Intensity-specific leisure-time physical activity and depressive symptoms among first-year university students: a four-wave longitudinal study 1School of Physical Education and Sports, Central China Normal University, Wuhan, Hubei, China 2Key Laboratory of Psychological and Physiological Regulation in Competitive Sports, Tianjin University of Sport, Tianjin, China 3School of Physical Education, Guangzhou Maritime University, Guangzhou, Guangdong, China DOI 10.7717/peerj.21498 Academic Editor...