Source: HIITscience
Hosts: Dr. Martin Buchheit & Paul Larsen
Guest: Professor Jean Benoit Morin

This video, titled “Go Hard to Go Fast – New Age Sprint Training,” features a deep-dive conversation between hosts Dr. Martin Buchheit and Paul Laursen with Prof. Dr. JB Morin, a leading expert in sprint mechanics. The discussion bridges the gap between complex biomechanical theory and practical application in elite sports like football (soccer) and rugby.

Addressing Criticisms of Force-Velocity (FV) Profiling

Morin addresses recent academic pushback against FV profiling. He clarifies that many critics confuse the concept (the physics of force and velocity) with the method (field-based computations versus laboratory force plates) [09:02].

• Scales of Measurement: He emphasizes that the “microscopic” force-velocity relationship of an isolated muscle is different from the “macroscopic” system output of a whole athlete sprinting, but both are valid within their respective contexts [10:22].
• Field Methods: While force plates are the gold standard, Morin defends validated field computations (like the Samozino method) as essential for practitioners who lack expensive lab equipment [12:08].

Horizontal vs. Vertical Force Production

A key takeaway is the distinction between vertical force (used to support body weight) and horizontal force (which drives forward acceleration) [13:33].

• Orientation of Force: Morin notes that some athletes are “monsters” in the gym (high vertical force/1RM squat) but fail to translate that strength into horizontal sprinting speed because they cannot orient their force effectively [17:47].
• Assessment: To truly profile an athlete, coaches should look at both vertical capabilities (e.g., jump squat or half-squat) and horizontal sprint data to find the “weak link” [19:14].

Heavy Resisted Sprint Training

The speakers discuss the evolution of using very heavy loads (sleds or the 1080 Sprint machine) to develop maximal horizontal force [40:44].

• Specific Strength: Morin argues that if you want to develop the “force” end of the spectrum, you must use loads heavy enough to keep the athlete at low velocities (e.g., below 3 m/s), treating the sprint more like a resistance exercise than a traditional run [41:40].
• Injury Prevention: Interestingly, Morin highlights that resisted sprinting is often safer for the hamstrings than unresisted sprinting because it involves less “velocity stretch” and peak strain, making it a valuable tool during congested schedules or rehab [50:34].

In-Situ Monitoring: Acceleration-Speed (AS) Profiles

The final segment explores “invisible monitoring”—using GPS data from matches and training to build a composite profile of an athlete’s acceleration capabilities across all running speeds [54:17].

• The Concept: By plotting every acceleration event against the velocity at which it occurred, coaches can see the “true” limits of a player’s locomotive engine [56:48].
• Limitations: Buchheit raises concerns that these profiles are heavily influenced by “training content.” If a coach doesn’t design drills that allow for maximal sprints, the profile might look poor even if the athlete is fit [59:51]. Morin agrees, suggesting it be used as a descriptor of the training stimulus rather than just a fitness test [01:03:22].

Summary Table: Practical Implications

Topic	Practical Recommendation
Gym vs. Pitch	Don’t assume a big squat equals a fast start; check horizontal force orientation [17:47].
Resisted Sprints	Use heavy loads (reducing speed to ~3 m/s) to target maximal force [44:36].
Hamstring Health	Use resisted sprints as a high-force, lower-strain stimulus during busy periods [50:42].
Monitoring	Use GPS AS profiles to understand the specific locomotive demands of your drills [01:03:29].

Note: This summary was generated with the assistance of Gemini based on the original article, with the aim of translating the research into practical insights for coaches and practitioners.