December 13, 2017

A spreadsheet for Sprint acceleration Force-Velocity-Power profiling

Written with Dr Pierre Samozino (University Savoie Mont Blanc)

Due to popular demand and frequent requests from sport practitioners and researchers, we have decided to publish a spreadsheet and tutorial for implementing our sprinting FVP field method based on split times measurements during a 30-m, all-out sprint acceleration, from a standing (2 or 3-point) start. This simple method has been initially proposed and validated against force plate data by Samozino et al. in 2016, and used afterwards in several publications (see here).

Download this spreadsheet HERE.

Watch the 10’ video tutorial here: 



This spreadsheet will automatically calculate the sprint force-velocity profile based on the following input variables: 5 split times over a 30 or 40-m acceleration, air temperature and pressure, stature and body mass of the athlete, based on the modeling of the position-time curve by an exponential function. 
After a quick adjustment of the 2 variables of the exponential model (maximal velocity Vmax and time constant Tau) to fit the actually measured split times, it will automatically display the FVP curves, the main mechanical outputs and the mechanical effectiveness. Note that you will need to install/use the Excel Solver add-in macro for this adjustment. 
For full details on the definition and practical meaning of these variables, please read this commentary paper.
In addition to exploring your athlete’s performance, it will indicate the underlying mechanical variables, and help you design more effective, individualized training content.
Furthermore, in the context of rehabilitation and return-to-sport processes, knowing an athlete’s pre-injury profile is gold to an effective, sprint-oriented rehabilitation and return-to-sport decision. See Jurdan Mendiguchia’s works on the topic in 2014, 2016 and 2017.
This “profiling” test may be done with only 4 split times (5, 10, 20, and 30m), but for more accuracy we recommend using 5 or 6.

As to the devices needed, well, it’s up to you, any device that accurately measures split times may be used: timing gates, iOS app MySprint, etc… But one thing is important to keep in mind: the most important thing to ensure that the measurements are valid and the data make sense is that the time measurement starts as soon as any propulsive action is produced. So what we recommend if you are using timing gates and not the iOS app MySprint, is that a system that reacts to the athlete’s first propulsive action triggers the timing (see review here). In case of a trigger by a first pair of cells (eg 20 or 50 cm in front of the athlete’s starting position), the split times will be underestimated, and thus F0 and Pmax variables will be largely overestimated. This is how soccer players are sometimes described as “faster than Bolt” in the News! When using this starting procedure, the athlete’s body has in fact a high forward velocity at the moment of triggering, which leads to erroneous values and performance/mechanics overestimations. For the same reasons, a standing start from a still position must be used.

Finally, this is a short list of normative values for the different mechanical variables, ranging from physically active (male) individuals with no specific sprint experience to elite athletes (mostly rugby players or sprinters), based on our own experience (please see the literature on the topic for more details).

F0 (N/kg): from 3-4 to 10-12 N/kg
V0 (m/s): from 5 to 12 m/s
Pmax (W/kg): from 6-7 to 25-30 W/kg
RF max (%): from 20 to 60%
Drf (%): from -10 to -4%

Note that our group will soon publish an extensive database for both male and female athletes. 
Should you obtain values beyond these standards, don’t blame the method or the spreadsheet, the issue is with the device used to measure split times, and/or the starting/triggering procedure. See our recent discussion on these overestimations here.

Using this model, this is the FVP profile of Usain Bolt during the current 100-m World Record:
  
Usain Bolt's 100-m record force-velocity-power profile

Ready, Set, Enjoy! 




3 comments:

  1. Dr. Morin,
    How do you propose one use external mechanical power-time signature to train effectively? Would the goal be to see maximum power delivery or the rise time of the power-time signal or both? Secondly, what is the implication of not being able to quantify internal power to move hands and limbs? This appears to be a significant omission to the analysis and (unfortunately) there maybe no easy field based way to quantify this? Shouldn't additional accelererometers on the hands for example be able to communicate this information to a center accelerometer?

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    1. Hi Ron, thanks for your comments,
      the training associated with the "signature" has been partly addressed in our invited comment in International Journal of Sports Physiology and Performance and we've started to run some experimental studies to test what training intervention is useful to improve what variable in the profile (eg recently published study on the effects of very heavy sled on the "Ratio of Force" variable
      Our approach is based on an integrative approach based on the overall motion of the body so yes we can not assess "internal" work but as it relates to sports performance the most important is how body moves relative to the ground rather than how segments move relative to the body
      as you said, no easy way to quantify it !!
      accelerometers may be a track of research, but tough game ! to eventually know something that may not be relevant to performance on the track/field, i.e. how segments move around the CoM
      jb

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  2. Your site is very useful for me,Thanks for your sharing.

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