Aging, strength and power loss, neurodegeneration, motor unit remodeling, muscle fiber type

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Health + Exercise Science
HES 319
Brian Tracy

30 April Some overt physical ramifications of neuromuscular aging Decreased maximal muscle force (muscle strength) Decreased maximal contraction velocity (decreased speed of movement) Decreased muscle size Decreased reaction time Reduced functional ability Altered (impaired) gait characteristics Decreased flexibility Increased fatigability Thigh muscles 150 → 75 Nm of force Average decrease 50% From age 20 to 80 Strength and Power Loss with Age The ability to produce relatively high muscle force over a period of time (muscle power) also declines with age This has a negative impact on functional activities work forcexdistance Power = time = time It is relatively well-maintained at first, followed by a steeper decline What is the underlying reason for performance decline with age? Changes with physical activity level vs. intrinsic changes with aging Must be a combination Neurodegeneration Aging reduces the number of neurons in the soleus motor nerve of the rat Aging reduces the number of motor neurons in the ventral horn of the human spinal cord Autopsy studies Died of accident or short-lived illness Teens → 60’s: relatively well maintained 60’s-95: linear loss Aging reduces the number of neurons in the human ventral root Motor unit remodeling Motor units undergo apoptosis Muscle fibers are de-innervated Muscle fibers atrophy and die Only p
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