A Pilot Study of the Manual Force Levels Required to Produce Manipulation Induced Hypoalgesia

Objective: A pilot investigation of the influence of different force levels on a treatment technique's hypoalgesic effect.

Design: Randomised single blind repeated measures.

Background: Optimisation of such biomechanical treatment variables as the point of force application, direction of force application and the level of applied manual force is classically regarded as the basis of best practice manipulative therapy. Manipulative therapy is frequently used to alleviate pain, a treatment effect that is often studied directly in the neurophysiological paradigm and seldom in biomechanical research. The relationship between the level of force applied by a technique (e.g. biomechanics) and its hypoalgesic effect was the focus of this study.

Methods: The experiment involved the application of a lateral glide mobilisation with movement treatment technique to the symptomatic elbow of six subjects with lateral epicondylalgia. Four different levels of force, which were measured with a flexible pressure-sensing mat, were randomly applied while the subject performed a pain free grip strength test.

Results: Standardised manual force data varied from 0.76 to 4.54 N/cm, lower-upper limits 95 CI, respectively. Pain free grip strength expressed as a percentage change from pre-treatment values was significantly greater with manual forces beyond 1.9 N/cm (P=0.014).

Conclusions: This study, albeit a pilot, provides preliminary evidence that in terms of the hypoalgesic effect of a mobilisation with movement treatment technique, there may be an optimal level of applied manual force.

Relevance: This study indicates that the level of applied manual force appear to be critical for pain relief.