PSIO 201 5th Edition Lecture 40Outline of Current Lecture Integration Lecture # 1 : Effects of exercise on muscle and boneObjectives:1) Apply knowledge gained in this course to physiological scenarios/problems.2) Integrate information across organ systems.Problem 1: Muscle will change in response to the stresses it encountersExercise Requires: 1) increased energy utilization (aerobic activity)2) increased force production (strength training)MRI shows increased cross sectional area with strength trainingWhat causes the increase in muscle cross sectional area (CSA) at the cellular and subcellular level?How do we get more myofilaments, sarcomeres, and myofibrils?- PROTEIN SYNTHESIS !- - Contractile proteins : actin, myosin- Structural proteins: titin, dystrophin- Regulatory proteins: troponin, tropomyosin- Enzymes: creatine phosphokinase, glycogen, phosphorylaseMuscle cells respond to environmental challenges (exercise) by changing the activityof the proteins responsible for the relevant cellular functions. How is the activity of proteins changes?- make the rate of reaction go faster or slower…2 Strategies 1. Modify the structure of existing proteins to make them operate faster or slower( post – translational modification)2. Express more or less of the proteinAcute Exercise- strategy 1 – modification of existing proteins- Glycogen phosphorylase is activated by phosphorylation the active form breaks down stored glycogen for use in glycolysis (calcium can activate the enzyme)Chronis ExerciseStrategy 2 : synthesis of proteins- Long term adaptation to training is due to the cumulative effects of each acute exercise session- Each session activates transcription factors that lead to expression of specific genes and accumulation of proteins needed to adapt to the exercise stressEffects of Exercise on Muscle :Heavy resistance exercise increases cross sectional area (CSA) of which fiber types?Problem #1 – Take Home Messages1. Muscle adapts to the exercise stress by modifying proteins (acute response) or by making more proteins (chronic response).2. Muscle cross sectional area increases with strength training3. Increased size of all muscle fibers recruited; muscle fibers are recruited from small to large4. Increased synthesis of proteins increased myofilaments, sarcomeres, myofibrils inside each muscle fiberProblem #2 – Take Home messagesBone will change in response to the stresses it encounters:1. Muscle pulling on bone joint reaction forces2. Impact ground reaction forcesEffect of exercise on bone- Bone Estrogen Strength Training (BEST) study- Postmenopausal women (n=266)- Split into exercise and control groups- Exercisers trained 3x per week, 2 sets of 1-10 reps for each exersice at 70-8-% rep maximum- All subjects took calcium supplements BEST :1. Wall squat2. One arm military press3. Leg press4. Lat pull down5. Seated row6. Back extensionHow does exercise cause a change in bone density?Effect of exercise on bone Mechanical force on bone 1. Machanocoupling 2. Biochemical Coupling (influx of calcium ) 3. Transmission of the biochemical signal (gap junctions) TrBone cell response (proliferation of osteoblasts)Bone formation > bone resorptionProblem #2 Take Home Message1. Bone adapts to stresses it encounters - muscle pull joint reaction forces- Ground impact ground reaction forces 2. Spongy bone is more metabolically active than compact bone- site rich in spongy bone can gain or lose bone density quicker- sites rich in spongy bone are more likely to fracture3. Force applied to bone is senses by osteocytes proliferation of osteoblasts bone formation is greater than bone resorption in
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