Muscular Strength and Endurance 1
Feb 08, 2016
Muscular Strength and Endurance
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Muscular Strength and EnduranceMuscles make up more than 40% of your body massWell-developed muscles can assist with:
Daily routinesProtection from injuryEnhancement of your overall well-being
Muscular strength is the amount of force a muscle can produce with a single maximum effort Muscular endurance is the ability to resist fatigue while holding or repeating a muscular contraction
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Basic Muscle PhysiologyMuscles consist of individual muscle fibers (cells) connected in bundles Muscle fibers are made up of smaller protein structures called myofibrilsMyofibrils are comprised of contractile units called sarcomeres (actin and myosin)Proper strength training causes individual fibers to increase the number of myofibrils resulting in hypertrophy Inactivity can reverse this process resulting in atrophy
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Skeletal Muscle Tissue
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SarcomereGives muscle its striated appearance.– Lighter area: I band– Darker area: A band
Smallest contractile unit in the body.– ~ 4.0 μm at rest– ~ 2.5 μm when contracted
Actin– Thin filament
Myosin– Thick filament
TroponinTropomyosin
SarcomereA band – Total length of the myosinH zone – Only myosinM line – Center of the sarcomereI band – Only actinZ lines – Ends of the sarcomere
Actin-Myosin OrientationActin is the “sliding” filament.Myosin heads can attach to the actin binding sites to create a crossbridge.Myosin heads can pivot at the cost of ATP.
Muscle ContractionThe Sliding Filament Theory
Step 1: Nerve signal arrives at the myofibril and releases neurotransmitter ACh.Step 2: ACH depolarizes the sarcolemmaStep 3: Sarcolemma releases Ca2+
Step 4: Ca2+ binds to tropomyosin and “pulls” it off of the actin binding site.Step 5: Myosin head binds with actin forming corssbridge.
Muscle ContractionThe Sliding Filament Theory
Step 6: ATP binds to the crossbridge causing the myosin heads to pivot and the actin filaments to slide towards the M line.Step 7: Crossbridge activation continues as long as Ca2+ remains high.Step 8: Muscle stimulation stops and Ca2+ moves back into sarcolemma.Step 9: Calcium removal allows tropomyosin to return to its resting position, covering the actin binding site.
Basic Muscle PhysiologyHypertrophy is the development of large muscle fibers
Atrophy is the reduction of the size of the muscle fiber due to inactivity or injury
Hyperplasia is the increase in the number of muscle fibers. It is not thought that hyperplasia plays a significant role in muscle size in humans.
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Basic Muscle PhysiologySlow-twitch fibers are:
Fatigue resistantDon’t contract as rapidly and forcefully as fast-twitch fibersRely primarily on the aerobic energy system
Fast-twitch fibers: Contract rapidly and forcefully Fatigue more quickly than slow-twitch fibersRely more on the anaerobic energy system
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Muscle Fiber Types
Muscle Fiber TypesCharacteristic Type 2B Type 2A Type 1
Color White Pink RedFiber Diameter Large Intermediate SmallCapillary Density Low Intermediate HighMitochondrial Density
Low Intermediate High
Glycolytic Capacity
High High Low
Oxidative Capacity
Low Medium/high High
Speed of Action Fast Fast SlowFatigue Resistance
Low Moderate/high High
Force Capacity High Intermediate Low
Motor UnitsA motor unit is made up of a nerve connected to a number of muscle fibers– Small motor units contain slow-twitch fibers while large
motor units contain fast-twitch fibers
Motor unit recruitment happens when strength is required; nerves assist with the action– The number and type of motor units recruited are
dependent upon the amount of strength required
Muscle learning is the ability to improve the body’s ability to recruit motor units
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Strength GainsNeural factors:– Adaptive alterations in nervous system
function that elevate motor neuron output largely account for the rapid and large strength increases early in training.
Muscular factors:– An increase in muscular tension with
exercise training provides the primary stimulus to initiate the relatively slow process of hypertrophy.
Contributions to Strength Improvements
Training Duration (weeks)
Neural Factors Muscular Hypertrophy
2 90% 10%4 60% 40%6 20% 80%8 10% 90%
Types of Muscle Actions
Benefits of Muscular Strength and Endurance
Improved performance of physical activities
Injury prevention
Improved body composition
Enhanced self-image and quality of life
Improved muscle and bone health with aging
Metabolic and heart health
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Assessing Muscular Strength and Endurance
Muscular strength is usually assessed by measuring the maximum amount of weight a person can lift one time (1 RM)– Also can use an estimated maximum test (submaximal
lift)– Need to train for several weeks before testing– Retest after 6-12 weeks
Muscular endurance is assessed by counting the maximum number of repetitions of a muscular contraction a person can perform to fatigue
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1RMOne-repetition maximum refers to the maximum amount of weight lifted one time using proper form during a standard weight-lifting exercise. – Not always practical– Can be difficult to attainEstimating 1RM1RM (kg) = 1.172 X 7-10RM (kg) + 7.704
Effects of Specific Repetition RangesGoal Reps
Power 1 - 6
Hypertrophy 6 -12
Strength 8 - 12
Endurance 10 - 25
Power RecommendationsLoading > 80% 1RMReps 1 - 6Sets 3 - 6Rest 1 – 2 minVelocity FastFrequency 2 - 4 X/week
Hypertrophy RecommendationsLoading 70-90% 1RMReps 6 - 12Sets 1 - 3Rest 2 - 3minVelocity Slow/moderateFrequency 4 - 6 X/week
Strength RecommendationsLoading 70 - 80% 1RMReps 8 - 12Sets MultipleRest 1 – 2 minVelocity SlowFrequency 2 – 6 X/week
Endurance RecommendationsLoading 50 - 70% 1RMReps 10 - 25Sets MultipleRest < 1 minVelocity ModerateFrequency 4 – 6 X/week
Creating a Successful Strength Training Program
Static (isometric) exercise involves a muscle contraction without a change in the length of the muscle or joint angle
An example is pushing against a brick wallConsidered useful in strength building after an injury/surgeryIsometric contractions are usually held for 6 seconds
Dynamic (isotonic) exercise involves a muscle contraction with a change in the length of the muscle
Two typesConcentric contractionEccentric contraction
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Static vs. Dynamic Strength Training
Comparing Static and Dynamic Exercises
Static exercises: Isometric exerciseMuscle contraction without a change in the length of the muscle or the angle in the jointRequire no equipmentBuild strength rapidlyUseful for rehabilitation
Dynamic exercises: Isotonic exerciseMuscle contraction with a change in the length of the muscleCan be performed without or with equipmentCan be used to develop strength or enduranceUse full range of motionAre more popular with the general population
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Training MethodsOther Dynamic Methods– Constant and variable resistance– Eccentric loading– Plyometrics– Speed loading – Kettlebells– Isokinetic
Other Training Methods and Types of Equipment– Resistance Bands - Medicine balls– Exercise (stability) balls - Suspension training– Pilates - Stones– No-equipment calisthenics
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Applying the FITT PrincipleFrequency: At least 2-3 nonconsecutive days/week allowing 1 day of rest between workouts– Based on the ACSM guidelines
Intensity: (Amount of Resistance) Strength requires lifting 70- 80% of your 1 RM; Endurance requires 50-70% of your 1 RMTime: (Repetitions and Sets) 8-12 reps for strength; 10-25 reps for endurance; making sure each set leads to overload of that muscle groupType: (Mode of Exercise) target large muscle groups (8-10 exercises) including opposing muscles– Agonist muscle groups – Antagonist muscle groups
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Warm Up and Cool DownEveryone should perform a warm-up prior to each weight training session
A general warm-up (like walking or easy jogging) and performing light reps of each exercise is recommended before every training session
To cool down after weight training, relax for 5-10 minutes by stretching—which could possibly prevent soreness
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Getting Started and Making Progress
First few sessions – Should be devoted to learning the movements– Choose a weight you can move easily 8-12 times; 1 set and
rest 1-2 minutes between exercise– Goal is to be doing 1-3 sets of 8-12 repetitions
Progress– “Two-for-two” rule– General guideline for increasing weight – increase by
approximately 5% of what you are currently lifting– Your rate of improvement depends on how hard you work and
your bodies response to resistance training
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Weight Training SafetyUse proper lifting techniques– ACSM recommends a moderate rate for
each repetition– Strive to maintain a neutral spine position
during each exerciseUse spotters with free weightsBe alert for injuries– R.I.C.E. principle
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A Caution About Supplements and Drugs
Supplement manufacturers often make claims that their products will promote or enhance sport performance or physique
Most of these substances are ineffective and expensive as well as possibly dangerous
Before purchasing and using these products, find other resources that document these dietary aids
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