A couple of glaring weaknesses, especially if this model is to find an application either you need to assess superiority over current models or make refinements to current models and I didn’t find this to be true. It’s not that I could have done better, I have been trying for 3 or 4 years now to do what you just did and obviously I haven’t come close. I am still collecting papers and having trouble expressing the thoughts into written words.
You have 3 Mero and Komi references which are not balanced by the majority of research papers in existence regarding Newtonian physics aka Classical Mechanics and sprinting.
No James Hay references, Hay has a great review article discussing step length and stride rate of acceleration. You did reference an article of his understudies I believe.
No Blickhahn, Farley, Hegland, Taylor, or McMahon references, you did reference Weyand, but even Weyand’s work has plenty of background from the aforementioned authors of what I would term as necessary and classical references concerning classical mechanics, modeling, and sprinting. If you are going to reference Weyand then you need to reference one of these giants as they are the link from Cavagna and Alexander to Weyand.
In no way does this invalidate your article, but I believe to apply your model to sprinting you need to show greater account of the existing models which describe movement already and not just the originators of said of models.
lastly, application of the model to other data, Coh’s subject and Johnson’s 1987 WR or Greene’s 1999 WR is fine, but apply the model to other existing sets of data and provide how well the model fits and if it doesn’t fit some data from differing data sets where does it fall apart. I would have tried to fit it to as much data as humanly possible.
Overall its a great paper and provides a ton of insight, the Di Prampero and Hunter references are something I liked seeing.
Firstly, the article is not intended to be superior to other models because I haven’t yet found a model that attempts to convey how much resistance to train against when training for sprinting. Whilst various researchers show the force produced during the start, first step, second step, 14-16m mark and top speed of approx 9.5 m/s I felt the need to know how much force is produced during the entire acceleration. In this way, training methods could be modified or developed in order to be more velocity or movement specific. For example, when nearing maximum speed only between 10 and 15 kg of horizontal force needs to be produced although it must be realised at great angular velocity. Therefore, when doing an exercise such as cable-kickbacks one only needs to lift this amount and move the leg at a practical speed. Strength training with this specificity would allow an adaptation in the prime moving muscles that could be progressed over time.
This model is described as Newtonian simply because we use Newton’s equations of motion. It is intended to be simple enough to be able to supplement a coaches plan. The classical work of researchers such as Blickhan, Farley, McMahon (spring mass) or research work on energy systems are difficult to relate to training methods for most coaches. The tools readily available to coaches are resistance training, plyometrics, ballistic jump squats, Olympic lifts, hill running etc. for which I’m hopeful the Newtonian model can provide some guidelines (on horizontal force). The work of the respected aforementioned researchers on the contribution of elastic recoil of muscle-tendon complexes is appreciated in the calculation of forces produced per stride as the forces are as a result of such mechanisms. Instead of focusing on internal mechanisms that are rather complex, the sprinter just needs to know that they should produce a horizontal force of the order of 79 kg from a split stance that would replicate the stance in a starting block, in 300 milliseconds. If they can’t then why not? A coaching strategy could be to focus on speed of movement if the sprinter can lift this load already, and a reasonable guide is to be able to take a first step length of 1.23 metres as a result. From there the step length should increase gradually as this could make efficient use of fuel sources within the muscle. The Newtonian model is a guide, a point of reference to help coaches who I’m sure would not take the information as the gold standard and take into account the various individual differences in their sprinters.
Apologies for the long explanation here. I tried to keep the Newtonian model article as short as possible as well.