Ground Reaction Force (GRF)
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Paul Roetert explains the physics of Ground Reaction Force (GRF) and how it relates to the serve. In this video he explains the minor differences in GRF when comparing the pinpoint and platform stance. At the higher levels of the game, GRF is used on the ground strokes as well.
Paul Roetert, Ph.D is the Managing Director of the United States Tennis Association's Player Development Program. In addition, he serves as Tournament Director of the U.S. Open Junior Tennis Championships. Before re-joining the USTA in November, 2001, Paul spent two years as the Executive Director of the American Sport Education Program. Prior to that position he spent eleven years as the Administrator of Sport Science for the USTA where he developed the sport science program. He also served as Vice Chairman of the sport science committee.
Paul has published extensively in the field of tennis, including two books, 16 book chapters and over 100 articles. He is a Fellow in the American College of Sports Medicine (ACSM), a member of the United States Professional Tennis Association (USPTA) and the Professional Registry (PTR). In 1998 he received the PTR's Plagenhoef Award for sport science; in 1999 the Editorial Excellence Award from the National Strength and Conditioning Association for his work on the Journal of Strength and Conditioning and Research; in 2000 the Outstanding Alumni award from the University of Connecticut. He is also the 2002 Educational Merit Award recipient from the International Tennis Hall of Fame for outstanding service to the game of tennis.
Paul holds a Ph.D. in biomechanics from the University of Connecticut. Originally from the Netherlands, he and his wife Barbara reside in Miami, Florida.