The effects of being habitually barefoot on foot mechanics and motor performance in children and adolescents aged 6–18 years: study protocol for a multicenter cross-sectional study (Barefoot LIFE project) - Hollander, K; van der Zwaard, B C; de Villiers, J E; Braumann, K M; Venter, R; Zech, A (J Foot Ankle Res, 2016)