Health experts recommend getting at least 30 minutes of moderate-intensity physical activity each day. In addition, strength training exercises, targeting all the major muscle groups, should be done two or more days of the week.
Strength training is especially important for older people, who typically lose about one-half pound of muscle annually after 25. Increasing muscle mass also builds strong bones, ligaments and tendons, improving the ability to carry out daily activities and decreasing the risk for some types of injury.
Concentric Versus Eccentric Training
Muscle movement involves two basic types of action. During concentric movement (the lifting phase), the muscle contracts or shortens. During the return phase (eccentric movement), the muscle fibers lengthen as they contract.
Standard strength training involves concentric training. Adding force during the lift overloads the skeletal muscle, creating microtrauma. The body responds by repairing the damage and building more muscle to reduce future damage at that same level of resistance.
In eccentric training, the stronger force is applied during the return phase of the lift. Adding extra force as the muscle lengthens increases the amount of microtrauma to the muscle.
Researchers report during the eccentric phase of weight training, people can generally lift 40 to 50 percent more load than during the concentric phase. Thus, over an equal time period, eccentric training can build more muscle than concentric training. In one small study, women who performed eccentric exercises also had higher rates of resting energy use and fat oxidation and improvements in insulin resistance, cholesterol levels and triglyceride levels.
Researchers at the University of Florida in Gainesville have developed special workout machines that provide eccentric muscle training, called the NeGator. The machines use weights, pulleys, counter balances and motors to produce lighter resistance during the lifting (concentric) phase and heavier resistance during the lowering (eccentric) phase.
Spine Surgeon Michael Mac Millan, M.D., says it takes a little time to get used to the NeGator because the system is totally different from how people traditionally weight train. The added eccentric force creates such an efficient workout, clients get the equivalent of a week’s worth of concentric training in just one hour. The training is only done once a week to give the muscles sufficient time to recover and repair.
Currently, the NeGator is only available at the University of Florida. Researchers there are still fine-tuning the equipment and studying its use on the university’s rugby, lacrosse and Ultimate Frisbee team members. Mac Millan says everyone can benefit from eccentric training. He hopes that in the future, eccentric training will be offered as an exercise prescription to increase bone density and improve joint health.
For general information on strength training or other types of exercise:
American Council on Exercise, http://www.acefitness.org
Centers for Disease Control and Prevention, http://www.cdc.gov/physicalactivity/everyone/guidelines/index.html
Gross, M., et al., “Effects of Eccentric Cycle Ergometry in Alpine Skiers,” International Journal of Sports Medicine, August 2010, Vol. 31, No. 8, pp. 572-576.
Parr, Jeffrey, et al., “Symptomatic and Functional Responses to Concentric-Eccentric Isokinetic Versus Eccentric-Only Isotonic Exercise,” Journal of Athletic Training, September-October 2009, Vol. 44, No. 5, pp. 462-468.
Paschalis, V., et al., “A Weekly Bout of Eccentric Exercise is Sufficient to Induce Health-Promoting Effects,” Medicine and Science in Sports and Exercise, May 27, 2010, electronically published before print.
Reeves, Neil, et al., “Differential Adaptations to Eccentric Versus Conventional Resistance Training in Older Humans,” Experimental Physiology, July 2009, Vol. 94, No. 7, pp. 825-833.