1. Introduction
Pain is complex and multidimensional perception, influenced by psychological factors, which include a set of cognitive (e.g., attention), behavioral (e.g., specific behavioral responses when experiencing pain), and emotional (sadness, hopelessness, fear, & anxiety respecting aggravate pain) aspects, which plays an essential role in modulating the perception of pain [3].
A psychological approach that can considerably relieve pain is power posture [4, 7]. Power posture, expressed in expansive body postures, can lead to changes in humans’ power-related feelings, thinking, and behavior. Therefore, the effects of using power posture mediated by hormonal and neurological factors on the pain threshold are expected. Bohns and Wiltermuth (2012) suggested that participants with a power posture had a higher pain threshold than individuals with a neutral or obedient gesture [7]. However, Ge, Bennett, and Oller’s (2017) findings did not reflect the effects of power gestures on pain threshold [4]. Therefore, considering the contradiction between the results of power gesture research, the present study aimed to investigate the effects of pretending high/low power gestures on pain threshold.
2. Materials & Methods
This study was a quasi-experimental study with pre-test-post-test and a control group design. Accordingly, the convenience sampling method selected 60 female students affiliated with Arak University with a mean±SD age of 20.2±2.5 years in 2016-2017. The study participants were randomly divided into 3 groups of 20 subjects, including high power posture (sitting on a chair with legs on the table, arms behind & head held up), low power posture (sitting on a chair with legs crossed, arms between legs & bending the head down), and without posture as the control group. After pre-test measurements and two minutes of poses, the post-test was performed immediately. Research tools included Rosenberg Self-Esteem Scale (RSES) and blood pressure cuff, and pain thresholds were recorded in millimeters of mercury, a standard unit used to report blood pressure [7]. To perform high/low power posture in this study, the gestures of Carney et al. (2010) were used with the exact instructions. The study subjects performed each gesture for one minute (two minutes per person per group) between the pre-test and post-test intervals [9]. The principles of confidentiality of the study participants’ information were observed. 
3. Results
One-Way Analysis of Covariance (ANCOVA) was used to evaluate the effects of power posture on pain threshold. The results of this test are reported in Table 1.

The ANCOVA results indicated that the difference in the adjusted mean score of pain threshold in the high-power posture group (81.94), the low- power gesture group (63.87), and the control group (74.41) was significant according to the F statistic at the level of 0.001 (Figure 1). Thus, pretending a high-power posture increases the pain threshold, and a low-power posture decreases it in university students.
4. Discussion & Conclusion 
This study aimed to investigate the effects of pretending power posture on changing the pain threshold of a group of female students. The obtained results were in line with the results of Bohns and Wiltermuth (2012) [7]; however, our findings were inconsistent with those of research by Ge, Bennett, and Oller (2017) [4]. According to Carney et al. (2010), the gesture of power increases testosterone and decreases cortisol [9]; increased power is also associated with the behavioral activation system, and decreased power is associated with the behavioral inhibition system [16]. Behavioral activation system with mesolimbic dopamine nerve cell activity leads to relief and the reduction of pain sensitivity [28, 29]. Furthermore, testosterone and the left prefrontal cortex activity increase the pain threshold by affecting beta-endorphins, neurotransmitters, and other neuropeptides [30, 31]. Cortisol also helps relieve pain by altering hippocampal. 
Bohns and Wiltermuth (2012) suggested that the study participants with a power posture had a higher pain threshold than those with a neutral or obedient gesture [7]. These studies indicated a negative relationship between cortisol and a positive relationship between testosterone and pain threshold [17], a negative relationship between the behavioral activation system, and a positive relationship between the behavioral inhibition system and pain [18]. Therefore, hormonal and neurological factors can be considered for power gestures’ effect on the pain threshold. To explain the inconsistency of the present study findings with those of the research by Ge, Bennett, and Oller (2017), it is necessary to outline the difference in gestation time, gesture differences, the lack of control group, and the use of hand muscle dynamometer to measure pain threshold in Ge et al.’s investigation; using power gestures as a simple tool in pain situations are recommended for pain management or as a supplement to analgesics.

Ethical Considerations
Compliance with ethical guidelines
The Research Ethics Committee of Arak University of Medical Sciences approved this study (Code: REC.1399.276). Participation in this study was informed and voluntary, and participants could withdraw at any study stage. 

Funding
This research was extracted from the MA. thesis of the first author at the Department of Psychology, Faculty of Humanities, Arak University, Arak.

Authors' contributions
All authors contributed equally to the preparation of this article. 

Conflicts of interest
The authors declared no conflicts of interest.


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