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The Journal of Strength and Conditioning Research: Vol. 15, No. 3, pp.
385-390.
A Review of Resistance Exercise and Posture Realignment
Con Hrysomallis, Craig Goodman
Victoria University, Melbourne, Australia.
ABSTRACT
<Exercise has been promoted in an attempt to correct postural deviations,
such as excessive lumbar lordosis, scoliosis, kyphosis, and abducted
scapulae. One of the assumed causes of these conditions is a weak and
lengthened agonist muscle group combined with a strong and tight antagonist
muscle group. Strengthening and stretching exercises have been prescribed
accordingly. It is implied that strengthening exercises will encourage
adaptive shortening of the muscle-tendon length, reposition skeletal
segments, and produce static posture realignment.
A review of the literature has found a lack of reliable, valid data collected
in controlled settings to support the contention that exercise will correct
existing postural deviations. Likewise, objective data to indicate that
exercise will lead to postural deviations are lacking. It is likely that
exercise programs are of insufficient duration and frequency to induce
adaptive changes in muscle-tendon length. Additionally, any adaptations from
restricted range-of-movement exercise would likely be offset by daily living
activities that frequently require the body segments to go through full
ranges of motion.
INTRODUCTION
Static posture refers to the alignment and maintenance of body segments in
certain positions, such as standing, lying, or sitting . Considerable
deviations from optimal posture may be aesthetically unpleasant, adversely
influence muscle efficiency, and predispose individuals to musculoskeletal or
neurological pathologic conditions.
It has been stated that if body segments are held out of alignment for
extended periods, the muscles will rest in a shortened or lengthened position
and over time adaptive shortening or lengthening may result. Adaptive
shortened muscles are described as tight and strong, maintaining the opposing
muscles in a lengthened and weakened position . Such changes in resting
muscle length may influence posture alignment.
It has also been postulated that adaptive muscle shortening may result from
overuse of a muscle, particularly in a shortened range. At times, claims are
made that a muscular imbalance from excessively working one muscle group will
lead to postural deterioration. An example is when the chest muscles are
overworked and there is an imbalance with the back muscles, allegedly leading
to poor, rounded posture.......
Does an increase in muscular strength allow a better posture to be held? If
this were the case, it would not be unreasonable to expect that individuals
with poor posture had weak muscles; however, this is not the general
finding....
....... another study, examining 90 healthy older adults .... demonstrated
that abdominal muscle strength (supine straight leg lowering test) was not
significantly associated with lumbar lordosis.....
Holding a posture for a long period requires constant low-level neural input
to maintain a muscular contraction of the postural muscles (if indeed muscle
activity is required). In light of this knowledge, it would seem that
muscular endurance would be a more appropriate physical quality than maximal
strength in the maintenance of "correct" posture. A recent study investigated
the association between abdominal muscle endurance and lumbar posture. No
significant relationship was detected. However, the study was flawed by
methodological limitations. Lumbar posture of 23 young elite gymnasts and 28
controls was subjectively assessed as lordotic, sway-back, or ideal.
Isometric abdominal muscle endurance was measured as the time subjects could
maintain
certain supine postures while contacting their abdominals to press their
lower back against a pressure cushion. Reliability and validity for the tests
were not reported........
Many studies (particular the early ones) have looked at the relationship with
only one variable at a time rather than a combination of strength and
flexibility variables. A multivariate analysis has been performed , but this
did not lend considerable support to the notion that lumbar lordosis is
significantly associated with combined abdominal muscular weakness and tight
erector spinae and hip flexors.
Analysis did not reveal a multivariate model for women. For men, the
multivariate analysis indicated that standing lumbar lordosis was weakly
associated with length of abdominals (not abdominal weakness) and 1-joint hip
flexor muscle length (but not back muscle length) and physical activity level
(R2 = 0.38). The authors of this study concluded that the use of abdominal
muscle strengthening exercises or stretching exercises of the back and
1-joint hip flexors to correct faulty posture should be questioned.........
It should be pointed out that a change in sarcomere number or muscle fiber
length might not be proportional to changes in the whole muscle-tendon
length. This is crucial when considering the potential for postural
realignment through adaptive changes. There may be no great change in muscle
fiber length but a considerable change in tendon length. Results from animal
research indicated that muscle-tendon shortening of rabbit soleus as a result
of immobilization was primarily (73%) because of adaptations of the tendon
rest length.
It would appear that immobilization can produce adaptive changes in
muscle-tendon length. In relation to immobilization of human body segments to
achieve postural realignment, there are 2 potential difficulties. It may not
be practical for an individual to wear a brace or taping for a considerable
period.
The other potential problem is once the immobilization is ceased what
prevents the muscle-tendon from returning to its original length? If an
individual still has the ability to move the body segment throughout its full
ROM during daily activities, the ROM the muscle is subjected to would be
counterproductive to the attempt to shorten the muscle. Support for this
notion comes from the finding of the rapid readjustment of cat soleus muscle
fiber length to normal after 4 weeks of remobilization. These muscle fibers
had previously been shortened by 4 weeks of immobilization preceding the
remobilization...............
In a review of intervention programs for scoliosis and kyphosis , doubt was
cast on the usefulness of exercises to correct these postural deviations. It
was suggested that the forces generated by corrective exercise are usually
low in amplitude, frequency, and duration and therefore not sufficient to
promote a permanent change in muscle length. A possible benefit of an
exercise program may be to re-educate the patient to be able to adopt more
optimal posture during daily activities. In turn, this may re-educate the
muscles and place them in a better position for long periods, which may
induce a change in muscle. This is somewhat related to the Alexander
principle, which involves the enhancement of proprioceptive awareness of the
body and inhibition of "inappropriate" muscle activity to establish certain
postures and movement patterns. Unfortunately, there are a lack of objective
data from controlled studies evaluating the effectiveness of this method for
posture realignment........
A very recent study investigated the influence of a 6-week strengthening and
stretching program on scapula posture of 20 asymptomatic subjects with
abducted scapulae. Subjects were considered to possess abducted scapulae if
the shoulder joint was clearly anterior to a plumb line aligned with the ear
lobe..... Scapula position and orientation were determined by a computerized
3-dimensional electromechanical digitizer (Metrecom). This device used a
linkage arm with position senses and a probe tip. The probe was placed on
landmarks on the scapula and vertebral column and captured location
coordinate data. This information was used to define scapula position and
orientation. The reliability of the Metrecom was determined by measurements
taken on 14 subjects at least 7 days apart. The average ICC (intraclass
correlation coefficients) and SEM for measurements (statistical measures)
defining scapula position and orientation were 0.85 and 1.4 degs,
respectively. The validity of the device was not reported.
'Theraband' rubber tubing was used to perform strengthening exercises for
the scapular retractors and elevators and for the shoulder abductors and
external rotators. Exercises were conducted 3 times per week. One set of 10
repetitions for one session was conducted in the first 2 weeks and 5 more
repetitions were added every week. No strength measure of the scapular
retractors was reported. It is unclear as to how much the exercise program
influenced the strength of the retractors. The stretching consisted of
bilateral horizontal shoulder extension. The stretch was performed 10 times
for 10 seconds, adding 5 more repetitions every 2 weeks. No measures of
flexibility were reported. After the 6 weeks, no change in scapula resting
posture was noted. The findings of this relatively short-term study question
the effectiveness of corrective exercises for abducted scapulae.......
Conclusion
Future research should address the limitations identified in some of the
studies. Given the available evidence, it is questionable as to whether
resistance training alone will produce an adaptive shortening of a muscle and
hence elicit postural changes. Even if the tight agonist is lengthened by a
stretching program, there is minimal evidence to suggest that resistance
training of the antagonist will cause adaptive shortening and a subsequent
change in static posture. It appears that the frequency and duration of
exercise programs are inefficient to produce adaptive shortening of muscles.
Even if individuals could exercise long enough in a restricted ROM, any
potential length adaptations would probably be offset by daily living
activities that often require full ROM.
Practical Applications
Based on the review of existing literature, it is inadvisable to strongly
promote strengthening exercises to correct postural malalignments, such as
abducted scapulae, excessive lumbar lordosis, scoliosis, or kyphosis.
Furthermore, the fear of developing static postural deviations from
exercising is not supported by objective data. >
cheers,klaus
