## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Variable** & **Horse Mean (SD)** & **Simulator Mean (SD)** & \(p\)**-Value** & **Cohen’s D** \\ \hline MeanHR & 74.28 (10.85) & 74.42 (9.44) & 0.887 & \(-\)0.014 \\ RR & 836.00 (126.57) & 830.30 (109.72) & 0.611 & 0.046 \\ SDNN & 65.47 (23.61) & 69.09 (21.55) & 0.083 & \(-\)0.156 \\ pNN50 & 31.61 (18.72) & 30.11 (16.25) & 0.431 & 0.083 \\ RMSSD & 59.10 (28.58) & 57.70 (25.10) & 0.591 & 0.050 \\ HF & 36.24 (16.05) & 31.95 (16.87) & 0.353 & 0.261 \\ LF & 63.68 (16.06) & 67.98 (16.87) & 0.354 & \(-\)0.261 \\ LF/HF & 2.48 (2.11) & 3.17 (2.45) & 0.198 & \(-\)0.300 \\ Total Capacity & 5865.04 (3640) & 516.16 (86 3877) & 0.602 & \(-\)0.079 \\ ApEn & 1.09 (0.09) & 1.06 (0.10) & 0.162 & 0.262 \\ SampEn & 1.61 (0.28) & 1.54 (0.23) & 0.118 & 0.301 \\ \hline \hline \end{tabular}  
* HR: Heart Rate; RR: Time between R-R intervals; SDNN: Standard deviation of all normal to normal RR intervals; pNN50: Intervals percentage \(>\)50 ms different from preceding interval; RMSSD: The square root of the squares mean of successive RR interval differences; LF/HF: Ratio of Low Frequency (LF) (ms\({}^{2}\)) / High Frequency (HF) (ms\({}^{2}\)); Total Power: The sum of all spectra; ApEn: Approximate Entropy; SampEn: Sample Entropy.  
\end{table} 
Table 2: Acute effects analysis of riding a horseback or in the simulator. load. Previous studies already went in that direction, studying the increase in HRV caused by physical activities with high emotional load, such as parachute jumps [24] or comparing the effects on the HRV of riding a simulator or a horse [9]. This last study found an increase in the parasympathetic activity two hours after riding the horse, which may be related to a compensatory relaxing effect. Therefore, and along with our results, we can state that although a riding simulator can provide a similar physical load to a horse movement, this type of equipment could not completely replace a horse, since they cannot induce similar emotions compared with real animals [25]; also, the simulator only oscillates in a programmed pattern, while a real horse, as a living being, provides a complex oscillation to the rider [26]. Future studies should consider this statement and increase the recording time by a few hours in order to identify the point at which sympathetic and parasympathetic activity change after exercise performance, as well as the role of emotions in this type of activity. In this line, future studies should examine the emotional experience of the participants during both simulator and horseback riding conditions. Previous research studies have examined the role of animals in therapy and education, stating the benefits of animal-assisted therapy [25], or the motivating effect caused by an animal in the educational environment [27]. Simulators have also been shown to have positive effects as horseback-riding substitutes [28], promoting therapeutic benefits associated with postural control and muscle strength, including low cost, as well as greater safety and accessibility [29]. However, mental or psychological effects appear to be more limited in simulators compared to animal-assisted therapies [8; 30]. The current manuscript supports the absence of psychological benefits since the physiological response seems to be different despite the similar physical load. This result could indicate the importance of emotions during the performance of physical activities. Our study also has some limitations. First, the sample was composed of healthy young adults, which limited the possibility of extrapolating the results to other pathological or special populations. Second, no emotional questionnaire was given to participants, which may limit the interpretation of the HRV parameters.