Laura Peeters

Trunk involvement in performing upper extremity activities | 39 2 specific tasks, but they may (partly) prevent movement of the trunk, especially when the support level is too high or the orthosis is too rigid [29]. This can limit patients in performing daily activities due to restrictions in the use of compensatory movements [29, 47, 48], even when performing tasks within arm length. Hence, there is a need for dynamic orthoses that allow all the trunk movements necessary to perform seated activities, while at the same time ensuring trunk stability. Clinical implications of compensatory trunk movements To optimize task performance, several compensatory trunk movements are seen in patients with a flaccid trunk as described in this review. These are strategies either to increase movement (i.e. to compensate for impaired arm function) or to maintain postural stability. By applying compensatory trunk strategies, daily tasks can often be executed which could otherwise not be achieved or tasks can be performed more efficiently (in terms of speed, accuracy or energy expenditure). However, the frequent use of compensatory trunk movements may also have a downside in the long-term due to overexertion of certain trunk muscles and joints and/or disuse of arm muscles and joints [49]. While overexertion may lead to muscle and joint pain, disuse should be avoided because of enhanced risk of muscle wasting and development of contractures. Hence, a balance needs to be found by patients and clinicians between, on the one hand, using compensatory strategies to achieve optimal task performance and, on the other hand, prevent long-term adverse effects of using such strategies. Study limitations This review has some limitations. First, although we performed a rigorous systematic search, the type and quality of the identified studies allowed a narrative rather than a systematic review. Second, we included only articles written in the English language using PubMed as an electronic database, and these were selected and read full text only by the first author (LP). However, all articles were carefully checked for relevant references to include unidentified studies. Further, we chose not to report and compare the exact movements of the trunk as these were expressed in degrees, movement path, or sometimes even in other measures. As a consequence, and because absolute measurements of trunk movement depend on trunk length, accurate comparisons of trunk movements were not possible. In addition, different definitions of arm length were used between the studies (e.g. from acromion to wrist, finger tip, or some other anatomical hallmark). This influences the interpretation of the timing of trunk involvement in the reaching strategy. Most studies stated that the trunk was already involved when reaching at 90% of arm length distance but, when the definition of arm length differs, the actual reaching distance is also different.