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Strength Training. Patricia A. Deuster, PhD, MPH Uniformed Services University. Outline of Presentation. Define strength training; Factors affecting force generation; Development of muscle strength; Muscular power and endurance; Approaches to strength training;

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strength training

Strength Training

Patricia A. Deuster, PhD, MPHUniformed Services University

outline of presentation
Outline of Presentation
  • Define strength training;
  • Factors affecting force generation;
  • Development of muscle strength;
  • Muscular power and endurance;
  • Approaches to strength training;
  • Benefits of strength training;
  • Designing a strength training program.
objectives
Objectives
  • Identify strength training terms;
  • Discuss trends in the prevalence of strength training;
  • Discuss factors that determine muscle force development;
  • Identify and differentiate skeletal muscle fiber types;
  • Discuss strength training terms and how to develop a strength training program;
  • Describe benefits of strength training.
strength training terms
Adaptation

Muscular Strength

Muscular Hypertrophy

Muscular Power

Muscular Endurance

Motor Performance

Progressive Overload

Specificity and Variation

Periodization

Loading

Training Volume, Impulse

Exercise Selection and Order

Rest Periods and Frequency

Muscle Action and Velocity of muscle action

Strength Training Terms

Kraemer et al; American College of Sports Medicine position stand. Progression models in resistance training for healthy adults. Med Sci Sports Exerc. 2002 Feb;34(2):364-80.

healthy people 2010 objective and strength training
Healthy People 2010 Objective and Strength Training
  • Increase to 30% the proportion of adults who perform physical activities that enhance and maintain muscular strength and endurance on > 2 days per week;
  • Also recommended by the American College of Sports Medicine.
factors affecting muscular force generation
Factors Affecting Muscular Force Generation
  • Muscle Architecture
  • Muscle Mechanics
  • Length-Tension Relationship
  • Muscle Fiber Types
  • Force-Velocity Relationship
  • Electromechanical Delay
muscle architecture
Muscle Architecture
  • Long axis of muscle determines arrangement of muscle fibers
  • Reflects muscle force and power
  • Two basic types
    • Fusiform: spindle shaped
    • Pennate: fan-shaped
pennation effects on force and fiber packing
Pennation Effects on Force and Fiber Packing
  • Pennation allows for packing a more fibers into a smaller cross-sectional area than parallel fibers.
  •  = surface pennation angle
fusiform fiber arrangement
Fusiform Fiber Arrangement

Fa = force of contraction of muscle fiber parallel to long axis of muscle

SFa = sum of all muscle fiber contractions parallel to long axis of muscle

Fa

pennate fiber arrangement
Pennate Fiber Arrangement

Fa = force of contraction of muscle fiber parallel to long axis of muscle

Fm = force of contraction of muscle fiber

 = pennation angle

Fa = (cos )(Fm)

SFa = sum of all muscle fiber contractions parallel to long axis of muscle

Fa

Fm

muscle mechanics
Muscle Mechanics
  • Active Force through contractile elements: actin and myosin mechanism;
  • Passive Force through elastic elements:
    • Series elastic elements (tendons) smooth out force of contraction and reduce effects of external forces from overloads
    • Parallel elastic elements (fascia) absorb energy input externally if muscle is stretched beyond normal "resting" length.
muscle mechanics15
The range of motion and amount of force a muscle can generate is largely determined by the arrangement of the muscle fibersMuscle Mechanics

PE = Parallel elastic component

SE = Series elastic component

CE = Contractile element

  • Fibers in series
    • Force production modest, but large range of shortening.
  • Fibers in parallel
    • Force production high, but minimal range of shortening.
length tension relationship
Length-Tension Relationship
  • Force generation optimized when muscle is slightly stretched.
  • Due to contribution of elastic components of muscle (primarily the SEC)
human muscle fiber types19
Human Muscle Fiber Types

CharacteristicsNames ST FTa FTd/x

SO FOG FG

Fibers/Motor Neuron 10-180 300-800 300-800

Motor Neuron Size Small Large Large

Nerve Conduction Velocity Slow Fast Fast

Contraction Speed (ms) 110 50 50

Type of Myosin ATPase Slow Fast Fast

SR Development Low High High

Motor Unit Force Low High High

force and types of muscle contractions
Force and Types of Muscle Contractions

Concentric

Eccentric

Isometric

isotonic contractions
Isotonic Contractions
  • Muscle changes length (changing angle of joint) and moves a load.
  • Two types of isotonic contractions
    • Concentric: Muscle shortens as it contracts
    • Eccentric: Muscle lengthens as it contracts
isometric contractions
Isometric Contractions
  • Tension increases without changes in length
  • Occurs if the load is greater than the tension the muscle is able to develop
force velocity relationship
Force-Velocity Relationship
  • Maximal force developed by muscle is governed by its shortening or lengthening velocity - holds true for all muscle types
force velocity relationships
Force Velocity Relationships
  • Concentric: CON

Ability to develop force is greater at slower contraction velocities - allows greater time for cross-bridges to generate tension

force velocity relationship28
Force-Velocity Relationship
  • Eccentric: ECC

Greater force with increasing velocity/ acceleration, due to lower metabolic cost, greater mechanical efficiency and greater contribution from series elastic components.

electromechanical delay
Electromechanical Delay
  • Time between arrival of neural stimulus and tension development by muscle
  • Varies among muscles (20-100 msec)
  • Short EMDs produced by muscles with high percentage of FT fibers
  • Not affected by muscle length, contraction type, contraction velocity, or fatigue
maturation and strength
Maturation and Strength

Factors contributing to muscle

strength during maturation

100% Adult potential

Lean body mass

Theoretical fiber type

differentiation

Testosterone

Neural myelination

development

Birth Puberty Adult

Strength primarily

via motor patterns

Consolidation

of strength

factors

Optimal strength

potential

Kraemer, 1989

adaptations to strength training
Adaptations to Strength Training
  • Physiological Adaptations
    •  muscle fiber size and strength;
    •  connective tissue density and bone integrity.
    • Muscle fiber type conversion?
  • Neural Adaptations
    •  recruitment of motor units;
    •  in firing rate of motor neurons;
    • Improved synchronization in motor neuron firing;
    • Counteraction of autogenic inhibition to allow greater force production.
skeletal muscle adaptations
Skeletal Muscle Adaptations
  • Muscle Fiber Size
  • Muscle Fiber Type Conversion
  • Muscular Strength
muscle fiber hypertrophy
Muscle Fiber Hypertrophy
  • Increase in numbers of myofibrils and actin and myosin filaments
    • Allows more cross-bridges.
  • Increases in muscle protein synthesis during post-exercise period.
  • Testosterone plays a role in promoting muscle growth.
  • High intensity training may promote greater fiber hypertrophy than low intensity training.
muscle fiber hyperplasia
Muscle Fiber Hyperplasia
  • Muscle fibers may split in half with intense weight training.
  • Each half may then increases to size of parent fiber.
  • Satellite cells may also be involved in skeletal muscle fiber generation.
  • Clearly shown in animal models, but in only a few human studies.
process of strength gains
Early strength gains influenced by neural factors.

Long-term strength gains due to muscle hypertrophy.

Process of Strength Gains
mechanisms of strength training adaptations
Mechanisms of Strength Training Adaptations
  • Mechanical stimuli
    • CON-only training equally effective as ECC, despite mechanical advantage of ECC (greater forces, muscle damage, etc)
  • Metabolic Stimuli
    • Greater metabolic costs with CON
    • Build-up of metabolic by-products may enhance release of anabolic hormones and lead to greater motor unit activation.
muscular power
Muscular Power
  • Power = Work/Time =
    • (Force X Distance)/Time =
    • Force X Velocity
  • Maximal power occurs at:
    • ~ 1/3 max velocity
    • ~ 1/3 max concentric force
  • Affected by muscular strength and movement speed;
  • Main determinant of performance for throwing, jumping, changing direction, and striking activities.
force power relationship
Force-Power Relationship
  • Power generated is greater in muscle with a high % of fast-twitch fibers at any given velocity of movement;
  • Peak power increases with velocity up to movement speeds of 200-300º•sec-1
    • Force decreases with increasing movement speed beyond this velocity
muscle load and shortening velocity

MaximumPower

Muscle

lengthening

-10

-20

Muscle Load and Shortening Velocity
  • Max velocity at minimum load
  • Max load at velocity 0

30

Power (force x velocity)

  • Power = 0 at 0 load and max load
  • Maximal power of muscle occurs at 1/3rd max load, or where Velocity X Load is greatest.

20

Velocity of Contraction (cm/s)

10

0

0.33

0.66

max

Load opposing contraction

muscular endurance
Muscular Endurance
  • The ability to exert tension over a period of time.
    • Constant: gymnast in iron cross
    • Varying: rowing, running, cycling
  • Length of time dramatically affected by force and speed requirements of activity.
  • Training involves many repetitions with light resistance.
approaches to strength training
Approaches to Strength Training
  • Static (isometric) actions
  • Dynamic actions
    • Free weights
    • Gravity dependent
    • Variable resistance
    • Isokinetic actions
    • Plyometrics
  • Other
    • Neuromuscular electrical stimulation
free weights
Free Weights
  • Gravity dependent
  • Resistance pattern constant or variable
  • Concentric and eccentric action of same muscles: antagonistic muscles not utilized
  • Momentum may be factor in resistance pattern
gravity dependent machines
Gravity Dependent Machines
  • Universal Gym
  • Resistance moves upward
  • Round pulleys changes direction of resistance
  • Constant resistance
variable resistance machines
Variable Resistance Machines
  • Nautilus
  • Cam design creates variable resistance
  • Designed to mimic strength curve
isokinetic devices
Isokinetic Devices
  • Biodex, Cybex, Orthotron, and hydraulic equipment
  • Accommodating resistance
  • Constant velocity
plyometrics
Plyometrics
  • Used to develop jumping, sprinting and explosive power;
  • Muscle is contracted eccentrically then immediately concentrically (muscle is lengthened before it is contracted);
  • Should not be done more than 2x/wk;
  • Requires 100% effort for all movements;
  • Need adequate rest time between exercises to recover: 1 to 5 work:rest ratio.
other devices
Other Devices
  • The body – pushups, sit-ups, pull-ups
  • Pushup variations
  • Sit-ups, curl-ups - changing resistance
  • Pull-ups – pronated vs. supinated grip
neuromuscular electrical stimulation
Neuromuscular Electrical Stimulation
  • Characterized by low volt stimulation targeted to stimulate motor nerves to cause a muscle contraction.
    • Brain sends a special signal via a nerve impulse to muscle "motor point" causing muscle to contract and exercise just as if it had received a signal from the brain.
  • TENS is designed to stimulate sensing nerve endings to help decrease pain. 
strength training benefits
Strength Training Benefits
  • Reduces:
    • # of injuries
    • Severity of injuries
    • Rehabilitation time
  • Increases and Maintains:
    • Strength and power
    • Endurance and stamina
    • Lean body mass
  • Develops:
    • Mental focus & toughness
designing strength training programs
Designing Strength Training Programs
  • Identify goals, depending on sport and equipment available;
  • Carry out strength testing to select appropriate resistance levels;
    • Repetition Maximum or RM - Maximum amount of weight lifted for a given number of reps
    • 1RM = amount of weight that can be lifted only one time.
determining a 1rm
Determining a 1RM
  • Warm up for 10 minutes then select weight light enough for > 10 reps;
  • Perform 12 - 15 reps, then rest 2 minutes;
  • Increase weight 2% - 10%, perform 10 - 12 reps, then rest 3 minutes.
  • Increase weight 2% - 10%, perform 6 - 8 reps then rest for 3 minutes.
  • Increase weight 2% - 10%, perform 5 reps - should be close to 5RM;
  • Multiply 5RM weight by 1.15 to get 1RM.
key training principles
Key Training Principles

Overload

Specificity

Progression

Individualism

Adaptation

Maintenance

Periodization

periodization
Periodization
  • Training technique that involves altering training variables over a specific period to achieve well-defined gains in strength, endurance, and overall performance.
  • Cycle of phases: activation (getting ready for new activity), strength development, muscular endurance development, and active recovery.
acute program variables
Acute Program Variables

Muscle Action

Rest Periods

Load and Volume

Repetition Velocity

Exercise Selection

and Order

Frequency

muscle action
Muscle Action
  • Dynamic repetitions of concentric (CON) and eccentric (ECC) actions;
  • Isometric actions serve stabilizing role;
  • Concentric actions elicit greater growth hormone response;
  • Training should include both CON and ECC.
loading and volume
Loading and Volume
  • Load: amount of weight - key variable
    • Determined by RM or % of 1RM
    • Increase by 2-10% when can perform load for 1-2 reps over desired # reps
    • Maximal strength gained with 12RM in untrained and 8RM in trained
  • Volume: total work performed
number of sets
Number of Sets
  • Multiple set programs and periodized multiple set programs are superior to single set programs over both short and long term periods for strength;
  • 3 sets better than 6 and 12 sets;
  • Altering frequency, intensity and volume best strategy to improve strength.

Galvao DA et al. J Strength Cond Res. 2004 Aug;18(3):660-667.

volume of training
Volume of Training

Sets x Repetitions x Resistance

impulse
Impulse

Product of force applied and time during which it acts:

Impulse = Force x Time of application

Impulse

Force

Time

exercise selection and order
Exercise Selection and Order
  • Single Joint (leg extension, biceps curl) - less risk because requires less skill
  • Multiple Joint: more neurally demanding and more effective for overall strength
  • Order - from large to small muscle mass/groups
rest periods
Rest Periods
  • Dependent on
    • Training goal
    • Relative load lifted
    • Status of individual
  • Primary determinant of intensity
  • Affects metabolic and hormonal demands
  • Determines amount of ATP-CR resynthesis
repetition velocity
Repetition Velocity
  • Not adequate research but:
  • “Gold Standard” = 2:1:4 or 2 s CON; 1 s pause; 4 s ECC
  • Slow: 2:4 ( good for novices)
  • Super Slow: 10:5
  • Moderate: 2:2
  • Fast: 1:1
frequency
Frequency
  • Function of type of training session, training status, and recovery of person
  • Typical: 2 -3 d/wk to allow for recuperation
  • Maintenance: 2 d/wk
  • Competitive Lifters: 5 - 7 d/wk
specific training outcomes
Specific Training Outcomes

Muscle

Endurance

Muscle

Hypertrophy

Maximal

Strength

Power

ECC:CON

1-3 Sets

15-20RM

30-60s rest

1:0:1

2-3x/wk

ECC:ISO:CON

4-6 sets

8-15RM

1-2m rest

2:1:2

3-5d/wk

ECC:ISO:CON

3-5 sets

3-8RM

3-5m rest

1:1:1

3-5d/wk

ECC:CON

3-5 sets

1-3RM

5-8m rest

Explosive

4-6d/wk

periodization plan

Cross Training/Rest

Develop Strength

Develop Strength

Develop Strength

Muscle Endurance

Muscle Endurance

Periodization Plan
optimal strength gains
Optimal Strength Gains
  • Maximal strength gains elicited with training intensity of 85% of 1RM (2 - 5 reps), 2 d/wk, with 8 sets per muscle group.
    • Peterson MD et al. J Strength Cond Res. 2004 May;18(2):377-382.
optimal power gains
Optimal Power Gains
  • Optimal load for maximal power gains depends on nature of exercise (single versus multiple joint exercises) and experience of athlete:
    • Untrained load 30-45% of 1RM
    • Trained load 40 - 70% of 1 RM
  • Explosive training best
  • Periodization important

Kawamori N et al. J Strength Cond Res. 2004;18(3):675-84.

eccentric loading
Eccentric Loading
  • Supra maximal loading to optimize force production
    • E.g. loads set at 100, 130 and 150% of 1RM
  • May be useful for recruiting high threshold motor units.
safety of strength training
Safety of Strength Training
  • Relative Safety of Weightlifting and Weight Training. Hamill 1994.
    • Injury rates were 0.0012 per 100 hours of participation compared to 0.03 for basketball, 0.1 for football, and 0.03 for all other athletics.
  • Regular participation in broad-based training that includes strength training can significantly lower sports-related injury rates and time for rehab of adolescents. Faifenbaum 2004.
physical performance and injury prevention model

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Physical Performance and Injury Prevention Model

Primary Exercises

1. Leg Press or Parallel Squat

2. Bench Press or Incline Bench

3. Lat Pulldown or Low Pull

4. Shoulder Press or Upright Row

Secondary Exercises

5. Leg Curl and Leg Extension

6. Biceps Curl and Triceps Extension

7. Low Back Extension and Abs Crunch

8. Grip/Forearm and Calves

contribution of strength to performance of tasks
Contribution of Strength to Performance of Tasks

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acsm position stand
ACSM Position Stand
  • To develop and maintain cardiorespiratory and muscular fitness, and flexibility in healthy adults
    • 8–12 repetitions for 8–10 exercises, including one exercise for all major muscle groups;
    • 10–15 repetitions for older and more frail persons.
summary strength training
Summary: Strength Training
  • Is a physiologic stimulus with multiple actions;
  • Is complex and requires administrative and physiologic planning;
  • Confers benefits to young and old, weak and strong;
  • Is safe when entered into with clearly defined goals;
  • Requires an understanding to be effective.
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