stre&cond: chapter 6 - adaptations to aerobic training

aerobic training

sustained, repetitive bouts of exercise that primarily rely on oxidative and slow glycolysis

• ex: running, jogging, swimming — cardio

• training adaptations: efficiency in aerobic, VO2max, metabolite clearance (buffer H+)

cardiac output

Q = SV x HR the total volume of blood your heart pumps thru ur system in one minute

• acute CV response

• initially increases rapidly then plateaus

• may increase 4x resting with maximal exercise — 5 L/min resting to 20-22L/min

stroke volume

the amount of blood pumped out of LV with each beat

• before exercise: increases slightly bc of anticipation — catecholamines and SNS

• during exercise: increases from rest → 40-50% in untrained VO2max → plateaus as filling time decreases bc of high HR

increased venous return → more blood in LV → increased EDV → increased SV

• venoconstriction: SNS constricts veins and pushes blood to the heart

• skeletal muscle pump: contracting muscles squeeze veins → one way valves direct

• respiratory pump: inhale → decreased pressure in thoracic cavity → pulls venous blood toward lower pressure by the heart

increased contractility of heart catecholamines and frank starling

• catecholamines/SNS: heart contracts more forceful → ejects more blood

• frank starling: increased venous return → increased EDV → greater LV stretch → stronger contraction → increased SV

hr and bp (acute)

acute CV response

HR:

• before exercise: may increase slightly due to anticipation — catecholamines/SNS

• during exercise: increases linearly with intensity

• continues to rise after SV plateaus → Q increases

BP:

• systolic bp: rises with intensity — increased VR → increased Q → increased SBP

• diastolic bp: abt the same or decreases slightly — working muscles vasodilate → decreased TPR

  • veins venoconstrict for VR

circulation: blood flow to working muscle increases with exercise

• vascular shunting: redirection of blood from nonworking to working areas because it needs more O2 and remove more waste

LV size

aerobic training increases the size/volume of the LV chamber

• central chronic adaptation

  • eccentric hypertrophy

  • occurs in the heart and directly affects Q → VO2 = Q x (a-vO2 difference)

• LV can fill with more blood → increase EDV → increase SV → heart becomes more efficient → increased Q → more O2 delivered to working muscles → increased VO2max

• pumps more blood per beat — decreases resting HR and HR at the same submax workout

hr and bp (chronic)

chronic adaptation

HR:

• decreased resting/submaximal HR from increased LV volume and SV

  • more blood pumped per beat so lower HR

• increased parasympathetic tone: slows SA node firing → decreases resting HR

• max HR generally stays the same/decreases slightly

bp:

• possible decrease in resting SBP and DBP

• due partly to decreased TPR

  • increased artery flexibility and expand more when blood enters → decrease resistance

  • increased endothelial function = blood vessel lining better at producing vasodilators → decrease ressitance

acute respiratory

minute ventilation: increase intensity → increase minute ventilation

• breathing frequency (breaths/min) x tidal volume (air per breath)

gas diffusion: working muscles use more O2 and produce more CO2 → larger pressure gradients

• CO2: venous blood from muscles have increased PCO2 → diffuses from blood to alveolar PCO2 more rapidly → exhale

• O2: venous blood from muscles have decreased PO2 → alveolar PO2 diffuses into blood more rapidly

maximal exercise: high int exercise → increase glycolysis → increase H+ → increase bicarbonate buffering → extra CO2 → increase ventilation to “blow off” CO2

chronic respiratory

at the same submaximal intensity: increased TV and decreased breathing frequency

• trained muscles produce less H+ → decreased frequent breathing

• more air per breath — greater efficiency

maximal intensity: increased TV and increased breathing frequency → increased ventilation

• greater respiratory capacity for O2 delivery and CO2 removal

SAID principle: respiratory/metabolic adaptations are partly specific to muscles being trained

• lower body training doesn’t carry over to upper body: not the same acid-base adaptations

fibers

muscle adaptation in _____

decreased CSA of type I and type II fibers:

• may become smaller but functional ability is maintained

• smaller muscle mass can be advantageous in endurance activity — less mass to move

increased oxidative capacity of type II:

• type IIx → type IIa (more oxidative and fatigue resistant)

a vo2 difference

muscle adaptation

increased a-VO2 difference: o2 in arterial - o2 remaining in venous blood

• after training: muscles extract more O2 from blood → less O2 in venous → increases VO2

• increased capillary density: new capillaries around muscle fibers — increase O2 delivery, increase removal of byproduct

• increased myoglobin: extracts O2 from blood → binds O2 inside the muscle or stores O2 within muscle toward mitochondria

• increased mitochondrial density: increased number and size → muscle uses more O2 → increased aerobic ATP production → increased oxidative capacity

muscle adaptations

increase oxidative enzyme levels/activity:

• muscle better at producing ATP

• spares glycogen at the same submaximal workload

• increased storage of glycogen and triglycerides

decrease H+ production:

• using more O2 and delay fatigue at the same absolute intensity

increased critical power:

• increases highest sustainable exercise int using oxidative systems

• ex: after training, maintain higher relative intensity than before with higher VO2max

bone

needs more stress/force than normal ADLs to adapt

• promotes bone formation → helps increase BMD

• cardiopulmonary limitations before enough mechanical force is placed on bone

• ex: swimming — non-weightbearing, so add RT for greater mechanical loading and increase BMD

connective tissue

tendons, ligaments, and cartilage adapt with correct movement/progressive training

• load dependent

• high INT weight bearing → stronger stimulus

• long term, appropriate progressed aerobic training does NOT cause osteoarthritis/knee pain

• poor training can cause overuse problems

neural adaptations

increased movement economy:

• less energy/O2 to perform the same movement at the same speed/workload

• activates muscles in efficient pattern

greater concentric:eccentric ratio:

• eccentric contractions require less metabolic energy

• ex: running — when you land, muscles work eccentrically to control/decelerate movement and prevent excessive joint flexion = efficient force with low energy!

increase leg stiffness:

• muscle-tendon acts as a spring — elastic energy released → less muscle energy

increased motor unit cycling:

• different motor units alternate bt active and inactive

• synergist muscles

multisport athletes & SAID principle: specific to the movement practiced and doesn’t transfer between activity with diff motor patterns — shows less movement-economy adaptation

endocrine adaptations

acute:

• increased anabolic hormone during maximal exercise — recovery

• increased cortisol response (greater with prolonged/mod-high int) — maintain blood glucose and lipolysis for fuel availability

chronic:

• decreased hormonal response at the same submax workload for homeostasis

• trained can perform more efficient

overtraining

functional overreaching: decreased short term performance but beneficial with recovery

• used for peaking

nonfunctional overreaching: excessive training and no recovery → decreased prolonged performance

OTS: severe maladaptation and decrease performance — unsustainable training volume + no recovery

• increased resting HR from increased SNS

• decreased submax and max HR: resting system is overstimmed

• increased DBP

• increased creatine kinase — possible marker for muscle damage

• decreased test:cort ratio — reduced anabolic environment

• decreased GH — blunted endocrine response

• decreased sensitvity to catecholamines

detraining vs retraining

detraining: typically from a result of injury

• decreases VO2max — loss of BV, decreased SV, increased resting HR, decreased max Q

• 4 weeks: 4-6% decrease, >4 weeks: 6-20% decrease

retraining: aerobic/VO2max adaptations take around the same time to regain as it took to detrain

• 4 weeks detrained → 4 weeks to retrain