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Strength Training for Muscular P

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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;
•   Benefits of strength training;
•   Designing a strength training program.
              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
                                             • Progressive Overload
•   Adaptation                               • Specificity and Variation
•   Muscular Strength                        • Periodization
•   Muscular Hypertrophy                     • Loading
•   Muscular Power                           • Training Volume, Impulse
•   Muscular Endurance                       • Exercise Selection and
•   Motor Performance                          Order
                                             • Rest Periods and Frequency
                                             • Muscle Action and Velocity
                                               of muscle action
    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
 • 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.
                                          Prevalence of Strength
                                            Training by Gender
Prevalence of Strength Training by Year


                                          40

                                                                                    Men
                                          32
                                                                                    Women

                                          24                                        2010 Goal


                                          16


                                          8


                                          0
                                               1998 1999 2000 2001 2002 2003 2004
                                                              Year
                                               Prevalence of Strength
                                                Training by Ethnicity
Prevalence of Strength Training by Year



                                          40



                                          30                                        2010 Goal
                                                                                    White Men
                                                                                    Black Men
                                          20                                        Hispanic Men
                                                                                    White Women
                                                                                    Black Women
                                          10
                                                                                    Hispanic Women



                                          0
                                               1998 1999 2000 2001 2002 2003 2004
                                                              Year
    Factors Affecting Muscular
        Force Generation
•   Muscle Architecture
•   Muscle Mechanics
•   Length-Tension Relationship
•   Muscle Fiber Types
•   Force-Velocity Relationship
•   Electromechanical Delay
      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
Muscle Fiber Architecture
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
               Fa = force of
               contraction of
               muscle fiber
               parallel to long
               axis of muscle
         Fa

               SFa = sum of all
               muscle fiber
               contractions
               parallel to long
               axis of muscle
Pennate Fiber Arrangement
                Fa = force of contraction
                of muscle fiber parallel to
                long axis of muscle
      Fa
           Fm   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
        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 Mechanics
                           PE = Parallel elastic
                           component
                           SE = Series elastic
                           component
                           CE = Contractile element
                                Fibers in series
• The range of motion      Force production modest,
  and amount of force a    but large range of
  muscle can generate is   shortening.
  largely determined by        Fibers in parallel
  the arrangement of       Force production high, but
  the muscle fibers        minimal range of
                           shortening.
Length-Tension Relationship
• Force generation optimized when muscle is
  slightly stretched.
• Due to contribution of elastic components of
  muscle (primarily the SEC)
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     Human Muscle Fiber Types
Other Terminology          Slow Twitch        Fast Twitch
                             Type Ia      Type lla    Type lld(x)
Aerobic Capacity              HIGH       MED/HIGH       MED

Myoglobin Content             HIGH         MED          LOW

Color                         RED          RED       PINK/WHITE

Fatigue Resistance            HIGH       MED/HIGH       MED

Glycolytic Capacity           LOW          MED       MED/HIGH

Glycogen Content              LOW          MED          HIGH

Triglyceride Content          HIGH         MED       MED/LOW

Myosin Heavy Chain (MHC)     MHCIb        MHCIIa      MHCIId(x)
   Human Muscle Fiber Types
     Characteristics                 Names
                            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
Comparison of Maximal
 Shortening Velocities
 Between Fiber Types
  Force and Types of Muscle
         Contractions




Concentric   Eccentric   Isometric
      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
• Tension increases
  without changes in
  length
• Occurs if the load
  is greater than the
  tension the muscle
  is able to develop
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
• Concentric: CON
  Ability to develop
  force is greater at
  slower contraction
  velocities - allows
  greater time for
  cross-bridges to
  generate tension
   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.
Force-Velocity Relationship
  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
Electromechanical Delay
Development of
Muscle Strength
  • Maturation
  • Training
 Maturation and Strength
                                          Factors contributing to muscle
100% Adult potential                      strength during maturation

                                                     Lean body mass

                                                     Theoretical fiber type
                                                     differentiation

                                                     Testosterone

                                                     Neural myelination
                                                     development




Birth             Puberty              Adult
  Strength primarily   Consolidation    Optimal strength
  via motor patterns    of strength         potential
                          factors

                                                                 Kraemer, 1989
             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
• Muscle Fiber Size
• Muscle Fiber Type Conversion
• Muscular Strength
  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 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   • Long-term strength
  influenced by neural     gains due to muscle
  factors.                 hypertrophy.
  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
• 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
• 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
Force-Power Relationship
                                 Muscle Load and Shortening Velocity
                                      Maximum         • Max velocity at minimum load
                                       Power          • Max load at velocity 0
Velocity of Contraction (cm/s)




                                 30
                                                             Power (force x velocity)
                                                      • Power = 0 at 0 load and max load
                                 20                   • Maximal power of muscle occurs
                                                        at 1/3rd max load, or where
                                 10                     Velocity X Load is greatest.


                                 0
                                       0.33   0.66   max
                                                                              Muscle
                        -10 Load opposing contraction                         lengthening


                          -20
      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
• Static (isometric) actions
• Dynamic actions
  –   Free weights
  –   Gravity dependent
  –   Variable resistance
  –   Isokinetic actions
  –   Plyometrics
• Other
  – Neuromuscular electrical stimulation
           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

• Universal Gym
• Resistance moves upward
• Round pulleys changes direction of
  resistance
• Constant resistance
     Variable Resistance
          Machines

• Nautilus
• Cam design creates variable
  resistance
• Designed to mimic strength curve
      Isokinetic Devices

• Biodex, Cybex, Orthotron, and
  hydraulic equipment
• Accommodating resistance
• Constant velocity
           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
• The body – pushups, sit-ups, pull-
  ups
• Pushup variations
• Sit-ups, curl-ups - changing
  resistance
• Pull-ups – pronated vs. supinated
  grip
         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
• 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
• 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
• 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
 Overload                      Specificity



Progression                   Individualism



Adaptation                    Maintenance



              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

  Muscle Action        Rest Periods




Load and Volume      Repetition Velocity



Exercise Selection
                         Frequency
    and Order
         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
• 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
• 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
Sets x Repetitions x Resistance

Sets     Reps   Weight   Volume

 3        5       87     1,305

 3        10      80     2,400

 2        15      70     2,100

 1        60      30     1,800
                      Impulse
Product of force applied and time during which it acts:

        Impulse = Force x Time of application

                          Impulse
Force




               Time
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
• 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
• 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
• 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
 Muscle         Muscle      Maximal
                                         Power
Endurance     Hypertrophy   Strength



 ECC:CON      ECC:ISO:CON ECC:ISO:CON   ECC:CON
  1-3 Sets       4-6 sets    3-5 sets    3-5 sets
 15-20RM         8-15RM       3-8RM       1-3RM
30-60s rest     1-2m rest   3-5m rest   5-8m rest
    1:0:1         2:1:2        1:1:1    Explosive
  2-3x/wk        3-5d/wk     3-5d/wk     4-6d/wk
                      Sept
Develop Strength
                      Oct
                      Nov
                      Dec



Muscle Endurance
                      Jan
                      Feb




Develop Strength
                      Mar
                      Apr




Muscle Endurance
                      May
                             Periodization Plan
                      Jun
                      Jul




Cross Training/Rest
                      Aug




Develop Strength
  Approximate Intensity
 Levels Relative to a 1RM
           Number of    Energy
% of 1RM
             Reps       System
  > 95         1        ATP/CP
 80 - 95     2-5        ATP/CP
 65 - 80     6 - 10    ATP/CP/LA
 50 - 65     8 - 15    ATP/CP/LA
 30 - 50    15 - 60    LA/Aerobic
   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 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
• 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
• 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
                8   Primary Exercises
                    1. Leg Press or Parallel Squat
        6
                    2. Bench Press or Incline Bench
    4       6       3. Lat Pulldown or Low Pull
3       2           4. Shoulder Press or Upright Row

7       7           Secondary Exercises
    1       5       5. Leg Curl and Leg Extension
                    6. Biceps Curl and Triceps Extension
5                   7. Low Back Extension and Abs Crunch
                    8. Grip/Forearm and Calves
8
        Contribution of Strength to
          Performance of Tasks
        Milwaukee PAT                                               Roof Ladder
         Relatve Contributions (N-22)                          Relatve Contributions (N-467)




                                                           23.9%               5.9%
                                  14.4%
39.7%


                                                   Size
                                   45.9%                                                 70.2%
                                                 Strengt
         Combat Testィ                               h         "Elite Firefighter"
         Relative Contributions (N-22)                         Relatve Contributions (N-174)


                                                 Fitness
                                                                     16.0%
        30.6%
                                                                                               26.6%
                                         28.6%


        40.8%                                               57.4%
      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
• 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.
Questions ?

				
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