Gross Motor Function Measure (GMFM‐66 & GMFM‐88) User’s Manual, 3rd Edition Dianne JRussell, MarilynWright, Peter LRosenbaum, Lisa MAveryLondon: Mac Keith Press, 2021 £80.00 (Paperback), pp. 320 ISBN: 978‐1‐911612‐49‐0

Much progress has been made from the 1980s’ print version to the very welcome GMFM App+, which coincides with this new edition of the manual. The measure has also been applied to other populations of children with neurological conditions (including acquired brain injury). Changes to this edition mostly relate to the GMFM App+. There is little difference in the standard use of the tool, with the notable exception of testing both with and without footwear; in the original print version there is just a short note about the use of footwear. The Gross Motor Ability Estimator (GMAE-2) program is freely downloadable but is incompatible with some computer operating systems, hence the need for users to obtain the GMAE-3. The case studies in the manual are not impacted by the change from GMAE-2 to -3, although Appendix 14 states that GMAE-3 scores are more accurate. The difference in favour of accuracy seems to be negligible when it comes to score interpretation, with some exceptions exemplified by a case study in Appendix 14. There is a brief section offering extra details about the Quality Function Measure, the GMFM Challenge assessment, and the Acquired Brain Injury Challenge assessment and studies of their validity, etc. since the last edition (detailed information is available online). Though the 3rd Edition offers little in the way of new material, all GMFM users would benefit from owning a copy as it is essential to enable accurate scoring of the test items. The GMFM App+ provides a basic reminder of what each score represents for each item (0–3 or not tested [NT]), but detailed information on decision-making for each level is only available in the manual. There is an online tutorial for use of the GMFM App+ and the GMAE-3, but the information is not as comprehensive as that obtained in the manual. Users familiar with GMAE-2 will have no difficulty adapting to the newer GMAE-3, which is easier to use and contains better summaries of the test data. Future developments might include the relationship of the GMFCS to other functional measures and scales in development to understand how the mobility skills relate to other aspects of function such as hand function (Manual Ability Classification System). In summary, the GMFM User’s Manual is essential for successful use of the measure and its interpretation. If you do not already own a manual and you are using the GMFM in any of its forms, this book is a must-have.