Individuals who exercise 30-60 minutes yield the highest reduction in poor mental health while individuals who exercise for 90 minutes have small reductions (The Lancet, 2018).
For individuals who exercise three hours a day however, their mental health may begin to suffer. Research shows that this amount of excessive exercise is much more harmful than no exercise at all to one's mental health (The Lancet, 2018)!
Individuals who depend on exercise as a "weight management strategy" are often more inclined to suffer from stressful health outcomes such as bulimia, purging, anorexia nervosa, and an increase in negative self-image (Mikkelsen et al., 2017).
Exercise dosage matters! Make sure to be cognizant of how much you're exercising. It's easy for time to slip away when you're in the zone. But to encourage your mental health, over-exercise is something to avoid. One possible way to prevent over-exertion is to have a workout playlist set to play for a certain amount of time (minimum of 30 minutes and maximum of 90). Once the playlist ends, then you know it's time for your cooldown!
Mikkelsen, Stojanovska, L., Polenakovic, M., Bosevski, M., & Apostolopoulos, V. (2017). Exercise and mental health. Maturitas, 106, 48–56. https://doi.org/10.1016/j.maturitas.2017.09.003
The Lancet. (2018, August 8). Exercise linked to improved mental health, but more may not always be better. Yale School of Medicine. Retrieved April 28, 2022, from https://medicine.yale.edu/news-article/18044/