Research ethics:~Institutional Review Board approval was sought out from University of Jordan before the beginning of the study.~Informed consent will be obtained from athletes guaranteed their approval to participate in the study.~To insure the privacy of participants, every athlete will be assigned a study identification number.~All results will be stored in a locked cabinet/computer.~Study design and participants:~This is double -blinded randomized placebo-controlled parallel trial. The study will be reported according to the Consolidated Standards of Reporting Trials (CONSORT) statement for non-pharmacological treatment (Boutron et al., 2008). Data will be collected prospectively from athletes from different sports in Jordan.~Sample Size calculation:~The sample size was calculated using G*Power software, according to the study of Acler et al,. 2013. The study found Cohen d=0.7012 effect size of transcranial direct current stimulation on PSQI. Based on 0.7012 effect size, bidirectional alpha of 0.05, and 80% test power, a minimum of 70 participants were needed to the study. The sample will be increased by 20 % to compensate possible dropouts, overall sample of 84 participants will be included in this study.~Procedures:~Eligible athletes will be approached via the Jordanian Olympic Committee to participate in this study.~A researcher will explain the whole procedures of the research study including the randomization.~Athletes will go through baseline assessment.~A randomization will be conducted using a computerized program.~Participants will be invited to start the intervention sessions.~At the end of the treatment, athletes will go through post-treatment assessment.~The demographic data will be collected from eligible participants by a blinded assessor at baseline period. The included participants will be randomly allocated to tDCS groups or control group by a website (www.randomization.com) in a balanced allocation ratio. Outcome measures will be conducted by an assessor blinded to group randomization at baseline, after tDCS interventions, and at 1-month follow up. Allocation will be concealed from the assessor until the end of the study.
Sleep disturbances in athletes was found prevalent and affect their cognitive and physical abilities and increase the risk of injury. Moreover, studies showed also that a better sleep produces a better athletic performance. Therefore, it is important to find out management strategies that improve quality of sleep in this population.~Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that modulates cortical activity. tDCS has been conducted to improve wide range of neurological impairments including sleep. tDCS was used in improving the quality of sleep in older adults and in athletes. Both studies found improvement in some sleep indices.