respiratory rate are the primary way Ve increases
(Franklin, 2001).
•Generally, increases in Ve are directly proportional to
an increase in oxygen consumption(VO 2 ) and carbon
dioxide produced(VCO 2 ); however, at a critical exer-
cise intensity (usually 47–64% of the VO2max in
healthy untrained individuals and 70–90% VO2maxin
highly trained individuals), Ve increases dispropor-
tionately relative to the VO 2 , paralleling an abrupt
increase in serum lactate and VCO 2. This is called the
anaerobic (ventilatory) threshold (AT) (Franklin,
2001).
•AT signifies the onset of metabolic acidosis during
exercise, and traditionally has been determined by
serial measurements of blood lactate. It can be non-
invasively determined by assessment of expired
gases during exercise testing, specifically Ve and
VCO 2. AT signifies the peak work rate or oxygen
consumption at which the energy demands exceed
circulatory ability to sustain aerobic metabolism
(Franklin, 2001).
MAXIMALOXYGENCONSUMPTION
- The most widely recognized measure of cardiopul-
monary fitness is the aerobic capacity,or VO2max. This
variable is defined physiologically as the highest rate
of oxygen transport and use that can be achieved at
maximal physical exertion (Franklin, 2001).
EFFECTS OF EXERCISE TRAINING
CARDIOVASCULARSYSTEM
- The effects of regular exercise on the cardiovascular
system can be grouped into changes that occur at rest,
during submaximal exercise and during maximal
work (Rupp, 2001).
Changes at Rest
- Heart rate (HR) decreases likely secondary to decreased
sympathetic tone, increased parasympathetic tone, and a
decreased intrinsic firing rate of the SA node. - SV increases secondary to increased myocardial con-
tractility. - Cardiac output is unchanged at rest.
- Oxygen consumption does not change at rest (Rupp,
2001).
Changes at Submaximal Work
- Submaximal work is defined as a workload during
which a steady state is achieved.
a. HR decreases at any given workload owing to the
increased SV and decreased sympathetic drive.
b. SV increases owing to increased myocardial con-
tractility.
c. Cardiac output does not change significantly for
a fixed workload; however, the same cardiac
output is generated with a lower HR and higher
SV.
d. Submaximal oxygen consumption does not change
significantly since oxygen requirement is the simi-
lar for a fixed workload.
e. a-vO 2 Diff. increases during submaximal work.
f. Lactate levels are decreased owing to metabolic
efficiency and increased lactate clearance rates
(Rupp, 2001).Changes at Maximal Work- Maximal heart rate (HRmax) does not change with
exercise training. - SV increases owing to increased contractility and/or
increased heart size. - Maximal cardiac output increases owing to increased
SV. - Maximal oxygen consumption (VO2max) increases
owing to increased SV and a-vO 2 Diff. - a-vO 2 Diff. increases owing to improved ability of the
mitochondria to use oxygen (Rupp, 2001).
Blood Pressure- In normotensive individuals, regular exercise does not
appear to have a significant impact on resting or exer-
cising blood pressure. - In hypertensive individuals there may be a modest
reduction in resting blood pressure as a result of reg-
ular exercise (Rupp, 2001).
BLOODLIPIDS- Total cholesterol may be decreased in individuals with
hypercholesterolemia. - High-density lipoprotein cholesterol (HDL) increases
with exercise training. - Low-density lipoprotein cholesterol (LDL) may
remain the same or decrease with regular exercise.
•Triglycerides may decrease in those with elevated
triglycerides initially. This change is facilitated by
weight loss (Rupp, 2001).
BODYCOMPOSITION- Total body weight usually decreases with regular
exercise.
•Fat-free weight does not normally change. - Percent body fat declines (Rupp, 2001).
BLOODVOLUMECHANGES- Total blood volume increases owing to an increased
number of red blood cells and expansion of the
plasma volume (Rupp, 2001).
78 SECTION 1 • GENERAL CONSIDERATIONS IN SPORTS MEDICINE