PSIO 201 5th Edition Lecture 39 Outline of Current Lecture Integration Lecture 1 Effects of exercise on muscle and bone Objectives 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 encounters Exercise Requires 1 increased energy utilization aerobic activity 2 increased force production strength training MRI shows increased cross sectional area with strength training What 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 phosphorylase Muscle cells respond to environmental challenges exercise by changing the activity of 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 protein Acute 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 Exercise Strategy 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 stress Effects of Exercise on Muscle Heavy resistance exercise increases cross sectional area CSA of which fiber types Problem 1 Take Home Messages 1 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 training 3 Increased size of all muscle fibers recruited muscle fibers are recruited from small to large 4 Increased synthesis of proteins increased myofilaments sarcomeres myofibrils inside each muscle fiber Problem 2 Take Home messages Bone will change in response to the stresses it encounters 1 Muscle pulling on bone joint reaction forces 2 Impact ground reaction forces Effect 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 squat 2 One arm military press 3 4 5 6 Leg press Lat pull down Seated row Back extension How 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 resorption Problem 2 Take Home Message 1 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 fracture 3 Force applied to bone is senses by osteocytes proliferation of osteoblasts bone formation is greater than bone resorption in exercise
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