Cardiovascular Response to Exercise Training

VO2 max

maximal capacity of the body to transport and use oxygen

• units = ml O2/kg x min

• other terms: maximal oxygen consumption, maximal aerobic power, maximal aerobic capacity

METS

measure of intensity of physical activity

• 1 MET = intensity at rest = 3.5 ml O2/kg x min

• Exercise Intensity

VO2 Max test

graded exercise test with open circuit spirometry directly measure VO2

• requires laboratory equipment and other considerations (submaximal exercise protocol have been developed to estimate VO2) 

Calculation of VO2 max

VO2 max: product of maximal CO and arteriovenous difference 

• VO2 max = HR max x SV max x (a-vO2) max 

Differences in VO2 max in different populations (age, sex, training state, health conditions) 

Factors affecting VO2 max

• genetics accounts for 50% of VO2 max

• training

• age: with aging SA node activity decreases

• body size: larger people may have a larger VO2max due to larger heart and lungs

• sex: women have lower VO2max due to smaller heart and less hemoglobin

  • altitude: VO2max lower at high altitude due to less O2 available

Training Affects VO2max

VO2max = HR max x SVmax x (a-vO2) max

• increases COmax due to increase in SVmax (HR max dependent on age)

• increase a-vO2 diff (genetics role most apparent) and faster rise in oxygen uptake at onset of exercise with less disruption of homeostasis

  • volume of mitochondria, # capillaries, # enzymes involved in production of ATP via aerobic pathways

Endurance training-induced changes in VO2 max 

improvements in VO2 max with training: 

• ~50% increase SV and a-vO2

• shorter duration training (4 months): increase SV > increase a-vO2

• longer duration training (32 months): increase a-vO2 > increase SV

Endurance (Aerobic) training and VO2 Max

genetic predisposition: accounts for about 50% of VO2 max and prerequisite for very high VO2 max

training to increase VO2 max: dosage dependent

• frequency > 3 times/week

• intensity > 50% VO2 max

• time: 20-60 minutes

• Type: dynamic activity utilizing large muscle groups

expected increase in VO2 max: impacted by baseline when initiating training

• average 15-20%

• high initially VO2 max: 2-3% requires training intensity of >70% VO2 max

• Low initial VO2 max: up to 50% training intensity of 40-50% VO2 max

Factors Increasing Stroke Volume

aerobic training effect:

• increase rest, submaximal exercise, and maximal exercise

changes occur rapidly (6 days)

• 11% increase in plasma volume, 10% increase in SV and 7% increase in VO2max

Aerobic Training: blood composition

increase in: 

• plasma volume increase rapidly then levels off, # red blood cells after 4 weeks of training, total blood volume, high density lipoprotein (“good cholesterol”): may increase 2% after 6 months regular exercise 

Decrease in hematocrit and decrease/maintained LDL (“bad cholesterol) 

High Level endurance training impact on blood composition

sports anemia, sports-related hemolytic anemia, if CBC shows decrease hematocrit, decrease hemoglobin, and decrease ferritin may need treatment for iron deficient anemia

Sports Anemia

intensive endurance training can result in increase in plasma volume reflected in a decrease in hematocrit, hemoglobin, and red blood cell count in a blood sample

iron deficiency: alterations of transport of oxygen to tissues

• associated with increased demands, dietary restrictions, decreased absorption and other factors

• more common in athletes with heavy training loads

Sports-related hemolytic anemia

rupture and destruction of erythrocytes during physical exercise 

• occurs during impact forces of foot strike during running or power walking 

• other causes: repeated muscle contractile activity, vasoconstriction of internal organs, hyperthermia, dehydration, oxidative stress and other metabolic abnormalities

Aerobic training

increase ventricular volume and small increase in ventricular wall thickness

• results in a volume overload

• increase in ventricle volume is a normal physiologic adaptation to this volume overload

• left side has greater changes than right

VO2max = (HRmax x SVmax) x a-vO2diff max

during acute aerobic ex cardiac contractile force increase (due to increase SNS activity)

Aerobic training:

• decrease in afterload

• vigorous aerobic training increase cardiac muscle strength

Skeletal muscle adaptation to endurance training

• fast-to-slow shift in muscle fiber types

• increase capillary and mitochondria density

• increase FFA utilization and decrease blood glucose and muscle glycogen utilization 

• high intensity training; Increase LT 

• increase antioxidants 

increase a-vO2 diffmax

increase in capillary perfusion (decrease in SNS vasoconstriction) 

increase in capillary density in trained muscles 

increase in mitochondria # in trained muscles

occurs rapidly, increase seen within 5 days of training

• increase dependent upon intensity and duration of exercise; may be 50-100% increase within 6 weeks of training 

  • increase in oxidative enzymes in trained muscles 

Summary of Effects of Aerobic training

effects of training on recovery from exercise

more rapid reduction in HR, SV, CO, and SBP to baseline (trained individuals recover in a shorter time period)

heart rate recovery (HRR)

• reflect balance in reactivation of PNS and withdrawal of SNS

• utilized as a predictor for CAD, cardiovascular mortality, and other health outcomes

  • improved with aerobic exercise training

HRR 

decrease in heart rate following cessation of exercise

effects of training on recovery from exercise

Aging aerobic training effecct

maximal HR decreases with aging

SV declines due to decrease in heart extensibility

VO2 max decreases 10% per decade after 25-35 years of age

adaptations can be realized at any age but extent of change may be limited by age

sex aerobic training effects 

in general SV, CO are larger at sub-max and max  work rates in men 

arterial oxygen content less in women (less hemoglobin) 

no gender differences in magnitude  of CV adaptations to exercise between the sexes

Normal vital sign response to acute aerobic exercise

HR is expected to increase = bpm for every 1 MET increase in exercise intensity

SBP is expected to increase 8-12 mmHg for every 1 MET increase in exercise intensity

CV response to aerobic exercise training

decrease RHR 5-25 bpm

decreases SBP and DBP at rest; Dec’s SBP 10-15 mmHg

increases VO2max 15-20% in 12 weeks

• improvement dependent upon fitness level. very deconditioned individuals may improve as much as 50%

Detraining and VO2 max

rapid decrease in VO2 max 

• decrease approximately 8% within 12 days; 20% decrease after 84 days 

initial decrease in VO2 max due to decrease SV max with later decrease due to a-vO2 max 

• decrease SV max

• decrease maximal a-vO2 difference (decrease mitochondria, oxidative capacity of muscle and type 2a fibers and increase type 2x fibers 

dynamic resistance exercise with light to moderate loads

CO increase but not as much as aerobic exercise

• mainly due to increase in HR; little change in SV

• similar to aerobic exercise SBP, DBP remains relatively constant

Dynamic and isometric resistance exercise with very heavy loads

increase CO

• increased HR

  • decreased SV due to: low preload and high afterload 

Adaptations to resistance training

-resting HR

-reduction in BP in those with prehypertension, hypertension, and elevated cardiometabolic risk

-submaximal exercise

VO2 max

muscle oxidative properties and/or muscle capillarization

improvement in glycemic control

improvement in HDL

decrease in total cholesterol and triglycerides

inflamation

improvement in body composition

depression and anxiety decrease