Maximizing Your Workout

Are you trying to lose weight or gain muscle? Are you striving to improve sports performance or free yourself of low back pain? Everyone has a different goal when it comes to exercise. Consequently fitness enthusiasts are always looking for new innovative exercises to improve their routines. But did you know that you can kick start your training program simply by teaching your muscles how to decelerate?

Muscles produce a variety of actions to effectively manipulate gravity, ground reaction forces, momentum and external resistance. There are three different contractions that muscles produce:
Eccentric (acceleration)
Isometric (stabilization)
Concentric (deceleration)

Let’s use the example of a bicep curl exercise to illustrate muscle contractions. If an individual is performing a bicep curl, the initial movement requires the bicep to shorten to generate force to overcome the weight of the dumbbell in the individual’s hand, allowing the dumbbell to move up toward the front of the shoulder. This is the concentric portion of the exercise. Once the dumbbell is raised to the front of the shoulder, the individual holds this position. Because the length of the muscle does not change while holding this position, this is considered the isometric portion of the exercise. As one lowers the dumbbell down back to the starting position, the muscle must now lengthen to decelerate the force of the dumbbell. This is the eccentric portion of the exercise.

Let’s use another common exercise, the squat, to illustrate muscle contractions. As one descends into the squat position, the gluteals lengthen and the individual must decelerate forces applied by one’s own body weight and gravity. This is the eccentric phase of the exercise. As one pauses at the bottom, there is no visible lengthening or shortening (acceleration/deceleration) of the gluteals. This is the isometric portion of the exercise. As the individual stands back up, the gluteals shorten and the body is accelerated upward overcoming forces of applied by gravity. This is the concentric phase of the exercise.

In traditional exercise, concentric force production is often emphasized in many routines. Individuals are so focused on lifting the weight, they often allow the weight fall back to the starting position ignoring isometric and eccentric motions. Ironically, the maximum amount of force that can be produced by a muscle occurs during eccentric motions (1). In all activities, muscles work as much eccentrically and isometrically as they do concentrically. Thus, it is important to train muscles to be strong not only concentrically, but eccentrically and isometrically as well to maximize strength potential, maintain proper joint range of motion (flexibility) and prevent injury(1). Additionally, most injuries occur during eccentric deceleration (such as landing from a jump, or slowing down to change direction). In fact, research has shown approximately 70% of all ACL (knee ligament) injuries are non-contact in nature resulting from the inability to properly decelerate (2).

Now that we understand the importance of training all muscle contractions (eccentric, isometric, concentric), how does one take this information and apply it to their workout routine?

Perform all exercises through a full range of motion to effectively train all muscle contractions.
When initiating an exercise routine, start with a slow tempo, especially during the eccentric phase. This will help improve muscular endurance, posture and eccentric strength (ability to decelerate).
For example, when performing a resistance exercise, take one second to lift the weight, hold the end-range for two seconds, and slowly lower the weight back to the starting point for four seconds (3).
Once fitness levels and eccentric strength improves; progress to faster tempo exercises to improve force production capabilities. Remember, it does little good for an individual to practice explosive exercises if they lack the ability to decelerate. That is why slower tempos are important when initiating an exercise routine.

By emphasizing all muscle contractions during an exercise program fitness enthusiasts and athletes will gain strength, muscular endurance, improve posture and prevent injury. Improvements in all of these areas will allow for higher intensity programs, leading to greater fat loss, increased muscle mass and improved athletic performance.

References
1. Lastayo, P. et al. Eccentric Muscle Contractions: Their Contributions to Injury, Prevention, Rehabilitation, and Sport. J Orthop Sports Phys Ther 2003;33:557-571.
2. Griffin LY, Agel J, Albohm MJ, et al. Noncontact anterior cruciate ligament injuries; risk factors and prevention strategies. J Am Acad Orthop Surg 2000;8(3):141-150.
3. Clark, M. Russell, A. NASM Essentials of Performance Enhancement. National Academy of Sports Medicine. 2004.

Brian Sutton MA, PES, CES, CSCS, NASM-CPT is an educator and author for the National Academy of Sports Medicine.