Adaptations to Resistance Training
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Adaptations to Resistance Training. Key Points. Eccentric muscle action adds to the total work of a resistance exercise repetition. Key Point.

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Adaptations to Resistance Training

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Adaptations to Resistance Training


Key Points

  • Eccentric muscle action adds to the total work of a resistance exercise repetition.


Key Point

  • The use of typical concentric-eccentric repetitions in heavy resistance training by using only concentric muscle actions, at least twice as many concentric-only repetitions may be required.


Key Point

  • Further research is needed to characterize the adaptations to resistance training strategies that incorporate extremely high intensity eccentric muscle actions.


Introduction

  • Understanding the roles of concentric and eccentric actions and the training adaptations that they promote are important when designing a resistance training program.


Introduction

  • Changes in muscle size, strength, and power may all be affected by the choice of exercise employed, and particularly by the type(s) of muscle action(s) that are utilized.


Introduction

  • Many times, the muscle actions will be predetermined by the choice of a particular type of resistance training equipment.


Introduction

  • Accordingly, understanding the capabilities of various types of resistance equipment to train specific muscle actions is vital for the proper selection of the “tools” of resistance training.


Introduction

  • The training adaptations that are achieved will be directly related to the decisions made regarding the muscle action(s) used during each repetition of an exercise.


Introduction

  • Such program design decisions should be dependent upon specific program goals (e.g., strength gain versus strength maintenance) of a resistance training program.


Muscle Actions

  • There are three types of muscle action:

  • isometric

  • concentric

  • eccentric


Muscle Actions

  • An isometric muscle action is one in which force is produced with no change in the length of the whole muscle and with no joint movement.


Muscle Actions

  • An example of an isometric muscle action is attempting to lift from the floor a barbell that is too heavy to move (i.e., the maximal force produced by the muscles is less than the downward force of gravity on the barbell).


Muscle Actions

  • Note that a submaximal attempt to lift the barbell would also produce an isometric muscle action.


Muscle Actions

  • A concentric muscle action is a dynamic action in which the whole muscle shortens and joint movement occurs.


Muscle Actions

  • Raising a barbell in an elbow flexion (curl) movement is an example of a concentric action of the biceps and other elbow flexors.


Muscle Actions

  • Lowering the barbell in a controlled manner back to the starting point is an example of an eccentric muscle action of the biceps.


Muscle Actions

  • In this case, the active muscle (e.g., biceps of the arm) is forcibly lengthened as it resists the force of gravity in lowering the barbell.


Muscle Actions

  • Both concentric and eccentric muscle actions can be performed maximally or at specific submaximal percentages of their respective one repetition maximums (1RM).


Muscle Actions

  • Furthermore, the eccentric 1 RM is greater than the concentric 1 RM.


Muscle Actions

  • It is important to note that most resistance training programs involves exercises at some percentages of the concentric 1 RM.


Muscle Actions

  • Thus, for each repetition, the percentage of the eccentric 1 RM is lower than the percentage of the concentric 1 RM.


Muscle Actions

  • This article primarily examines the influence of eccentric muscle actions in resistance training programs.


Muscle Actions

  • The maximal force a muscle can develop concentrically at a given length varies inversely with the velocity of the movement (i.e., the faster the velocity of movement, the lesser the maximal force that can be produced).


Muscle Actions

  • Within a certain range of velocities, eccentric actions develop greater force at faster velocities of lengthening.


Muscle Actions


Muscle Actions

  • Several concepts emerge from an analysis of figure 1.


Muscle Actions

  • First, maximal concentric muscle actions at any velocity always result in lower force development than do either maximal isometric or maximal eccentric contractions.


Muscle Actions

  • Second, force development for eccentric actions attains a plateau at the greater velocities of lengthening.


Muscle Actions

  • Third, maximal force production for concentric actions is greatest just below the isometric point on the curve (i.e., zero velocity); thus, a concentric 1 RM exertion for many exercise movements is a low speed exertion.


Increasing Muscle Strength

  • One of the primary goals of most resistance training programs is to increase the strength of various muscles or muscle groups.


Increasing Muscle Strength

  • Strength is defined as the maximal force or torque a muscle or muscle group can generate at a specified velocity of movement.


Increasing Muscle Strength

  • Improved strength provides an individual with a greater functional capacity.


Increasing Muscle Strength

  • It appears that a combination of concentric and eccentric actions in resistance exercises produces the greatest net gains in strength.


Increasing Muscle Strength

  • The mechanisms responsible for the significant role of the eccentric component of resistance training exercises are not clear.


Increasing Muscle Strength

  • Potential mechanisms include: an enhancement of neural adaptations with eccentric muscle actions caused by increased activation of the CNS, improved synchronization of motor units, and/or decreased input from neural inhibitory reflexes that limit strength in untrained subjects.


Increasing Muscle Strength

  • Further research is needed to clarify optimal strategies of eccentric loading for different muscle groups.


Increasing Muscle Strength

  • One of the major issues concerning maximal or near maximal eccentric training is the delayed muscle soreness and the tissue injury that accompanies such training.


Increasing Muscle Strength

  • To minimize excessive muscle damage, there should be a slow progression in resistance as well as careful monitoring of the athlete’s perceived soreness when prescribing eccentric training against great resistance (I.e., 105-120% concentric 1 RM).


Strength Maintenance

  • During a four week detraining period, strength was maintained above pre-training values only when both concentric and eccentric phases of the exercises had been employed during the training phase.


Muscle Pain

  • As one becomes progressively better trained with predominantly eccentric based exercises, soreness and tissue damage are reduced.


Muscle Pain

  • The mechanisms responsible for these adaptations remain speculative but may include better neural control of muscle actions, enhanced strength of muscle and connective tissue, and/or improved structural organization of the contractile elements within the muscle.


Summary

  • Eccentric muscle actions appear to be crucial for optimal adaptations in muscle strength and hypertrophy in resistance training programs employing multiple set, 6-10 RM regimens in which both concentric and eccentric phases of resistance exercises are performed.


Summary

  • Furthermore, concentric plus eccentric actions better preserve strength during brief periods of detraining than do training programs utilizing only concentric muscle actions.


Summary

  • On the other hand, eccentric training using exceptionally high resistance exercise has produced mixed results on muscular adaptations.


Summary

  • Further research is needed to determine the efficacy of high force eccentric training with or without accompanying eccentric actions.


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