A number of research studies have looked at the Effectiveness of Shoe Stiffening Inserts for First Metatarsophalangeal Joint Osteoarthritis to test how well they do or do not work.
In this study by Jerilyn et al in 2015, they reported that in the 31 subjects in their study, at 1 and 3 months, statistically significant improvements in foot pain and foot-related disability were observed using the rigid shoe stiffening inserts. The treatment was reported to be effective by 78% of participants.
In this 2021 study by Munteanu et al that compared the rigid carbon fiber plate to a fake insert (the placebo) in 100 people for 12 weeks found that the rigid insert group did better.
The conclusion of the research to date is that these sorts of rigid insoles to stiffen the shoes is that they can help those with osteoarthritis pain in the first metatarsophalangeal joint. There is no research been done of other types of problems yet.
There are some other studies done on inserts that are similar to these, but are not the same so we have not included them here. There are some issues with the terminology used to describe the inserts or insoles that are used in some studies and it is important that when reading any of the research that you are not comparing apple to oranges.