Postural Muscles
Those muscles which respond to stress by shortening comprise the following:
Gastrocnemius, soleus, medial hamstrings, short adductors of the thigh, hamstrings,psoas, piriformis, tensor fascia lata, quadratus lumborum, erector spinae muscles, latissimus dorsi, upper trapezius, sternomastoid, levator scapulae, pectoralis major and the flexors of the arms.

Janda has also shown that before any attempt is made to strengthen weak muscles any hypertonicity in their antagonists should be addressed by appropriate treatment which relaxes them, for example by stretching using MET. Relaxation of hypertonic muscles leads to an automatic regaining of strength of their antagonists. Should the hypertonic muscle also be weak it commonly regains strength following stretch/relaxation.

Commenting on this phenomenon, chiropractic rehabilitation expert, Dr.Craig Liebenson states:
‘Once joint movement is free, hypertonic muscles relaxed, and connective tissue lengthened, a muscle-strengthening and movement coordination program can begin. It is important not to commence strengthening too soon because tight, overactive muscles reflexively inhibit their antagonists, thereby altering basic movement patterns. It is inappropriate to initiate muscle strengthening programs while movement performance is disturbed, since the patient will achieve strength gains by use of ‘trick’ movements’.

Where Do Joints Fit Into the Picture?
Janda has an answer to the emotive question when he says that it is not known whether dysfunction of muscles causes joint dysfunction or vice versa.

He points out however that since clinical evidence abounds that joint mobilisation (thrust or gentle mobilisation) influences the muscles which are in anatomic or functional relationships with the joint, it may well be that normalisation of the muscles’ excessive tone in this way is what is providing the benefit, and that by implication normalisation of the muscle tone by other means (e.g. Muscle Energy Technique - MET) provides an equally useful basis for joint normalisation. Since reduction in muscle spasm/contraction commonly results in a reduction in joint pain, the answer to many such problems would seem to lie in appropriate soft tissue attention.

Liebenson not unnaturally has a chiropractic bias, ‘The chief abnormalities of (musculoskeletal) function include muscular hypertonicity and joint blockage. Since these abnormalities are functional rather than structural they are reversible in nature....Once a particular joint has lost its normal range of motion, the muscles around that joint will attempt to minimise stress at the involved segment.’

After describing the processes of progressive compensation as some muscles become hypertonic while inhibiting their antagonists, he continues, ‘What may begin as a simple restriction of movement in a joint can lead to the development of muscular imbalances and postural change. This chain of events is an example of what we try to prevent through adjustments of subluxations.’

We are left then with one view which has it that muscle release will frequently normalise joint restrictions, as well as a view which holds the opposite, that joint normalisation sorts out soft tissue problems, leaving direct work on muscles for rehabilitation settings and for attention if joint mobilisation fails to deal with long-term changes (fibrosis etc).

It is possible that both are to some extent correct, however it is worth restating that once soft tissues have shortened and become fibrotic the degree of shortening they display is no longer under neurological control,a structural modification has occurred in the tissues and no amount of joint manipulation can ever restore normality. Some additional approach is vital. What emphasis each practitioner gives to their prime focus - be it joint or be it soft tissues - the certainty is that what is required is anything but a purely local view, as Janda helps us to understand.