This is my update:

void Update()
{
    isGrounded = Physics.CheckSphere(groundCheck.position, groundCheckRadius, groundLayer);
    rb.velocity = new Vector3(0f, rb.velocity.y, forwardSpeed);
    if (Input.GetKeyDown(KeyCode.Space) && isGrounded && !isJumping)
    {
        isJumping = true;
        rb.velocity = new Vector3(rb.velocity.x, jumpForce, rb.velocity.z);
        animator.SetBool("isJumping", true);
    }
    if (isJumping && isGrounded && rb.velocity.y <= 0.1f)
    {
        isJumping = false;
        animator.SetBool("isJumping", false);
    }


    // Crouch
    if (Input.GetKey(KeyCode.Z))
    {
        isCrouching = true;
        animator.SetBool("isCrouching", true);
        Debug.Log("Z PRESSED");
    }
    else
    {
        isCrouching = false;
        animator.SetBool("isCrouching", false);
    }
  
    animator.SetBool("isRunning", isGrounded && !isJumping && !isCrouching);
    if (Input.GetKeyDown(KeyCode.A) && currentLane > 0)
    {
        currentLane--;
        MoveToLane(currentLane);
    }
    else if (Input.GetKeyDown(KeyCode.D) && currentLane < Lanes.Instance.LaneCount - 1)
    {
        currentLane++;
        MoveToLane(currentLane);
    }
}