HSS 395 Responses & Adaptations to Aerobic Training

Aerobic training

A form of exercise that involves repetitive, structured activity that increases heart rate and breathing rate because it requires the body’s metabolic system to use oxygen to produce energy (aerobic systems)

• Might include: walking, jogging, running, swimming, cycling, dancing, rowing, etc.

• Aka: cardiovascular exercise, endurance training, cardio

Acute responses — cardiovascular

• ↑ sympathetic and ↓ parasympathetic stimulation

• ↑ cardiac output (↑ heart rate & ↑ stroke volume)

• ↑ systolic BP w/ minimal change in diastolic BP

Acute responses — respiratory

• ↑ pulmonary minute ventilation (breathing rate x tidal volume)

• ↑ respiratory exchange ratio (RER) — higher RER reflects higher percent reliance on carbohydrates

Acute responses — metabolic

↑ metabolism → ↑ CO₂ & ↑ lactate

Acute responses — endocrine

• ↑ glucagon & ↓ insulin secretion (enhances lipolysis)

• ↓ cortisol with low-intensity & ↑ with moderate- to high-intensity

• ↑ catecholamines (E & NE)

Chronic adaptations — cardiovascular

• ↑ VO₂ max

• At rest/submax — ↓ HR (w/i 2-10 wks) & ↑ SV

  • ↑ cardiac output primarily driven by ↑ SV

• ↑ red blood cell volume

Chronic adaptations — respiratory

• Submaximal: pulmonary minute ventilation decreases:

  • ↑ tidal volume

  • ↓ breathing frequency

• Maximal: pulmonary minute ventilation increases:

  • ↑ tidal volume

  • ↑ breathing rate

Chronic adaptations — skeletal muscle

• Small ↑ in type I & ↓ in type IIx fibers

• ↑ capillary density

• ↑ mitochondrial density & size

• ↑ activity of oxidative enzymes

• ↑ intramuscular glycogen stores

Chronic adaptations — metabolic

• ↑ reliance on fat as energy

• ↑ lactate threshold

• ↑ VO₂ max of 10-30%

Chronic adaptations — body composition

Weight loss more likely to occur with moderate intensity activity >150 min per week (balances % energy from fat and total kcals expended)

Chronic adaptations — bone & connective tissue

• Moderate-high bone-loading forces = ↑ bone mineral density (BMD)

• Tendon, ligaments, cartilage appear to remodel when mechanical stress occurs over time

Influencing factors — specificity

Adaptations are specific to the type of exercise (e.g., running, swimming, cycling, etc.)

Influencing factors — genetics

• Theoretical “genetic ceiling” on human performance, dependent on training stimulus & motivation

• Genetic factors account for ~20-30% of VO₂max differences & ~50% of differences in HR

Influencing factors — sex

• Physiological changes similar for males & females

• Absolute values differ due to body differences (smaller heart & lungs in females = lower VO₂max)

Influencing factors — age

• VO₂ max increases as children mature (highest values ~12-15 for females and ~17-21 for males)

• Then, VO₂ max decreases with aging (decrease can be negative with training)

Parasympathetic dominant overtraining

Primarily found when aerobic endurance overtraining occurs as the result of excessive volume; responses include early onset of fatigue, decreased resting HR, rapid HR recovery after exercise, decrease resting BP

Sympathetic dominant overtraining

Primarily found with anaerobic or resistance overtraining occurs as the result of high-intensity overload; responses include increased resting HR, increased BP, loss of appetite, decreased body mass, sleep disturbances, emotional instability, elevated basal metabolic rate

Aerobic detraining

• 2 weeks after training is stopped:

  • ↓ muscular endurance

  • ↓ VO2max and cardiac output

  • ↓ aerobic enzyme levels

• 4 weeks after training is stopped:

  • ↓ muscle’s respiratory ability

  • ↓ glycogen level

  • ↑ lactate production