The answer is Yes and also No. There are 2 versions with some believing that sweat as a result of exercise helped to remove the skin debris and prevent acne, while still others believe that sweat clogs the pores and causes acne. However it is best to understand the difference between sweat glands and sebaceous glands.
Sweat glands do not necessarily cause acne with clogged pores, but a lot of sweat caused with intense exercise if not washed away effectively could aggravate acne.
It is to be best understood that exercise does helps to eliminate toxins from the body that could help cure acne, but it could actually provide full benefit only when your hair is pulled off your face during your exercise and you wash your skin with an acne cleanser after exercising.
To conclude, exercise is important and great for acne if a regular regimen of exercise is followed by effective cleansing methods.