Physiological Adaptations to Exercise Training

• Effects of chronic endurance training:

  • improve VO2max
• VO2max depends on Q:

  • increase Q = increase VO2max
  • to improve Q, we must improve HR and SV
  • however, there is a negative relationship between VO2max and HR
  • therefore, we rely on improving SV to improve Q
• How does training improve SV:

  • preload
  • exercise must increase preload to increase SV
  • with training, blood volume increases within the first 10 days
  • increased blood volume contributes to increased preload; heart accepts more volume as it relaxes
  • increase in blood volume mainly comes from an increase in plasma in the blood
• How does training improve SV:

  • inotropy/contractility
  • in trained people, myocardium is thicker and allows for more forceful contractions
  • chambers are bigger so we can accept more blood
  • therefore, we pump more blood which increase SV
• Ventricular dimensions:

  functional differences:

  • SV is higher in athletes
  • SV is not different between LV and RV

  structural differences:

  • those with bigger/stronger hearts have a greater VO2max in both LV and RV
• How does training improve SV:

  • a reduction in afterload/resistance = an increase in SV for a given EDV
• RBC volume:

  • initial increase in blood volume is due to plasma
  • after, it is due to more RBCs
  • RBC content increases by ~ 10%
  • therefore, we further increase VO2max
  • we also increase O2
• CaO2:

  • an increase in Hb = an increase in CaO2
  • increase RBC volume via exercise training = increase VO2max due to an increase in CaO2
  • therefore, there is a widening of the a-vO2difference
• Muscle blood flow (Q):

  • TPR --> we focus on the radius
  • the more we dilate, the less resistance, and the more blood flow
• Arterial Remodeling:

  • training changes anatomical characteristics of vessels
  • with exercise = increase vessel diameter = increase blood flow
  • larger diameter and thinner walls (widen lumen and thinner arterial wall)
  • wider diameter = thinner wall; smaller diameter = thicker wall
• Flow-mediated dilation:

  • with training, there is a greater ability to dilate vessels
  • stimuli for vasodilation = flow-mediated dilation (shear stress) --> leads to smooth muscle vasodilation/relaxation
  • greater vessels reactivity for the same stimulus
  • increase diameter + thinner walls + greater ability to vasodilate = decrease resistance + increase blood flow at any intensity
• Peripheral resistance during exercise:

  • vasoconstriction during exercise comes from SNS
  • this is reduced in trained people during exercise to maintain high blood flow
  • therefore, there is less TPR in trained people
• Capillarization:

  • we grow more capillaries when we exercise
  • therefore, we extract more O2
  • we improve diffusive capacity
  • the fitter you are = the more capillary contact you have
• Mitochondria:

  • with exercise...
  • we increase the number of mitochondria
  • we produce more enzymes for oxidative phosphorylation to help us utilize more O2
• Mitochondrial volume density:

  • with training...
  • we increase cellular stress...
  • we increase signaling molecules...
  • we increase gene transcription factor...
  • we go through mitochondrial biogenesis
  • we increase the number of mitochondria and we increase the size of the mitochondria
  • more mitochondria = more VO2max
• Mitochondria...

  • endurance athletes have more mitochondria
• Effects of increasing mitochondria volume density:

  • with greater training, there is an increase in activation of previously mentioned enzymes
  • increase mitochondria volume density --> within mitochondria, we are increasing the capability to perform oxidative phosphorylation and our ability to increase ATP