usually feels more difficult. This difference has to do with gravity
stress. The gravity-stress difference between swimming and running
is significant; there is very little gravity influence in the water, but
gravity maximally affects your body during running. A lot of energy
may not have to go into countering gravity stress in the pool but just
the opposite is true during a run. Another way of looking at this phe-
nomenon is that the heart rate during swimming is lower compared
to running at the same perceived effort, since the stress level is dimin-
ished in the water.
Riding a bike falls between the two extremes of swimming and
running, along with cross-country skiing, skating and most other
endurance activities. In these actions, there is some gravity stress
along with mechanical factors, which relates to technique.
Technique can influence the heart rate significantly. For the begin-
ning swimmer, the heart rate is usually much higher. As your tech-
nique improves, you waste less energy and the same intensity (pace)
results in lower heart rates. Looking at this another way, you need to
swim faster to maintain your maximum aerobic heart rate.
The benefits of training with a heart monitor are many, and only
with time and experience will you come to truly appreciate them. One
other significant benefit of applying the 180 Formula to your exercise
is the body’s chemical response to exercise at a relatively lower level
of intensity. Normally, the body produces oxygen free radicals in
response to many stresses, especially anaerobic exercise. Too many of
these free radicals contribute to degenerative problems such as
inflammatory conditions, heart disease and cancer. Increased free
radicals also speed the aging process. Exercising above your maxi-
mum aerobic level causes the body to produce large amounts of free
radicals, even if you’re only a little above the level. Using the 180
Formula as your guide minimizes free-radical production. Studies
show that training at this efficient intensity is ideal when free-radical
stress is a concern.
The MAF Test
Another important benefit of using a heart monitor is the ability to
objectively measure your aerobic progress. Feeling good is one of the
benefits of aerobic exercise. And feeling like you’re improving is good
202 • IN FITNESS AND IN HEALTH