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Craig Liebenson의 논문을 찾아야겠다.
참 멋진 논문.
Spinal stabilization. part 1. biomechanics. Craig Liebenson.pdf
Spinal stabilization. an update. Part 3 training.pdf
Introduction
The concepts of stability and instability are integral to modern musculoskeletal care. There are two distinct types. One is the whole body stability/instability and pertains to whole body equillibrium. Whereas the other is segmental or relates to an individual joint and pertains to its stiffness.
- 안정성 불안정성 개념은 현대 근골격계 질환 치료의 통합개념임.
- 하나는 전체 몸 안정성/불안정성 그리고 전체몸 균형
- 다른 하나는 분절 또는 개별 관절읠 안정성/불안정성 그리고 그것과 연관된 stiffness
According to Panjabi three subsystems work together to maintain spine stability (Panjabi, 1992). They are the central nervous subsystem (control), an osteoligamentous subsystem (passive), and a muscle subsystem (active). He says ‘‘The neural subsystem receives information from the transducers, determines specific requirements for spinal stability, and causes the active subsystem to achieve the stability goal.’’
- 판자비의 3 서브시스템에 의한 척추 안정성.
- 신경조절 안정성, 수동안정성, 능동안정성
The spine or any joint becomes injured or irritated by end-range overload. This can involve either macrotrauma or repetitive micro trauma. Two main factors involved in whether or not extrinsic end-range overload will result in injury
or irritation are intrinsic motor control and fitness level.
Motor control is a key component in injury prevention. Impaired motor control consists of failure to control a joint’s ‘‘neutral range’’ usually by a dysfunction or incoordination of the agonist–antagonist muscle co-activation. The eminent researcher Pr. Stuart McGill states that ‘‘evidence from tissue-specific injury generally supports the notion of a neutral spine (neutral lordosis) when performing loading tasks to minimize the risk of low back injury.’’ (McGill, 1998 ).
Injury or irritation occurs when the tissue’s
threshold is surpassed by external load. The threshold
is dependent on the individual’s level of fitness.
Therefore, injury or irritation can occur with either
high levels of external load in a normal system or
low levels in a compromised one. The bottom line is
that a history of too little or too much external
tissue load will create an environment conducive to
tissue failure (see Fig. 1 ).
Motor control can be trained. The process
focuses on neuromuscular re-education of patterns
of agonist– antagonist muscle co-activation during
low-load manoeuvres. These are progressed to
more functional tasks to ensure stability during
activities of daily living (ADL), sport or work
demands.
Biomechanics of low back injury
The spinal column devoid of its musculature has
been found to buckle at a load of only 90 N (about
20 lb) at L5 (Crisco and Panjabi, 1992 ; Crisco et al.,
1992 ). However, during routine activities, loads 20
times this are encountered on a routine basis. Load
profiles of various activities are shown in Table 1 .
Panjabi (1992) says, ‘‘This large load-carrying
capacity is achieved by the participation of
well-coordinated muscles surrounding the spinal
column.’’ Surprisingly, the motor control system
functions well when under load. Muscles stabilize joints by stiffening like rigging on a ship (see
Fig. 2 ). But, when load is at a minimum, such as
when the body is relaxed or a task is trivial, the
motor control system is often ‘‘caught off guard’’
and injuries are precipitated.
Low back injury has been shown to result from
repetitive motion at end range. According to
McGill, it is usually a result of ‘‘a history of
excessive loading which gradually, but progressively,
reduces the tissue failure tolerance.’’
(McGill, 1998 ).
Coordination of agonist and synergist muscles,
not strength, plays a pivotal role in resisting injury.
Sparto et al. showed that spinal loading forces
increased during a fatiguing isometric trunk extension
effort as substitution by secondary extensors
such as the internal oblique and latissmus dorsi
muscles occurred to maintain a constant strength
(Sparto et al., 1997 ). This demonstrates the
limitations of strength testing as an indicator of
normal function. When synergist substitution occurs
spinal load increases, even without a compromise
in power or strength (i.e. torque output).
According to Cholewicki and McGill (1996) spine
stability is greatly enhanced by co-contraction of
antagonistic trunk muscles (e.g. abdominal and
extensor muscles). Co-contractions increase spinal
compressive load, as much as 12– 18% or 440 N, but
they increase spinal stability even more by 36– 64%
or 2925 N (Granata and Marras, 2000 ). This mechanism
is present to such an extent that without cocontraction
the spinal column is unstable in upright
postures! (Gardner-Morse and Stokes, 1998 ).
In particular, these co-contractions are most
obvious during reactions to unexpected or sudden
loading (Lavender et al., 1989 ; Marras et al., 1987 ).
Stokes et al. (2000) have described how there
are basically two mechanisms by which this co-activation occurs.
One is a pre-contraction to
stiffen and thus dampen the spinal column when
faced with unexpected perturbations. The second
is a sufficiently fast speed of contraction of the
muscles to react quick enough to prevent excessive
motion that would lead to buckling following either
expected or unexpected perturbations (Carlson
et al., 1981 ; Cresswell et al., 1994 ; Lavender
et al., 1989 ; Marras et al., 1987 ; Stokes et al.,
2000 ; Thelen et al., 1994 ; Wilder et al., 1996 ).
Wilder et al. (1996) concluded in a study of body’s
reaction to sudden, unexpected loads that ‘‘muscles
will respond rapidly to stabilize the body, i.e.,
they will try to maintain balance and posture’’. This
has also been verified by Radebold et al. (2000,
2001) and Cholewicki et al. (2000a, b) in a series of
studies.
Inappropriate muscle activation sequences during
seemingly trivial tasks (only 60 N of force) such
as bending over to pick up a pencil can compromise
spine stability and potentiate buckling of the
passive ligamentous restraints (Adams and Dolan,
1995 ). This motor control skill has also been shown
to be compromised under challenging aerobic
circumstances (McGill et al., 1995 ). When a spinal
stabilization and respiratory challenge is simultaneously
encountered the nervous system will
naturally select maintenance of respiration over
spine stability. An example of this occurs when
during repetitive bending or lifting activities the
back becomes vulnerable due to poor aerobic
fitness even if the motor control system is well
trained.
Good abdominal strength is not sufficient to
maintain spine stability. Lack of proper coordination
between the abdominals and diaphragm will
lead to spine instability during challenging aerobic
activities (Hodges et al., 2000 ; O’Sullivan et al.,
2002 ).
Prospective studies have shown that decreased
enduranceF not strengthF of the trunk extensors
can predict recurrences and 1st time onset of LBP
in healthy individuals and increased likelihood of
future recurrences (Biering-Sorensen, 1984 ; Luoto
et al., 1995 ).
Hodges and Richardson reported that a slow
speed of contraction of the transverse abdominus
during arm or leg movements was well correlated
with LBP (Hodges and Richardson, 1998, 1999 ).
O’Sullivan et al. found that synergist substitution of
the rectus abdominus for the agonist transverse
abdominus during an abdominal ‘‘drawing in’’
manoeuvre strongly correlated with chronic back
pain and that specific rehabilitation which improved
this dysfunction was superior to a more
general exercise approach (O’Sullivan et al., 1997 ).
The multifidus in the low back has been shown to
be atrophied in patients with acute low back pain.
(Hides et al., 1994 ). The acute patients’ atrophy
was unilateral to the pain and at the same
segmental level as palpable joint dysfunction.
Recovery from acute pain did not automatically
result in restoration of the normal girth of the
muscle (Hides et al., 1996 ). However, it has been
demonstrated that segmental spinal stabilization
exercises can prevent multifidus muscle atrophy in
acute LBP subjects (Hides et al., 1996 ). Recent
research has demonstrated that such exercises
have a secondary preventive effect by reducing
recurrences (Hides et al., 2001 ).
Biomechanical advice
Karel Lewit recommends ‘‘the first treatment is to
teach the patient to avoid what harms him’’. LBP
patients are generally vulnerable in the morning,
when sitting for prolonged periods of time, and
during lifting. Specific activity modification advice
is therefore needed during these circumstances.
Certain times of day are the most vulnerable for
the back. For instance, in the first hour after
awakening or after prolonged static full flexion
such as sitting or stooping the body is at greatest
risk. (Adams et al., 1987 ). Therefore, it is wise to
avoid full trunk flexion early in the morning (Snook
et al., 2002 ).
Prolonged sitting is one of the most deleterious
activities for LBP patients. It has been shown that after just 20 min of full flexion of the spine
ligamentous creep or laxity occurs which persists
even after 30 min of rest! (McGill and Brown, 1992 ).
In a porcine model just 2 min of full flexion has
been shown to lead to a substantial loss of the
normal spinal ligamentous stiffness (Gunning et al.,
2001 ). Therefore, regular micro-breaks involving
standing and elongating the spine are recommended
for every 20– 40 min of sitting (see Fig. 3 ).
Suggestions to teach workers to lift with their
knees not their backs are overly simplistic. Most
workers have learned various techniques to avoid
injury which are inconsistent with this advice.
Better advice is consistent with the following
principlesF pre-contract the trunk muscles (bracing);
maintain slight lordosis; rotate jobs to vary
loads; allow frequent rest breaks; and keep loads
close to the spine (McGill and Norman, 1993 ).
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