• Heart Rate
• Stroke volume
• Cardiac Output
• Blood pressure and flow
• The blood
• Integration

During graded exercise to maximum, we observe parasympathetic withdrawl (HR increases from ~ 70 to 100 bpm) followed by sympathetic activation (increase from 100 to age-predicted maximum) until max HR is achieved.

Linear relationship between HR and exercise intensity and between HR and oxygen uptake.

NOTE: %HRmax is higher than %VO₂max! At 75% HR max this subiect is at 65% VO₂ max. If you want HR to better represent % VO2, use calculation of heart rate reserve!

VO2:HR relationship (oxygen pulse) depends on mode of training

• Oxygen Pulse = VO₂(ml/min)/HR(b/min)
• Oxygen Pulse tells us how much oxygen is extracted per beat of the heart.
• The pulse is higher when prone in water than upright on land. Why?

Stroke volume response to exercise: an exciting controversy.

Conventional idea: SV increases with exercise intensity, but only up to about 40-60% VO2 max. True for untrained and moderately trained. But…

Gledhill et al. MSSE 1994, found elite athltes increase SV all the way to max. Gold line = endurance-trained athletes Navy line = untrained

Faster filling and prolonged ejection with training results in higher stroke volumes at all heart rates!

Cardiac Output: Rest vs. Max Exercise -- HR and SV

(Table from Wilmore and Costill, 1999)

		HR (b/min)	SV (ml/beat)	Q (L/min)
Running	Rest	60	70	4.2
	Max ex.	190	130	24.7
Cycling	Rest	60	70	4.2
	Max ex.	185	120	22.2
Swimming	Rest*	55	95	5.2
	Max ex.	170	135	22.9

Blood pressure response to dynamic exercise

SBP increases while DBP remains stable

Example: 120/78 mmHg increases to 200/80

MBP increases from 92 to 120

Equations:

Earlier I showed this one:

MBP = [SBP + (2 x DBP)]/3

Using 200/80 as an example:

MBP =[ 200 + (2 x 80)]/3 = 120 mmHg

Wilmore & Costill’s formula:

MBP = DBP + [0.333(PP)]

Using 200/80 as an example:

MBP =[ 80 +0.333 (200-80)] = 120 mmHg

Redistribution of blood flow w/ exercise

In relative terms…

At rest, muscle receives only 15-20% of Q, but during exercise, 80-85%!!!

Blood flow is redistributed away from the splanchnic (liver and guts) and renal (kidney) beds and toward working muscles.

Magnitude of effect depends on exercise intensity and environmental conditions.

Blood composition

Hemoconcentration is an acute response to exercise

plasma volume will decrease -10 to -15%

Why? (a) Hydrostatic pressure; and (b) Osmotic gradient between plasma and interstitial space.

But remember...Hemodilution is a CHRONIC response to training.

Integration:

I provided a handout describing all the mechanisms responsible for CV regulation during exercise. Complicated, yes?