For one thing, taking activities can exert positive influence on student's intelligent development, especially full time student who aim to study hard for their future. (Firstly, taking part in activities can positively contribute to a student's intellectual development, especially a full time student who aims to study hard for the future.) According to scientific researches, taking activities everyday help student promote their blood flow so that it can improve their intelligence and concentration. (I think you should not mention scientific research here. Just mention what you know.) What's more, those who often do exercises are more likely to be smart than those who seldom take activities. ('What's more' is a bit too informal. Use other connectors: Moreover, Besides that, Apart from that., etc.)
Secondly, taking activities can cultivate a kind of ability of resisting pressure, regardless of working or studying. (..., taking part in activities can help one's ability to manage stress.
It is said that activities are also best characterized by competition. Once they are gradually