Applying force to lengthening muscle has broad benefits for the elderly and for people with chronic diseases, researchers are finding.
A recent special edition of the Journal of Applied Physiology focused on eccentric training, best defined as using active force to produce muscle tension while the muscle is lengthening.
One of the journal’s most attention-grabbing articles—which has direct applications for personal trainers—was on the safety, feasibility and application of eccentric training in rehabilitation settings, particularly with older populations (LaStayo et al. 2014). While previous research has focused primarily on athletes, new studies are discovering the benefits of eccentric training rehabilitation for older adults and for people with chronic diseases.
[Editor’s note: Personal trainers typically do not work with clients until they reach the postrehabilitation phase of recovery from an injury; nonetheless, this research is highly relevant to trainers.]
How Does Eccentric Training Succeed in Using Less Energy and More Force?
The early work (1924) of Nobel Prize winner A.V. Hill and one of his students, W.O. Fenn, observed that stretching a muscle while it contracts reduces the energy liberated to do the work, as compared with when the muscle contracts isometrically or concentrically (LaStayo et al. 2014). Yet, as LaStayo and colleagues state, eccentric training actions produce the greatest force of any muscle action.
Current investigations into how this remarkable muscle phenomenon occurs are developing a new understanding of the role of the protein titin in the sarcomere of muscle (see Figure 1). It is hypothesized that during eccentric contractions, titin may become “twisted” around the protein actin, creating more force in muscle (Nishikawa et al. 2011). Nishikawa et al. have proposed this winding filament hypothesis to account for force enhancement during eccentric muscle actions.
How Can You Introduce More Muscular Force Into Eccentric Training Rehabilitation, With Less Muscle Soreness?
From a theoretical standpoint, the concept of doing a rehabilitation exercise that produces maximum force with minimum energy is quite advantageous (LaStayo et al. 2014). LaStayo et al. say people with chronic diseases such as cancer, chronic obstructive pulmonary disease, and muscular and cardiovascular conditions are often frail and weak, and thus unable to fully challenge their wasting muscles. Summarizing the research, these authors conclude that appropriately administered eccentric muscular strength and endurance exercise—as well as fall prevention exercises—reduce vulnerability to life-threatening falls, making people better able to manage their health conditions.
Alas, one of the greatest concerns exercise professionals have is the fact that eccentric training can cause damage, called delayed-onset muscle soreness, or DOMS (Proske & Allen 2005), which should be avoided when working with frail elderly and chronic-disease populations. LaStayo et al. (2014) propose a solution, noting that there is much less muscle soreness when eccentric training intensities are introduced gradually over a period of time. This is called the repeated bout effect, or RBE (see Figure 2) (Proske & Allen 2005).
With this training technique, a personal trainer begins by having the client perform a targeted eccentric exercise at approximately 50%–60% of the client’s normal load intensity about 1 week before the more challenging eccentric workout. For example, say a client normally does 8 repetitions of a 100-pound bench press; using the RBE, the trainer would have the client (after a normal concentric and eccentric warm-up set) complete 8 repetitions at 50%–60% intensity (in this case, 50–60 pounds), using a 1-second concentric action (upward phase: elbow joint extension with shoulder joint horizontal adduction) with a 3- to 4-second eccentric action (downward phase: lowering the weight to the chest).
If the client is doing multiset training with a particular muscle group, the personal trainer may wish to do two RBE sets as prescribed above. Then, the trainer must wait 1 week before proceeding with a challenging eccentric training session for that same particular muscle group. The week after this session, there will be much less DOMS from the challenging eccentric training. Proske and Allen (2005) explain that several structural (in the muscle cell) and neuromuscular changes (see Figure 2) occur during the week prior to the higher-load eccentric training. LaStayo et al. (2014) emphasize that progressively phased-in eccentric training is the key to success with 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 and cardiac index (a heart performance measure similar to cardiac output) are all lower with eccentric exercise than with concentric exercise in older (average age, 65) ambulatory men and women (Vallejo et al. 2006). This clearly shows a reduced cardiovascular disease risk when integrating eccentric exercise into programs for these at-risk populations. Eccentric exercise is also associated with high levels of exercise adherence in older populations (LaStayo et al. 2014). Additionally, LaStayo et al. observe 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 Is Eccentric Training Desirable for Type 2 Diabetes Management and Prevention?
Older people who have type 2 diabetes suffer more muscle loss than their peers without the disease, studies have found. LaStayo et al. (2014) note 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 say prolonged eccentric training leads to increases in muscle mass and muscle strength, which improve glucose metabolism. They also suggest that incorporating cardiovascular exercise into programs for those with type 2 diabetes is the most favorable approach for disease management.
What About Eccentric Training in People With Neurologic Conditions?
Research on the impact of eccentric training in people with peripheral nervous system and neurological disorders is inconclusive. LaStayo et al. (2014) recommend doing traditional resistance training (with 1- to 2-second concentric and eccentric muscle actions) until more is known about the effects of eccentric training on people with neurological conditions.
What About Eccentric Training After Knee Surgery?
Importantly, eccentric training that is progressively introduced does not increase joint pain, instability or injury recurrence in people undergoing postsurgery knee-joint rehabilitation (LaStayo et al. 2014). LaStayo et al. report that eccentric exercise is a safe and feasible method to implement in a knee rehabilitation program. However, they suggest that eccentric training (and/or any bone and joint-loading technique) should be discontinued if it produces any adverse effects, such as joint swelling or loss of range of motion.
What About Eccentric Training in People With Sarcopenia?
The contemporary definition of sarcopenia is loss of muscle mass, muscular strength and mobility (LaStayo et al. 2014). With older populations, the research confirms that eccentric training is equivalent to and often better than traditional resistance training (LaStayo et al. 2014). LaStayo et al. say muscular power enhancements are greater in older populations who have incorporated eccentric training into their exercise programs. The authors say outcomes have been encouraging in studies that have monitored activities of daily living, as well as precarious movements with a high risk of falls (e.g., descending stairs), in people who were doing eccentric training.
The Rehabilitation Eccentric Exercise Application
LaStayo et al. (2014) stress that successful eccentric training with special populations such as the elderly and those with chronic diseases needs to be progressive, using the repeated bout effect to gradually introduce intensity. As clients progress, they eventually become able to work with loads greater than their maximum isometric loads. The authors suggest incorporating functional movements that capture the benefits of eccentric loading; for example, downhill walking, descending stairs, and movement exercises that favor more eccentric patterns (e.g., slow lowering movements that work on balance).
In athletes and special populations (like the elderly and those with chronic disease), using eccentric exercises after joint surgery offers great promise if presented in a progressive manner (LaStayo et al. 2014). It is terrific news that a new era of rehabilitation training is forging ahead, with eccentric training proving to have significant benefits for clinical and biometric measures, muscular strength, physical function and quality of life.