Muscle Action Spectrum

Introduction The characteristics of muscle and how they produce movement is important for your understanding. We will cover muscle the following topics in this lecture: Muscle action spectrum (isotonic, concentric, eccentric, isometric, and isokinetic muscles contractions. Functional anatomy of muscles Muscular Force Length-Tension Relationships Force-Velocity Curve Force-Couple Relationships

Muscle Action Spectrum Isotonic = same tension (load) Eccentric = moving in the same direction as resistance Concentric = moving in the opposite direction as resistance Isometric = same length Isokinetic = same speed

Muscular Actions Concentric contraction Eccentric contraction Muscle acts as the motive force and shortens as it creates tension. Motion is created by the muscle contraction. Eccentric contraction Muscle acts as the resistive force and lengthens as it creates tension. External force exceeds the contractive force generated by the muscle. Motion is controlled (slowed) by the muscle contraction. Isometric contraction Muscle tension is created, but there is no apparent change in length. Resistance can come from opposing muscle groups, gravity, an immovable object, or weight training. Motion is prevented by the muscle contraction (equal opposing forces).

Gravity and Muscular Actions The primary muscles must contract concentrically to lift an object or create movement. The direction opposite to the pull of gravity The primary muscles must contract eccentrically to lower an object or control movement. The same direction as the pull of gravity If gravity is eliminated [e.g., in movements being performed perpendicular to the pull of gravity (parallel to the floor)], each muscle group acts concentrically to produce the movement.

Functional Training Train the movement, not the muscle. Benefits: Strengthens bone and connective tissues in multiple directions. Promotes muscle balance (prevents muscle imbalances) Promotes the development of healthy movement patterns. Improves function in ADL’s (activities of daily living)

Principles of Functional Training Train throughout the muscle action spectrum (i.e. concentric, eccentric, and isometric predominantly). Train in multiple planes to develop muscles and movement patterns in a variety of directions. Focus on multi-joint versus single joint exercises. Train the primal movement patterns: Squat -Pull Lunge -Push Bend -Twist Gait

Muscular Force Force = An influence applied by one object to another, which results in an acceleration or deceleration of the second object. The muscle can produce a force which is used to either hold (isometric), lift (concentric), or lower (eccentric) a resistance (i.e. weight).

Forces Force is a push or pull exerted by one object on another. External force Muscular contractions Human movement is often described in terms of motive and resistive forces. Motive force causes an increase in speed or a change in direction. Resistive force resists the motion of another external force.

Muscle Length - Tension Relationship Length-Tension Relationship = The resting length of a muscle and the tension the muscle can produce at this resting length. Manual of Structural Kinesiology Neuromuscular Fundamentals

Muscle Length - Tension Relationship If length is too short (tight) or too long (weak), muscles will not be able to perform optimally. Postural distortions commonly cause inferior movement efficiency. Muscle imbalances in one area affect other areas in the kinetic chain (thus the saying, you are only as strong as your weakest link). Manual of Structural Kinesiology Neuromuscular Fundamentals

Muscle Force – Velocity Relationship When a muscle is lengthening eccentrically, the force generated increases with speed. This is thought to be due to the elastic nature of the connective tissue. When a muscle is shortening, there is an inverse relationship between force generated by the muscle and velocity. The faster one contracts, the less resistance the muscle can exert (which is why you want to lighten a load when focusing on speed or power).

Force-Couple Relationships Force Couple = Muscle groups moving together to produce movement around a joint. The synergistic action of muscles work together to initiate movement.

Common Force-Couples

Summary Characteristics of muscle contractions and how the muscle responds in different situations will help the Fitness Trainer and Group Fitness Instructor better plan safe and effective workouts for their clients or students.