Lecture notes, lectures 1-5 - Patricia Doyle-Baker PDF

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Patricia Doyle-Baker...

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KNES 203 (lecture 1-6)

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Physical activity o

Encompasses all leisure and non leisure body movement produced by the skeletal muscles which result in an increase in energy expenditure over resting levels

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Classifications: Occupational, Domestic, Transportation, Leisure-time

Physical Fitness o

A set of attributes (measureable) or characteristics that people have or achieve that relates to their ability to perform physical activity

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General fitness (state) vs Specific fitness (task)

Health related fitness o

Components of fitness that exhibit a relationship with health status (aerobic, muscles, functional fitness)

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Ability to carry out daily tasks with vigor and alertness, without undue fatigue, and ample energy to adjust to unforeseen emergencies

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More health related than sports related

Performance Related Fitness o

Physical training for a specific task (job or sport?)

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Can be different than training for general health (agility, speed, power)

Risks of Physical Inactivity o

Recognized as ¼ common risk factors for non-communicable diseases

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Ranks 4th among 5 leading causes of global mortality

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Costs: (2009) $2.4 billion dollars directly, $4.3 billion indirectly

PA benefits o

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Common Physical activity barriers o

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Strengthen muscles and bones, reduce stress, maintain healthy body weight, improve sleep, smoking cessation, management of chronic disease, etc

Time, inconvenience, no motivation, not enjoyable, lack confidence, injury fears, lack goals, lack encouragement, lack of infrastructure

MET (metabolic equivalent) o

1 MET = resting VO2 (3.5mL/kgxmin)

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Activities are often expressed as mulitples of the MET unit 

The harder your body works during the activity, the more oxygen is consumed and the higher the MET level

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METs express absolute rather than relative units (ratings of observed exertion)

Physical fitness components:

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Flexibility o

Range of motion around a joint or a series of joints

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Decreases substantially with age

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Eg sit and reach

Cardiorespiratory (cardiovascular) o

Cardiovascular fitness: the ability of the cardiovascular and cardio pulmonary systems to deliver and adequate supply of O2 to the working muscles

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VO2 max = oxygen uptake attained during maximal exercise intensity that could not be increased despite further increases in exercise workload

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VO2 max determinants: pulmonary diffusing capacity, maximal cardio output, O2 carrying capacity, skeletal muscle characteristics

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Ave VO2 18-22 y/o: women 38-42, men 44-50

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After 25-30 years, VO2 max values drop by 1%/year

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Females generally have lower values due to less fat free mass, less blood hemoglobin and lower Qmax

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Training can increase values depending on training status

Musculoskeletal o

Strength endurance: capacity to resist fatigue during repeated contractions with loads greater than 30% of maximal concentric strength

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Muscular endurance: the ability of a muscle to resist fatigue during repeated contractions

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Often trained in the 15-30 rep range, important in the performance of everyday tasks

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Eg push up test and back extension

Muscular strength: maximum force developed by a muscle/muscle group in a single maximal voluntary contraction 

Force developed irrespective of time

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1-5 rep range, large dependence on maximal activation of the neuromuscular system

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eg Grip strength

Muscular power: ability to produce a large amount of work in a short period of time (power = force x velocity) 

Ability to produce muscular strength quicky

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Eg vertical jump

Body Composition o

Assessing body weight and body far distribution is important.

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Excess body fat contributes to: type 2 diabetes, hypertension, heart disease, stroke

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BMI and waist circumference

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Assessment techniques 

Hydrostatic weighing (costly and difficult)

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Skin folds (estimation)

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Bioelectrical impedence (estimation)

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DXA (current gold standard)

Structure of skeletal muscle o

Human body contains more than 600 muscles (~40-50% body mass)

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All human activities require the contraction of skeletal muscles

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75% water, 20% protein, 5% salts and others

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Each muscle consists of cylindrical cells called fibers that lie parallel to each other 

Smaller muscles for precise activities may only have 100-300 fibers, large may have 1000000

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Fiber lengths vary from few mm to 30 cm

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Long muscles = high velocity of shortening

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Short muscles = high force production

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Epimysium (upon) surrounds the entire muscle and blends into intramuscular tissue sheaths to form tendons

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Perimysium (around) surrounds a bundle of fibers called fasciculus

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Endomysium (within) wraps each muscle fiber and separates it from neighboring fibers

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Sarcolemma surrounds each muscle fiber and encloses fibers cellular content (where everything is contained)

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Sarcoplasm contains nuclei that house genes, mitochondria, and other specialized organelles.

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Sarcoplasmic reticulum provides structure integrity

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Tendons connect both ends of muscle to periosteum (bones outermost cover) 

Origin – tendon joins relatively stable skeletal part (usually proximal)

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Insertion – point of distal muscle attachment to moving bone

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Fusiform muscles: produce faster velocities

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Pennate muscles: shorter fibers, more individual fibers less range of motion, greater force

Skeletal muscle blood supply o

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Arteries and veins lie parallel to muscle fibers 

Divide into arterioles and capillaries and venules to form a network

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Extensive branching = adequate gas exchange

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During intense exercise, vascular bed delivers large quantities of blood through active tissues to accommodate increased O2 need

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Blood flow oscillates during rhythmic activities (compressed during contraction, open during relaxation)

Skeletal Muscle microstructure o

Single multinucleated muscle fiber contains myofibrils that lie parallel to the fibers long axis (myofibrils contain smaller subunits called myofilaments that lie parallel to long axis of myofibril)

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Myofilaments consist of actin and myosin that account for ~85% of myofibillar complex

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Other proteins either serve structural function or affect protein filament interactions during muscle action (tropomyosin, proponin, alpha-actin (actin binding), beta actin, M protein, and C protein

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Myofibril has a cross0striation pattern 

I-band represents lighter area

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A-band represents darker area

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Centre of A band contains the H zone

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M band bisects H zone and consists of protein structures that support arrangement of myosin filaments

Z line bisects I band and adheres to sarcolemma to provide structural stability

Sarcomere consists of basic repeating unit between two Z lines; comprises the functional unit of a muscle fiber

Muscle shortening o

Sliding filament model: muscle shortening occurs due to movement of actin filament over the myosin filament (myosin filaments cyclically attach, rotate and detach from actin filaments with energy from ATP hydrolysis, each power stroke, actin filament moved 5nm

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Reduction in the distance between these micro units of contractile proteins (aka sarcomere)

Skeletal muscle fiber types o

Type I and II, differing in: primary ATP mechanism, neuron innervation, type of myosin heavy chain expressed

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The proportions of each type of muscle fiber vary from muscle to muscle and person to person

Type II fibers o

High capacity for electro chemical transmission of action potentials

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High myosin ATPase activity

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Rapid Ca2+ release and uptake by efficient sarcoplasmic reticulum

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High rate cross bridge turnover

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These factors contribute to this fibers rapid energy generation for quick powerful muscle actions

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Intrinsic speed of shortening and tension development ranges from 3-5 times faster than slow twitch fibers

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Short term glycolytic system for energy transfer

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Activation predominates in anaerobic type sprint activities and other forceful muscle actions that rely entirely on anaerobic energy transfer

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Stop and go, change of pace sports: basketball, soccer, tennis

Type I fibers o

ATP synthesis for aerobic energy transfer

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Low myosin ATPase activity

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Slow calcium handling and shortening speed

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Less developed glycolytic capacity than fast twitch fibers

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Large and numerous mitochondria

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Highly resistant to fatigue

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Slow oxidative fibers with slow shortening speed and rely on oxidative metabolism

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Both slow and fast twitch muscle fiber types contributes during near maximal anaerobic and aerobic exercise

Training principles o

Overload: training must be greater than what the body is accustomed to (pebble, rock, stone, boulder) 

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Progression: initial workload must increase to ensure continued improvement

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Specificity: training effects are specific to the energy system used, as well as muscle groups, joint actions and type/speed of muscle contraction

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Reversibility: discontinuing or lowering the intensity or volume will have a detraining effect but the losses can be regained my resuming the program

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Individuality: each individual responds uniquely to a training stimulus

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Other variables sport scientist: gravity, speed, range of motion, lever length

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Type of muscle actions:

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Increase frequency, intensity, duration or reps or sets, or decrease recovery

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Concentric: the tension developed in the cross-bridges of a muscle is sufficient to overcome any resistance to shortening

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Isometric: the tension in the cross bridges equals the resistance to shortening and the muscle length remains relatively constant

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Eccentric: The tension in the cross bridges is less than the external resistance and the muscle lengthens despite contact between the myosin cross-bridges heads and actin filaments

Skeletal muscle fiber types (I and II) o

3 differences: primary mechanisms used to produce ATP, type of motor neuron innervation, type of myosin heavy chain expressed

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the proportions of each type of muscle fiber vary from muscle to muscle and person to person

Muscle actions o

Dynamic constant contraction: muscle action against a constant external resistance (free weights)

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Dynamic variable contraction: muscle action against changing external resistance (bungee)

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Isokinetic muscle contraction: muscle action occurs at a constant velocity allowing for maximal force generation throughout the entire movement (biodex)

Training frequency: number of training sessions completed in a given time period (usually week) o

Training status: number of sessions may need to be increased to obtain training effect

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Sport season: technical in-season, vs conditioning and strength in off season (reduce frequency)

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Training load and exercise type: higher intensities and multi-joint exercises require longer recovery times 

Beginner: 2-3 sessions/week

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Intermediate: 3-4 sessions/week

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Advanced: 4-7 sessions/week

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Off season: 4-6 sessions/week

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Pre season: 3-4 sessions/week

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In season: 1-2 sessions/week

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Post season (active rest) 1-3 sessions/week

Exercise order: sequence of resistance exercises performed during one training session, usually arranged to maximize force capabilities o

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PCE  power, other core, then assistance exercises 

Power (snatch, power clean) which require highest level of skill and are most affected by fatigue

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Other non power core exercises should go next

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Assistance exercises (help develop muscle strength associate with power or core exercise) should go last (leg press)

Upper and lower body exercises (alternated) 

Permits a longer recovery between series of the same exercise 

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Decreases overall training time as a lower body exercise can be done directly after an upper body, gives rest. 

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Another way of improving recovery between series of the same exercise 

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Push: bench press, tricep extension

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Pull: lateral pull down, biceps curl

Supersets and compound sets: 

Consists of performing a pair of exercises with little to no rest

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Superset: two exercises that stress two opposing muscle groups

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Bicep curl then tricep extension

Compound set: entails sequentially performing two different exercises for the same muscle group 

Barbell bicep curl, then hammer curl

Training loads and repetitions o

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Helpful with beginners and limited time

Ensure that same muscle group is not used consecutively

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Rest periods minimal: circuit training

Push and pull exercises (alternated) 

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Helpful with beginners, and when training time is limited)

Load: the amount of weight assigned to an exercise set 

Number of repetitions is inversely related to weight lifter

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Described as a 1-RM: the most weight lidted for a specific number of repetitions

Number of repetitions and goals: 

Heavier loads are associated with development of strength and power

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Moderate loads are optimal for hypertrophy

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Repetition ranges for power are not consistent with the %1-RM repetition relationship (force velocity curve)

Training Loads and Repetitions based on Goals o

Strength: 12 reps,...