Make script run faster or acceleration integration problems

I am trying to implement "dead reckoning" using IMU in my Unity project. Currently I can't get good results: the velocity gets negative, so the character moves backwards, or the character sometimes comes forth and back after moving IMU just forward. I suspect the frequency of script being called is not as high as IMU data sending frequency or my script is incorrect.
Is there a way to make the method/script called more often? Or is there something I'm doing wrong in the code:

Code (CSharp):

1.     /// <summary>
2.     /// This is the coroutine called in the start Method. It keeps running in the background and keeps track of the user making steps.
3.     /// </summary>
4.     /// <returns>WaitForSeconds</returns>
5.     IEnumerator StepcounterLeft()
6.     {
7.         float prev_zVel = 0;
8.         float prev_zAcc = 0;
9.        
10.         for (var a = 0; a < 1;)
11.         {
12.             yield return new WaitForSeconds(0.0001f);
13.  
14.             float zAcc = (float)vn100l.CurrentMeasurements.LinearAccelerationBody.Z;
15.             float zVel = prev_zVel + (prev_zAcc + ((zAcc - prev_zAcc)/2.0f)*Time.deltaTime);
16.             if (zVel > -0.1 && zVel < 0.1)
17.                 zVel = 0;
18.             speed = zVel / 10;
19.             prev_zVel = zVel;
20.             prev_zAcc = zAcc;
21.             if ((zAcc > -0.1 && zAcc < 0.1) && (prev_zAcc > -0.1 && prev_zAcc < 0.1))
22.                 prev_zVel = 0;
23.         }
24.     }