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Musculoskeletal & Biomechanical Adaptations to Training HPER 6310 Dr. Suzan Ayers Western Michigan University Lecture Overview Effects of Physical Activity on: bone joints and ROM muscle-tendon units body size, shape & composition Biomechanical Adaptations to Training: muscular neuromuscular Biomechanical Adaptations to Injury Physical Activity & Bone Disuse results in osteopenia (bone loss) Genetically determined baseline mass for normal function (certain level of PA to ↔ bone health) ↓ PA=bone loss, ↑ PA=bone growth (see below) Weight-bearing PA= bone growth Too much intense PA problematic; optimal levels exist for each individual Physical Activity & Joints/ROM Short-term effects of cyclical exercise (bike, run) Articular cartilage thickens (improved force dissipation) 2-3x ↑ in volume of synovial fluid in a joint (lubricant) Evidence supports endurance exercise’s benefits over sprint training on ligament strength Degenerative joint disease (osteoarthritis) Thinning articular cartilage Thickening compact bone under articular cartilage Possible genetic, aging & environmental factors impact DJD dev’t Regular runners do NOT have > incidence of osteoarthritis HMMMM… Physical Activity & Muscle-Tendon Units Flexibility: The ability to move a joint through its complete range of motion (ROM) (ACSM, 2000) Laxity: The degree of abnormal motion of a given joint (Heyward, 2002) depends on muscle-tendon units crossing joints is joint-specific ↑ flexibility related to ↑ extensibility of connective tissue strength and flexibility training can promote ↑ ROM ↑ injury risk Hypermobility: Excess ROM at a joint (Heyward, 2002) Active Passive Slow, sustained stretch held for 10-30 sec Preferred in Physical Education settings PNF (Proprioceptive Neuromuscular Facilitation) Partner provides force of stretch Static Self-stretching Combo active/passive techniques NOT for children 6-10 yrs Ballistic/Dynamic Quick movements, bouncing, using momentum Reserve for those 15+ yrs Helpful to prepare athletes for competition Static stretches should be held to the point of mild discomfort “No pain, no gain” is INAPPROPRIATE! Training principles Frequency: Daily (min 3x/wk) Intensity: To point of mild discomfort Time: 10-30 sec Type: Static, PNF, partner, etc. Strength changes Weeks 6-8 primarily neuromuscular Weeks 9+ gains due to ↑ fiber size/volume Long-term benefits Tendon Adaptations Much slower rate of adaptation than muscle Collagen synthesis ↑ Fiber changes resulting in improved fatigue-resistance ↑ relative amount of connective tissue Fibers align more regularly longitudinally Muscle strains often occur @ junction of tendon and muscle Physical Activity’s Effect on Body Size, Shape & Composition Endomorph relaxed, sociable, tolerant, comfort-loving, peaceful, plump, buxom, developed visceral structure Mesomorph active, assertive, vigorous, combative, muscular Ectomorph quiet, fragile, restrained, non-assertive, sensitive, lean, delicate, poor muscles Dr. William Sheldon’s “somatotypes” Endomorph Mesomorph Ectomorph Somatotype challenge In the 1940s, Dr. William Sheldon (1898-1977) proposed a theory about how certain body types ("somatotypes") are associated with certain personality characteristics. He claimed that there are three such somatotypes: endomorphy, mesomorphy, and ectomorphy. You can rate yourself on each of these three dimensions using a scale from 1 (low) to 7 (high) with a mean of 4 (average). Therefore, a person who is a pure mesomorph would have a score of 1-7-1. A pure endomorph would be 7-1-1. A pure ectomorph would score a 1-1-7. A mostly average person who has some endomorphic tendencies would have a score of 6-4-4 ... etc. Rate the degree to which you think you possess each of the three body types. Endomorphic Body Type soft body underdeveloped muscles round shaped over-developed digestive system Associated personality traits: love of food tolerant evenness of emotions love of comfort sociable good humored relaxed need for affection Mesomorphic Body Type hard, muscular body overly mature appearance rectangular shaped thick skin upright posture Associated personality traits: adventurous desire for power and dominance courageous indifference to what others think or want assertive, bold zest for physical activity competitive love of risk and chance Ectomorphic Body Type thin flat chest delicate build young appearance tall lightly muscled stoop-shouldered large brain Associated personality traits: self-conscious preference for privacy introverted inhibited socially anxious artistic mentally intense Lifestyle Factors ↑ PA while ↓ caloric intake=fat loss Training can make physiological changes at any age (it’s never too old to teach an old dog new tricks Height is genetically predetermined Weight can be altered to a given genetic point Somatotype can change as strength and endurance requirements change Biomechanical Training Adaptations Training influences both contractile properties of muscle (strength, speed) and neural control (coord.) Strength changes due to ↑ net neural drive to muscle (motor unit recruitment) ↑ muscle size both neural and structural changes Contraction speed changes due to Δ in shape of muscle’s force-velocity curve Δ in value of the intrinsic max shortening velocity both shape and max shortening velocity changes Muscular Training Adaptations Max force produced depends on length of muscle during contraction Initial strength gains (wk 2-8) primarily neural 10+ wk gains primarily hypertrophic Isokinetic training can change force-velocity curve Contraction speed changes also influence forcevelocity curve shape, ergo power (strength x speed = power) Neuromuscular Training Adaptations Incidence of serious knee injury 6x F>M athletes Intrinsic risk factors for ACL injury Lower extremity malalignment ↓ intercondylar notch width at the knee ↑ knee joint laxity Hormonal influences (Relaxin) Extrinsic risk factors for ACL injury Imbalanced quad/ham strength Inadequate neuromuscular control GOAL: improve stability (balance, coordination), proprioception, & strength ACL injury-prevention neuromuscular programs Knee stability/function improve with ↑ in postural equilibrium, intermuscular control & leg muscle strength Means of ↑ aforementioned factors: Stretching Plyometric exercises (AKA, jump training) Weight lifting Evidence supporting neuromuscular training’s role in ↓ incidence of sport-related knee injuries Ham:Quad strength ratio key to ACL injury prevention Neuromuscular training can ↑ knee joint stability ↑ H:Q Fine-tune neural control over hamstrings