## 2 Materials and Methods
### Task  
The goal of the experiment was to qualitatively assess the realism of the presented rowing models for different aspects of the rowing movement. Experts were asked to mainly perform a full-body rowing cycle by coordinating their body limbs. They could also try other types of movements, e.g., half-slide, body-arm, only-arms rowing, if they wanted. They were free to decide to row with a feathered, i.e., horizontal oar blade with respect to water surface, or a squared blade in the recovery. In Training-1 and Training-2, the rowers could also pause at a certain posture and insert the squared blade into virtual water or tap the feathered blade onto the virtual water surface.  
Experts were instructed to consider the experiment on the rowing simulator as if it was a technical training on the water, i.e., rowing with low to medium stroke rates and 40-70% of maximum force application. To capture the realism of the rowing forces with both compared models, participants were not explicitly constrained to any stroke rate. However, due to our instruction, they were observed to row with a range between 12 and 28 strokes per minute.  
Figure 5: Experimental protocol. Training 1 to 5 were run in the first part of the experiment. Training 6 was run in the second part. Conf. and Assm. stand for Configuration and Assessment, respectively.  
In the first part of the study, expert rowers were asked to focus on specific aspects of the rowing movement. To familiarize the expert rowers with the simulator and compare the presented force models, rather secondary/inessential aspects of a rowing stroke were considered in the first two trainings. In Training-1, the focus was on the horizontal movement of the blade above the water surface. Rowers deliberately slid the feathered blade on the virtual water surface and tried braking with the squared blade, which is a typical move to stop the boat during water outings. In Training-2, vertical movement of the oar during air to water transition was considered. In this training, rowers tried to distinguish the vertical forces between the squared blade insertion into water and the feathered blade tapping onto water surface. In addition, they were requested to purposely square the oar blade near to the water surface to feel the vertical reaction forces from the water surface.  
In Training-3, the focus was on the forces during drive and recovery. In Training-4, the focus was given to the oar blade forces during the air-water transition, i.e., catch and release. In Training-5, the rowers were asked to rate the overall perception of the rowing forces considering the whole cycle. Finally, they were asked to rate the realism of the flow (speed) of the visual scenario with respect to their stroke rate and the force they applied. Completion of every trial was followed by filling out a questionnaire.  
In the second part of the study, i.e., Training-6, participants were asked which particular forces they would have liked to adjust for their individual preferences. Upon participants' requests, the study instructor set the respective parameters from the graphical user interface to update the relevant forces of the active rowing model. Participants were asked to give their verbal comments to fine tune the force model according to their rowing preferences. The configurable parameters were \(G_{dl}\), \(\varphi_{bias}\), \(\tau_{rcc}^{min}\), and \(C_{Bdng}\). Once the participants were satisfied with the final individualized parameter settings, they were asked to assess the realism again.