TABLE 1.

Appraisal of the hierarchy of records.

Level	Type of record	No.	Authors
Level I	Systematic reviews and clinical commentaries	2	Bertapelli et al. (2016), Shields et al. (2018)
Level II-1	Randomised controlled trials	6	Shields and Taylor (2010), Gupta and Singh (2011), Ulrich et al. (2011), Lin and Wuang (2012), Ordonez et al. (2012), Silva et al. (2017)
Level III-1	Pseudo-randomised controlled trial	0
Level III-2	Comparative study with concurrent controls	0
Level III-3	Comparative study without concurrent controls	10	Ordonez and Rosety-Rodriguez (2007), Aguiar et al. (2008), Flore et al. (2008), Fernhall et al. (2009), Rosety-Rodriguez et al. (2010), Izquierdo-Gomez et al. (2015), Wee et al. (2015), Krause et al. (2016), Izquierdo-Gomez et al. (2017), Shields et al. (2017)
Level IV	Case series/studies with either post-test or pre-test/post-test outcomes	1	Berg et al. (2012)