Introduction

Today’s show welcomes back JB Morin.  JB Morin is currently full professor and head of sports science and the physical education department at the University of Saint-Etienne.  He has been involved in sport science research for over 15 years, and has published over 50 peer-reviewed journals since 2004.  JB is a world-leading researcher on all things sprint related, having collaborated with and analyzed some of the world’s best sprinters, such as Christophe Lemaitre. JB also does lots of sprint research that is highly applicable to team sport settings, such as information that can be gleaned from force-velocity profiling.  He has been a 2x previous guest on this podcast, speaking on elements of heavy sled training, force-velocity profiling, and much more. When it comes to sprinting from point A to point B, the time on the clock does not necessarily represent the strategy an athlete used to get there.  Athletes who can direct their sprint forces in more of a horizontal vector are going to be able to reach higher top velocities, and be more resilient towards injury. The question then becomes, how do we assess, and train athletes in respect to the direction they are producing sprint forces?  In today’s episode, JB speaks on how the specifics of an athlete’s force production (in the horizontal vs. vertical direction) will highlight elements of how fatigued that individual is, and their predisposition to injury in the short term.  JB also goes into how to measure force production in sprinting, new research on joint actions in early and late acceleration, hill training vs. sleds, hamstring research, and more. Today’s episode is brought to you by SimpliFaster, Inside Tracker, and Lost Empire Herbs. For 25% off of an Inside Tracker order go to info.insidetracker.com/justflysports For 15% off your Lost Empire Herbs order, head to lostempireherbs.com/justfly. View more podcast episodes at the podcast homepage. Timestamps and Main Points 5:00 –  Some new work that has come out in sprint research recently, showing the importance of the hip and ankle outputs in sprinting, even in the first few steps of acceleration 16:20 –  Thoughts on sprint technique, or force-velocity profiling and how that might link to potential injury in team sport situations 24:00 –  The relationship (and differences) between one’s maximal horizontal force, and their maximal sprint speed, and what it means for injury risk 30:50 –  How having a poor maximal horizontal force output can show up in the biomechanics of how an athlete is sprinting 37:15 –  How elite athletes will start to change their force-production orientation (less horizontal, over time) once fatigue starts to set in during a training session 45:00 –  How hill training compares to heavy sled training in terms of forces and velocity 50:30 –  New studies and thoughts on hamstring injury in athletics 54:20 –  Thoughts on training the feet and lower leg for the sake of sprinting 58:40 –  JB’s thoughts on how to set up good research on sprinting in athletics “75% of the energy that is generated to run is generated at the hip and calf level” “Team sport is so chaotic, it’s the worst way to assess an athlete’s acceleration capability, the game environment is not reproducible” “Our studies show that pre-season maximal force output is not related to (injury risk) but when you measure that maximal force output throughout the season, the last measurement is related to the risk of injury in that measurement period” “You need to measure (force/velocity) regularly, not only in the pre-season period… there are so many changes throughout the season” “You can have people with the same 25 meter splits, but different profiles at the beginning of the spectrum or the end of the spectrum” “If you take two athletes with the same magnitude of ground reaction force, the best in acceleration will be the most horizontally oriented vector”