[This is a guest blog by John Evans. John is an Exercise Science student at Slippery Rock University and participated in the summer internship program at Athletic Lab]
When it comes to sprinting, max velocity is extremely important. Force plate research from Peter Weyand shows us that the ability to apply large mass specific vertical forces with minimal ground contact times are the main limiting factor in running at top end. If an athlete is unable to apply force vertically, they are slowing down or braking. In addition to these findings, Carl Valle’s blogs on plyometrics cited Jon Goodwin in saying “The athletes cannot run any faster because they won’t be able to generate sufficient [appropriate]airtime to recover their swing leg.” The reason they are unable to create sufficient airtime is because they aren’t able to apply a large enough force. Another article Carl Valle posted mentions Al Vermeil’s force / velocity curves, but fails to mention information on the use of a weighted vest. Granted there is little longitudinal research (that I have seen) on the use of weighted vests in elite sprinters, it seems that a quick analysis on the rationale and use of weighted vests is necessary.
Top end sprinting is an odd bird in that there doesn’t seem to be significant improvement by doing modalities that have been shown to increase acceleration. Acceleration and Max Velocity appear to be very different physical qualities. This is logical in that weightlifting, med ball throws, and plyometrics all have ground contact times that are much longer than anything seen during max velocity sprinting. There is simply not enough time to produce large vertical forces. Although a weighted vest has been shown to increase ground contact time, and decrease flight time, it is interesting to speculate the training effect that sprinting with a light weight vest (~5%) would have on top end mechanics.
The rationale behind using a weighted vest include:
- Increased Eccentric Demand: The amount of total stiffness from soft tissue would increase due to greater mass
- Greater Neural Demand: The stretch is larger and therefore overloads the stretch reflex
- Short Ground Contact Times: Although longer, the ground contact times would ideally be shorter than what is seen in any other modality. This is why the weight must be very low
- Specificity: The athlete is still sprinting with correct top end mechanics
- Force Vector: The resistance is being overcome by vertical forces, which appears to be the limiting factor in top end sprinting
Because no longitudinal research has been done on elite sprinters (as usual), the application is somewhat limited to case study type experience. I would suspect it would fit nicely on max velocity days as a lead in to speed endurance. I would also expect that max velocity volume would be capped at around 150 meters per week depending on what set up you decide to use.