Overloading in relation to ROM loss and recovery

It is well established that in frozen shoulder the patient will recover their ROM over time and without assistance.³ This means that range improvement is possible by performing functional tasks, but where is the overloading threshold in this recovery?

There is the possibility that lower loading thresholds are required when ROM losses are present. In contractures, the restricted end-range may represent a lowered functional threshold. This means that normal daily activities that require greater ROM may provide the forces and ranges necessary to challenge this threshold (Fig. 6.2). For example, in the ankle during walking, the normal total dorsiflexion and plantarflexion range is about 30°.⁴ If, because of contractures, this range drops to, say, 20°, this would represent a lowered functional threshold. In this situation, walking, which requires 30°, may generate sufficient loading forces to challenge the limited range. Walking on a steep, sloped surface and stairs could further raise the functional loading levels.^4,5

In the presence of ROM losses there is often a shift in the discomfort zone to include the functional range of activities (Fig. 6.2). In the example above, the ROM losses in the ankle are likely to be accompanied by discomfort during functional activities such as walking or climbing stairs. The patient should be made aware that this is normal and even desirable.

Impediments to overloading

Sensitivity/pain and failure to provide sufficient force are common factors that may interfere with overloading during ROM rehabilitation.

ROM losses are often accompanied by pain and anxieties about movement (Chs 9 and 10). Under these circumstances, the patient may terminate the stretching well before it reaches the necessary loading thresholds. This can be resolved partly by dissociating the discomfort from the damage and by focusing on alleviating pain levels before commencing the ROM challenge programme (Ch. 9). For example, in frozen shoulder, the ROM challenges can start when the condition is no longer in the painful phase.

Another impediment is related to the failure of many traditional stretching approaches to generate sufficient forces to reach the loading thresholds (Table 6.1). For example, techniques such as side-lying flexion articulation or manipulation of the spine are unlikely to result in any permanent increase in range (except for the inconsequential elongation discussed below). Such manually applied forces are nowhere close to those imposed by bending and lifting or sitting. The capsular ligaments of the apophyseal joints can by themselves support twice the body weight.⁶ Failure to generate sufficient forces can be encountered elsewhere in the body. The Achilles tendon or the plantar fascia can withstand considerable forces during functional activities. In walking, the vertical forces on the foot are 1–1.5 times the body weight, in running 2–3 times the body weight and during a triple jump 7–12 times the body weight.^7,8 A therapist is likely to injure their hands long before the functional thresholds are reached during stretching. In patients with adaptive ROM losses, the practical solution is to exploit daily activities and to amplify them to provide the necessary loading forces (Ch. 12).

Try this home experiment: stretch your index finger into full extension and maintain that angle. After a short while you will experience a certain “give” in resistance. When this happens the joint can be stretched further without any additional force (creep deformation; Fig. 6.3A) or maintained at the same position with less force (force relaxation; Fig 6.3B).^9–15 This drop in resistance is related to a biomechanical property of muscle and connective tissues called viscoelasticity.^16–18 Musculoskeletal tissues are composed of fibres embedded within a viscous, gel-like medium.^{14,15,19–22} The fibrous elements provide strength and resistance during loading. The viscous gel elements endow the tissues with a slow, flow-like elongation experienced during stretching (Box 6.1).²³

Creep deformation and force relaxation can be observed during all forms of tensional loading.^24,25 During sustained muscle stretching creep deformation accounts for 75–85% of the elongation that occurs within the first 15–20 seconds.²³ In cyclical stretching about 80% of the elongation will take place in the first four repetitions.^19,26 This is often experienced during stretching exercise; most of the range gains occur within the first three or four repetitions, after which the range gains tend to plateau. Force relaxation has been demonstrated in the anterior longitudinal ligament of the spine and during sustained dorsiflexion of the ankle. The force needed to maintain the longitudinal ligament at a given tension halved within the first minute of loading.¹⁶ In the ankle joint it takes about 5 minutes to achieve full force relaxation.²⁷

The viscoelastic behaviour of tissues can be deceptive to the therapist and patient. It gives the impression that stretching culminates in longer fibres. However, the immediate change in ROM during stretching is not due to true length changes in the tissue. All that happens is that the tissue has transformed from a stiff into a “softer”, more compliant spring, which means that for a given force it can extend further (Fig. 6.4). These viscoelastic changes in the tissue are transient. At the termination of stretching the tissues will gradually return to their original biomechanical/structural state (Fig. 6.4). The rate at which this recovery occurs varies between tissues. In the hamstrings force relaxation recovers within an hour, whereas in the Achilles tendon it will take several hours.^{9–11,27–29}

Related posts:

Stretch-tolerance Model Functional and Dysfunctional ROM Exposure and Scheduling the ROM Challenge Pain Management and ROM Desensitization Summary Demonstration of Functional Approach in ROM Rehabilitation

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