This creates difficulties in assessing how the field of research is progressing and in determining what questions remain unanswered. These questions are important for researchers and science policy makers associated with this research domain.
In this paper, we proposed a categorisation for multiscale models in biomechanics. The categorisation is based on what motivates a given model. One possible motivation is to simply confirm that the ’cause’ assumed by a multiscale model agrees with observations. A more ambitious motivation is to show that the model can ‘predict’ accurately. The most ambitious motivation is to demonstrate that the multiscale model determines an ‘effect’ that is not possible by the best available single-scale model. In this review paper, we provided tests to determine the category of motivation for a given model. The tests are obviously stricter when going from a causal confirmation type model to one that is motivated by determination of effect. We showed how these tests could be put to practice by applying them to a large body of original research articles.
From this exercise, a unified picture emerged for the first time regarding the progress made in multiscale modelling in biomechanics. It was found that the overwhelming number of models (73/85) were motivated by causal confirmation, whereas only one model (out of 85) was motivated by determination of effect. From a medical perspective, musculoskeletal biomechanics and cardiovascular biomechanics are especially important sub-domains of biomechanics. Therefore in this review we highlighted open questions in these sub-domains which, if answered, would advance the state-of-the-art along more ambitiously motivated models.