exercise, such as lifting weights, require straining and cause momentary increase in your heart rate
The strain and increase in blood flow builds up pressure in your head, which causes blood vessels to dilate, including those in your eyes.
If the pressure is too great, the tiny blood vessels in your eye can burst and make the sclera -- the white part of your eye -- appear red called as subconjunctival hemorrhage
The more strenuous the exercise, the greater the amount of pressure that builds in your head.
so you should restrict yourself in heavy exercise to aviod such problems