1. Introduction
ttention Deficit/Hyperactivity Disorder (ADHD) is one of the most common mental disorders in children, with a worldwide prevalence of about 5% [1]. One of the common disorders in ADHD is attention deficit disorder. Accordingly, attention can be categorized into selective attention, alternating attention, and sustained attention [4]. Children with ADHD have difficulty with sustained, alternating, and selective types of attention. This limitation may be due to the high level of arousal and their focus on more stimuli at a time and may make it difficult for them to find stimuli. High and low levels of arousal in children with ADHD may limit and interfere with information processing and attention capacity and impair the performance of these children [6].
Researchers believe that cognitive rehabilitation can be effective in improving attention disorders and working memory in ADHD children [7, 8]. In addition to these interventions, progressive physical exercise can also affect functional and cognitive deficits in ADHD children [9]. In addition to being an effective way for learning and practicing basic motor skills, physical exercises can affect cognitive processes, attention, perception, concentration, and the development of personal relationships and social skills [11]. Since the studies in this area are often concise, despite the favorable results, the present study aims to investigate the effects of cognitive rehabilitation and progressive physical exercises on sustained, selective and alternating attention of children with ADHD.
2. Materials and Methods
In this clinical trial, the study population consists of 40 female elementary school students with ADHD aged 9-12 years referred to Imam Hussein Counseling and Psychological Services Center in Yazd, Iran. They were purposefully selected based on the inclusion criteria. The Conners’ Teacher Rating Scale was used for initial assessment of children. Goodenough-Harris drawing test was used for intelligence screening [15]; the Integrated Visual and Auditory (IVA) Continuous Performance Test (CPT), as the most common laboratory-based measure for ADHD [16], was used to assess their sustained attention; the Wisconsin Card Sorting Test (WCST) was used to measure alternating attention; and the Stroop test was used to measure selective attention [18]. The cognitive rehabilitation program used in this study was My Brain application in Persian presented at sixteen 60-minute sessions, 3 per week. In the pre-test phase, all students performed IVA CPT Test, WCST and Stroop test. After the pre-test assessment, participants were randomly divided into four groups of rehabilitation, exercise, rehabilitation + exercise, and control. Analysis of Covariance (ANCOVA) was used to compare the means of study variables in post-test phase, after controlling the impact of pre-test score. To test the study hypotheses, one-way ANCOVA was used. The analyses were performed in SPSS v. 20, considering a significance level of P<0.05.
3. Results
The results of ANCOVA showed that the effect of pre-test on post-test was significant (P<0.05) in the variables of commitment error, number of correct answers, interference score, errors, interference time and consistency error. According to the Bonferroni post hoc test results, the mean score of error in children was significantly higher in the control group (P<0.05). In omission response variable, the mean score in the combined group was significantly lower than in the control group (P<0.05). There was a significant difference between the mean scores of children in the control group (P<0.05) in the control group children (P<0.05). In the number of correct answers, the mean score of correct answers in the control group was significantly lower than in the combined and exercise groups (P<0.05).According to the Bonferroni post hoc test for the interference score and time, the mean scores in the control group were significantly higher than in other three groups (P<0.05) (Table 1).


4. Discussion and Conclusions 
The results if this study showed that, the combined group performed better than the control group in sustained attention, whole in alternating and selective attention, the combined group performed better than all other groups. For explaining the results, two theories can be proposed. Based on the theory of arousal mechanism, children with ADHD may not pay attention to the main stimuli and cues related to performance due to very high levels of arousal. Or those with a low level of arousal may have access to a wide range of cues, a limited number of which are related to the effective execution of the task and impose more than once on the individual processing system. In both cases, the performance is impaired. According to Barkley’s (1997) Cognitive Inhibition Theory [22], the lack of inhibition is a good explanation for the structures of distraction, inattention, and impulsivity in children. Inability to inhibit in children results in impulsive behaviors. The child’s attention is also easily distracted by disturbing stimuli and fails to correct inappropriate responses. 
Continuous and regular combined exercises can affect attention deficit, lack of focus, and lack of selective attention. Combined exercises in our study significantly reduced interference score (improved inhibitory response). Overall, it was concluded that physical exercise and cognitive rehabilitation can improve attention in children with ADHD. 

Ethical Considerations
Compliance with ethical guidelines
This study has been registered in the clinical trial site with the code IRCT20180618040143N1 and in the Ethics Committee of the Institute of Physical Education and Sports Sciences (Code: SSRI.REC.1397.245). All ethical principles are considered in this article. The participants were informed about the purpose of the research and its implementation stages. They were also assured about the confidentiality of their information. They were free to leave the study whenever they wished, and if desired, the research results would be available to them.

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors. 

Authors contributions
Conceptualization and methodology: Amir Shams and Mahdieh Eslami Nusratabadi; Editing and review: Mandana Sangari; Writing and data analysis: Masoud Mirmoezzi.

Conflicts of interest
The authors declared no conflict of interest.


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