Eccentric training is a type of strength training that involves using the target muscles to control weight as it moves in a downward motion. Eccentric training focuses on slowing down the process of muscle elongation to challenge the muscles, which can lead to stronger muscles, faster muscle recovery, lower risk of injury, and increased metabolic rate.
An eccentric contraction is one of two distinct phases in the movement of muscles and tendons, following concentric contraction (shortening). An eccentric contraction is the motion of an active muscle while it is lengthening under load. Eccentric training is repetitively doing eccentric muscle contractions. For example, in a biceps curl, the action of lowering the dumbbell back down from the lift is the eccentric phase of that exercise – as long as the dumbbell is lowered slowly rather than letting it drop (i.e., the biceps are in a state of contraction to control the rate of descent of the dumbbell).
A negative repetition (negative rep) is the repetition of a technique in weight lifting in which the lifter performs the eccentric phase of a lift. Instead of pressing the weight up slowly, in proper form, a spotter generally aids in the concentric, or lifting, portion of the repetition while the lifter slowly performs the eccentric phase for several seconds.
Eccentric movement provides a braking mechanism for muscle and tendon groups that are experiencing concentric movement to protect joints from damage as the contraction is released. Eccentric training is beneficial for casual and high-performance athletes or the elderly and patients looking to rehabilitate certain muscles and tendons.
Mechanics Physiological mechanisms The muscle has "tension producing tissue comprising small contractile units referred to as sarcomeres" that each contain a "thick (myosin) and thin (actin) myofilament (muscle filaments or proteins) that overlaps to format a cross-bridge bond (attachment)".
When in a concentric exercise, shortening of a muscle occurs as the myosin and actin cross-bridges repeatedly attach and detach to draw the actin across the myosin – creating force. Each cross-bridge attachment and detachment cycle is powered by the splitting of one molecule of adenosine triphosphate (ATP). Examples of such exercises include kicking a ball or lifting a weight.
In controlled release reversals of such concentric motions, the eccentric movement stretches the muscle with opposing force that is stronger than the muscle force. When myofilaments of the muscle fiber are stretched in such eccentric contractions there can be reduced numbers of detachments of cross bridge myosin and actin links. With more cross bridges remaining attached there is greater force production in the muscle. Examples of activities involving eccentric muscle contraction include walking down a hill or resisting the force of gravity while lowering a heavy object.
Eccentric actions place a stretch on the sarcomeres to the point where the myofilaments may experience strain, otherwise known as exercise-induced delayed onset muscle soreness (DOMS). One area of research that has much promise in relation to DOMS and eccentric exercise is the repeated-bout effect (RBE). To help prevent or lessen DOMS from eccentric exercise, or to facilitate recovery from it, the exerciser would eccentrically stimulate the muscle, then repeat at weekly intervals to build up strength and allow the strain (in response to a given force level) to reduce over time.
Energy This movement has been described as negative training. This "negative" movement is necessary to reverse the muscle from its initial trajectory. Eccentric contractions use less metabolic energy, even though they can create more force than concentric actions.
In an eccentric muscle action, the load exceeds the force that can be developed by the muscle at a constant length. During eccentric contractions, the muscle is stretched, so the muscle absorbs mechanical energy. Such exercises involve negative work. The mechanical energy is dissipated or converted into one or a combination of two energies: elastic recoil energy and thermal energy.
Elastic recoil The energy that is absorbed by the muscle can be converted into elastic recoil energy, and can be recovered and reused by the body. This creates more efficiency because the body is able to use the energy for the next movement, decreasing the initial impact or shock of the movement.
For example, kinetic energy is absorbed in running every time one's foot strikes the ground and continues as one's mass overtakes the foot. At this moment, elastic recoil energy is at its maximum and a large amount of this energy is absorbed and is added to the next stride.
This movement is similar to the action of springs, where the muscle is continually shortened and stretched resulting in enhanced effectiveness and force. It can lead to the perception of "less effort" even though dealing with higher force.
Time matters in elastic recoil. If energy is not used quickly, then it is dissipated as heat. Eccentric training aims to use the principles of energy conversion to strengthen muscle and tendon groups.
Heat The energy that is absorbed by the muscle will be dissipated as heat if the muscle is being used as a "damper or shock absorber". This leads to an increase in body temperature.
Health benefits Muscle hypertrophy The primary way that the eccentric contraction promotes muscle hypertrophy is that it produces higher mechanical output at lower metabolic cost when compared to the concentric contraction. This higher mechanical tension is considered essential for growth. Additionally, eccentric exercise causes a significant increase in exercise-induced muscle damage (EIMD), as seen by the microlesions in muscle fibers, sarcolemmal disruption, and an inflammatory response that leads to delayed-onset muscle soreness (DOMS).
There is also evidence to support that eccentric contractions activate specific molecular pathways, which cause greater anabolic signaling and gene expression than concentric contractions. This is shown in the structural remodeling differences in the muscle when comparing the two training contractions. Eccentric training seems to cause a greater increase in fascicle length (sacromeres are added in series), while concentric training leads to an increase in the pennation angle (sacromeres are added in parallel).
Due to its mechanical properties, this form of training can be used for both healthy individuals and individuals who are in rehabilitation. Studies have shown that negative repetitions combine a high amount of force on the muscle with a lower energy cost than normal concentric training, which requires 4–5 times the amount of energy. In other words, lifters are stronger in the eccentric portion of an exercise, allowing for heavier weights and in turn, greater stretches under tension. Moreover, eccentric movements tend to improve stimulus to fatigue ratio and allow for more comprehensive training routines. This justifies why this type of training is more beneficial and less of a risk to subjects rehabilitating or with a limited exercise capacity.
One 8-week study found that subjects training with the same intensity, one with primarily eccentric contractions, increased muscle fiber mass by approximately 40%, while the concentric contraction group showed no change. However, this difference might not be the same when the total load is matched between training types. When matched for load, the increase in muscle volume seems to be the same between concentric and eccentric training.
The concept of eccentric overload, where the eccentric phase is loaded with more weight than the concentric phase, is a strategy that advanced lifters use to maximize hypertrophic stimulus. This method works because of the unique properties of the eccentric phase mentioned above. Due to the low metabolic cost relative to the high force production, eccentric exercise is also used for rehabilitation training, especially for elderly patients with chronic conditions who are unable to perform strenuous activity.
Advantages Eccentric training has multiple health benefits:
Eccentric contractions use less energy and actually absorb energy that will be used as heat or elastic recoil for the next movement. Eccentric training creates greater force owing to the "decreased rate of cross-bridge muscle detachments." Patients and athletes will have more muscle force for bigger weights when eccentric training. Eccentric training has proven to be an excellent post rehabilitation intervention for lower-body injuries. Increased DOMS leads to more tenderness in eccentric, rather than pure pain or tendon swelling amongst patients. Older individuals are less vulnerable to injury from eccentric exercise, primarily because of the reduced strain on muscle-tendon groupings as compared to traditional concentric exercise. Repeated-bout Effect markedly reduces DOMS. "Completing bouts of eccentric training and then repeating the workout 1 week (or more) later will result in less DOMS after the second workout." Stretching of the muscles and eccentric training provides protection from injury or re-injury. Subjects report less weariness from eccentric training than from concentric training. Total body eccentric training can raise resting metabolic rate by about 9 percent, with the greatest magnitude in the first two hours. While energy costs remain low, the degree of force is very high. This leads to muscles that respond with significant increases in muscle strength, size, and power.
Sports training
With eccentric training, muscles are able to create more for less work, which has special meaning in the realms of high-performance sports – both for injury prevention and optimal-performance training. For athletes and sports enthusiasts, this eccentric model can help with explosive force training to prevent injuries or recurring injuries, and trains the body to use the kinetic force driven by eccentric training more efficiently. Canadian Olympian Kim St-Pierre uses eccentric training as part of her regime. The Esmonde Technique takes eccentric training and makes it available to the masses through Classical Stretch and Essentrics. After having hip surgery in the summer of 2007, St-Pierre began to practice the Esmonde Technique with experts Miranda Esmonde-White from PBS's Classical Stretch and Sahra Esmonde-White host of the Essentrics workout to heal her hip.
According to tests, increases in both strength and muscle fiber are higher in eccentric training than in traditional concentric training.
The rehabilitative nature, low energy costs, high magnitudes of force, and low uptake of oxygen all align eccentric exercise for both the elderly and rehabilitative functions. Eccentric training has been found to be beneficial to those with a variety of physical ailments.
According to one systematic review and meta-analysis on shoulder impingement syndrome, eccentric training didn't improve pain or function more than other types of training.
Rehabilitation
Eccentric exercise or resistance training is currently being used as a form of rehabilitation for sports injuries, but also as an alternative form of exercise for the elderly and those affected by neurological disorders, COPD, cardiopulmonary disorders, and cancer. Muscle loss is a big problem faced by people afflicted with the above disorders and many cannot participate in rigorous exercise protocols. Eccentric muscle contractions produce high forces with low-energy costs. According to Hortobágyi, due to these properties, eccentric exercise has the greatest potential for muscle strengthening. To strengthen muscle the external force must exceed the muscle while it lengthens.
Perceived muscle damage: