12/3/2011

1

Physiology of TrainingPhysiology of Training

Physical Activity and Aging

Relationship Among Average Body Mass and Waist Circumference and Age for Men who maintain constant weekly  varying distances (<16km Vs. > 16km)

By age 50 a physically active man will gain 10lbs or more and increase waist circumference by at least 2inches. Despite maintaining a physically active lifestyle

Remedy:  Gradually increase the amount of weekly exercise the equivalent of running 1.4 miles for each year of age starting at age 30yrs.

Am J Clinical Nutrition. 65:1391, 1997

General Training General Training PrinciplesPrinciples

• Overload Principle:The regular application of a specific exercise overload enhances physiologic function to produce a training response.

• Specificity Principle:Ad t ti i t b li d h i l i t th tAdaptations in metabolic and physiologic systems thatdepend on the type of overload imposed andmuscle mass activated.

– SAID Principle: Specific Adaptations to Imposed Demands

• Individual Differences Principle:All individuals do not respond similarly to a given training stimulus.

• Reversibility Principle:Detraining occurs relatively rapidly when a person quits their exercise training regimen.

12/3/2011

2

Metabolic and Physiological DifferencesMetabolic and Physiological Differencesbetween Trained and  Untrainedbetween Trained and  Untrained

Aerobic and Anaerobic TrainingAerobic (endurance) training• Improved central and peripheral blood flow• Enhances the capacity of muscle fibers to generate ATP

Anaerobic trainingAnaerobic training• Increased short‐term, high‐intensity endurance 

capacity• Increased anaerobic metabolic function • Increased tolerance for acid–base imbalances during 

highly intense effort

Changes in VO2max With 12 Monthsof Endurance Training

.

12/3/2011

3

Adaptations to Exercise Training:Adaptations to Exercise Training:Aerobic System ChangesAerobic System Changes

Enhancement in a muscle fiber’s capacity to   aerobically generate ATPAn increase in mitochondrial size and  

numberTwo‐fold increase in the level of aerobic 

system enzymesAn enhancement in both fiber types’ existingAn enhancement in both fiber types  existing 

aerobic capacity and lactate  threshold levelImprovement in the ability to oxidize fatty  

acids, particularly triacylglycerols  stored within  active muscle during steady‐rate exerciseEnhancement in the capacity to oxidize 

carbohydrateProvides for a considerably faster aerobic energy 

transfer than from fat breakdownLiberates about 6% more energy than fat per 

quantity of oxygen consumed

Adaptations to Adaptations to Exercise Training: Exercise Training: Cardiovascular Cardiovascular AdaptationsAdaptations

IMPROVEMENT ISIMPROVEMENT ISDEPENDENT ON DEPENDENT ON PREPRE‐‐TRAINING TRAINING 

LEVEL LEVEL 

Percentage Differences in Heart Size Among Three Groups of Athletes Compared With Untrained Group

•The left ventricle changes significantly in response to endurance training

•The internal dimensions of the left ventricle increase as an adaptation to an increase in ventricular filling secondary to an increase in plasma volume and diastolic filling time•Left ventricular wall thickness and mass increase, allowing for greater contractility

12/3/2011

4

Changes in Stroke Volume

With Endurance Training

• Increased SV at rest and during submaximal and maximal exercise

•Increases LV end-diastolic volume, caused by an increase in blood plasma and greater diastolic filling time (lower heart rate), contribute to increased SV

•Increased ventricular filling (preload)leads to greater contractilityleads to greater contractility (Frank-Starling mechanism)

•Reduced systemic vascular resistance (afterload)

Changes in Heart RateWith Endurance Training

Resting• Decreases by ~1 beat/min with each week of trainingIncreased parasympathetic (vagal) tone

Submaximal• Decreases heart rate for a given absolute exercise intensity

Maximal• Unchanged or decreases slightly

Changes in Heart Rate RecoveryWith Endurance Training

• The time it takes the heart to return to its resting rate after exercise

• Faster rate of recovery after trainingg

• Indirect index of cardiorespiratory fitness

• Prolonged by certain environments (heat, altitude)

• Can be used as a tool to track the progress of endurance training

12/3/2011

5

Changes in Cardiac Outputwith Endurance Training

Q = HR x SV• Does not change at rest or 

during submaximalexercise (may decrease li htl )slightly)

• Maximal cardiac output increases due largely to an increase in stroke volume

Blood Pressure (BP) Adaptationsto Endurance Training

• Resting BP decreases in borderline and hypertensive individuals (6‐7 mmHg reduction)  

• Mean arterial pressure is reduced at a given submaximal exercise intensity (↓ SBP ↓ DBP)exercise intensity (↓ SBP, ↓ DBP)

• At maximal exercise (↑ SBP, ↓ DBP)

Increases in Total Blood Volume and Plasma Volume With Endurance Training

BV increases rapidly with endurance trainingPlasma volume increases due to:

Increased plasma proteins (albumin)Increased antidiuretic hormone and aldosterone

Red blood cell volume increases

Hemoglobin increases

12/3/2011

6

Respiratory Adaptationsto Endurance Training

Key Points• Little effect on lung structure and function at rest• Increase in pulmonary ventilation during maximal 

exercise 

• ↑ Tidal volume • ↑ Respiratory rate

• Pulmonary diffusion increases at maximal exercise due to increased ventilation and lung perfusion 

• (a‐v)O2 difference increases with training, reflecting increased extraction of oxygen at the tissues

Adaptations in Muscleto Endurance Training

• Increased size (cross‐sectional area) of type I fibers• Transition of type IIx → type IIa fiber characteristics• Transition of type II → type I fiber characteristics• Increased number of capillaries per muscle fiber and for a 

given cross‐sectional area of musclegiven cross sectional area of muscle• Increased myoglobin content of muscle by 75% to 80%• Increased number, size, and oxidative enzyme activity of 

mitochondria

TrainabilityTrainabilityand and 

GenesGenes• The limits for developing fitness capacity link closely to natural• The limits for developing fitness capacity link closely to natural 

endowment. Genetics accounts for 40‐60% of ones VO2max• For two individuals in the same exercise program, one might 

show ten times more improvement than the other.• Genetics research indicates a genotype dependency for much of 

one’s sensitivity in responding to maximal aerobic and anaerobic power training, including adaptations of most muscle enzymes.

12/3/2011

7

Variations in the Percentage Increase in VO2max for Identical Twins

.

From D. Prud'homme et al., 1984, “Sensitivity of maximal aerobic power to training is genotype-dependent,” Medicine and Science in Sports and Exercise 16(5): 489-493. Copyright 1984 by American College of Sports Medicine. Adapted by permission.

Comparisons of VO2max in Twinsand Nontwin Brothers

.

Adapted, by permission, from C. Bouchard et al., 1986, “Aerobic performance in brothers, dizygotic and monozygotic twins,” Medicine and Science in Sports and Exercise 18: 639-646.

Muscle Adaptationsto

Anaerobic Training• Increased muscle fiber recruitment• Increased cross‐sectional area of type IIa and type IIx  

muscle fibersmuscle fibers 

12/3/2011

8

Adaptations to Exercise Training: Adaptations to Exercise Training: Anaerobic System ChangesAnaerobic System Changes

• Increased levels of anaerobic substrates• Increased quantity and activity of key enzymes that control the anaerobic phase of 

glucose catabolism• Increased capacity to generate high levels of blood lactate during all‐out exercisep y g g g

Energy System Adaptationsto Anaerobic Training

• Increased ATP‐PCr system enzyme activity• Increased activity of several key glycolytic enzymes• No effect on oxidative enzyme activity

Changes in Creatine Kinase (CK)and Myokinase (MK) Activities

With Anaerobic Training

12/3/2011

9

Performance in a 60 s Sprint Bout After Anaerobic Training

Specificity of Trainingand Cross‐Training

• To maximize cardiorespiratory gains from training, the training should be specific to the type of activity that the athlete usually performs

• Cross‐training is training for more than one sport at a time

• Gains in muscular strength and power are less when strength training is combined with endurance training

Cardiovascular limitations during combined exerciseof the

upper and lower body musculature

12/3/2011

10

Resistance Training and Gainsin Muscular Fitness

Muscle is very plastic, increasing in size and strength with trainingstrength with training and decreasing with 

immobilization

© BananaStock

Muscle HypertrophyTransient hypertrophy is the increase in muscle size that develops during and immediately following a single exercise bout

– Fluid accumulation in the interstitial and intracellular space from the blood plasma 

Chronic hypertrophy is the increase in muscle size after long‐term resistance training 

– Changes in both the size of muscle fibers (fiber hypertrophy) and the number of muscle fibers (fiber hyperplasia)

Fiber Hypertrophy: Microscopic Views of Muscle Cross Sections Before and After Training

• Net increase in muscle protein synthesis—possibly increasing the number of actin and myosin filaments, and increasing the number of myofibrils

• Facilitated by postexercise nutrition

• Testosterone plays a role in promoting muscle growth

12/3/2011

11

Heavy Resistance Training in CatsHYPERPLASIA/MUSCLE FIBER SPLITTING

• Muscle fibers can split in half with intense weight training (cat research)

• Each half then increases to the size of the parent fiber• Conflicting study results may be due to differences in the 

training load or mode• Satellite cells may also be involved in the generation of new 

skeletal muscle fibers• Hyperplasia has been clearly shown to occur in animal 

models; only a few studies suggest this occurs in humans too

The Satellite Cell Responseto Muscle Injury

Reprinted, by permission, from T.J. Hawke and D.J. Garry, 2001, “Myogenic satellite cells: Physiology to molecular biology,” Journal of Applied Physiology 91: 534‐551.

Training to Improve Muscular Strength

Strength Training Adaptations• Increased muscle mass

– Hypertrophy • Increased muscle fiber diameter • Responsible for most of the increase in muscle size

– Hyperplasia I d b f l fib• Increased number of muscle fibers

• Conversion of IIx→IIa fibers• Central nervous system changes

– Increased motor unit recruitment– Altered motor neuron firing rates– Enhanced motor unit synchronization– Removal of neural inhibition

12/3/2011

12

GOALS OF ENDURANCE AND STRENGTH TRAINING

ENDURANCE• Increase the cardiovascular 

systems ability to deliver blood to working muscles

STRENGTH• To cause adaptations in the 

muscle (increase quantity of contractile proteins)which 

t ti ll i fli t

• Increase the muscles capability to produce energy aerobically

are potentially in conflict with adaptations associated with running or cycling

Do the effects of these two training programs interferewith each other?

Combined Strength and Endurance Training Program

• Combined strength and endurance training may result in lower gains in strength than strength training alone– Depends on:

• Training state of subject

Training to Improve Muscular Strength

g j• Volume and frequency of training• Way the two methods are integrated

• Strength and endurance training should be performed on alternate days for optimal strength gains– May be due to fatigue

Gender Differences in Muscular Gender Differences in Muscular StrengthStrength

• Absolute Muscle Strength– Men possess considerably greater strength compared with women for all muscle 

groups tested– Women score about 50% lower than men for upper‐body strength and about 30% 

lower for leg strength

• 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)– A relative score increases the “fairness” when comparing two individuals’ strength 

performances

12/3/2011

13

Gender Differences in Response to Strength Training

• Untrained males have greater absolute strength than untrained females– 50% stronger in upper body, 30% stronger in lower body

• However, strength related to cross‐sectional area of muscle is similar

Training to Improve Muscular Strength

of muscle is similar– 3–4 kg of force per cm2 of muscle in males and females

• There does not appear to be a gender differences in response to short‐term strength training– Men exhibit greater hypertrophy as a result of long‐term training

• Due to higher testosterone levels

Strength as a Function of Muscle Cross‐Sectional Area in Men and 

Women

Training‐Induced Strength Changes in Men and Women

Training to Improve Muscular Strength

12/3/2011

14

• Muscular Adaptations– 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

• Neural Adaptations– A development in how well an untrained person recruits more motor units to achieve a maximal muscle 

actionIncreased synchronization of motor unit firing causing more motor units to fire simultaneously

Adaptations to Resistance TrainingAdaptations to Resistance Training

– Increased synchronization of motor unit firing, causing more motor units to fire simultaneously• Connective Tissue and Bone Adaptations

– Ligaments, tendons, and bone correspondingly strengthen as muscle strength and size increase.– Connective tissue proliferates around individual muscle fibers; this thickens and strengthens the muscle’s 

connective tissue structures.– Such adaptations from resistance training help to protect joints and muscles from injury, and also justify 

resistance exercise for preventive and rehabilitative strategies• Body Composition Adaptations

– Small decreases occur in body fat, with minimal increases in total body mass and FFM.– The largest FFM increases amount to about 3 kg over 10 weeks, with results about the same for men and 

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

Cardiovascular AdaptationsCardiovascular Adaptationsto to 

Resistance TrainingResistance Training

Delayed Onset of Muscle Soreness(DOMS)

• Appears 24–48 hours after strenuous exercise– Due to microscopic tears in muscle fibers or connective tissue

• Results in cellular degradation and inflammatory 

Training to Improve Muscular Strength

g yresponse

• Not due to lactic acid– Eccentric exercise causes more damage than concentric exercise

– Slowly begin a specific exercise over 5–10 training sessions to avoid DOMS

12/3/2011

15

Muscle SorenessMuscle Sorenessand and 

Stiffness Stiffness Armstrong’s Sequence

of Events in DOMS

1. Structural damage to the muscle cell and cell membrane

2. Impaired calcium availability, leading to necrosis

3. Increased microphage activity and the accumulation of irritants inside the cell, which stimulate free (pain) nerve endings

Electron Micrograph of a Muscle Sample Taken Immediately After a 

Marathon

From R.C. Hagerman et al., 1984, "Muscle damage in marathon runners," Physician and Sportsmedicine 12: 39‐48.

Electron Micrograph Showing Normal Arrangement of Actin and Myosin Filaments and Z‐disk Before and 

Immediately After a Marathon

From R.C. Hagerman et al., 1984, "Muscle damage in marathon runners," Physician and Sportsmedicine 12: 39‐48.

12/3/2011

16

Steps Leading to DOMS

• Strenuous muscle contraction results in muscle damage• Membrane damage occurs

– Including sarcoplasmic reticulum• Calcium leaks out of SR and collects in mitochondria

Training to Improve Muscular Strength

– Inhibits ATP production– Activates proteases which degrade contractile proteins

• Results in inflammatory process– Increase in prostaglandins/histamines

• Edema and histamines stimulate pain receptors

Proposed Theories to Explain the “Repeated Bout Effect”

•A bout of unfamiliar exercise results in DOMS

– Following recovery, another bout of same exercise results in minimal injury

•Theories for the repeated bout effect

– Neural theoryNeural theory•Recruitment of larger number of muscle fibers

– Connective tissue theory•Increased connective tissue to protect muscle

– Cellular theory•Synthesis of protective proteins within muscle fiber

Estimated Contributions of Physical Disruption, Contractile Protein Loss, and Excitation–Contraction 

Coupling Failureto the Loss of Strength Following 

Muscle Injury 

Reprinted, by permission, from G.L. Warren et al., 2001, “Excitation‐contraction uncoupling: Major role in contraction‐induced muscle injury,” Exercise and Sport Sciences Reviews 29: 82‐87.

12/3/2011

17

The Delayed Response to Eccentric Exercise of Various Physiological Markers

Adapted, by permission, from W.J. Evans and J.G. Cannon, 1991, “The metabolic effects of exercise induced muscle damage,” Exercise and Sport Sciences Reviews 19: 99‐125.

Reducing Muscle Soreness

1. Reduce the eccentric component of muscle action during early training

2. Start training at a low intensity and gradually increase it3. Begin with a high‐intensity, exhaustive bout of eccentric‐

i i hi h ill h i i i ll baction exercise, which will cause much soreness initially but will decrease future pain

WHAT ABOUT FLEXIBILITY?

12/3/2011

18

Training to Improve Flexibility

• Stretching exercises to improve flexibility and efficiency of movement– Limited evidence that flexibility reduces injury risk

• Static stretchingContinuously holding a stretch position

Training to Improve Flexibility

– Continuously holding a stretch position• Hold position for 10–60 seconds• Repeat each stretch 3–5 times

– Preferred technique• Less chance of injury or soreness• Less muscle spindle activity

• Dynamic stretching– Ballistic stretching movements

Training to Improve Flexibility

• Proprioceptive neuromuscular facilitation (PNF)– Preceding a static stretch with isometric contraction of muscle being stretched

Training to Improve Flexibility

• Contraction stimulates Golgi tendon organ– Requires a training partner