Muscles at Work Chapter 4 Sport Books Publisher

Objectives To be able to identify and describe the different types of muscle contractions To identify the components of strength To gain an understanding of the relationships among strength components To describe the factors that influence strength development To evaluate resistive force and power patterns of exercise devices To analyze sports movements and make movement-oriented exercise prescriptions Sport Books Publisher

Types of Muscle Contractions Sport Books Publisher

Types of Muscle Contraction Forms and types of muscle contraction Static Dynamic Isometric Isotonic Auxotonic Isokinetic Plyocentric Concentric Eccentric Concentric Eccentric (overcoming, accommodating) (resistive) Sport Books Publisher

Types of Muscle Contraction Forms and types of muscle contraction Static Dynamic Sport Books Publisher

Types of Muscle Contraction Forms and types of muscle contraction Static Isometric Concentric Eccentric Sport Books Publisher

Types of Muscle Contraction Forms and types of muscle contraction Dynamic Isotonic Auxotonic Isokinetic Plyocentric Sport Books Publisher

Types of Muscle Contraction Dynamic Isotonic Auxotonic Isokinetic Plyocentric Concentric Eccentric (overcoming, accommodating) (resistive) Sport Books Publisher

Types of Muscle Contraction Concentric Eccentric Isometric Static Isotonic Auxotonic Isokinetic Plyocentric (overcoming, accommodating) (resistive) Forms and types of muscle contraction Dynamic Sport Books Publisher

Static Contraction Muscle tension or internal force exerted against an external load Internal force is equal to, or weaker than, the external load No visible movement of the external load occurs Sport Books Publisher

Static Contraction In most sports, the need for maximal static contraction is rare Maximal static contraction is most often seen in gymnastics, wrestling, and judo Sport Books Publisher

Activities Requiring Maximal Static Muscle Tension Sport Books Publisher

Static Contraction Most sports require low to sub-maximal static contraction Examples of sports that require this type of contraction include sail-boarding, alpine skiing, and shooting events Sport Books Publisher

Activities Requiring Sub-Maximal Static Muscle Tension Sport Books Publisher

Dynamic Contraction Muscle tension or force is exerted against an external load Internal force exerted is greater than the external load Visible movement of the external load occurs Sport Books Publisher

Isometric Contraction A static contraction Muscle contraction against an external force No visible change in muscle length External load is greater than the force generated by the internal force No external movement occurs No work is performed because no movement occurs A high amount of tension is developed, energy is used Sport Books Publisher

Pushing against a stable wall is an example of an isometric contraction Sport Books Publisher

An isometric contraction occurs during an arm wrestling match when opponents generate equal forces Sport Books Publisher

Auxotonic Contraction A dynamic contraction During dynamic work, continual changes in joint angle and speed result in changes in strength needs That is, the tension required to move an external load varies The involvement of more or less motor units allows the muscle to adapt to changing tension requirements Sport Books Publisher

Auxotonic Contraction For example, the strength needed to perform a barbell curl depends on a number of internal factors These factors include: The athlete’s physique The athlete’s leverage The angle position of the limbs The speed of the movement Sport Books Publisher

Auxotonic Contraction Although the weight of the barbell remains the same, these factors may compromise an athlete’s capacity for strength gains at all joint angles Therefore, it is not easy to gain equal strength gains at all joint angles when training with free-weights alone Sport Books Publisher

Isotonic Contraction A dynamic contraction A change in muscle length occurs Constant tension is achieved and maintained Rarely encountered in sports and athletic events because a change in tension is usually required with a change in joint angle Sport Books Publisher

Isotonic Contraction Lowering a heavy weight at a slow and constant speed is an example of an isotonic contraction Sport Books Publisher

Isokinetic Contraction A dynamic contraction Involves a constant speed contraction against a preset high resistance Generation of a high level of tension within a muscle at all joint angles Thus, muscle strengthening also occurs at all joint angles With the use of certain machines, constant tension can be achieved as joint angle and movement velocity are controlled Sport Books Publisher

Isokinetic Contraction Examples of dynamometers that allow for isokinetic contraction include: CYBEX KINCOM LIDO HydraGym Nautilus Sport Books Publisher

Concentric and Eccentric Contractions Concentric Contraction: Involves muscle shortening as it goes through a range of motion; usually termed flexion Eccentric Contraction: Involves muscle lengthening during movement; usually termed extension Sport Books Publisher

Examples of Concentric & Eccentric Contractions Moving the heel closer to the buttocks is an example of a concentric contraction of the hamstring Moving the heel away from the buttocks is an example of an eccentric contraction of the hamstring Sport Books Publisher

Plyocentric Contraction A hybrid contraction The muscle performs an isotonic concentric contraction from a stretched position Involves a “pre-stretching” of the muscle to initiate the Golgi tendon organ reflex The reflex causes the muscles to contract Plyocentric training can result in functional strength gains beyond those that can be achieved through strength training alone Sport Books Publisher

Plyocentric Training Sport Books Publisher

Factors Influencing Muscle Contraction Sport Books Publisher

Factors Influencing the Force and Power of Muscle Contractions: The individual’s state of health The individual’s training status Joint angle Muscle cross-sectional area Speed of movement Muscle fibre type Age Gender Sport Books Publisher

Joint Angle The type of contraction and the force required to resist an external load change as the joint angle changes The contraction type and force required depend on whether the external force exceeds, or is less than, the internal (applied) force Static, dynamic, concentric, and eccentric contractions may all be required Coordination between agonist and antagonist muscles is required Sport Books Publisher

Joint Angle Maximal force is produced at a joint angle that corresponds to maximal cross-bridge interaction Sport Books Publisher

Muscle Cross-Sectional Area Body mass is positively correlated with strength, provided that the mass is primarily muscle tissue or lean mass The larger the muscle cross-sectional area, the more force it can generate Sport Books Publisher

Muscle Cross-Sectional Area Sport Books Publisher

Muscle Cross-Sectional Area The heaviest weights of all are lifted by athletes in the super-heavyweight category Sport Books Publisher

Maximal and Absolute Strength The greater the active body mass, the greater the maximal or absolute strength However, individuals of a smaller and lighter physique may possess a relatively high strength potential when the following factors are considered: Intramuscular coordination Intermuscular coordination Anatomical structure Muscle elasticity Sport Books Publisher

Maximal and Absolute Strength Maximal and absolute strength are important to athletes who are required to overcome the resistance of a partner or equipment Sport Books Publisher

Relative Strength The performance of athletes classified by weight, or athletes who must overcome their own body mass, depends on the proportion of maximal strength to body mass Relative Strength = Maximal Strength Body Mass Sport Books Publisher

Relative Strength Gymnasts rely heavily upon the development of relative strength Sport Books Publisher

Relative Strength Recreational athletes are usually interested in increasing active strength and reducing body mass This method is also used by overweight athletes who want to lose fat mass Sport Books Publisher

Relative Strength Relative strength can also be gained by increasing strength and stabilizing body mass Sport Books Publisher

Relative Strength Young recreational athletes should strive to develop strength in addition to increasing active body mass Sport Books Publisher

Speed of Movement As speed of movement increases, the force a muscle can generate decreases Cross bridges are compromised since they cannot couple and uncouple fast enough Thus, there is a decreased ability to establish and maintain a large number of cross bridges Sport Books Publisher

Speed of Movement Three main components of strength related to speed of movement are: Maximal strength Power Muscular endurance Sport Books Publisher

Maximal Strength Maximal Strength: The ability to perform maximal voluntary muscular contractions in order to overcome powerful external resistances One Repetition Maximum (1RM): The greatest force that can be exerted during one repetition for a given contraction of muscles Sport Books Publisher

From Greek Mythology… The alertness and great strength of Hercules, the hero of Greek mythology, allowed him to perform extraordinary deeds The name Hercules suggests a human being of giant stature and great physical strength Sport Books Publisher

Maximal Strength Greater absolute strength is necessary for activities such as weightlifting and field events in track & field Sport Books Publisher

Power Power: The ability to overcome external resistance by developing a high rate of muscular contraction; also known as ‘speed-strength’ Sport Books Publisher

Power Important for performance in activities that require mastering quick movements Includes sprinting, speed-skating, jumping, throwing, rowing, etc. Sport Books Publisher

Muscular Endurance Muscular Endurance: The ability to resist fatigue in strength performance of longer duration; also known as ‘strength endurance’ Muscular endurance determines performance capacity in events that occur over longer periods of time, such as rowing, swimming, and cross-country skiing Sport Books Publisher

Muscular Endurance Muscular endurance is important in acyclic events that involve strength and endurance, including gymnastics, wrestling, boxing, and downhill skiing Sport Books Publisher

The Relationship Between Maximal Strength and Power Common misconception that increases in maximal strength lead to slowed muscle performance In fact, The more internal force that can be generated to overcome external resistance, the more movement acceleration increases The higher the external resistance to be overcome, the more important the maximal strength for power performance Sport Books Publisher

The Relationship Between Maximal Strength and Power Fast-twitch muscle fibres increase in diameter in response to high-resistance training Sport Books Publisher

The Relationship Between Maximal Strength and Power Development of maximal strength through hypertrophy of myofibrils Sport Books Publisher

The Relationship Between Maximal Strength and Power Improved intra-muscular coordination results in a progressive increase in the number of fast motor units that can be mobilized Sport Books Publisher

The Relationship Between Maximal Strength and Power Development of maximal strength through increased intra-muscular coordination Sport Books Publisher

The Relationship Between Maximal Strength and Power Therefore, maximal strength training can be beneficial to the development of power Sport Books Publisher

The Relationship Between Maximal Strength and Power Development of maximal strength through hypertrophy and increased intra-muscular coordination Sport Books Publisher

The Relationship Between Maximal Strength and Muscular Endurance The number of repetitions that can be performed against a high-resistance is dependent on maximal strength That is, the greater an athlete’s maximal strength, the greater the muscular endurance at a particular load (as a percentage of 1RM) Sport Books Publisher

The Relationship Between Maximal Strength and Muscular Endurance Resistance Level 100% 95% 90% 85% 80% 75% Repetition Maximum 1 2-3 5-6 7-8 10-12 12-16 Sport Books Publisher

Issues Related to the Relationship Between Strength and Endurance Vigorous cardiovascular training can lead to an associated decrease in the diameter of fast-twitch muscle fibres Thus, increased endurance can be associated with decreased muscle strength as a result of a corresponding decrease in muscle volume Sport Books Publisher

Issues Related to the Relationship Between Strength and Endurance Repetitive maximal strength training decreases endurance, but increases strength Sport Books Publisher

Issues Related to the Relationship Between Strength and Endurance A Nordic event skier competing in ski jumping and cross-country skiing must combine training for maximal strength as well as muscular endurance Sport Books Publisher

Issues Related to the Relationship Between Strength and Endurance Relatively high levels of both strength and endurance can be achieved either by training for strength and endurance in separate training sessions, or in combination Sport Books Publisher

Muscle Fibre Type The greater the fast-twitch fibre content of a muscle… The greater the force output; The greater the overall speed of contraction; and The greater the fatigability will be when the muscle has been maximally activated Sport Books Publisher

Muscle Fibre Type The greater the slow-twitch fibre content of a muscle… The lower the force-producing capacity The slower the contraction speed The greater the endurance characteristics of the muscle Sport Books Publisher

Age Aging affects muscle force output There is a loss of fast-twitch fibres associated with aging May occur as a result of apoptosis May occur as a result of disuse ‘Sarcopenia’ is the medical term that describes muscle loss Sport Books Publisher

Age Diminished strength and balance is associated with muscle loss This may lead to falls and bone fractures Falls and fractures are a major cause of age-related disabilities Sport Books Publisher

Gender The absolute force and power capacity of women is often less than that of men However, there is not much difference between males and females when force and power data are normalized to selected anatomical variables Sport Books Publisher

Gender The differences between males and females is mainly due to the difference that exists in muscle volume Sport Books Publisher