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44C H A P T E R
Bone, Muscle, and Connective Tissue Adaptation to Physical Activity
Bone, Muscle, and Connective Tissue Adaptation to Physical Activity
Chapter Outline
Adaptation of bone to exercise
Adaptation of muscle to exercise
Adaptation of connective tissue to exercise
Types of bone cells Osteoblasts - mononuclear cells found
along bone surfaces; promote bone formation, synthesis of bone matrix
Osteocytes - osteoblasts that have been incorporated into previously synthesized bone matrix
Osteoclasts - multinucleated cells derived from hemopoietic stem cells; promote bone resorption
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Bone PropertiesBone Properties
Bone size & shape are influenced by the Bone size & shape are influenced by the direction & magnitude of forces that are direction & magnitude of forces that are habitually applied to themhabitually applied to them
Bones reshape themselves based upon the Bones reshape themselves based upon the stresses placed upon themstresses placed upon them
Bone mass increases over time with Bone mass increases over time with increased stressincreased stress
Bone Architecture: Cortical and Trabecular Bone
Bone Architecture: Cortical and Trabecular Bone
Trabecular (Cancellous) bone is able to respond to mechanical stimuli more rapidly than cortical bone.
Minimal Essential Strain (MES) refers to the threshold stimulus that initiates new bone formation.
Bone Modeling in Response to Mechanical LoadingBone Modeling in Response to Mechanical Loading
Bone Remodeling Coupling, or the linked activation of
osteoblasts and osteoclasts, is the basis of bone turnover or remodeling; the continuous skeletal activity related to mineral homeostasis and bone repair
© 2007 McGraw-Hill Higher Education. All rights © 2007 McGraw-Hill Higher Education. All rights reserved.reserved. 1-1-88
Bone PropertiesBone Properties
Composed of calcium carbonate, calcium Composed of calcium carbonate, calcium phosphate, collagen, & waterphosphate, collagen, & water 60-70% of bone weight - calcium carbonate & calcium 60-70% of bone weight - calcium carbonate & calcium
phosphatephosphate 25-30% of bone weight - water25-30% of bone weight - water
Collagen provides some flexibility & strength in Collagen provides some flexibility & strength in resisting tensionresisting tension
Aging causes progressive loss of collagen & Aging causes progressive loss of collagen & increases brittlenessincreases brittleness
© 2007 McGraw-Hill Higher Education. All rights © 2007 McGraw-Hill Higher Education. All rights reserved.reserved. 1-1-99
Bone PropertiesBone Properties
Most outer bone is cortical with cancellous Most outer bone is cortical with cancellous underneathunderneath
Cortical bone – low porosity, 5 to 30% Cortical bone – low porosity, 5 to 30% nonmineralized tissuenonmineralized tissue
Cancellous – spongy, high porosity, 30 to 90%Cancellous – spongy, high porosity, 30 to 90% Cortical is stiffer & can withstand greater stress, Cortical is stiffer & can withstand greater stress,
but less strain than cancellousbut less strain than cancellous Cancellous is spongier & can undergo greater Cancellous is spongier & can undergo greater
strain before fracturingstrain before fracturing
Effects of Immobilization on Load to Failure of Bone
Due to the lack of strains, immobilization results in weakened, less mineralized bone tissue.
High load and low repetitions (i.e., resistance training)
or Low load and high repetitions
(i.e., walking, running)?
Specificity of Loading Running is a good stimulus for the femur, but not for the
wrist. Osteoporosis: disease in which bone mineral density and
mass are critically low. High impact loading during early adulthood may maximize
both bone mineral density and mass to protect individuals later in life.
Osteogenic stimuli: factors that stimulate new bone. Use exercises that direct forces thru the spine and hip,
avoid machines that isolate body parts. For ex – standing arm curls is better than a curl bench in loading spine & hip.
Follow Progressive Overloading Don’t over-train, as it may lead to stress fractures. Training variation is very good for bone.
Table 4.1 Exercise Prescription Guidelines for Stimulating Bone Growth
Variables Specific recommendations
Volume 3-6 sets of up to 10 repetitions
Load 1-10RM
Rest 1-4 min
Variation Typical periodization schemes designed to increase muscle strength and size
Exercise selection Structural exercises: squats, cleans, deadlifts, bench presses, shoulder presses
The components of mechanical load that
stimulate bone growth are
1. the magnitude of the load (intensity)
2. rate (speed) of loading
3. direction of the forces
4. volume of loading (number of repetitions).
Stimulating Muscular Adaptations
For strength: high loads, few repetitions, full recovery periods
For muscle size: moderate loads, high volume, short to moderate rest periods
For muscular endurance: low intensity, high volume, little recovery allowed
A general connective tissue
response to aerobic endurance
exercise is increased collagen
metabolism.
Specific changes within a tendon that
contribute to the increase in its cross-sectional
area and strength in response to a functional
overload include
an increase in collagen fibril diameter,
a greater number of covalent cross-links
within a fiber of increased diameter,
an increase in the number of collagen fibrils,
and
an increase in the packing density of
collagen fibrils.
Stimulating Connective Tissue Adaptations: Tendons, Ligaments, Fascia
Exercise of low to moderate intensity does not markedly change collagen content of connective tissue.
High-intensity loading results in a net growth of the involved connective tissues.
Stimulating Connective Tissue Adaptations: Cartilage
Weight-bearing forces and complete movement throughout ROM seem essential to maintain tissue viability.
Moderate aerobic exercise seems adequate for increasing cartilage thickness. Strenuous exercise does not appear to cause degenerative joint disease.
Review Increases in bone density are greatest during weight bearing
activity at a high intensities (overload). Muscular adaptations – periodization Tendon – increased collagen fibril diameter
What decreases collagen formation? Cartilage – moderate aerobic = increased thickness. Which activity will result in the greatest BMD: Rowing,
Volleyball, Basketball, Swimming, Running, Weights, Gymnastics. Greatest Cartilage thickness? Tendon Elasticity?
Lumbar BMD of Different Athletic Groups
90
95
100
105
110
115
120
Row Volleyball Basketball Swim Run Weights Gymnasics
% S
eden
tary
Con
trol
s
Sports Drinkwater, B.L. (1994)
Response and Adaptations to
Training
Adaptations to Training Chronic exercise provides a stimulus for the
systems of the body to change to better meet the demands placed upon them (BODY ADAPTS TO THE DEMANDS PLACED UPON IT)
These systems will adapt according to the level, volume and intensity of exercise training (ADAPTATION IS SPECIFIC TO THE TRAINING)
Specificity of Training
Type of Training Prescription (Aerobic vs Anaerobic
Differences within activity (Sport Specific)
Factors that AffectAdaptations to Training
Environmental factors Climate Altitude
Genetic endowment Fiber type patterns Somatotype
Adaptations FollowingExercise Training: Neuromuscular
Neuromuscular adaptations “Disinhibition” of the proprioceptors
Autogenic inhibition of the Golgi tendon organ (GTO) Training may reduce the sensitivity of these receptors to allow
for greater force production
Increase in the number of vesicles that store acetylcholine More neurotransmitter secretion Greater force production Improvement of recruitment patterns
Adaptations FollowingExercise Training: Muscular
Muscle fiber type adaptations Normal recruitment pattern: Type I IIa IIb More precise and efficient mode of recruitment
Less neural activity is required to produce any level of submaximal force measured by electromyography
Increased synchronization increases the amount of time that maximal force output can be sustained
Fiber “transformation” (IIb IIa) may also result in increased or altered recruitment patterns
Table 4.2 Proportion of Type II Fibers in Athletes Who Perform Anaerobic Activities
Type of athlete Type II fibers
Bodybuilders 44%
Javelin throwers 50%
800-m runners 52%
Weightlifters 60%
Shot-putters 62%
Discus throwers 63%
Sprinters and 63% jumpers
Specific Adaptations from Resistance Training Changes in fiber area Hypertrophy of the muscle fibers Muscle fiber “transformation”
Type IIb Type IIa fibers
Increased high energy phosphate pool Improved motor unit firing synchronization Improved neural function
Neuroendrocrine Adaptations Increased synthesis of hormones Improved transport of hormones Reduced time needed for clearance of tissues Reduced amount of hormonal degradation Increased number of hormones receptors in the
tissues Increased magnitude of signal sent to the cell
nucleus Improved interaction with cell nucleus
Specific Adaptations fromAerobic Training Increased myoglobin content Increased oxidation of glycogen Increased VO2 and a-vO2 difference Biochemical changes in Type I and II
muscle fibers Increased heart size and efficiency
Combination Training Combining maximal resistance training
and aerobic endurance training interferes primarily with muscular strength and power performance
Biochemical Changes Induced by Training Aerobic
Increased myoglobin content Increased oxidation of
glycogen Inc. # & size of
mitochondria Inc. activity of Krebs cycle Inc. muscular stores of
glycogen
Anaerobic Increased capacity of the
ATP-PC system Inc. stores
Increased glycolytic capability
Fiber Type Characteristics
Substrate Depletion and Repletion Phosphagen and ATP
Repletion: work:rest ratio recommendations
Application Divide into equal groups and develop a sport
specific workout. You must address the Aerobic and Anaerobic needs of the Athlete. Assumptions
You are not coaching the athletes you are preparing them physiologically for their sport.
We will assume a total body focus to your anaerobic training…highlight the areas of specific interest pertaining to your athlete.
BE EVIDENCE BASED!
Athlete1) Distance Runner
2) Soccer Midfielder
3) Shot Putter
4) Basketball Forward
5) Baseball Pitcher
6) Swim Sprinter
7) Distance Swimmer
8) Long Jumper