pull-ups, dips, and squats. Besides being well suited to eccentric emphasis, compound exercises tone the body in a much more comprehensive way than isolation exercises do (I’ll discuss this more in a future blog).
Go forth and be eccentric! But don’t overdo it. As with any exercise regimen, good form and knowing your limits are everything. Check with your doctor for guidance before beginning. It’s not hard to injure yourself by being overly ambitious with this kind of exercise. Warm up, take it slow and listen to your body.
Besides being a neglected aspect of exercise and a way to get stronger faster, eccentric resistance can actually help in the repair of certain kinds of muscular problems, specifically tendonitis (AKA tendinitis). At one or both ends of a muscle, the fleshy muscle tissue merges into firmer springy material called tendon, that attaches the muscle to bone. The work of a muscle/tendon unit – the shortening and lengthening – occurs in the muscle part, and this length-change is transmitted through the tendon which causes a joint to move or holds a bone in place. Both muscle and tendon are susceptible to damage through overwork, overlengthening, or impingement. When this occurs to a tendon, especially repeatedly or without rest or treatment, tendonitis – tendon inflammation – is often the result.
Tennis elbow and golfer’s elbow often involve tendonitis. Achilles tendonitis is common in athletes, and occurs at the thick tendon at the back of the ankle. Patellar tendonitis (jumper’s knee) is inflammation of the tendon that envelops and extends below the knee cap. Hamstring tendonitis is inflammation of the thick tendons that run along the back of the thigh. It’s usually felt near the bony area at the base of the butt, though it could also occur near the back or outside of the knee. Biceps tendinitis occurs at the front of the shoulder, above the bulkier part of the biceps muscle. Tendonitis can occur in a number of other locations, such as the shoulder, neck, wrist, or ankle.
Treatment for tendonitis is usually pretty conservative – rest, ice, compression, sometimes a cortisone injection nearby, and taking anti-inflammatory drugs. But repeated, slow eccentric contractions of the muscle involved can be tremendously helpful – sometimes an outright cure.
Here are the basics. (I cannot say if this therapy is appropriate for you without knowing the particulars of your pain, so, if you have tendonitis, consult with your doctor before undertaking any new treatment program. This is provided for informational purposes only.) Typically, the muscle will be set up with a concentric contraction with help from a friend or the use of a more functional part of your body. Then you’ll slowly return to starting position using just the affected muscle (over a period of about 3 seconds). This is done 10 to 15 times, usually for 3 sets, with a minute or two of rest in between. And the whole process can be done once or twice a day.
Now for an example. For Achilles tendonitis, you could stand with the balls of your feet on a stair or a block (such that the heel is unsupported). Then use both feet to press yourself up to your tiptoes. Next, lift up the good leg (just a simple bend of the knee is fine) so that all your weight is on the hurt leg. Then, slowly lower yourself down completely. This is one rep. After progressing for a few weeks, it is sometimes helpful to begin adding extra weight (by strapping weights to your belt or wearing a weighted backpack).
For patellar tendinitis, you can do a one-legged squat to eccentrically contract the affected tendon. This is ideally done while standing on a slight decline (like a wedge of about 30 degrees). Bend the good leg back, then slowly squat on the injured leg. You don’t need to go down to the deepest squat possible. Even just a 45 degree thigh is fine. Then put the other foot on the wedge, and use both legs to straighten up again. This is one rep. As with the Achilles exercise, you can gradually add weight as you progress with this.
A novel approach to delivering eccentric contraction to the extensors of the forearm was developed by Dr. Timothy Tyler using a rubber resistance bar (cheaply available on Amazon and sporting goods stores in a few different grades of firmness). This exercise is now famous with physical therapists, who refer to it as the “Tyler Twist.” You can check it out HERE. And for golfer’s elbow, there’s a similar maneuver called the “Reverse Tyler Twist.”
I hope you have become more eccentric as a result of reading this series!
1. Clarkson, Priscilla. “Eccentric Exercise Testing and Training.” Department of Exercise Science, University of Massachusetts at Amherst, n.d. Web. 10 Dec 2011. <http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940023860_1994023860.pdf>.
2. Sayers, Stephen P., Priscilla M. Clarkson, Pierre A. Rouzier, and Gary Kamen. “Adverse Events Associated with Eccentric Exercise Protocols: Six Case Studies.” Medicine & Science in Sports & Exercise 31.12 (1999): 1697-707.
3. Paschalis, V., M.G. Nikolaidis, et al. “A weekly bout of eccentric exercise is sufficient to induce health-promoting effects.” Medicine & Science in Sports & Exercise. 43.1 (2011): 64-73. Web. 12 Dec. 2011. <http://journals.lww.com/acsm-msse/Abstract/2011/01000/A_Weekly_Bout_of_Eccentric_Exercise_Is_Sufficient.9.aspx>