## 5 Discussion
### Principal Findings  
The usability was measured with a scale derived from the Technology Usage Inventory. There was no significant difference, according to this scale, between the SET and ET exergames. Therefore, Hypothesis 1 cannot be rejected, and the alternative hypothesis H2 must be rejected, which implies that the two exergames are equally perceived as simple and easy to understand. Compared to the reference group in [PERSON]'s TUI study, both VR exergames (SET and ET) were rated more highly in terms of usability (>65 years old (y.o. ): M = 14.06) [16]. Preliminary investigations with small samples also demonstrated high usability in endurance training with immersive exergames [27]. One of the few papers that examined strength endurance in VR showed that overall, 59.4% of middle-aged adults and 37.5% of older adults were very and moderately willing to perform the VR dumbbell exercise. The group provided positive feedback about the usability [51]. Acceptance was also measured with the TUI, so the intention to use was examined. Hypothesis 3 cannot be rejected, and Hypothesis 4 must be rejected. There was no significant difference according to the scale measuring intention to use between both exergames. In [PERSON]'s TUI study [16], similar scores were reached in the same age group (>65 y.o. : M = 112.43) [16]. [PERSON] et al. [52] evaluated the technology acceptance model with older Chinese adults and VR exergames. The results showed that a more favorable attitude toward VR exergames was evident among older adults who are younger and retired, in addition to having higher education, better financial resources, and good health. This could be included as participant frame data in future research. In an investigation by [PERSON] [53], who did not examine older adults, the participants preferred aerobic (arm swings) more than strength exercise (squats) for a long period of exercise in VR. However, for a short period of exercise, they favored strength exercise more. The subjective task load was examined with the NASA-TLX. There were no significant differences between the two exergames in the weighted rating. For this reason, Hypothesis 5 cannot be rejected. The similar results of the weighted task loads confirm the comparability of the two exergames. This would be useful if the two types of training were applied in a joint exercise program, as then a similar task load could be assumed, and an overload could be avoided. Exercise programs in a physiotherapeutic or sports medicine field include a variety of different training components, e.g., endurance, strength, mobility and coordination. Thus, both SET and ET could be present as single courses in one therapy program for hypertensive people. [PERSON] et al. [32] also used the NASA-TLX but not the weighted and adjusted ratings. They reported the NASA-TLX as the mean value, and by calculating the mean value for our dataset, we obtained values of M: 28.22, SD: 12.41 for ET as well as M: 39.36, SD: 8.41 for SET, which in comparison to those of [PERSON] et al. (M: 19.77, SD: 11.91) indicates a higher task load for our SET and ET. These results were to be expected considering the exercises in the two studies. The results for the scale of the NASA-TLX measuring frustration were significantly higher for the ET than for the SET exergame. This leads to a rejection of Hypothesis 7, which implies we fail to reject alternative Hypothesis 8. One possible explanation is that the gamification of the ET allows for a greater motivational impact as well as more action options and therefore more opportunities for potential errors that may not occur as frequently in a guided instruction setting (SET). This could lead to increased frustration for the gamified ET exergame. According to the results of the qualitative interviews described in the paper by [PERSON] et al. [41], the dance sequence was too fast for some participants, and the steps were too difficult. This could explain why frustration was rated more highly in the ET.