Activity tracker-based intervention to increase physical activity in patients with type 2 diabetes and healthy individuals: study protocol for a randomized controlled trial oleh M. Mähs, J. S. Pithan, I. Bergmann, L. Gabrys, J. Graf, A. Hölzemann, K. Van Laerhoven, S. Otto-Hagemann, M. L. Popescu, L. Schwermann, B. Wenz, I. Pahmeier, A. Teti