tESting AnD tRAining LUMBAR SPinE
important because in the flexed position exercise of the lumbar muscles (lifting also support the validity of the gravity
of a lumbar extension movement, the and lowering a selected level of weight correction procedures .
10

patient must lift his or her torso weight, stack resistance). The use of a cam
whereas in the extended position torso ensures that the resistance varies in Effects of lumbar extension training
weight assists the patient. line with changes in strength that occur on strength
throughout the range of motion.
7
When exercised in this manner, the lumbar
Given that some individuals may have extensors in most participants are capable
weaknesses at specific points in a Validity and reliability of rapid and large increases in lumbar
muscle’s range of motion, it is important to The validity of the pelvic restraint strength. For example, Graves et al.,
11

be able to measure strength through a full system used in the machine has been Carpenter et al.
7
and Pollock et al.
12
have
range of motion. Due to acceleration and established by several studies. One study all shown increases in isometric lumbar
deceleration occurring at the beginning using radiography showed that when extension strength of more than 100%
and end of a movement, dynamic tests participants were properly restrained in in the fully flexed position from one set
cannot measure strength through a full the machine, backward rotation of the of 8-12 repetitions of lumbar extension
ROM.
3
Also, impact forces and kinetic pelvis was less than 3°.
8
Also, Graves et exercise performed to volitional fatigue
forces can be recorded (incorrectly) as al.,
9
in comparing the effects of training once per week for 10-12 weeks. Strength
torque, giving an inaccurate measure of on the lumbar extension machine with increases in the extended position tend to
muscular strength.
4, 5
training on commercially available lower be lower, with average increases in peak
back machines that do not stabilise the torque of 37 to 41% found by Graves et
In contrast, isometric strength tests pelvis (Nautilus, Cybex), found that the al.13 from 12 weeks of lumbar extension
can measure strength through a full no-stabilization groups did not increase training. This compares favourably with the
ROM if multiple joint angles are tested.6 their lumbar extension strength, whereas typical strength increases of between 20
Therefore, the lumbar extension machine the former group enhanced their strength and 30% reported by Fleck and Kraemer
14

uses an isometric testing method. significantly at all joint angles. for resistance training programs of 10-12
Testing can be conducted at 3° intervals weeks. Graves et al.
11
and Pollock et al.
12

throughout a full range of lumbar Therefore, the pelvic restraint system speculated that this may be due to the
extensor motion. is effective in achieving the necessary lumbar extensors initially being very weak.
isolation of the lumbar extensors. Test- As the lumbar extensors are not isolated
As well as testing lumbar strength, retest reliability of the machine is very during normal daily activities, they receive
the machine is also used for dynamic high at all angles (r = .94-.98 6), and data little exercise effect from such activities.
The Backcare Journal 25
backcare Winter 2009/10.indd 25 8/1/10 11:19:55
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