We will include women who (1) have not been able to have sexual intercourse in at least the last 6 months conformed to DSM-5, as indicated by scores ≤ 1 on Primary Endpoint Questionnaire (PEQ) item 7 (60), (2) are at least 18 years of age, (3) whose penetration difficulties are not due to a medical condition, (4) are in a heterosexual relationship or have a heterosexual (training) partner, (5) who have Internet access, (6) have sufficient German skills in reading and writing, and (7) are willing to give informed consent.

We will exclude individuals reporting to have been diagnosed with (1) psychosis or dissociative symptoms in the past or present, (2) posttraumatic stress disorder or traumatization due to sexual abuse in the past or the present, (3) substance abuse or dependency in the present, or (4) moderate or severe depression or bipolar disorder in the present assessed with the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders (fourth edition) Axis I Disorders (SCID-I) (66), and those (5) currently being treated for GPPPD.

We will recruit patients via (1) the study website and Facebook page, (2) articles in women’s online magazines, (3) online forums, (4) advertisements on websites related to the topic of sexual dysfunctions, and (5) Google AdWords. Recruitment is scheduled to take place between April 2016 and December 2017. The trial is open to all women fulfilling the inclusion criteria. The research website www.paivina-care.info provides information on the program and details about the study. If they want to participate in the study, applicants can sign up on this website by leaving their email address.

Women who sign up as potential participants will receive an online information letter with detailed information on the study procedures. They will be asked to provide an email address that they want to use for the study and a first and last name (which can be pseudonyms if desired). The women will be informed that they can withdraw from the intervention and/or study at any time without any negative consequences. Applicants who intend to participate in the study will be asked to complete online screening questionnaires that assess inclusion and exclusion criteria. If responses to this questionnaire indicate that participants might be affected by one of the mental health disorders listed as exclusion criteria above, participants will be scheduled for the SCID-I via telephone. Women who meet all of the inclusion criteria and none of the exclusion criteria and who complete the baseline assessment and return the informed consent form will be considered for the study and randomly allocated to one of the two study conditions. Randomization will take place at an individual level. This process will be completed by an independent researcher not otherwise involved in the study using an automated computer-based random integer generator (randlist). Until this process has been completed, the results will not be known by participants, researchers involved in recruitment or eCoaches. Participants will be informed of the outcome of the randomization, and participants in the IG will receive immediate access to the program. Participants in the WCG will receive access to the program 6 months after study intake.

The participants will be provided with psychoeducational information on GPPPD and the multifactorial causes of its development. Core elements in the first session are (1) overview of the program: intervention components and the expectations placed on the participants are presented; (2) goal setting: participants are asked to define realistic individual treatment goals, which will be shown and can be modified over the course of the program; (3) strengthening motivation: personal treatment motivation is assessed, participants can schedule the exercises and plan how to deal with difficulties they may face during treatment, for example non-adherence to treatment and exercises; (4) self-support: participants learn about effective support, e.g., in terms of self-gratification; (5) couples’ communication: rules for communication are introduced to facilitate the discussion between participants and their partners about the intervention and the partner’s role in the program, especially with regard to exercises, the expression of emotional needs, and sexual preferences.

In the second part of psychoeducation (Session 2), participants will be introduced to the fear-avoidance model and thereby learn more about the causal and maintaining factors of GPPPD and the rationale behind the treatment. Participants are given the opportunity to individualize their own fear-avoidance model by including their cognitions, emotions, physical reactions, and behaviors. Participants also learn about the function of emotions and their influence on GPPPD symptoms.

In the first step, participants identify negative cognitions and distorted beliefs about sexual intercourse, genital pain, and sexuality in general, and learn how cognitions can influence emotions and behavior. In the second step, they restructure and replace these cognitions with more helpful and encouraging ones. These cognitions are also rehearsed as coping self-statements during the exercises.

By learning about and practicing non-judgmental awareness, participants might be able to interrupt automatic processes of negative cognitions. They are instructed to observe their cognitions and emotions in response to sexual situations without interpreting, judging, reacting to or suppressing them. To get used to the principles of non-judgmental awareness, participants are asked to practice it not only in sexual but also in nonsexual day-to-day situations.

Participants will learn PMR in combination with breathing relaxation (69). By learning to flex and relax muscles voluntarily, participants can begin to control their body tension. Guided by an audio file, they start to practice PMR and eventually switch to a shorter version that can also be integrated into day-to-day activities. Based on the principles of PMR, pelvic floor exercises are then introduced in a video tutorial. These exercises are meant to increase proprioception and decrease hypertonicity of the pelvic floor.

In Session 3, participants are also introduced to the relationship between vaginal pain and anxiety, and the consequences of pain and fear of pain on sexual arousal and muscle tension. They are asked to explore exacerbating and alleviating factors that influence their genito-pelvic pain. During attention-focusing, patients localize the pain center, describe the pain as images, and use suggestive pain transformation to alter the pain.

The internal and external female genitals and the anatomy of pelvic floor are introduced and illustrated with drawing. This treatment component also addresses the physiological processes during arousal and sexual intercourse. Participants are introduced to a body exposure exercise and asked to explore their vagina in front of a mirror. The approach taken here is non-judgmental and mindful of negative cognitions and emotions. Genital self-exploration is complemented by other, shorter body exposure exercises that are meant to enhance participants’ positive self-perception of their bodies and desirability.

The aim of the sensate focus exercises is to promote physical intimacy and reduce associated stress, pressure, and anxiety by emphasizing the experience of sensual pleasure by the couple over intercourse or orgasm (70, 71). Sensate focus exercises foster sensual body awareness and allow participants to become better acquainted with their own and their partners’ bodies and erogenous zones. These exercises involve progressive steps in which partners touch and give massages to each other (1) first nongenitally, wearing clothes and then only underwear, (2) with genital touching but not aiming for sexual arousal, and (3) genital touching that can lead to sexual arousal. During the exercises, the participants and their partners switch active and passive roles and are asked to communicate their feelings and experiences to learn more about their own and their partner’s sensual and sexual pleasures.

One of the goals of the treatment is to increase sexual desire and arousal, as both influence vaginal penetration and pain. Information on self-stimulation and masturbation, e.g., techniques, is provided.

Gradual vaginal exposure is combined with PMR and pelvic floor exercises. The exercises involve (1) insertion of one and two fingers by the woman and (2) one and two fingers by the partner, whereby the woman guides the partner’s hand while inserting his finger or fingers, (3) self-insertion of dilators of increasing sizes, with the largest dilator being similar in size to a penis, and (4) insertion of dilators of increasing sizes by the partner guided by the woman. Additionally, participants are encouraged to keep the dilator inside the vagina for a longer period of time (up to an hour) to get used to the feeling and to increase the habituation effect. Participants are advised to choose a larger dilator if they are comfortable with repeated insertions. These gradual exposure exercises are accompanied by detailed step-by-step instructions and also include, for example, suggestions for preparing for the exercises, sitting postures and recommendations that will help women deal with possible difficulties.

Step-by-step insertion exercises with the penis include (1) touching the vagina with the erect penis without insertion, (2) inserting the erect penis without moving, and (3) moving the erect penis inside the vagina.

In the last session, participants will be asked to reassess their training goals and to identify their personal warning signs for GPPPD setbacks. Additionally, they will be given the opportunity to write a letter to themselves describing their life after 4 more weeks of exercises, which they can refer to in the future if they wish.

Four weeks after completing the intervention, participants will be given the option of completing a booster session and evaluating their training progress. They will revisit the letter they wrote to themselves in the last session, reassess their goals, and make plans concerning insertion exercises or sexual activities.

The seven-item PEQ will be used as a primary outcome measure. Successful intercourse penetration (SIP) will be measured by one item assessing the degree to which the insertion of the partner’s penis was possible. The items will be answered on a 4-point Likert scale (0 = not attempted; 1 = attempted, but unsuccessful; 2 = attempted and sometimes successful; 3 = attempted and always successful). Previous cases of women reaching SIP prior to treatment completion have shown that they are susceptible to study dropout (67). For that reason, participants who do not fill out the PEQ online, (1) are scheduled for a telephone assessment or (2) can report to their eCoach whether intercourse penetration was successful.

Successful nonintercourse penetration will be measured by the remaining six items of the seven-item PEQ. These items assess the degree to which insertion of one or two fingers or another object such as a tampon or a dilator by the woman or her partner was possible. Participants will be asked to answer questions referring to the past two weeks. Cronbach alpha was found to be good (α = 0.81) for this scale (67).

The frequency of a woman’s fear experienced in different sexual situations will be measured using the Fear of Sexuality Questionnaire (FSQ) (73). The FSQ consists of the five-item subscale fear of noncoital sexual activity and the three-item subscale fear of coitus. The items are answered on a 5-point Likert scale ranging from 1 = never to 5 = always. The internal consistency of this measure has been found to be good with a Cronbach alpha of α = 0.82–0.84 for fear of noncoital sexual activity and α = 0.82–0.86 for fear of coitus in samples of women with vaginismus (67, 73).

Vaginal penetration cognitions will be assessed with the Vaginal Penetration Cognition Questionnaire (VPCQ) (74), which is comprised of the five subscales: control, catastrophic and pain, self-image, positive, and genital incompatibility cognition. This self-report instrument uses a 7-point Likert scale anchored by 0 = not at all applicable and 6 = very strongly applicable. Reliability of these five VPCQ subscales ranges from α = 0.70 to α = 0.83 in a sample of women with vaginismus and dyspareunia.

To measure different domains of female sexual functioning, the Female Sexual Function Index will be used (75–77). This self-report instrument consists of the following 6 subscales: sexual desire, sexual arousal, lubrication, orgasm, pain and sexual satisfaction. The questionnaire uses a 6-point Likert scale anchored by 0 = no sexual activity and 5. The measure allows for the calculation of specific indexes for each dimension and of an overall sexual function index. The internal consistency ranges from α = 0.82 to α = 0.93 in women with female sexual arousal disorder (76) and from α = 0.76 to α = 0.93 in a sample of women with vaginal penetration difficulties (67).

Patient satisfaction with the intervention will be measured by using an adaptation of the Client Satisfaction Questionnaire (CSQ-8, German: ZUF-8) optimized for the assessment of client satisfaction with Internet interventions (CSWIQ-8) (78, 79). The CSQ-8 is a validated eight-item instrument with high internal consistency (α = 0.93) (79). The adapted version, validated for the assessment of client satisfaction in Internet-based interventions, has repeatedly proven to have high internal consistency (α = 0.92–0.94) (56, 80, 81) and is associated with treatment adherence and outcome (80).

Other measurements include the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I), socio-demographic variables (e.g., age, gender, duration of symptoms, etc.), the Well-Being Index (WHO-5) (82–84), the Self-Esteem Scale (85, 86), and the Health Action Process Approach Questionnaire (87) adapted to treatment adherence. Experiences of sexual abuse will be measured with the sexual abuse subscale of the Childhood Trauma Questionnaire (88, 89) and an item adapted to experiences following the age of 18. To assess relationship quality, we will use the Dyadic Coping Inventory (90, 91) and the Partnership Questionnaire Short Form (92). The State Trait Anxiety Inventory (93, 94) and the Generalized Anxiety Disorder 7-item Scale (GAD-7) (95, 96) will be used to assess general anxiety sensibility. Potential negative effects of the Internet-based intervention will be assessed using the Inventory for the Assessment of Negative Effects in Psychotherapy (97). We will also measure potential dropout reasons and the utilization of additional help with self-developed items. Participants will need approximately 40 min to complete all questionnaires at baseline and 30 min at follow-ups. For an overview of all outcome measures, see Table 2.

Sexual dysfunction disorders of the partners will be examined using the German version of the International Index of Erectile Function for Men (98, 99). Including 15 items, the questionnaire consists of five subscales: erectile function, orgasmic function, sexual desire, intercourse satisfaction, and overall satisfaction. The first 10 items are rated on a 6-point scale (0–5) with 0 = no intercourse (attempt) and the remaining 5 items are presented with 5-point scales (1–5). High internal consistency has been reported for all subscales with Cronbach alpha between α = 0.71 and α = 0.96 (98, 99).

Adherence will be assessed by session completion (0–8) tracked by the system of the intervention platform. Participants will also be asked to report how often they completed the exercises in a given week with one item measured on a 4-point Likert scale ranging from 0 = less than once a week to 3 = every day.

Analyses will be conducted and reported in accordance with the statement by Consolidated Standards of Reporting Trials (102). Data will be analyzed on an intention-to-treat basis. Additionally, study completer analyses including only participants who filled out the questionnaires and intervention completer analyses including only participants who have completed the 8 treatment sessions will be conducted. Missing data will be handled using multiple imputations (MIs) calculated by a Markov Chain Monte Carlo multivariate imputation algorithm of 100 estimations per missing value. MI is especially robust with respect to missing data (103). We will use chi-square test (χ²) to examine differences in the primary outcome. Differences in secondary outcome measures will be analyzed between and within the two study groups based on regression. For all analyses, Cohen’s d (104), including 95% confidence intervals, will be calculated for the differences between baseline and follow-up scores calculated by using the mean difference in change between the IG and WCG divided by the pooled standard deviation of the change score. For all statistical analyses, the significance level will be set at p < 0.05, 2-sided. All analyses will be performed with IBM SPSS v. 24.

Predictors and moderators of changes in SIP will be analyzed on an exploratory basis. They will include, e.g., lifelong and acquired GPPPD, experiences of sexual abuse, and symptom severity. Fear of sexuality, penetration-related cognitions and exercise intensity will be examined as mediators of changes in SIP via structural equation modeling. Separate moderator analyses will be conducted using the PROCESS macro for SPSS. The analyses will include the main effect of the baseline variable, the main effect of the treatment condition (IG and WCG), and the interaction of the baseline variable and the treatment condition. To assess relevant subgroup effects, follow-up simple slope analyses for possible significant interaction effects will be conducted. Therefore, the slope and the significance of the intervention main effect will be evaluated for conditional values (one SD below and one SD above the mean) of the moderator.