Hello Colleagues,

 

Is anyone else using the spring-mass (SM) model to understand their own or another runner's performance?

 

I modified my home treadmill so I can capture my step-frequency and duty-factor (stance time/step time) from a standstill (v=0 m/s) to my maximum velocity (4 m/s = 9 mph = 6:45 min/mile).

 

From my step-frequency at zero velocity I can compute my leg-stiffness.  If I put that value into the model, it comes close to predicting the step-frequency and duty-factor I measure on the treadmill (Exp).

 

 

I am unable to measure my vertical CM Displacement while running so I can't verify the CM displacement from the model.

 

The model also calculates the mechanical energy expended in spring compression and the specific power (watts/kg) expended in mechanical spring compression. 

 

The “Power Spring/mass” curve in the lower right graph that is close to the specific power expended by a mid-pack cyclist of 3 to 4 watts/kg.  In addition, 3 watts/kg is about a third of the typical value for metabolic Cost of Transport of 1 Kcal/(Kg-Km).
 
Does anyone else work with the model to understand his, her or other runners’ performance?

 

Ted Andresen
Math Department
St. Petersburg College
St. Petersburg, Florida

 

The output from the SM model is at: