Copyright © 2012 American College of Sports Medicine Chapter 5 Connective Tissue Adaptations to Training

Copyright © 2012 American College of Sports Medicine Stimuli for Connective Tissue Adaptations Mechanical Stress –Connective tissue (CT) adaptation via progressive overload by increasing stress –Internal force divided by cross-sectional area of CT structure –CT increases tolerance for loading by: Increasing size Altering structural properties –Important ramifications for: Injury prevention in sports Force transmission from muscle to bone

Copyright © 2012 American College of Sports Medicine Stimuli for Connective Tissue Adaptations (cont’d) Types of Stress –Tension stresses Pulling forces on tissue Stretching or elongation occurs (with tendons during muscle contraction) –Compression stresses Push structure inwardly Compressing longitudinal length –Shear stresses Skewing Oblique force

Copyright © 2012 American College of Sports Medicine Stimuli for Connective Tissue Adaptations (cont’d) Stress-Strain Relationship –Stress: level of force encountered by a tissue –Strain: magnitude of deformation in proportion to stress applied Linear strain Compressive/tensile stresses that change tissue length Quantified as % relative to resting length Shear strain Bending of tissue (bone) Quantified by angle of deformation Poisson’s ratio: ratio of longitudinal to lateral strain

Copyright © 2012 American College of Sports Medicine The Stress-Strain Relationship in a Ruptured Achilles Tendon

Copyright © 2012 American College of Sports Medicine Skeletal System Overview –206 bones (177 of which involved in voluntary movement) –Provides: Support Area for muscular attachment Protection to several organs Storage site for minerals –Produces: Movement upon skeletal muscle contraction Red blood cells

Copyright © 2012 American College of Sports Medicine Skeletal System: Two Divisions Axial Skeleton –80 bones in skull & trunk: Vertebral column Ribs Sternum Sacrum Coccyx Appendicular Skeleton –126 bones in: Limbs Shoulder Pelvic girdle

Copyright © 2012 American College of Sports Medicine The Axial and Appendicular Skeletons

Copyright © 2012 American College of Sports Medicine The Skeletal System Roles: Provides support Area for muscular attachment Protection for several organs Produce movement upon skeletal muscle contraction Bones are a storage site for minerals when dietary intake is low Bones produce red blood cells (for transporting oxygen)

Copyright © 2012 American College of Sports Medicine Skeletal System (cont’d) Bone Anatomy (5 forms) 1.Long bones: femur & humerus 2.Short bones: carpals & tarsals 3.Flat bones: ribs, scapula, skull, sternum 4.Irregular bones: vertebrae 5.Sesamoid bones: patella

Copyright © 2012 American College of Sports Medicine Anatomy of a Long Bone (Femur)

Copyright © 2012 American College of Sports Medicine Internal Anatomy of a Long Bone

Copyright © 2012 American College of Sports Medicine Skeletal System (cont’d) Bone Remodeling –Process of bone being constantly broken down & built up again –Osteoblasts Cells that secrete a collagen-rich ground substance that aids in bone formation Secreted by periosteum & endosteum –Osteoclasts Cells involved in bone resorption or breakdown Digest mineralized bone matrix via acid & lysosomal enzymes

Copyright © 2012 American College of Sports Medicine Skeletal System (cont’d) Bone Growth –Longitudinal bone growth (developmental years) Intramembranous ossification: bone growth from CT membranes Endochondral ossification: bone growth from cartilage Takes place at growth plates Epiphyses enlarge, diaphysis extends Some bones reach full length in 18 years, others in 25 years –Appositional bone growth (widening)

Copyright © 2012 American College of Sports Medicine Model for Bone Adaptation to Loading

Copyright © 2012 American College of Sports Medicine Skeletal System (cont’d) Bone Adaptations to Exercise –Minimal Essential Strain (MES) Minimal threshold volume & intensity needed for new bone formation (increased bone mineral density [BMD]) Depends on athlete’s training status & age 1/10 th of force needed to fracture bone –Dynamic, high-intensity loading to bones is paramount –Weight-bearing exercise more effective than non-weight-bearing –Athletes have higher BMD than non-athletes

Copyright © 2012 American College of Sports Medicine Skeletal System (cont’d) Training to Increase Bone Size and Strength: Necessary Components –Specificity of loading –Speed & direction of loading –Volume –Proper exercise selection –Progressive overload –Variation

Copyright © 2012 American College of Sports Medicine Skeletal System (cont’d) Training to Increase Bone Size and Strength: General Recommendations (Skeletal Loading) –Multijoint exercises preferred –Loading should be high with moderate to low volume (≤10 reps) –Fast velocities of contraction preferred –Rest intervals should be moderate to long (≥2-3 min) –Variation in training stress is important for altering stimuli

Copyright © 2012 American College of Sports Medicine Components of Dense CT Tendons and Ligaments –Dense fibrous CT structures –Composed of: Water (60-70% of content) Fibroblasts: collagen-producing cells Fibrocytes: mature cells Elastin: protein with elastic quality Collagen: great tensile strength, most abundant protein in the human body-2 types: Type I in skin, bones, tendons and ligaments and Type II in cartilage Ground substances: structural stability

Copyright © 2012 American College of Sports Medicine Fascia: CTs that surround and separate different organizational levels within skeletal muscle. Fascia contains bundles of collagen fibers arranged in different planes to provide resistance to forces from different directions. Fascia within skeletal muscle converges to form a tendon through which the force of muscle contraction is transmitted to bone.

Copyright © 2012 American College of Sports Medicine Structure of Collagen

Copyright © 2012 American College of Sports Medicine Components of Dense CT (cont’d) Tendon, Ligament, and Fascial Adaptations to Training –Mechanical loading Major stimulus for growth Leads to cascade of events leading to hypertrophy –Degree of adaptation is proportional to intensity of exercise –Sites where CT can increase strength At junctions between the tendon/ligament & bone surface Within the body of the tendon/ligament In the network of fascia within skeletal muscle

Copyright © 2012 American College of Sports Medicine Components of Dense CT (cont’d) Cartilage Adaptations to Training –Types Articular (hyaline) cartilage Fibrous cartilage Elastic cartilage –Lacks its own blood supply & must receive nutrients from synovial fluid –Long recovery from injuries –Potential for degeneration, leading to osteoarthritis