“…Six of the included studies followed a randomized controlled study design [ 8 , 23 , 29 , 30 , 34 , 35 ], four had no control group [ 24 , 27 , 32 , 33 ], one was a matched pair control [ 28 ], and one had a convenience sample [ 31 ] (patients, who chose to not participate in accordance with the exercise protocol, were asked to be part of the control group). It was further possible to classify all included studies into one of the following groups: randomized pilot studies [ 8 , 29 , 35 ], non-randomized pilot studies [ 24 , 28 , 32 , 33 ], or feasibility studies [ 23 , 27 , 30 , 31 , 34 ]. This classification was done in accordance with the conceptual framework to define the feasibility and pilot studies of Eldridge et al [ 17 ].…”