The Efficacy and Application of Eccentric Exercises for Hypertrophy and Strength
by Oren Whiting
The purpose of this synthesis is to review current literature in respects to the efficacy and application of eccentric resistance training. Compared to a concentric muscle contraction, which is the shortening of a muscle, an eccentric contraction is the resistance to lengthening of the muscle. Eccentric training is commonly studied and used for strength (dos Santos Rocha, 2011), hypertrophy (Cadore et al., 2014), rehab (Lepley & Palmieri-Smith, 2013) and prevention (Seagrave et al., 2014). Despite the abundance of applications, eccentric exercises are rarely seen being practiced within a gym setting. An explanation could be that current research has not sufficiently studied the efficacy of such exercises. Perhaps it is believed that concentric exercises are more beneficial than eccentric exercises. Finally, it could be that the facilitation of eccentric exercises is perceived to be impractical. Within this synthesis, current research will be synthesized in order to establish the efficacy (or lack thereof) of eccentric resistance training by exploring physiological responses, hypertrophic effects, strength effects, and a detailed comparison to the effects of concentric resistance training. Given sufficient evidence that eccentric exercises are effective for strength and hypertrophy would imply practical applications within the fitness community for individuals seeking to maximize their fitness potential. This would also influence researchers to further the field of study in order to establish best-practice protocols and facilitation of eccentric exercises.
Physiological Effects of Eccentric Resistance Training
Muscle anabolism is achieved through many distinct biochemical pathways in response to certain stimuli. In an official statement by the National Strength and Conditioning Association in regards to resistance training for adults, it is argued that concentric exercises are to be implemented in different fashions as the “gold standard” for muscle growth and strength (Fragala et al., 2019). Since concentric exercises are well accepted to elicit strength and hypertrophy, they will often be compared to eccentric exercises within this synthesis in order to measure effectiveness. When researchers such as Kudrna et al. (2019) are looking for physiological responses of muscle anabolism, blood growth hormone (GH) is a key indicator that the stimulus has elicited an anabolic effect. In response to a concentric squat exercise, a significant increase of GH was measured, indicating that the concentric muscle action has started a biochemical reaction that leads to muscle growth (Kudrna et al., 2019). Likewise, Calixto et al. (2014) also measured significant increases in blood GH after a bout of eccentric bench pressing. Researchers Ojasto and Hakkinen (2009) also measured significant increases in blood GH after performing various loading protocols of eccentric exercises. Note should be taken that all research parties took baseline measurements before the resistance training began. Therefore, the increases in GH can be directly attributed to the exercise stimulus. Research shows that the bioindicator of muscle anabolism, GH, is released in response to both eccentric and concentric exercises alike.
Hypertrophic and Strength Effects of Eccentric Resistance Training
Eccentric resistance training is an effective means to gaining larger muscle cross-sectional area (CSA) (Cadore et al., 2014). Muscle hypertrophy is the increase in muscle mass and muscle CSA. Increasing muscle hypertrophy is sought after by individuals seeking improvement to performance, strength, and aesthetics (Coratella & Schena, 2016). One might expect that training a muscle in any fashion would lead to muscle gain, but research has shown eccentric resistance training to be especially effective, even within short periods of time. Cadore et al. (2014) measured a 12.2% increase in quadricep muscle CSA in only six weeks compared to a 10.9% increase in the concentric group. Friedmann-Bette et al. (2010) also measured significant quadricep muscle CSA gains in only six weeks of eccentric training. Knowing that a significant amount of muscle could be gained within such a short amount of time could be reason enough to start implementing eccentric exercises. The implementation of eccentric motions for the purpose of increasing muscle size is well studied and lend credibility to the modality as being effective for hypertrophy.
Effects of lifting experience. What about individuals who have been lifting for a long time? Can they expect to make similar progress? It is important to note the personal aspects of subject selection within research in order to gauge whether or not a particular study would be applicable to the reader’s target population. Admittedly, some research articles do use untrained adults for their subject selection (Guilhem, Cornu, Maffiuletti, & Guével, 2013). Muscles that are formerly untrained have much more room for growth than those who have been at it for years, therefore rapid progress is expected. Yet, resistance trained males participating in an eccentric bench press training group for 6 weeks saw a significant increase of chest circumference (4.5cm) (Coratella & Schena, 2016). Trained males also saw significant quadricep CSA in just 6 weeks during their participation with Friedmann-Bette et al. (2010). Previous training experience does not impede the effectiveness of eccentric resistance training.
Intermuscular effectiveness. A point of concern may be that eccentric resistance training is only effective for certain muscle groups. Reading only one study of one muscle group, then blanketing it’s application to the entire body would neither be credible or ethical. Many current studies seem to choose the quadriceps as their muscle of choice as seen by Cadore et al. (2014), Friedmann-Bette et al. (2010), and Guilhem et al. (2013). It may be that the quadriceps are simply easier to study. They are a large muscle group, and access to a leg extension machine is readily available. Despite the quadricep ease-of-access, Alonso, Docampo, and Martinez (2018) measured a significant increase to hamstring CSA. The muscles of the chest (pectoralis major, mainly) have also been shown to react significantly to eccentric resistance training (Sheppard & Young, 2010). The biceps of the upper arm were another muscle shown to increase significantly in CSA after a short bout of eccentric training (Moore, Young, & Phillips, 2012). Eccentric hypertrophy gains are consistent despite muscle group selection.
Another area that should be explored are the strength building effects of eccentric exercises. Although the lines often get blurred, strength and hypertrophy are not the same thing. Strength has more to do with the generation of force, while hypertrophy is primarily concerned with muscle size. Increases to strength are primarily due to neurological adaptations to stimulus and motor unit recruitment (dos Santos Rocha, 2011). This is not to say that hypertrophy cannot lead to greater strength by increasing total muscle fiber density. Eccentric resistance training has been shown to increase force generation, which helps lifters to lift heavier loads. Increases to power and torque are key components of lifting heavier weight and increasing muscular strength. Cadore et al. (2014) showed a 30% increase in eccentric peak torque after just 6 weeks of training. Guilhem et al. (2013) also showed that a 9-week bout of eccentric training increases torque generation significantly. These studies suggest that eccentric exercises a credible modality for those seeking to increase strength.
Effects of lifting experience. Does prior lifting experience limit strength gains from eccentric exercise? As with hypertrophy, strength gains with eccentric training are not limited to inexperienced lifters as those studied by Guilhem et al. (2013). Due to increases in neurological recruitment, even experienced lifters have been reported to show significant increases to strength (Friedmann-Bette et al., 2010). Within a 6-week time period, highly trained athletes saw an increase in their bench press 1RM/body mass ratio (Coratella & Schena, 2016). Knowing this, athletes, such as powerlifters, who need to increase their bench press 1RM as part of their competition could implement eccentric overload training and reap similar benefits as those of new lifters.
Intermuscular effectiveness. Many may ask if this modality only strengthens certain muscle groups. But it has been researched that strength gains also are not specific to certain muscle groups. Increases to strength can be seen in the hamstrings (Alonso, Docampo, & Martinez, 2018), quadriceps (Cadore et al., 2014), biceps brachii (Moore et al., 2012) and pectoralis major (Sheppard & Young, 2010). Lifters who are seeking to gain strength need not concern themselves as to whether or not eccentric training would be effective for a target muscle group.
Comparison of Eccentric and Concentric Exercise Effects
Again, concentric resistance training has been established and accepted to be the standard for strength and hypertrophy (Fragala et al., 2019). Thus, an extensive comparison of eccentric to concentric training in regards to hypertrophy, strength, retention, prevention of injuries, rehabilitation of injuries and the facilitation of these exercises is needed to establish credibility.
The goal of many lifters is to increase muscle CSA, or hypertrophy. But knowing which exercises would be the most effective use of their time is often a conflicting topic. As with most scientific questions, there is no definitive conclusion within the research between concentric and eccentric exercises, but many comparative studies. After 9 weeks of working concentric contractions on one arm and eccentric contractions on the other, a group of healthy males saw similar increases to muscle CSA (Moore, Young, & Phillips, 2012). Similarly, another group saw similar increases in quadricep CSA after a 6-week exercise protocol (Cadore et al., 2014). Contrarily, Shan et al. (2016) reported greater eccentric quadricep hypertrophy after their 10-week intervention when total work was matched between the eccentric and concentric protocols. This is important because ensuring that each exercise method is being equally worked helps to eliminate the possibility that one condition is simply growing more muscle due to the fact that they’re doing more work. An additional consideration would be the work of Coratella and Schena (2016) who showed that the retention of muscle hypertrophy following a 6-week intervention and 6-week detraining period was significantly greater for the eccentric group than the concentric group. Losing progress due to unforeseen circumstances is frustrating, but if it can be avoided through exercise modality selection then a lifter could remain prepared in case of forced-detraining. Current research suggests that both methods of exercise are effective for hypertrophy but there appears to be a slight advantage being given to eccentric exercises due to greater retention.
Force generation is a primary concern for strength athletes and exercise modality selection is equally as important for developing strength. The 9-week study of Moore et al. (2012) also showed similar increases to strength between arms when one was exercised eccentrically and the other concentrically. Although the eccentric group showed about a 10% higher increase in strength, it wasn’t found to be statistically significant. Cadore et al. (2014) reiterated similarities between training modalities by showing similar increases to quadricep strength in their 6-week study. But, a study of highly trained males by Walker et al. (2016) were measured to show significantly higher strength gains through eccentric training in comparison to the group of concentric lifters and a control group. Implementing highly trained athletes lends extra credibility to the study and their findings. Additional research by Shan et al. (2016) seems to back the findings of Walker, in that they also measured significant increases to strength in comparison to concentric exercises. Finally, the work of Coratella and Schena (2016) may again tip the scale in favor of the eccentric group showing that strength gains from eccentric training are also retained after 6-weeks of detraining better than the concentrically trained group.
Injury Prevention Comparison
Although the primary focus of many athletes are strength and aesthetics, there exist other reasons to target and strengthen muscle groups. Injury prevention is crucial for the longevity and peak performance of athletes. Seeking the most appropriate and effective methods for injury prevention elicits a comparison of concentric versus eccentric exercises. Eckard et al. (2018) argued that squat strength is a major predictor of injury for college basketball players. The weaker athletes were shown to have higher incidence of injury than those who performed the motion optimally. The authors suggested that athletes should implement the back squat (mostly concentric) as a means of injury prevention. Eccentric exercises are also suggested as a viable means of injury prevention by Seagrave et al. (2014). These authors compared baseball athletes within a professional organization who were prescribed the nordic hamstring curl (eccentric) within their exercise regimen to those who were not. It was found that the athletes performing the nordic hamstring curl had significantly less hamstring injuries than those who did not have them as part of their exercise prescription. It would seem that both methods are effective for injury prevention. But, a study that directly compared the nordic hamstring curl to the ball leg curl (concentric), which are both used for injury prevention, found that the nordic curl elicited significantly more hamstring muscle activation than the ball leg curl (Monajati et al., 2017). Although both eccentric and concentric exercises can be used for injury prevention, the research suggests using eccentric exercises for the hamstrings.
Injury Rehabilitation Comparison
Muscle exercises are a primary focus during rehabilitation from injury. During injury, muscles may have atrophied and will need to regain strength for stability and prevention of future injury. Lepley and Palmieri-Smith (2013) argued that eccentric strengthening showed significant benefits to athletes recovering from anterior cruciate ligament surgery. Similarly, Drake, Pidcoe and Ericksen (2011) saw significant improvement to their patient who was suffering from patellofemoral pain syndrome through concentric strengthening of the vastus medialis oblique. When compared directly, Peterson et al. (2014) found that the patients performing eccentric exercises for tennis elbow were found to have a 10% faster pain reduction rate than those performing concentric exercises and also saw a greater increase in strength. Although both modalities can be used for rehabilitation, certain circumstances may favor the use of eccentric exercises versus concentric.
One aspect that cannot be neglected is the facilitation of eccentric and concentric exercises. Concentric exercises come naturally. The majority of gym equipment is built around concentric motions. Thus, performing eccentric exercises will require an added degree of effort and creativity. One simple method is to slow down the motion during the eccentric phase of a concentric to eccentric exercise, such as the bench press. Calixto et al. (2014) showed significant increases to growth hormone when the lifter lowered the bar over a 5 second time period instead of a 0.5 second eccentric phase. A more complicated method for the same exercise (bench press) would require the lifter to recruit a spotter (or two) that could do the majority of the concentric phase lifting, allowing the lifter to mainly engage during the eccentric portion (Coratella & Schena, 2016). Although this would allow the lifter to properly load heavier resistance onto the bar, this may not always be practical for those who lift alone. Another option for an exercise such as the leg extension would be to lift the weight with both legs, then let one leg slowly work through the eccentric phase (Shan et al., 2018). Practical facilitation favors concentric exercises.
Research suggests that implementing eccentric exercises elicits the same anabolic responses as concentric exercises. It has also been researched that eccentric resistance training will increase both muscular strength and hypertrophy effectively. The benefits of this training style are not limited to new lifters or specific muscle groups. When choosing between exercise modality type, considerations should be given to the compared categories in the light of the goals of the lifter. Both modalities elicit strength and hypertrophy effectively, but there was a slight advantage to the eccentric exercises in both categories since they show better retention. Even when considering injury prevention and rehabilitation there exists a slight advantage to the eccentric motion when compared directly. Although each category favors eccentric exercises, it may still not be worth the extra hassle for the casual gym-goer to facilitate eccentric exercises into their routine. But for elite level athletes who require the most out of their performance, the extra effort could pay dividends.
Much of the cited research is directly comparing eccentric to concentric exercises. I believe this to be due to the fact as I mentioned; concentric exercises are the standard. They are widely accepted as the primary tool to elicit muscle growth. So, if it can be established that an eccentric exercise is even more effective than what is believed to be the best method, this lends credibility to the novel approach. Although, despite the direct comparison, there doesn’t have to be such a hard line. Lifters would benefit from implementing a variety of both concentric and eccentric exercises as part of a well-balanced routine. Moving forward I believe that the efficacy of eccentric exercises should be taught and implemented within academic curriculum and through professional avenues alike.
Alonso, F. D., Docampo, B. P., & Martinez, F. J. (2018). Changes in muscle architecture of biceps femoris induced by eccentric strength training with nordic hamstring exercise. Scandinavian Journal of Medicine and Science in Sports, 28(1), 88–94.
Cadore, E. L., González, I. M., Pallarés, J. G., Rodriguez, F. J., Häkkinen, K., Kraemer, W. J., … Izquierdo, M. (2014). Muscle conduction velocity, strength, neural activity, and morphological changes after eccentric and concentric training. Scandinavian Journal of Medicine and Science in Sports, 24(5), 343–352.
Calixto, R. D., Verlengia, R., Crisp, A. H., Carvalho, T. B., Crepaldi, M. D., Pereira, A. A., … Lopes, C. R. (2014). Acute effects of movement velocity on blood lactate and growth hormone responses after eccentric bench press exercise in resistance-trained men. Biology of Sport, 31(4), 289–294.
Coratella, G., & Schena, F. (2016). Eccentric resistance training increases and retains maximal strength, muscle endurance, and hypertrophy in trained men. Applied Physiology, Nutrition and Metabolism, 41(11), 1184–1189.
Dos Santos Rocha, C. S., Baroni, B. M., Lanferdini, F. J., de la Rocha Freitas, C., Frasson, V. B., & Vaz, M. A. (2011). Specificity of strength gains after 12 weeks of isokinetic eccentric training in healthy men. Isokinetics and Exercise Science, 19(3), 221-226.
Drake, D. F., Pidcoe, P. E., & Ericksen, J. (2011). Botulinum toxin type A for nonsurgical lateral release in patellofemoral pain syndrome: A case study. Military Medicine, 176(6), 696–698.