60% maximum = * .60 = beats/minute
(max. HR)
85% maximum = * .85 = beats/minute
(max. HR)
Endurance athletes may work anywhere in this range depending on their goals. Typically
recovery workouts are done near the low end of the range, while higher intensities are used to
improve aerobic fitness. Intensities above 85% of maximum should be done in an interval fashion
and are discussed in the next chapter.
In general, bodybuilders should stay at low aerobic intensities to avoid losing muscle mass
and strength. If lactate threshold (LT) has been determined (see below), 15 beats per minute
below LT should be used as a guideline for aerobic intensity (3). If LT has not been established, a
heart rate of 60% of maximum should be used.
Non-bodybuilders looking solely at maximum weight/fat loss will benefit most from
exercising at the highest intensity they can safely maintain to maximize caloric burn. On a
standard ketogenic diet, about the highest intensity which can be maintained is 75% of maximum
heart rate. Higher intensities can be sustained following a carb-up for CKDers or pre-workout
carbs on the TKD.
Determining the lactate threshold (LT)
Determining the LT is typically done in a lab using highly accurate and specific testing
devices. However, the LT can be determined roughly in the gym as well. The LT is highly specific
to a given activity. That is, determining LT on a bicycle tells you nothing about your LT on a
treadmill or a Stairmaster. Therefore LT should be determined on the specific piece of equipment
an individual will be using during their exercise session.
Recall from the previous chapter that lactic acid is the primary cause of the burning
sensation felt in muscles during high-intensity exercise. Since LT is defined as the point where
lactic acid begins to accumulate in the bloodstream, it can be roughly determined by noting when
a burning sensation in your muscles is felt.
To most accurately determine LT, individuals need to be proficient at taking their heart
rate or have access to a digital heart rate monitor. Many aerobic exercise machines have heart
rate monitors built in. To determine LT, intensity should be gradually increased, while monitoring
heart rate, until a significant burning sensation is felt. As a general rule, each increase in
intensity level should be maintained for three minutes to allow for lactic acid to accumulate.
When a significant burning sensation is felt in the muscles being used, heart rate should be taken,
and assumed to roughly indicate the LT for that exercise.
Time
For health benefits, a minimum duration of twenty minutes per session is necessary (1).
For fat loss, a duration sufficient to expend 300 calories three times per week or 200 calories four