The Navy SEAL Physical Fitness Guide - Human Performance

The Navy SEAL Physical Fitness Guide 33

Terms Related to Conditioning

Many terms are used to define or describe exercise conditioning and work rate, also
referred to as exercise intensity or work load. The two terms used throughout this chapter
for describing how to gauge your work rate will be maximal oxygen uptake and energy
expenditure as calories/hour, or kcal/hr. Other terms to describe work rate and their
interrelationships will be discussed at the end of this chapter.

Maximal Oxygen Uptake

The primary measure or predictors of one's capacity to sustain work performance is
maximal oxygen uptake (VO2max) or maximal aerobic (cardiorespiratory) capacity.
VO2max is measured in milliliters per minute (ml/min), Liters/min, or after adjusting for
body weight in kilograms, as ml/kg/min; a higher value indicates a higher level of
cardiorespiratory fitness.

Your maximal aerobic capacity or oxygen uptake

is the best indicator of how much work you

can sustain without fatigue.

Typical VO2max values range from 30 ml (of oxygen)/kg/min for an unfit person up
to 80 ml/kg/min for an exceptionally fit, endurance athlete. If the unfit and highly fit
persons both weighed 70 kg (155 lb) then their respective absolute maximal aerobic
capacities would be 2.1 liters (of oxygen)/min and 5.6 liters (of oxygen)/min.

Using 1 liter of oxygen/min is equivalent

to expending 5 kcal/min

As such, the unfit person can only work at a rate of up to 10 kcal/min (2.1 L x 5)
whereas the highly fit could work at up to 25 kcal/min (5.6 L x 5 kcal) if needed. If a
specific task required 2 L/min, then this would amount to 10 kcal/min of energy. Resting
energy expenditure requires less than one kcal/min, or about 0.200 to 0.250 L (of oxygen)/
min. In order to account for different body sizes, resting energy expenditure for an
individual is usually defined as:

3.5 ml of oxygen/kg body weight/minute.

Thus, for a 70 kg (155 lb) SEAL, resting energy expenditure would be approximately 245
ml/min or 0.245 L/min (3.5 x 70). This is equivalent to expending around 1 to 1.25 kcal/
min.