Howdy,
An eccentric (lengthening) muscle contraction occurs when a force applied to the muscle exceeds the momentary force produced by the muscle itself, resulting in the forced lengthening of the muscle-tendon system while contracting. Single muscle fibers can produce 150% more force during eccentric v. concentric motion. Overall, we are 125-130% stronger when lowering a weight. This means you are generally stronger when muscles lengthen. Muscles are always contracting even when lengthening. Contracting is pulling; even when you are lengthening. This is why muscle damage is much greater with eccentrics.
Maximal effort eccentric training causes preferential increases in type 2 muscle fiber size. This may be because titin isoforms are stiffer in those muscle fibers. Yet, normal strength training with slow eccentric phases causes preferential increases in type 1 muscle fiber size. This is due to the low levels of effort (and motor unit recruitment) in those phases relative to the lifting phases of the same set. Bodybuilders can use both types of training in their programs. Athletes may wish to avoid normal strength training with slow lowering phases and use maximal eccentrics instead. Thus, they can achieve the largest increases in maximum strength and high-velocity strength relative to muscle size. We are able to exert much higher forces in eccentric contractions than in concentric contractions due to the greater forces that each fiber can exert when lengthening than when shortening. This means that motor unit recruitment during the eccentric phase of normal strength training is very low compared to in the concentric phase. Consequently, true eccentric training (when we lower weights that are heavier than we can lift) has very different effects from just lowering a weight slowly than you just lifted. Athletes in particular should not confuse these two, quite different types of training.
The mental effort or “cognitive load” required to perform eccentric contractions is greater than the mental effort necessary to do a similar bout of concentric contractions, even when the absolute force level is the same (and therefore the physical effort is less during the eccentric contractions because of the lower level of motor unit recruitment and corollary discharge). This may help explain why it is more difficult to achieve high levels of voluntary activation during eccentric contractions, since the high level of mental effort could inhibit our ability to achieve high levels of motor unit recruitment.
High-intensity eccentric exercise can cause muscle damage, if the exercise is repeated (eccentric contractions with high levels of effort). Delayed-onsed muscle soreness (DOMS) is the most common symptom of exercise-induced muscle damage. In general, DOMS occurs between 24-48 hr after exercise (sometimes faster) and eventually induces a reduction in muscle function and range of motion with a concomitant increase in creatine kinase (CK) activity, thus causing psychological discomfort.
Fatigue occurs during and after (strength) training exercise for a number of reasons. Eccentric contractions (especially those performed with intra-set rests) are very interesting, because they cause quite prolonged fatigue after exercise, even without triggering any metabolite accumulation. Fatigue after concentric training is mainly caused by metabolites, and fatigue after eccentric training is mainly caused by disruptions to excitation-contraction coupling and damage.
Eccentric training generally causes substantial and sustained losses in strength, which are often ascribed to muscle damage. Motor nerve conduction velocity also reduces alongside the losses in strength.
With slow eccentrics, tendons become more resilient to stretch. Emphasizing the eccentrics can thicken the tendons and the part of the muscle fibers closer to the tendon. This will make the body feel „more secure“ about lifting heavy weights. Slow eccentric works well in developing technique, and the better your technique, the more you will be able to apply your strength.
Eccentric overload involves using a heavier load in the lowering phase than in the lifting phase. This way of training leads to a higher level of motor unit recruitment in the lowering phase, exposing the less oxidative muscle fibers of the high-threshold motor units to stretch, thereby damaging them and causing more muscle damage, greater losses in strength, and slower strength recovery.
I particularly like using eccentrics to improve the extesibility of the targeted tissue (increasing the sarcomeres in series to add „length“ to the tissue). Loading eccentrics and some other forms of mobility work have been shown to help with this. By utilizing a movement with a slow eccentric, it has been found in the research that mobility is maintained better than static stretching. By utilizing the slow eccentric, it’s training the body to control the movement and in turn, allows the mobility to be maintained. Often times, mobility will improve and then regress back to where the athlete started.
PRACTICAL RECOMMENDATIONS
- Don’t just let the bar drop and bounce off your chest in a bench press (for example). Slow down and barely kiss the chest with it. This way you will likely hurt yourself less (plus you will have better motor control, mobility and muscle growth at least). The majority of athletes get injured because they lack the ability to decelerate. They can’t slow down and stop efficiently.
- It seems that eccentric training causes more hypertrophy than concentric training. If you only do eccentrics, you will probably grow more than if you do only concentrics. It’s not very significant difference though. So you need to do some sort of eccentric training to maximize hypertrophy. It seems there is no additional benefits from doing eccentric overload training. So, keep doing traditional strength training but you can include slower eccentrics (tempo: 401… or 411, 311… if you want to include isometrics a bit – which is helpful for hypertrophy at least as well because of the greater time under tension first and foremost – just make sure to do more than 5 reps).
- Maximal effort eccentric training and normal strength training with slow eccentric phases could serve bodybuilders well. Athletes may wish to avoid normal strength training with slow lowering phases (I mean on 3+ seconds on lowering) and use maximal eccentrics instead (except in cases of learning new movements, improving motor control and/or fixing form). Thus, they can achieve the largest increases in maximum strength and high-velocity strength relative to muscle size. So, true eccentric training (when we lower weights that are heavier than we can lift) has very different effects from just lowering a weight slowly than you just lifted. Athletes in particular should not confuse these two, quite different types of training.
- Eccentric training can maybe give you: Lower overall fatigue, lower perceived exercise, lower cardiorespiratory demands, greater anabolism signaling, reduced central nervous activity, increased resting energy expenditure, nice motor control and fixing form by strengthening some imbalances… but, make sure to do normal heavy lifting with slow eccentrics because you will not achieve these benefits if solely do plyos (it can be even dangerous from the injury standpoint). In the end, remember that it all depends on your goals though… But, plyometric training is necessary for improvement of athletic performance (especially speed, jumping and change of direction abilities). When it comes to change of directon ability, enhancing eccentric strength is what is very important. Slow eccentric training always comes first in proper periodisation (normal strength tr. with slow ecc.) because we need to strengthen passive tissue properly first, plus learn proper mechanics. If we do heavy eccentric training (e.g. 120% of 1RM) or heavy plyo training unprepared, we are risking injuries via: Acute ruptures, ultrastructural damage, damage of extracellular matrix, tenderness, swelling, stiffness, impaired proprioceptive function, modified locomotion of biomechanics, decreased athletic performance, etc. Heavy eccentric training phase (true ecc. tr.) should be done before plyometric phase for sure.
- Eccentric work like any option can be cycled in and is dose dependent. The body can adapt to eccentric work, but it’s best to be more aggressive on the offseason. Use a minimal amount of eccentric work in the competitive phase, depending on your sport. Some research indicates that improvement without DOMS is possible, and that also applies to eccentric-heavy options. We need an incremental build-up of ecc. training (slow progression) and opportunistic timing (early in the offseason). So while soreness is normal and part of training, eccentric training doesn’t need to be crippling to be effective. Just like regular training, a focus on eccentrics can be done without excessive soreness. A good rule of thumb is the more soreness in the offseason, the less soreness in the regular season. Remember that after eccentric training/workouts, strength is often reduced for a few days (this is termed „fatigue“). Some research has shown that the eccentric forces involved and the muscle fiber lengthening achieved are predictors of strength loss – which makes sense. However, since fast twitch muscle fibers are more easily damaged than slow twitch muscle fibers, the degree of motor unit recruitment during exercise should also predict the amount of fatigue that occurs afterwards. This means that after highly demanding eccentric training (FTF recruitment – heavy load and demanding plyo, greater ROM…), things that will take a long time to recover from will happen… But, everything depend on our short and long-term goals.
- With slow eccentrics, tendons become more resilient to stretch. Emphasizing the eccentrics can thicken the tendons and the part of the muscle fibers closer to the tendon. This will make the body feel „more secure“ about both lifting heavy weights and any movement that requires high eccentric demands. Slow eccentric works well in developing technique, and the better your technique, the more you will be able to apply your strength.
- Eccentric overload training (true ecc. tr.) in general causes very slow recovery and high CNS fatigue in most cases. This training could be useful for tendons, max strength, foundation for COD demands, etc., but it needs to be very short (2-3 sets of 5-6 reps is plenty, 1-2 exercises per training, 1-2 times a week). Short eccentric training (15-20 mins) before normal strength or techniqual training is something we can also see in practice (not bad). The same rule stands for the flywheel training (e.g. „kBox“).
- Don’t forget that it has been found in the research that slow eccentric maintains mobility better than static stretching. By utilizing the slow eccentric, it’s training the body to control the movement and in turn, allows the mobility to be maintained (long story short, when we don’t control moves well and have issues with stability, the prime movers need to stabilize what needs to be stable – which will make us stiff and not much mobile because that’s not their main job, …I mean eccentrics can cause stiffness too but we aren’t talking about the same kind/cause of stiffness…). So, I particularly like using eccentrics (full or almost full ROM) to improve the extesibility of the targeted tissue (increasing the sarcomeres in series to add „length“ to the tissue).
For the love of movement,
Luka