Week 4 Flashcards
CO _____ proportional to O2 consumptions during exercise
increases
CO is typically ___L to every ____L of oxygen
6L CO to 1L O2
Activity of left and right cardiac vagus nerves ______ heart rate
decrease
Activity of right sympathetic nerves ______ heart rate
increase
Reducing the brake (L and R cardiac vagus nerves) ____ the heart
speeds
Reducing the accelerator (right sympathetic nerves) ____ the heart
slows
Heart rate is increased by _______ parasympathetic activity (vagal withdrawal) and ______ sympathetic activity
decreasing, increasing
At low HR (<100bpm), it is varied by adjusting _____ activity
vagal
At high HR (>100bpm), it is varied by adjusting _____ activity
sympathetic
Size-dependent cardiac variable (SV and CO) are traditionally related to …?
Body surface area (however, BSA does not account for body fat/composition)
According to dimensionality theory, heart mass or volume should related to BSA by exponent ____??
1.5 -> (heart mass/volume is 3 dimensional, and BSA is 2 dimensional —> 3/2 = 1.5)
What are 4 indirect methods of measuring CO in children?
- Indirect Fick (CO2 breathing)
- Acetylene-rebreathing
- Electrical bioimpedance
- Doppler ultrasound
Resting CO progressively ______ relative to body mass as children grow
decreases
Why does CO decrease relative to body mass as children grow?
Due to decrease in resting HR as children age
How much does the HR decrease in children as they grow?
Falls 10-20 bpm between ages 5 to 15 yrs (it stays 3-5 bpm higher in girls)
SV ______ in direct proportion to body mass
increases (or stays in proportion with body mass)
At rest, HR is _____ related to mass and age in children
inversely (decreases as they get bigger)
In maximal exercise, max HR is _______ of body size between ages 6-16yrs
independent (stays fairly consistent regardless of body size)
Sady et al (1981) compared HR response between men (aged 30) and boys (aged 10) and found that…
time to reach half the HR increase was significantly shorter in boys than men—> children have quicker HR responses to exercise
At a given work rate, steady state HR is _____ in children (by as much as 40-60 beats) than adults and ______ with increasing age
higher, declines
A higher steady state HR in children is a compensatory mechanism for…?
smaller hearts and lower SV
Highest HR to lowest HR…?
- young girls
- young boys
- adult girls
- adult boys
HR recovery post exercise is _____ in children than adults
faster
The faster HR recovery in children may be related to…?
lower acidic levels, and quicker response of removal of metabolites
SV response in children vs adults…
Adults: have nearly double SV from rest to maximal exercise
children: Children rest to max only ranges from about 1.1 to 1.35
CO is ____ in children vs. adults for a given Vo2 due to _____ SV
lower, lower
Lower CO in children is compensated for by higher….
arteriovenous O2 difference (a-vo2)
Vo2 is determined by 2 things…?
- How much O2 is delivered to cells (CO)
- How much O2 us used by cells (O2 extraction –> arterial-venous difference)
HR and ___ ____ resistance were higher in children than adults (boys slightly lower HR than girls—> bigger difference in adulthood)
total peripheral
Gender differences in SV and HR _____ reaching adulthood
increase (difference widens)
A smaller amount of muscle mass performing a given amount of work would be stressed to a greater extent, this generating more metabolic by-products and ____ per unit of muscle
heat
More metabolic by-products and heat per unit of muscle from children having a smaller muscle mass would result in (3)?
- Increase in O2 release by Hb (by decreasing its affinity for O2 at the muscle)
- Increase in vasodilation of the arteries entering the muscle (increase blood flow)
- Increase in feedback to medulla via group III and IV afferents contributing to higher HR in children
Ontogenetic improvements in VO2max relative to body mass may be determined by increases in the _____ of the exercising tissue (skeletal muscle) and changes in the ______ _____ of its energy system (aerobic enzyme capacity)
size, functional capacity
Rest: reductions in resting cardiac output relative to body size are accounted for by decreases in …
resting HR
Exercise: increases in __________ are responsible for matching maximal cardiac output to body size as children grow.
maximal SV
During dynamic exercise at a given work rate, children have _____ heart rates and _____ stroke volumes than adults.
higher, lower
Lower cardiac output in children during exercise is compensated for by an increase in ..?
a-vo2 difference (arteriovenous O2 difference)
There are _____ in absolute Vo2max as children age
increase
Between the ages of 6-12yrs, the Vo2 max of a boy ……..
more than doubles (from 1.2L/min to 2.7 L/min)
- females are about 200mls lower
How does a growing child meet the increasing O2 demands?
Cardiac size increases in concert with the increases in muscle mass to match O2 delivery to consumption within the exercising muscle
How does increase in left ventricular mass help to match O2 delivery (and what is behind the increase)?….
Increase in left ventricular mass —> increase in resting stroke volume —> determines maximal exercise SV —> maximal CO —-> therefore, maximal O2 uptake
Factors influencing left ventricular size are (3)?
- blood volume
- heart rate (vagal tone)
- hormonal effects on the heart
Is vo2 max closely related to endurance performance in children
Increasing in endurance performance as children grow is NOT related to Vo2 max
Can levels of habitual activity in children predict Vo2max?
No, not a useful predictor of VO2max.
When body size and composition are taken into account, does Vo2 max differ between boys and girls?
Most gender differences are due to greater size (body size, heart mass) and body composition (skeletal muscle mass) in boys versus girls. Once these factors are accounted for, there is little difference between boys and girls in maximal aerobic power
