Maximal Eccentric Resistance Exercise for Muscle Hypertrophy..

Eccentric Exercise

Bodybuilding Science for Maximal Knowledge

fitFLEX Articles - Learn, Share and Discover

Resistance training produces muscle tissue hypertrophy and increases muscular strength in both men and women. During conventional dynamic resistance exercise, the muscles perform both concentric (CON) and eccentric (ECC) actions. CON exercise consists of muscle shortening; it's characterized when muscle torque exceeds the load torque and the weight is raised. ECC exercise produces muscle lengthening; it occurs when the muscle torque is less than the load torque and the weight is lowered.

Most people go to the gym and go through their normal weight training routine forgetting the true purpose of what all those weights and dumbbells are there for- to overload skeletal muscle. Without progressive overload in your weightlifting routine, don't expect to make gains in strength and size. Overloading skeletal muscle through maximal contractions causes damage to skeletal muscle resulting in an increase in muscle protein synthesis and muscle hypertrophy.

So now that you realize overload is an important concept for increasing muscle hypertrophy, one way of achieving this is through the use of maximal FCC contractions. It must be stressed that maximal ECC contractions produce unusually high forces and are rarely performed in most training routines, but they maybe the exact shock to your training routine that will pack on some serious strength and size.

A Better Stimulus

It's no surprise that ECC contractions produce greater muscular forces than CON contractions. As early as 1965, a study by Doss and Karpovich reported that maximal eccentric force was 13.5 percent greater than isometric force and 39.7 percent greater than CON force.' It's been suggested by some researchers that ECC exercise could be a better stimulus for muscle hypertrophy than CON exercise because more sarcomeres are damaged during ECC exercise. Although the exact mechanism by which resistance exercises stimulate strength and muscle hypertrophy is unknown, previous research indicates the FCC component is essential for the promotion of muscular strength and hypertrophy.23 Maximal ECC muscle forces have been found to be about 1.3 times greater than concentric forces, thus the ability to train with higher muscular forces should result in greater tissue hypertrophy.

What all that means, basically, is that you can handle a greater workload or weight by lowering the weight than you can by lifting the weight. So what makes maximal ECC contractions so important for muscle hypertrophy? During maximal FCC contractions, fewer motor units (i.e. myofibers) are activated at the same workload than during CON contractions. This places more stress on muscle cross-bridges and can lead to damage of sarcomeres and surrounding tissues.

Incorporating maximal ECC contractions into your training routine will cause you to be extremely sore. Although the initial damage to skeletal muscle after ECC exercise can be severe, over time muscle soreness, injury and damage disappear and the muscles seem to adapt to the ECC stress by becoming more "resistant" to damage. Don't be surprised if you're walking like you're 80 years old during the first few times you perform maximal ECC contractions; you will reap the benefits from the training as you grow bigger and stronger.

The damage resulting to skeletal muscle from maximal ECC exercise can be classified into two phases: (1) Primary phase (initial insult results in sarcolemmal damage and connective tissue injury) and (2) Secondary phase (release of intracellular proteins and histological mediators). Following this intense damage to the muscle ultrastructure, increases in protein synthesis and increases in intramuscular growth factors increase, resulting in muscle hypertrophy.

Primary Stage: Structural Disorganization The exact mechanism of ECC exercise damage to myofilaments remains be clarified, but a possible mechanism for exercise induced injury is the "breaking" actions of ECC exercise, which result in the forcible detachment of cross-bridges between the actin and myosin filaments. Gibala et al examined muscle ultra-structure and contractile properties of CON only ECC only contractions in men 48 hours after resistance exercise biceps curls (eight sets of eight reps at 80 percent of one rep maximum (1-RM). After ECC exercise, there was an 82 percent disruption of biceps brachii fibers after pure ECC exercise and only a 33 percent disruption of fibers after pure CON strength exercise.

In a later study using the same protocol (eight Sets of eight reps at 80 1 RM) Gibala et al. reported that trained athletes do not have the same magnitude of myofibrilliar disruption as untrained men after ECC training. Trained athletes following the same experimental protocol did not experience any difference in muscle damage with CON biceps contractions. However, the ECC lengthening caused considerable damage to the Based on these results, the proportion of disrupted fibers and the magnitude of disruption in muscle produced from the lengthening of sarcomeres, the severity of damage is less in strength-trained athletes compared to untrained athletes. This may explain why untrained athletes starting a resistance training program experience intense soreness after their workout. Based on this research it seems skeletal muscle becomes more to damage after a period of time and becomes less susceptible to myofibrilliar damage from intense contractions.

Secondary Stage of Muscular Damage: Histological Activators Inflammatory enzymes may be released from damaged cells and cause muscle proteolysis (i.e., muscle breakdown), which can cause further damage to muscle. Injury from repeated bouts of ECC exercise can cause chemotaxis (movement toward or away from a chemical stimulus) of immune modulators and other direct mediators of inflammation. Intense ECC contractions are associated with an increase in circulating intracellular enzymes and immunologic events such as an increased number of circulating leukocytes, monocytes and neutrophils.' Macintyre et al. examined the response of neutrophils in response to ECC contractions of the quadriceps in men and women. The study was designed so that one leg was exercised with ECC contractions while the other leg was left untrained. Neutrophils increased in the ECC-trained leg focal to the site of injury as documented by the greater presence of neutrophils in the ECC exercised leg compared to the untrained leg.

Additionally, other inflammatory mediators such as cytokines, elevated intracellular Ca+, bradykinin, and interleukins (i.e. lL-1 and lL-6) have all been reported to be increased after heavy ECC exercise and may contribute to the immunological events that follow. lnterleukin-1 (IL-1) has been called 'endogenous pyrogen" and is an important mediator of acute-phase reactions such as infection, including fever and activation of cellular and humoral immune mechanisms. Macintyre et al.' found significant relations between IL-i post-exercise and the estimates of DOMS (delayed onset muscle soreness) produced 24 hours post-exercise. IL-1 is a mediator of prostaglandin E that has an effect on muscle protein metabolism by increasing muscle lysosome function.

Prostaglandins PG and PGF increase skeletal muscle protein synthesis and degradation rates, respecnistivoly." Smith et al. found that after four ECC sets of 12 repetitions using workload of 100 percent of a CON 1-RM on supine bench press, prostaglandin E along with CK increased significantly 24 and 48 hours after exercise. Anti-inflammatory drugs such as ibuprofen and acetaminophen have been shown to have different effects on PG synthesis. Acetaminophen has been shown to blunt PGa and PGF, actions after 10 sets of 10 repetitions of isotonic knee extensions at 120 percent of a CON-1- RM, whereas ibuprofen was reported to only inhibit PGF.

In a later study, using the same exercise protocol and anti-inflammatory drugs, both ibuprofen and acetaminophen inhibited post-exercise muscle protein synthesis rates normally seen 24 hours post exercise." Based on this research, it seems the use of an over-the-counter anti-inflammatory can have detrimental effects on muscle anabolic effects, so only use anti-inflammatory when you're injured and not just to alleviate soreness. Muscle damage and inflammation seem to be important mediators of muscle protein synthesis.

After the initial insult, ECC contractions seem to provide protection against further damage. Maximal ECC contractions performed for seven consecutive exercise sessions resulted in an attenuated CK and lL-1J3 and lL-6 response. This study seems to provide some evidence that damage to skeleal muscle after the initial insult is not exacerbated by additional ECC exercise and inflammation." Many athletes may think that by not exercising they may be helping the recovery process, but it has been shown that repeated bouts of ECC exercise three and six days after the initial insult of ECC contractions does not attenuate the recovery process or result in further dam- age of sarcomeres. In fact, it's been reported that exercising can reduce the symptoms of muscle soreness, while inactivity can delay the recuperation process. However, it has been publicized that following intense ECC contractorque production (muscle force) can be suppressed for several weeks the initial insult. It may be prudent to exercise with a lower training volume until adequate recovery has taken place. So, now you understand that maximal ECC contractions lead to a high degree of muscle damage and inflammation and that both of these mediators may stimulate increases in protein synthesis.

ECC Contractions and Intramuscular Growth Factors

Although the exact mechanisms in which maximal ECC contractions cause muscle hypertrophy have yet to be determined, several investigators have determined that ECC contractions: (a) cause greater damage to type II fibers than type I, which have greater hypertrophy potentiation;(b) increase protein synthesis rates; (c) cause greater activation of intramuscular growth factors.

The increased rates of protein synthesis are speculated to be greater than with CON training due to the greater exercise-induced muscle damage, protein degradation and lysosomal enzymes. Noted an increase in protein synthesis three days after ECC contractions as indicated by an increase in the number of ribosomes adjacent to the sites of muscle fiber disruption. This increase in inflammatory mediators (macro increase phages and associated cytokines) may lead to an increase in satellite cell activation. Satellite cells fuse to existing myofibers or fuse together to form new myofibers during the regeneration of damaged muscle. The mechanism by which satellite cells undergo regeneration and contribute to muscle hypertrophy is unknown. Additionally of satellite cell activation include muscle overload and injury.

The pathology of aging muscle atrophy has been implicated to be due to decreases in satellite cell number and expression. Without activation of satellite cells, skeletal muscle does not hypertrophy in experience to overload. A proposed treatment in the inherited disorder Duchenne Muscular Dystrophy (DMS) has been the implantation of normal satellite cells in the muscles of patients with genetically damaged satellite cells. Satellite cells increase muscle hypertrophy by fusing with adjacent satellite cells to form new fibers. ECC contractions, which overload muscle, have been shown to increase intra significantly muscular IGF-1 concentration, which a potent stimulator of satellite cell activation.

Barnman et al was the first to document that maximal ECC squat contractions increased IGF-1mRNA levels and reduced GE binding protein-4, which has a high binding affinity for IGF-1. In that study, subjects per set formed either CON (eight sets of eight repetitions at 85 percent of a CON 1- RM) or ECC (eight sets of eight repetitions at 110 percent of a CON 1-RM) squat contractions. While there were significant alterations in ECC contractions, the changes after CON exercise increased, but did not reach statistical.

In conclusion, the uses of maximal ECC contractions are rarely used during dynamic resistance training routine due to the limiting force production of CON contractions. Based on animal and human studies, maximal ECC contractions have the capacity to produce greater muscle strength and hypertrophy than CON contractions. Although unaccustomed maximal contractions can produce muscle soreness and decreases in torque production for several days afterward, these symptoms do not occur if the athlete gradually starts his routine with low force and gradually increases the force and volume of ECC contractions in a periodized routine. Therefore, if used properly, ECC overloading could be gradually incorporated into an athlete's training routine with- out producing force decrements and soreness.

Practical Applications

Now that I've given you all this great advice on the benefits of maximal ECC training, the question everyone is asking is: How do I incorporate them into my routine? A common problem when trying to incorporate heavy ECC contractions into a training routine is that the weight room is concentrically oriented. An athlete is limited to using submaximal ECC contractions during conventional resistance training due to CON contractions being the limiting factor. Resistance-trained athletes have learned to incorporate ECC overloading sets into their workout routines, such as doing leg extensions with two legs for the CON phase and then lowering with one leg, or having partner-assisted lifts (e.g., doing barbell preacher curls with a partner pressing down on the weight for the ECC component). Recently, there have been several commercial devices that allow athletes to maximally overload the ECC component Hopefully, more training devices will become accessible to athletes. Basically, hooks hold weights and then detach once the weight is lowered, Eccentric movements should be performed with the help of a spotter whenever possible. I currently do at least five sets of heavy ECC contractions, rotating muscle groups every week. For example, if I were to do ECC contractions for chest I would load up about 80 percent of my concentric 1- AM on the barbell and have my work-out partner push down on the barbell as hard as he can while I'm resisting it for about 10 repetitions. Once I get to the bottom, I say "Up!" and my work- out partner yanks the bar up as hard as he can, minimizing the concentric contraction. Maximal ECC contractions should only be performed sparingly because they are highly destructive and pro- duce a lot of muscle soreness. I have seen no evidence that would contraindicate the frequent use of negatives in a "bodybuilding" routine. They can be incorporated into just about any pressing movement such as leg press, bench press, barbell curls, triceps press, etc. I know some people may think that by performing super significance slow contractions on the way down may be just as effective, but it will not.

Remember, muscle hypertrophy and protein synthesis are primarily stimulated because of the tension produced by maximal contractions. Just be sure to use moderation when performing maximal ECC contractions and you'll be on your way to bigger gains in strength and size.

Related Articles