Video analysis of 100 matches in male semi-professional football reveals a heading rate of 5.7 headings per field player and match.
J. Weber, A. Ernstberger, C. Reinsberger, D. Popp, M. Nerlich, V. Alt, W. Krutsch, BMC Sports Sci Med Rehabil 14 (2022) 132.

Angle-specific analysis of isokinetic quadriceps and hamstring torques and ratios in patients after ACL-reconstruction.
C. Baumgart, W. Welling, M. Hoppe, J. Freiwald, A. Gokeler, BMC Sports Sci Med Rehabil 10 (2018) 23.