Chapter 14

Training Muscles to Become Stronger

Slide Show developed by: Richard C. Krejci, Ph.D. Professor of Public Health Columbia College 11.22.11

Objectives 1. Describe the following four methods to assess muscular strength: (1) cable tensiometry, (2) dynamometry, (3) onerepetition maximum (1-RM), and (4) computer-assisted isokinetic dynamometry. 2. Outline the procedure to assess 1-RM for bench press and leg press. 3. Explain how to ensure test standardization and fairness when evaluating muscular strength. 4. Compare absolute and relative upper- and lower-body muscular strength in men and women. 5. Define concentric, eccentric, and isometric muscle actions, including examples of each. 6. Recommend appropriate frequency, overload, and sets and repetitions for dynamic exercise resistance training.

Objectives (Cont.) 7. Explain the specificity of training response for muscular strength related to enhanced performance in sports and occupational tasks. 8. Compare isokinetic resistance training to conventional dynamic and static resistance training. 9. Describe the rationale for plyometric training to improve muscular strength and power, and give examples of exercises for these purposes. 10. Indicate how psychological and muscular factors influence maximum strength capacity.

11.Outline the major physiologic adaptations to resistance training. 12.Demonstrate the ability to develop a circuit resistance training program to improve muscular strength and aerobic fitness simultaneously.

Objectives (Cont.) 13.Describe tests to assess muscular endurance for the abdominals and chest-shoulder areas. 14.Describe delayed-onset muscle soreness (DOMS) related to (1) type of exercise most frequently associated with DOMS, (2) best way to minimize DOMS effects when beginning a training program, and (3) cellular factors related to DOMS.

Resistance Training Areas • Weight lifting and power lifting competition

• Body building • General strength training • Physical therapy

• Sport-specific resistance training • Muscle physiology studies

Weight Training is....... the use of moderate weights (resistance), reasonable numbers of repetitions (lifts) and sets (group of lifts) to increase muscular strength and endurance for increasing physical fitness and improving overall health. Training volume is the sum of all of the repetitions performed multiplied by the resistances used during a strength training session. Example: Bench Press: 1 set X 8 reps X 80 pounds = 640

Weight Training is not....... Power Lifting - an Olympic Competition based upon maximum weight lifted on three precise lifts. Body Building - a showmanship competition incorporating special lights, oils, and specific poses to emphasize (showcase) well defined muscles.

Types of Muscle Action • Concentric contraction: Occurs in dynamic activities where muscles shorten and produce tension through the range of motion

• Eccentric contraction: Occurs when external resistance exceeds muscle force, and muscle lengthens as tension develops • Isometric contraction: Occurs when a muscle generates force and attempts to shorten but cannot overcome the external resistance • Dynamic constant external resistance (DCER): Implies that the external weight or resistance remains constant throughout the movement (also known as isokinetic contraction if the speed of movement is under strict control).

Resistance Training Methods

Isotonic Exercise

Isometric Exercise

Isokinetic Exercise

Isotonic vs Isometric Contractions Isotonic Contraction

Isometric Contraction

The Two Movement Phases of Isotonic Training Concentric Movement

Lifting or Positive Phase

Eccentric Movement

Lowering or Negative Phase

Types of Muscle Action (Cont.)

Measurement of Muscular Strength • Muscular strength: The maximum force, tension, or torque generated by a muscle or muscle groups. • Isometric muscle testing: Muscle force is measured at a specific joint angle. • Available instruments

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Cable tensiometer Dynamometers Computer-assisted devices

Measurement of Muscular Strength

Measurement of Muscular Strength • Eccentric/Concentric muscle strength testing:

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One-Repetition Maximum (1-RM) • Choose the initial weight close to, but below maximum lifting capacity • Weight is progressively added on subsequent attempts until the person reaches maximum lift capacity • The weight increments usually range between 1 to 5 kg depending on the muscle group evaluated. • Rest intervals of 1 to 3 minutes

Measurement of Muscular Strength

Measurement of Muscular Strength • Computer-Assisted Electromechanical and Isokinetic Determinations:  Microprocessor technology integrated with exercise equipment quantifies muscular force and power during a variety of movements.

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Isokinetic dynamometer, an electromechanical accommodating resistance instrument with a speed-controlling mechanism, accelerates to a preset, constant velocity with applied force regardless of the force exerted on the movement arm.

Strength Testing Considerations • Standardize instructions prior to testing

• Ensure uniformity in duration and intensity of the warm up • Provide adequate practice prior to testing to minimize “learning” that could compromise initial results • Ensure consistency among subjects in the angle of limb measurement and/or body position on the test device

Strength Testing Considerations • Predetermine a minimum number of trials (repetitions) to establish a criterion strength score • Select test measures with high test score reproducibility • Recognize individual differences in body size and composition when evaluating strength scores among individuals and groups (use relative strength tests)

Training Muscles to Become Stronger • A muscle strengthens when trained near its current maximal force-generating capacity. • Importantly, overload intensity (level of tension placed on muscle), not the type of exercise that applies the overload, generally governs strength improvements. • Progressive-resistance (isotonic) weight training, isometric training, and isokinetic training represent three common exercise systems to train muscles to become stronger.

Strength Training Principles and Guidelines • Overload (Intensity)  Muscles respond to the intensity of the overload rather than the form of overload

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The amount of overload reflects a percentage of the 1-RM of a nonfatigued muscle or muscle group

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Minimal intensity for muscular overload occurs between 60-70% of 1-RM

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Three approaches apply muscular overload: • Increase load or resistance; increase number of repetitions; increase speed of muscle action

Strength Training Principles and Guidelines (Cont.) • Force–Velocity Relationship  Absolute or peak force generated in a movement depends on the speed of muscle lengthening and shortening

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Muscles shorten (and lengthen) at different maximum velocities depending on the load placed on them

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As the load increases, maximum shortening velocity decreases A muscle’s force-generating capacity rapidly declines with increased shortening velocity

Strength Training Principles and Guidelines (Cont.)

Strength Training Principles and Guidelines (Cont.) • Power–Velocity Relationship

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An inverted U relationship exists between a muscle’s maximal power output and speed of limb movement during concentric muscle action.

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Peak power rapidly increases with increasing velocity to a peak velocity region and after that maximal power output decreases because of reduced maximum force at faster movement speeds.

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Each muscle group has an optimum movement speed to produce maximum power.

Strength Training Principles and Guidelines (Cont.)

Strength Training Principles and Guidelines (Cont.) • Load–Repetition Relationship

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The total work accomplished by muscle action depends on the load (resistance) placed on the muscle.

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The area from 60% to 100% 1-RM represents the strength training zone- the training stimulus that optimizes strength improvement.

Strength Training Principles and Guidelines (Cont.)

Gender Differences in Muscular Strength • Absolute Muscle Strength  Comparisons of muscular strength on an absolute score basis indicate that men possess considerably greater strength than women for all muscle groups tested.

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Women score about 50% lower than men for upper-body strength and about 30% lower for leg strength.

Gender Differences in Muscular Strength (cont.) • Relative Muscle Strength  Computes in one of three variables: • Body mass (strength score in lb or kg ÷ body mass in lb or kg) • Segmental or total fat-free mass (strength score in lb or kg ÷ fat-free mass in lb or kg) • Muscle cross-sectional area (MCSA (strength score in lb or kg ÷ MCSA)

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A relative score increases the “fairness” when comparing two individuals’ strength performances.

Resistance Training for Children • Incomplete skeletal development raises concern about the potential for bone and joint injury with heavy muscular overload. • Limited evidence indicates that closely supervised resistance training programs using concentric-only muscle actions with high repetitions and low resistance improve children’s muscular strength without adverse effect on bone or muscle.

Muscular Strength Training Systems • Isometric training • Dynamic constant external resistance training

• Variable resistance training • Isokinetic training • Plyometric training • Body weight-loaded training

Isometric (Static) Training • Maximal voluntary isometric actions produce greater gains in isometric strength than submaximal actions. • Duration of muscle activation directly relates to increases in isometric strength. • One daily isometric action does not increase isometric strength as effectively as repeated actions. • Isometric training does not provide a consistent stimulus for muscular hypertrophy. • Gains in isometric strength occur predominantly at the joint angle used in training.

Isometric (Static) Training (Cont.) • Limitations of Isometrics

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The difficulty in monitoring exercise intensity and training results.

• Benefits of Isometrics

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Effectively improves strength of a particular muscle or group of muscles when the applied isometric force covers four or five joint angles through the ROM.

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Works well in orthopedic and physical therapy applications that isolate strengthening movements during rehabilitation.

Dynamic Constant External Resistance (DCER) Training • Involves lifting and lowering phases with each repetition using weight plates or exercise machines that feature different applications of muscle overload

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Progressive Resistance Exercise

Variable Resistance Training • Alters external resistance to movement by use of a lever arm, irregularly shaped metal cam, air, hydraulics, or a pulley to match increases and decreases in force capacity related to joint angle throughout a ROM. • This adjustment, based on average physical dimensions of a population, theoretically should facilitate strength gains because it allows near-maximal force production throughout the full ROM.

Isokinetic Resistance Training • Employs a muscle action performed at constant angular limb velocity • The isokinetic device controls movement velocity • The muscles exert maximal forces throughout the ROM while shortening at a specific velocity • Exerting maximal force throughout the full ROM optimizes strength development • Concentric-only actions minimize potential for muscle and joint injury and pain

Plyometric Training • Explosive jump training • Involves rapid stretching followed by shortening of a muscle group during a dynamic movement • The basic principle for all jumping and plyometric exercises is to absorb the shock with the arms or legs and then immediately contract the muscles. • Plyometric maneuvers avoid the disadvantage of having to decelerate a mass in the latter part of the joint ROM during a fast movement; this provides for maximal power production.

Plyometric Training

Body Weight-Loaded Training • Also known as closed-kinetic chain exercise • Suspension training introduces the added component of instability to further challenge trunk and back muscle neuromuscular control.

Specificity of Strength Training Response • A muscle group strengthened and enlarged by dynamic resistance training does not demonstrate equal improvement in force capacity when measured isometrically or isokinetically.

• Functional strength training or functional resistance movement training: To improve a specific physical performance through resistance training, it is important to train the muscle(s) in movements that mimic the movement requiring force–capacity improvement, with focus on force, velocity, and power requirements rather than simply an isolated joint or muscle action.

Periodization • Varies training intensity and volume to ensure that peak performance coincides with major competition • Subdivides a specific resistance-training period such as 1 year (macrocycle) into smaller periods or phases (mesocycles), with each mesocycle again separated into weekly microcycles • The training model progressively decreases training volume and increases intensity as program duration progresses to maximize newly acquired improvements in muscular strength and power.

Periodization (Cont.) • Preparation phase: Emphasizes modest strength development with high-volume, low-intensity workouts • First transition phase: Emphasizes strength development with workouts of moderate volume and moderate intensity • Competition phase: Selective strength development is emphasized with low-volume, high-intensity workouts plus short periods of interval training that emphasize sport-specific exercises • Second transition phase (active recovery): Emphasizes recreational activities and low-intensity workouts that incorporate different exercise modes

Periodization (Cont.)

Practical Recommendations for Initiating a Resistance-Training Program • Avoid maximum lifts in the beginning stages of resistance training • Use lighter resistance to perform more repetitions at the start of training • After several weeks of training decrease repetitions to between 6 and 8 • Add more resistance after reaching the target number of repetitions. • The exercise sequence should proceed from larger to smaller muscle groups to avoid premature fatigue of the smaller group.

Practical Recommendations for Initiating a Resistance-Training Program (Cont.)

Practical Recommendations for Initiating a Resistance-Training Program (Cont.)

Practical Recommendations for Initiating a Resistance-Training Program (Cont.)

Adaptations to Resistance Training • Neural Adaptations

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A development in how well an untrained person recruits more motor units to achieve a maximal muscle action

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Increased synchronization of motor unit firing, causing more motor units to fire simultaneously

Adaptations to Resistance Training (Cont.) • Muscular Adaptations

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Muscle fiber hypertrophy • Growth takes place from: • Increased amounts of contractile proteins • Increased number and size of myofibrils per muscle fiber • Increased amounts of connective, tendinous, and ligamentous tissues • Increased quantity of enzymes and stored nutrients

Adaptations to Resistance Training (Cont.) • Connective Tissue and Bone Adaptations

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Ligaments, tendons, and bone correspondingly strengthen as muscle strength and size increase.

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Connective tissue proliferates around individual muscle fibers; this thickens and strengthens the muscle’s connective tissue structures.

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Such adaptations from resistance training help to protect joints and muscles from injury, and also justify resistance exercise for preventive and rehabilitative strategies.

Adaptations to Resistance Training (Cont.)

• Cardiovascular Adaptations

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Physiologic hypertrophy of the heart wall Resistance exercise more acutely increases blood pressure than lower-intensity dynamic movements but does not produce any long-term increase in resting blood pressure.

Adaptations to Resistance Training (Cont.)

Adaptations to Resistance Training (Cont.)

• Body Composition Adaptations

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Small decreases occur in body fat, with minimal increases in total body mass and FFM.

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The largest FFM increases amount to about 3 kg over 10 weeks, with results about the same for men and women.

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No one resistance training system proves superior for changing body composition.

Muscle Soreness and Stiffness

• Delayed-onset muscle soreness (DOMS)  Minute tears in muscle tissue or damage to its contractile components

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Osmotic pressure changes that cause fluid retention

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Acute inflammation

Muscle spasms Overstretching and perhaps tearing of portions of the muscle’s connective tissue harness Alteration in cell’s mechanism for calcium regulation Combination of the above factors

Muscle Soreness and Stiffness (Cont.)

The End