Help With Sprinting Audio

I followed a tutorial in C# and i mainly have knowledge in Javascript and i would like to know how i would add a sprinting mechanic to the script below using UnityEngine; using System.Collections;

 public class footStep : MonoBehaviour {    
 
     public AudioClip[] footsteps;    
     public float nextFoot;    
 
 IEnumerator Start () 
     {         
     CharacterController controller = GetComponent<CharacterController>();
 
     while(true){ 
         if(controller.isGrounded && controller.velocity.magnitude > 0.3F){  
 
         audio.PlayOneShot (footsteps[Random.Range(0, footsteps.Length)]);    
         yield return new WaitForSeconds(nextFoot); 
 
         }else{ 
 
         yield return 0;  
                 }
             }        
         }
     }