Analyzing Cardiac Output, Stroke Volume, and Heart Rate Across Populations
Understanding the Key Metrics
Let's break down how cardiac output (CO), stroke volume (SV), and heart rate (HR) vary between different populations and during exercise. Remember, these three metrics are related by the formula:
CO = (HR x SV)
Resting Values Across Populations
Untrained Individuals
- Resting Heart Rate: 60-80 beats per minute (bpm)
- Resting Stroke Volume: 70-80 mL/beat
- Resting Cardiac Output: ~5 L/min
Endurance Athletes
- Resting Heart Rate: 40-60 bpm
- Resting Stroke Volume: 90-110 mL/beat
- Resting Cardiac Output: ~5-6 L/min
Despite having a lower resting heart rate, athletes maintain similar cardiac output due to their higher stroke volume.
Exercise Response Patterns
Untrained Individuals
During exercise:
- HR increases linearly with intensity up to ~200 bpm
- SV increases until ~40-50% of max intensity, then plateaus
- CO can reach 20-25 L/min at maximal effort
Endurance Athletes
During exercise:
- HR increases linearly but maxes out at lower values (~180-190 bpm)
- SV continues to increase throughout exercise intensity
- CO can reach 30-40 L/min at maximal effort
When analyzing data, look for the SV plateau point - it's a key indicator of training status!
Population-Specific Variations
Age-Related Differences
- Children:
- Higher resting HR (80-100 bpm)
- Lower SV due to smaller heart size
- Lower overall CO
- Elderly:
- Reduced maximal HR (220 - age = estimated max HR)
- Decreased SV response to exercise
- Lower maximal CO
Gender Differences
- Females typically show:
- Slightly higher resting HR
- Lower SV due to smaller heart size
- Lower maximal CO compared to males
Don't assume that a lower CO always indicates poor fitness - consider the person's age, gender, and body size when analyzing data.
Exercise Intensity Analysis
Submaximal Exercise
- HR increases linearly
- SV increases initially then:
- Plateaus in untrained individuals
- Continues to rise in trained athletes
- CO increases proportionally to exercise intensity
Maximal Exercise
- HR reaches age-predicted maximum
- SV reaches individual maximum
- CO peaks at individual capacity
A 20-year-old untrained individual exercising at 50% intensity might show:
- HR: 130 bpm
- SV: 110 mL/beat
- CO: 14.3 L/min
While a trained athlete at the same intensity might show:
- HR: 120 bpm
- SV: 140 mL/beat
- CO: 16.8 L/min
When analyzing data, always consider the relationship between all three variables (CO, SV, HR) rather than looking at them in isolation.
