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Rehabilitation Breakthroughs with Eccentric Training
Len Kravitz, Ph.D.

Recently, the Journal of Applied Physiology published a special edition which highlighted the topic of eccentric training (i.e., active force producing tension of a muscle occurring simultaneously with lengthening of the muscle). It featured several articles addressing contemporary scientific understandings on the mechanisms and new applications of this mode of training. One of the most attention-grabbing articles, with direct applications to the personal trainer, was on the safety, feasibility and application of eccentric training in rehabilitation settings, particular with older populations (LaStayo, et al., 2014). Much of the previous research on eccentric training and rehabilitation has focused its attention in athletic populations. The new arena of eccentric training rehabilitation is targeting older men and women (with and without disease), and persons with chronic diseases.

Eccentric Training uses Less Energy and More Force…How?
From the early work (1924) of Nobel Prize winner A.V. Hill and one of his students, W.O. Fenn, it was observed that when a muscle is stretched while contracting, the energy liberated to do the work is reduced, as compared to isometric and concentric contractions (LaStayo et al., 2014). Yet, as LeStayo and colleagues state, eccentric training actions produce the greatest force of any muscle actions. Recent research is starting to theorize how this remarkable phenomenon of muscle occurs. All current investigations focus on a new understanding of the role of the protein titin in the sarcomere of muscle. It is currently hypothesized that during eccentric contractions, titin becomes 'twisted' around actin, creating more force in muscle (Nishikawa et al., 2011). Nishikawa et al. herald this new hypothesis of titin's role in eccentric muscle action the 'winding filament hypothesis' for force enhancement during stretch.

How to Introduce More Muscular Force in Eccentric Training Rehabilitation, with Less Muscle Soreness?
From a theoretical standpoint, the concept of doing a rehabilitation exercise that produces the greatest force with the least amount of energy is quite advantageous (LeStayo et al., 2014). LeTayo et al. continue that persons with chronic diseases such as cancer, COPD, muscular and cardiovascular conditions are often frail and weak, and thus unable to fully challenge their wasting muscles. The authors summarize research concluding that appropriately administered eccentric muscular strength and endurance exercise, as well as fall prevention exercises, will help these individuals be less vulnerable to life-threatening falls, and better able to manage their health condition. Alas, one of the greatest fears of exercise professionals is the known fact that eccentric training is also implicated with more muscle damage, called delayed-onset muscle soreness or DOMS (Proske and Allen, 2005), which is something to be avoided when working with frail elderly and chronic disease populations.

LeStayo et al. highlight than when eccentric training doses (i.e., intensities) are introduced gradually over a period of time, there is much less muscle soreness. This is referred to as the repeated bout effect) (Proske and Allen, 2005). With this training technique, a personal trainer begins by having the client perform a targeted eccentric exercises at approximately 50% to 60% of the client's normal load intensity, about one week prior to the more challenging eccentric workout. For example, if a client normally does a 100lb bench press for 8 repetitions, with the RBE the personal trainer would have the client complete (following a normal concentric and eccentric warm-up set) 8 repetitions with 50% to 60% intensity (i.e., 50 to 60 lbs) using a one second concentric (extending the arms to full extension) with a 3-4 second eccentric (lowering the weight to the chest). If the client is doing multi-set training with a particular muscle group the personal trainer may wish to do two RBE sets as prescribed above. Then, the personal trainer waits ONE week before proceeding with a challenging eccentric training session for that same particular muscle group. There will be much less DOMS (from the challenging eccentric training the next week). Proske and Allen explain that several structural and neuromuscular changes occur during the week prior to the higher loading eccentric training. LeStayo et al. emphasize that progressively phased in eccentric training is the key to successful implementation of this training mode to the special rehabilitation populations.

Are There Other Advantages to Using Eccentric Training in Rehabilitation Settings?
Uniquely, it has been shown that systolic blood pressure, peak heart rate, expired ventilation, cardiac index (a heart performance measure similar to cardiac output) are all lower with eccentric exercise as compared to concentric exercise in older (ave. age 65 yrs) ambulatory men and women (Vallejo et al., 2006). This clearly shows a reduced cardiovascular disease risk when integrating eccentric exercise into these at risk populations. As well, it has also been shown that eccentric exercise is associated with high levels of exercise adherence in older populations (LeStayo et al., 2014). LeStayo et al continue that older populations tend to report lower ratings of perceived exertion with eccentric training exercise, thus allowing for greater forces with less perceived effort.

Why Eccentric Training is Desirable for Type 2 Diabetes Management and Prevention?
It has been shown that muscle mass losses in older populations are greater in those individuals with type 2 diabetes. LeStayo et al. summarize that chronic exposure to eccentric training leads to lower levels of circulating blood glucose and insulin, thus indicating an improvement in insulin sensitivity. The authors state the prolonged eccentric training leads to increases in muscle mass muscle strength, which improve glucose metabolism. The authors also suggest that the incorporation of cardiovascular exercise with the type 2 diabetes population has been shown to be the most favorable approach for disease management.

What About Eccentric Training in People with Neurologic Conditions?
The incorporating of eccentric training in people with peripheral nervous system and neurological disorders is inconclusive at this time. LeStayo et al. (2014) suggest the traditional resistance training (with a 1-2 second concentric and eccentric muscle actions) is recommended until more research is completed with these neurological conditions.

What About Eccentric Training Following Knee Surgery?
Importantly, when progressively introduced, no safety issues (i.e., joint pain, instability, injury recurrence) are increased with the use of eccentric training in post-surgery knee-joint rehabilitation (LeStayo et al., 2014). LeStayo and colleagues suggest that if any adverse responses do occur, such as joint swelling or a loss of range of motion, that the eccentric training should be discontinued.

What About Eccentric Training in Persons with Sarcopenia?
The contemporary definition of sarcopenia is loss of muscle mass, muscular strength and mobility (LeStayo et al., 2014). With older populations, the research confirms that eccentric training is equivalent to and often better than traditional resistance training (LeStayo et al., 2014). LeStayo et al. continue that muscular power enhancements are furthermore greater in older populations who have incorporated eccentric training into the exercise program. The authors additionally highlight that studies that have monitored activities of daily living, as well as precarious movements (i.e., high fall-risk tasks like descending from stairs) with eccentric training have encouraging outcomes.

The Rehabilitation Eccentric Exercise Application
LeStayo et al. (2014) stress that successful eccentric training interventions with special populations such as the elderly and those with chronic diseases need to be progressive, utilizing the RBE (described above) as a way to gradually introduce the eccentric training intensity. As the client progresses, she/he will eventually be able to work with loads greater than their maximum isometric loads. The authors suggest incorporating functional movements that capture the benefits of eccentric loading such as downhill walking, descending walking on stairways, and movement exercises that favor more eccentric patterns (i.e., slow balance lowering movements). LeStayo et al. recap that eccentric interventions with athletes and special populations (i.e., elderly and those with chronic disease) after joint surgery are very promising if presented in a progressive manner. Terrifically, a new era of rehabilitation training is forging ahead with eccentric training proving to have significant clinical, biometric, muscular strength, physical function and quality of life improvements and benefits.

LaStayo, P., Marcus, R., Dibble, L. et al. (2014). Eccentric exercise in rehabilitation: safety, feasibility, and application. Journal of Applied Physiology, 116:1426-1434.
McHugh, M.P., Connolly, D.A.J., Easton, R.G., and Gleim, G.W. (1999). Exercise-induced muscle damage and potential mechanisms for the repeated out effect. Sports Medicine, 27(3): 151-170.
Nishikawa, K.C., Monry, J.A., Uyeno, T.E. et al. (2011). Is titin a 'winding filament'? A new twist on muscle contraction. Proceedings of the Royal Society, 279, 981-990, 2012.
Proske, U., & Allen, T.J. (2005). Damage to skeletal muscle from eccentric exercise. Sport Science Reviews, 33(2), 98-104.
Vallejo, A.F., Schroeder, E.T., Zheng, L. et al. (2006). Cardiopulmonary responses to eccentric and concentric resistance exercise in older adults. Age Ageing, 35(3), 291-297.