These units are used by the Center for Disease Control
to recommend exercise intensity.- Energy expenditure for activities such as eating,
dressing, and walking around the house range from 1
to 4 MET, whereas the cost of climbing a flight of
stairs, walking on level ground, scrubbing floors, or
playing a game of golf ranges from 4 to 10 MET.
Strenuous sports, such as swimming, singles tennis,
and football often exceed 10 MET.
BASIC CONCEPTS IN AEROBIC AND
ANAEROBIC EXERCISE
MAXIMAL AEROBIC POWER
- Maximal aerobic power, or VO2max, is the greatest
amount of O 2 a person can consume during physical
exercise. It is a useful measure for characterizing the
functional capacity of the cardiovascular, pulmonary,
and O 2 transport systems, and is considered “power”
because it is a rate: L of O 2 /min. - If two individuals had absolute VO2maxvalues of 4.2
and 3.2 L/min and both weighed 70 kg, then normaliz-
ing for body weight would yield values of 60 and 45.7
mL/kg/min respectively. If person one weighed 70 kg
and person two 53 kg, then normalized VO2maxvalues
would be 60 mL/kg/min for both persons. VO2max
values above 50 mL/kg/min are considered high.
TESTING FORMAXIMALAEROBICPOWER
- The best tests for measuring VO2maxare incremental
tests. A number of issues and concepts are important
for VO2maxtesting. - Requirements for maximal testing: Minimal require-
ments for a valid maximal exercise test are that the
exercise must involve large muscle groups and the rate
of work must be measurable and reproducible. In addi-
tion, the test conditions should be standardized and the
test should be tolerated by most people. Motivation
should not be a major factor, and little to no skill should
be required. The primary ways to assess aerobic power
are by treadmill walking/running, cycle or arm ergom-
etry, and step tests. The test protocol should be incre-
mental or progressively increasing work so a true
VO2maxis achieved. Different values will be obtained
when the mode of exercise changes, and the absolute
value will reflect the muscle mass involved. Combining
upper and lower body work will yield higher values
than treadmill, cycle, and arm work alone. - Concept of plateau:During a progressive exercise
test, when a step increase in work does not result in a
further (or minimal) increase in VO 2 , then VO 2 has
begun to level off. The leveling off or plateauing effect
is considered the single best criteria for attaining a
true VO2max. For many treadmill protocols, an increase
in VO 2 <0.150 L/min is indicative of a plateau.- Criteria for achieving VO2max:If a leveling off or
plateauing of VO 2 cannot be seen, then other criteria
are used to document a true VO2max. At least two of the
following criteria should be met for a true VO2maxtest:
blood lactate levels above 7 or 8 mM; HR equal to or
within 15 beats of the age-estimated maximal HR;
RER ≥1.15; and/or RPE ≥17. - VO2peak:When an exercise tests is terminated and the
criteria described are not met, the higher VO 2
achieved is referred to as VO2peak. - Ventilatory threshold:Ventilatory threshold is the
point where VE begins to increase disproportionately
to VO 2 during incremental exercise testing. It is a
measure of “excess” ventilation and has been termed
anaerobic threshold. - Estimating VO2max:VO2maxcan be estimated using the
known linear relation between HR and VO 2. HR at sub-
maximal work rates can be plotted against VO 2 and then
the estimated maximal HR can be used to extrapolate to
VO2max. Cycle tests are most appropriate because there
are expected VO 2 values as a function of Watts (see
Table 8-5). Walking tests, step tests, endurance runs, and
nonexercise data can also be used to estimate VO2max.
Potential errors exist for all these estimates and care
needs taken in interpreting these data.
DETERMINANTS OF ANDFACTORSAFFECTINGVO 2 MAX- Intrinsic and extrinsic factors: Intrinsic factors
affecting VO2maxinclude genetics, gender, body com-
position/muscle mass, age, and existing pathologies.
Extrinsic factors include training/activity levels,
dietary intake (alcohol, caffeine), nutritional and
hydration status, and environmental conditions. - Determinants:All systems serving a role in the deliv-
ery of O 2 can affect VO2max. Central factors include car-
diac output, pulmonary ventilation, arterial pressure,
hemoglobin(Hb) content, O 2 diffusion into and through
the lungs, the alveolar ventilation: perfusion ratio, and
42 SECTION 1 • GENERAL CONSIDERATIONS IN SPORTS MEDICINE
TABLE 8-5 Expected VO 2 Values at Designated Power
Outputs Between 1 and 3 Min with Cycle Ergometry
POWER (W) OXYGEN UPTAKE (L/MIN)
50 0.9
100 1.5
150 2.1
200 2.8
250 3.5
300 4.2
350 5.0
400 5.7