5.2.1 User Manual Isoforce
REV 5
01st July 2014
page 10 von 77
TUR Therapietechnik GmbH | Grubenstr. 20 | 18055 Rostock | Germany
Finally, the Passive mode may be used for passive stretching. When this is performed, the torque limits
in each direction should be set low and the time delay at least at the edge in interest should be set high.
It is not necessary to have a wide range of motion.
Attention! Ensure torque limits are set to overcome limb weight.
1.2.3. Isometric Mode
In this mode, the dynamometer maintains zero velocity at any selected point in the range of motion.
Significant change in joint angle and overall muscle length does not occur.
The interruption of normal function from musculoskeletal injury and immobilization leads to a loss of
strength not only in the muscles of a damaged extremity but also in those of uninjured extremities. This
loss can be largely avoided with the proper use of isometric exercise. In most cases, uninjured body
parts can be exercised even on the first day of immobilization of the injured part. The injured and
immobilized extremity can be isometrically tensed and thus exercised while still in a cast or in a splint
after the immediate pain has subsided. In this way, much of the potential loss of muscle strength can be
avoided. The muscle atrophy already setting-in can also be countered. A primary advantage of
isometric exercise in musculoskeletal rehabilitation lies in the opportunity for localized muscle exercise
without moving involved joints.
Strength increases more rapidly in isometric than in dynamic exercises. On the other hand, strength is
also lost more rapidly after cessation of exercise. A primary disadvantage is that the muscular
coordination necessary for many types of musculoskeletal activities is not integrated in this exercise,
which is why isometrics must, in time, be combined with dynamic exercises in the treatment of various
musculoskeletal conditions. Isometric exercise places great compression stress on the joint; thus,
people with arthritic conditions should not participate in intense isometric contractions. Also, people in
danger of heart attacks should not engage in intense isometric training because of the danger of
compression narrowing blood vessels.
There are thus unique advantages to isometrics due to the fact that they do not move a joint and
therefore can be used early in a rehabilitation program. Static strength increases, and atrophy retards.
Most other advantages to isometrics focus around the lack of special facilities and equipment needed to
perform them.
Disadvantages must also be carefully understood. A major disadvantage is a limited overflow of strength
development. Approximately 20° of overflow from the angle of application occur: strength gains will be
noticed for 10° on each side of the application. This is a small amount, and therefore, realistically,
isometric exercise at one point in a plane will not increase strength at another point in the plane. Other
problems also exist with isometrics such as difficulty with patient motivation, minimal gains of endurance,
and lack of eccentric workloads.
When we apply an isometric contraction, the general rule to follow is known as the “Rule of Tens,”
wherein we build tension in 2 seconds, hold the desired tension for 6 seconds, and then gradually relax
tension in 2 seconds. Applying this to isometrics, we usually recommend a 10-second contraction, 10
seconds of rest between each contraction, ten repetitions, and ten sets at ten different angles in the
ROM.
