## 2 Factors Affecting the IOP Response to Exercise
### Body Position  
IOP has demonstrated sensitivity to the body position adopted in a variety of non-exercise contexts (i.e., sleeping, reading) [41]. For instance, a heightened IOP response has been observed when individuals are in a recumbent position with neck flexion compared to when they are seated with their neck in a neutral position [42]. Similarly, reading while lying in a supine position results in a higher IOP than when reading while sitting upright [43]. These findings suggest that even minor changes in body position can have a notable impact on IOP.  
During exercise, the body frequently adopts various positions depending on the type of activity being performed. For example, in exercises such as yoga or CrossFit, head-down positions are often required to execute specific movements, while some resistance training exercises, such as the bench press, are typically performed in a supine or seated position. These different postures could lead to varying effects on IOP [41]. Notably, certain exercises that involve head-down positions, such as those commonly practiced in yoga, have been shown to cause significant increases in IOP [44; 45; 46]. For glaucoma patients or those at risk, it is important to avoid some yoga positions (e.g., Adho Mukha Svanasana and Uttanasana) since they cause an acute IOP rise [44]. These findings are of particular concern for individuals with glaucoma or those at risk of developing the condition, as sustained or excessive increases in IOP could potentially exacerbate disease progression.  
For strength-based exercises, research from our group has demonstrated that IOP responses can differ based on body position. Specifically, we found that performing the bench press in a supine position leads to greater IOP increases compared to performing the exercise in a seated position [47]. This difference highlights how even slight changes in body posture during exercise can influence IOP levels, which may have implications for exercise prescription in individuals with or at risk for glaucoma. While the supine position is common for certain resistance exercises, its impact on IOP suggests that adopting alternative positions, such as sitting or standing, may be beneficial in maintaining stable IOP levels.  
Taken together, the current evidence indicates that body positions involving head-down or supine postures should be avoided, when possible, by individuals at risk for glaucoma onset or progression. These positions appear to exacerbate IOP rises, which may increase the risk of damage to the optic nerve in susceptible individuals. However, further research is needed to better understand the long-term effects of these positions on IOP and their potential role in the progression of glaucoma. Future studies should focus on examining the cumulative impact of different body positions across various types of exercise and assessing whether specific postures can be modified or avoided to mitigate the risk of IOP spikes during physical activity. This knowledge will be crucial in developing exercise recommendations tailored to individuals with glaucoma or those at heightened risk of the condition.