## 4 Discussion  
This study used a smartwatch to investigate whether a dance-based aerobic group exercise affects participants' affective responses depending on their level of physical fitness. In the analysis of the difference in exercise intensity of Zumba fitness according to physical fitness, the high-fit and low-fit groups exhibited differences in HR and exercise intensity (%HRmax) during 35 min of Zumba exercise from warm-up to just before cool-down. Specifically, HR during exercise was 109 ppm with 57% HRmax exercise intensity for the high-fit group and 130 ppm with 66% HRmax intensity for the low-fit group. The ACSM [25] indicated that the relative intensity of aerobic exercise is 57-63% HRmax for low intensity and 64-76% HRmax for moderate intensity. Therefore, the Zumba fitness program used in this study is of moderate intensity for the low-fit individuals and low-intensity for the high-fit participants. This study's Zumba exercise intensity supports the findings of [PERSON] et al. [24] that the exercise intensity of Zumba for the general public is 66 \(\pm\) 10.5% of the average VO2 max, which meets the ACSM criteria for maintaining a healthy weight. Furthermore, by tracking HR during exercise in real-time using a smartwatch, our study verified that exercise intensity differs depending on the performer's fitness level. Our study's Zumba fitness program consisted of a warm-up, basic dance steps, merengue, and reggaeton. In the comparison of exercise intensity according to the exercise section, we found that the exercise intensity of reggaeton was the highest compared to warm-up, basic steps, and merengue. This result is consistent with [PERSON] et al. [28], who reported the highest HR during reggaeton exercise among the four Zumba rhythms: merengue, reggaeton, salsa, and cumibia. While merengue consists of up-down movements of the pelvis, reggaeton creates up-down motions of the entire lower body through flexion and extension, thus intensifying the exercise. In addition, since the reggaeton steps use  
Figure 8: Two-dimensional circumplex model of affect by the level of fitness, (**a**) high fitness and (**b**) low fitness. Note: the circumplex model is a method to observe a change of ‘core’ affect (valence + activation). Quadrant I represents activation–pleasure; Quadrant II represents activation–pleasure; Quadrant III represents deactivation–displeasure; Quadrant IV represents deactivation–pleasure. two steps per 1 bpm [42], it is possible to double up the speed of the movements up to 192 bpm [43]. Therefore, to control the intensity of a Zumba fitness program within a limited time, instructors often control the speed of choreography by adding or subtracting the portion of reggaeton rhythm or breaking down the rhythm. In the analysis of the change in affect (valence) and arousal (activation) by exercise section of the Zumba fitness program, we found an interesting difference between the high-fit and low-fit groups. There was no significant change in high-fit group's affect from pre-exercise, warm-up, and basic steps. However, the affect improved after the merengue, and participants maintained that affect throughout the rest of the exercise program. On the other hand, there were no significant changes in affect throughout the entire exercise section in the low-fit group, but the affect improved immediately after the cool-down. Furthermore, similar affective changes were observed in pre, mid, and post-exercise depending on fitness in arousal. In the high-fit group, arousal increased after merengue, and participants maintained this affect until the end. In contrast, the low-fit group showed no difference between pre and during-exercise arousal. As shown in the two-dimensional circumplex model, which presents the changes in the core affect (valence + activation) (Figure 8), the core affect of the high-fit group increased from the beginning. It proceeded to the first quadrant after merengue, and the participants maintained the affect until the end of the exercise.