Normal male sexual function includes the physiological processes of erection, orgasm, and ejaculation (1). Premature ejaculation (PE) and erectile dysfunction (ED) are prevalent sexual dysfunctions globally and lead to a range of negative outcomes for men and their partners. More physical activity, better autonomic nervous system reactivity, and better interoceptive awareness have been associated with fewer PE problems (2). However, few studies have explored the associations between these variables simultaneously. Therefore, we aimed to investigate the association and potential mediation effects between physical activity, autonomic nervous system reactivity, interoceptive awareness, and both PE and ED.
PE and ED
PE refers to the inability to control or delay the timing of ejaculation also with a short intravaginal ejaculation latency time (i.e., the time between when penetrating the vagina and ejaculating) which also leads to subjective distress (3,4). Almost 3% of men fulfill the above criteria including shorter than one minute of intravaginal ejaculation latency time (3). A range of negative psychological outcomes occur in men with PE and their female partners, including men’s lower self-confidence (5) and self-esteem (5,6), higher anxiety and depression (7) and interpersonal difficulties (5,8,9), their female partners’ lower relationship and sexual satisfaction (5,10) including an increased prevalence of sexual dysfunctions (5,10). In addition, PE problems were reported to be the main reason for one in five women to break up or divorce men in a large cross-cultural study (11).
ED refers to the inability to attain or maintain an erection sufficient for satisfactory sexual intercourse (12). The prevalence of ED varied from 35% to 45% in Chinese samples (13,14). ED also leads to negative outcomes for men, for example, lower self-esteem, more depression, and lower sexual satisfaction (15,16). In addition, several studies have revealed that men with ED have an increased risk of PE (17–19). The underlying mechanism may be the association between the autonomic nervous system and both erection and ejaculation processes (1).
Sympathovagal Imbalance Hypothesis
The understanding of the etiology of PE is limited (1). Although the autonomic nervous system mechanism of the male sexual response is not entirely clear, the balance and appropriate timing between the sympathetic and parasympathetic nervous systems seem crucial for a well-functioning sexual response (1). During the erection phase, first, while sympathetic activity decreases, parasympathetic activity has the dominating role in inducing the relaxation of muscles that otherwise constrict the flow of blood into the penis, enabling an erection (1). Then, in the ejaculation phase, the sympathetic nervous system has the dominating role, facilitating the emission of seminal fluid (1).
A few preliminary studies suggest sympathovagal imbalance may have a role in PE (20,21). Sympathovagal imbalance refers to an autonomic state of sympathetic overactivation which is associated with a higher risk of stress, cardiac morbidity, mortality (22), and psychopathology (23). Men with PE may have higher levels of sympathetic activation than men with normal sexual function in non-aroused (21,24) and aroused (25) settings. In addition, compared with men without PE, men with PE displayed lower levels of parasympathetic activity and a higher sympathetic/parasympathetic ratio which is an indicator of sympathovagal balance in a 24-hour heart rate monitoring examination (20). More importantly, a sympathetic/parasympathetic ratio greater than 2.7 may serve as a predictive indicator for PE with high sensitivity (20). Therefore, we assumed that sympathovagal imbalance during sexual activity might have a role in the causation of PE.
Physical Activity
Physical activity has been associated with fewer PE symptoms (26,27). Previous studies have demonstrated that multiple physical exercises can alleviate PE symptoms, for example, yoga and running (28–30). For example, men with lifelong PE have reported a longer intravaginal ejaculation latency time after undergoing moderate physical exercise training (running for 30 minutes) five times a week for thirty days compared with before the intervention and a sham (walking for 30 minutes) group (29).
A possible underlying mechanism may be that physical exercise positively affects sympathovagal balance (31,32). Brenner and colleagues (2020) found that a 12-week period of low-intensity exercise (pain-free walking) enhanced autonomic nervous system regulation compared to a control group in patients with peripheral artery disease (33). This intervention resulted in increased parasympathetic activity and decreased sympathetic activity which indicates improved sympathovagal balance (33). In addition, another study found that 20 minutes of high-intensity interval training (HIIT) - consisting of repeated high-intensity exercises separated by short recovery interval periods - for two weeks improved sympathovagal balance in physically active men (34). A recent study found that seven minutes of HIIT for two weeks improved ejaculation control for men with PE (35). Also, this study found that higher heart rate increases during exercise were associated with more decrease in PE symptoms (35). We, therefore, expected autonomic nervous system activity during sex to potentially mediate the relationship between physical activity and ejaculation control.
Importantly, more frequent participation in physical activity has also been associated with less erectile dysfunction (36,37). Based on the dominating role of parasympathetic activity in enabling penile erection, we also expected that autonomic activity during sex may mediate the relationship between physical activity and erectile function.
Interoceptive Awareness
Interoception refers to sensing internal signals from the body, including physical aspects such as the heartbeat, breathing rate, temperature, pain, and other somatic feelings (38,39). Interoception is crucial for maintaining bodily homeostasis (38,39), regulating emotion, and memory (40), and developing the sense of the self (41). The bidirectional communication between the central nervous systems, autonomic nervous systems, and the other internal tissues of the body generates interoception (38,39,42). Sympathovagal balance may play some role in the neural circuits of interoception, for example, the vagus nervus serves as a prominent conduit for interoceptive signals, predominantly functioning as an afferent pathway that conveys information from bodily interoceptors (43). Additionally, the vagus nerve plays a role (43).
Interoceptive awareness refers to the individual’s ability to perceive, identify, and appropriately respond to internal signals from the entire body (44,45). Previous studies have shown that individuals with higher interoceptive awareness tend to have better emotion regulation (41,46). In addition, a study indicated that less interoceptive awareness was associated with more difficulty delaying ejaculation (2). However, to our best knowledge, previous studies have not found any significant association between interoceptive awareness and erectile function (2). Therefore, we hypothesized that less interoceptive awareness would be associated with more PE symptoms and just explored the association between interoceptive awareness and ED symptoms. Furthermore, physical exercise may enhance interoceptive accuracy (47) which refers to the accuracy of perception or detection of interoceptive signals (48) and is closely associated with interoceptive awareness (49). Considering the association between physical exercise and ejaculative control, we explored if interoceptive awareness would mediate the association between physical activity and PE and ED symptoms.
Body awareness refers to the sensitivity to internal bodily signals from body functions (50). According to the definition of interoceptive awareness, body awareness seems to be part of it. However, one previous study found no significant association between body awareness and interoception accuracy (48). Therefore, we only explored the association between body awareness, physical activity, and PE and ED symptoms.
Hypotheses
We expected that more physical activity would be associated with fewer PE and erectile problems (Hypothesis 1). We expected that more participation in physical activity would be associated with more parasympathetic activity during sex (Hypothesis 2) which in turn would be associated with fewer PE and erectile problems (Hypothesis 3). We also expected that more physical activity would be associated with heightened interoceptive awareness (Hypothesis 4) which in turn would be associated with fewer PE problems (Hypothesis 5).