by Lyle McDonald
Hi guys. This is the second part of my intro to basic exercise.
Today, I will focus in a little more specifically on weight
training and on some of the terminolgy involved.
Isotonic: A type of resistance training where the resistance
does not change throughout the range of motion. The mahority
of training equipment falls into this category. A dumbbell
provides the same resistance throughout the motion of a bicep
curl. Admittedly, it may feel heavier or lighter during certain
parts of the movement but this is due to changing biomechanical
factors around the elbow joint. The mojority of machines
fall into this category as well. Some machines (notable Cybex
and Nautilus) attempt to overcome this and provide different
resistance throughout the motion by using an elliptical cam.
The usefulness of these cams is open to debate. I have my own
opinions about Nautilus but will keep them to myself.
Isokinetic: A type of resistance where the speed of motion
is determined by the machie (i.e. 60 degrees per second). Unless
you work in a physical therapy setting with very expensive
machines, you will never see a true isokinetic machine for the
most part. These machines have to use a computer to adjust
the resistance constantly in order to keep the speed of motion
constant. Thus they reun about $50k. I don't care what NordicGold
says, it is not a true isokinetic machine. The hydraulic type of
machines found in some gyms might be a little closer but they are
still not true isokinetic machines.
Isometric: A type of resistance where there is no motion at a joint.
This is the theory behind the dynamic tension type of workouts that
we all saw in the back of comic books. It's usefulness to the average
body shaper and fitness entusiast is very debatable. It is useful if
no equipment at all is available but even then most exercise can
be duplicated with body weight or elastic straps. The biggest problem
with isometric exercise is that strength gains are only realized at
the joint angle used. Thus, if you do an isometric biceps curl with the
elbow bent 90 degrees, you will get stronger only at 90 degrees. But,
if you do a full motion biceps curl, you will gain strength across the
whole range of motion.
The next set of terminology concerns the type of muscle contractions
which can occur.
Concentric: This is the shortening portion of the movement. In a
biceps curl, raising the weight is the concentric portion of the
exercise.
Eccentric: This is the lengthening portion of the exercise, also known
as the negative. In a biceps curl, lowering the weight is the eccentric
portion. Within eccentric, there are two subdivisions. The first is
a controlled or voluntary eccentric motion. This is when you are able
to hold the weight in a contracted position but slowly lower the weight.
The second is an uncontrolled or involuntary eccentric motion. This is when
you are physically unable to stop the weight from lowering down (like
at the end of an all out set). You are able to slow the weight but it will
lower eventually. As an aside, due to some very boring physiological
reasons, eccentric strength is always greater than concentric strength.
This is why you are able to do extra negatives at the end of the set
but cannot do any further concentric contractions. For the same
reasons, lots of eccentric work has been implicated in the cause of
post workout soreness. Also, in conjunction with this, some studies
have found larger muscle growth has been found to occur with
concentric plus eccentric motions versus either eccentric only or
concentric only.
Isometric: Any exercise where there is no motion involved. See
the above description of isometric exercises for more info.
That's about it for now. Til next time.
Lyle
source: misc.fitness newsgroup, 25 Nov 93.
Beginner Info Part 2
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