Optimal loading: Key variables and mechanisms
Philip Glasgow,1 Nicola Phillips,2 Christopher Bleakley3
1, Ulster University
2, Cardiff University
3, High Point University
OPTIMAL LOADING (POLICE VS PRICE)
The acronym PRICE (protection, rest, ice, compression and elevation) has traditionally been the cornerstone for treating acute soft tissue injury. Recently, its relevance in some cases has been questioned;1 of particular concern is that protection and rest may correspond with an excessively conservative approach that fails to harness the benefits of progressive tissue loading through exercise.
WHAT IS ‘OPTIMAL LOADING’?
Optimal loading may be defined as the load applied to structures that maximises physiological adaptation. Achieving optimal loading is challenging but should be driven by variables such as the tissue type, pathological presentation and the required tissue adaptation for eventual activity. Specific loading goals may include increased tensile strength, collagen reorganisation, increased muscle?tendon unit stiffness or neural reorganisation. Optimal loading works through various cellular and neural mechanisms to induce a wide range of changes (summarised in figure 1). Manipulation of loading variables can have profound effects on the nature, structure and function of the wider neuromusculoskeletal system. One variable with the potential to influence outcome is the magnitude of the load. Arampatzis et al2 showed that during cyclical loading of the Achilles tendon complex, magnitude was a strong factor in promoting morphological changes. The authors reported that loads of 90% maximum voluntary contraction (MVC) resulted in an increase in tendon?aponeurosis stiffness and tendon elastic modulus and a region-specific hypertrophy of the Achilles tendon compared with no alteration at 55% MVC. These findings suggest that some tissues have a threshold level of mechanical strain to facilitate adaptation.