34 Cardiorespiratory Conditioning
Anaerobic Power
How much strenuous work can you sustain without oxygen? Most people can do
very little for more than a couple of minutes. It is very important to realize that most people
cannot work for very long at even 90% of their maximal aerobic capacity. This is because
everyone has a threshold at which the balance between aerobic and anaerobic energy
systems begins to favor the anaerobic; your muscles cannot extract enough oxygen to
produce the required energy. This is called your anaerobic threshold; the turning point can
be monitored by the accumulation of lactate in your blood. Of course, your body will know
when there is too much lactate, because once lactate goes above a certain value, it starts to
accumulate and unless you decrease your work rate, you will become too tired to continue
working.This anaerobic threshold, or “break point” varies among individuals, but ranges
between 60% and 100% of your VO2max; all SEALs should be able to work at 70% of their
VO2max for an extended period, and should have a break point above 70%. Conditioning
programs for SEALs should strive to raise the anaerobic threshold or break point to as high
as possible, because that means you can work at a higher rate for a longer period of time.Interval workouts stress the anaerobic energy systems
and will increase your anaerobic threshold and power.Interval and fartlek workouts for running and swimming are described in their
respective chapters, and such workouts for other forms of exercise are described later in this
chapter.Determination of Work Rate
One common denominator across all types of cardiorespiratory conditioning
programs is exercise intensity and work rate. The term exercise intensity typically refers to
how hard you are working as a percent of your maximal aerobic capacity. For example, you
could work at an intensity equivalent to 50% (easy), 70% (moderate), or 90% (strenuous)
of your maximal aerobic capacity or maximal heart rate. You will learn how to estimate
your maximal aerobic capacity below, but on average, a maximal capacity of 45 to 55 ml
of oxygen/kg/min and a maximal heart rate of 200 beats per min would be typical for a 20
to 29 year old SEAL. Table 3-1 presents the relation between exercise intensity, oxygen
uptake, and heart rate for a 20 year old SEAL with a maximal heart rate of 200 and a
maximal oxygen uptake of 55 ml of oxygen/kg/min. Easy exercise would use 25 to 30 ml