Training Adaptations

When the human body engages in a physical task, a series of changes happen in the physiologic systems to complete the task at hand. When the physical task is of a demanding nature beyond usual for a sustained period of time, the body’s physiologic systems undergo adaptations in order to keep up with the prolonged physical demand. Such physiologic adaptations obtained by demanding physical tasks can also be obtained through tailored physical activity or exercise.

Anaerobic training adaptations: The physical activities that load the immediate and short-term energy supply systems stimulate adaptations in the anaerobic metabolism, without a much parallel increase in aerobic fitness.

  • ↑ levels of ATP, PCr, Creatine, Glycogen
  • ↑ amounts and activation of enzymes that regulate glycolysis (anaerobic phase)
  • ↑ capacity to produce high levels of blood lactate

Aerobic training adaptations: The physical activities that load the long-term energy supply system stimulate adaptations in the aerobic metabolism.

The following physiologic variables are altered due to long-term exercise training (1):

  • Muscular
    • ↑ size and number of mitochondria
    • ↑ myoglobin content: increases oxygen reserve in the muscle (2)
    • muscle fibre adaptations
      • ↑ aerobic capacity of type IIa and IIb fibres (after endurance training)
      • ↑ type IIa fibres (after resistance training)
  • Metabolic
    • ↔ resting / ↑ maximal exercise arterio-venous oxygen difference
    • ↔ resting / ↑ maximal oxygen consumption
    • ↔ resting / ↑ maximal blood lactate levels
    • carbohydrate metabolism adaptations
    • fat metabolism adaptations
  • Cardiovascular
    • ↓ resting / ↓ maximal heart rate
    • ↑ resting / ↑ maximal stroke volume
    • ↑ resting / ↑ maximal cardiac output
    • ↓ resting / ↓ maximal blood pressure (systolic and diastolic)
    • ↑ total heart volume
    • ↓ myocardial oxygen demands (3)
    • ↑ myocardial blood flow distribution
    • ↑ myocardial oxygen extraction (arterio-venous oxygen difference) (4)
    • improved myocardial supply/demand balance
    • cardiac muscle hypertrophy
  • Pulmonary
    • ↓ resting / ↑ maximal respiratory rate
    • ↔ resting / ↑ maximal tidal volume
    • ↓ resting / ↑ maximal minute ventilation
    • improved minute ventilation/oxygen consumption ratio
  • Blood
    • ↑ total plasma volume
    • ↑ total blood volume
    • ↑ haemoglobin concentration
  • Skeletal
    • ↑ bone density
    • ↑ synovial fluid production
    • ↑ joint range of movement
  • Neural
    • Intramuscular
      • improved synchronisation of motor unit firing
      • improved recruitment of motor units
      • improved motor unit firing rate
    • Intermuscular
      • improved coordination of motor unit firing along the kinetic chain
      • improved efficiency of motor unit firing (i.e., reduced motor unit activation to lift a larger load)
    • Disinhibition of inhibitory mechanisms
    • Spinal cord and Cortical plasticity
  • Other
    • body composition adaptations: fat/muscle/bone ratio
    • stronger tendons and ligaments
    • body fluid adaptations
    • thermal adaptations
    • cognitive adaptations

 

References:

  1. Kenney, W. Larry, Jack Wilmore, and David Costill. Physiology of Sport and Exercise 6th Edition. Human kinetics, 2015.
  2. Takakura, Hisashi, et al. “Endurance training facilitates myoglobin desaturation during muscle contraction in rat skeletal muscle.” Scientific reports 5 (2015).
  3. Barnard, R. JAMES, et al. “Effect on training on myocardial oxygen supply/demand balance.” Circulation 56.2 (1977): 289-291.
  4. Detry, Jean-Marie R., et al. “Increased arteriovenous oxygen difference after physical training in coronary heart disease.” Circulation 44.1 (1971): 109-118.
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