As a clinical exercise researcher, I frequently have found it difficult to study exercise effects in people with health complications, even though this is critical information to know in order to make appropriate exercise guidelines. Try convincing your university Institutional Research Board, or IRB, that it is advisable to exercise people with eye issues like unstable proliferative retinopathy to find out if breath-holding, jumping, jarring, or head-down activities cause them to experience retinal hemorrhages. Understandably, that is not going to happen, nor should it.
In some cases, I have not even been allowed to study relevant populations—like when we wanted to study older adults with type 2 diabetes and balance or gait issues related to peripheral neuropathy. Our IRB required so many exclusionary criteria that we were only able to recruit healthy, older subjects with diabetes, not the ones for whom an exercise training intervention to improve balance would be most relevant (i.e., those with actual balance issues).
It is still worth revisiting the latest recommendations for exercising safely and effectively with a variety of diabetes-related health complications. Most of these are derived from clinical observations and practical experience rather than clinical studies, though. The table that follows is a compilation of all these recommendations. (Please access the entire ADA Position Statement online, including redacted references, at http://care.diabetesjournals.org/content/39/11/2065).
Table 5: Physical activity consideration, precautions, and recommended activities for exercising with health-related complications (Modified from (1))
View the full table with all the complications listed in my WordPress blog here:
https://shericolberg.wordpress.com/2017/09/22/what-do-we-really-know-about-exercising-with-complications/
Reference cited:
Colberg SR, Sigal RJ, Yardley JE, Riddell MC, Dunstan DW, Dempsey PC, Horton ES, Castorino K, Tate DF: Physical activity/exercise and diabetes: a position statement of the American Diabetes Association. Diabetes Care 2016;39:2065-2079. http://care.diabetesjournals.org/content/39/11/2065