Letter to the Editor concerning ‘The Calf Raise App shows good concurrent validity compared with a linear encoder in measuring total concentric work’: Let's not compare apples to oranges

Hébert-Losier, Kim2025-05-102025-05-102025Hébert-Losier, K. (2025). Letter to the Editor concerning ‘The Calf Raise App shows good concurrent validity compared with a linear encoder in measuring total concentric work’: Let's not compare apples to oranges. Knee Surgery, Sports Traumatology, Arthroscopy, 33(2), 760-764. https://doi.org/10.1002/ksa.125150942-2056https://hdl.handle.net/10289/17367The authors state that this study was designed as a validity study, yet it appears to be an add‐on to another prospectively registered study (NCT05323773) with no initial intention of concurrent validation of the Calf Raise App. To properly assess the validity of the systems, similar reference points (e.g., the lateral side of the foot) should be used, and outcomes should be compared to a gold standard, such as 3D motion analysis.enFree Access article at https://doi.org/10.1002/ksa.12515 © 2025 European Society of Sports Traumatology, Knee Surgery, and Arthroscopy (ESSKA)Letter to the Editor concerning ‘The Calf Raise App shows good concurrent validity compared with a linear encoder in measuring total concentric work’: Let's not compare apples to orangesJournal Article10.1002/ksa.125151433-734732 Biomedical and Clinical Sciences4201 Allied Health and Rehabilitation Science42 Health Sciences3202 Clinical Sciences4207 Sports Science and Exercise3202 Clinical sciences4201 Allied health and rehabilitation science4207 Sports science and exercise3 Good Health and Well Being