For sprinters running at 6 m/sm/s around a curved track of radius 26 mm, how much greater (as a percentage) is the average total force on their feet compared to when they are running in a straight line

The percentage is   1.02%

Explanation:

From the question we are told that

   The speed of the sprinter is  

    The radius of the curve is  

The centripetal acceleration at the curve is mathematically represented as

substituting values

Now the force acting on the sprinter around the curve are

      which represents centripetal force which  is mathematically evaluated as

   and   which is the centrifugal force which is generally represented as

Now the resultant force which is the force acting on the sprinter when running around the curve is mathematically represented as

substituting values

the average total force on their feet compared to when they are running in a straight line is mathematically evaluated as

    1.02%