Iowa Code 598.21(8A) (1999): Section 598.21(8A) changed at least one facet of the law applicable to custody modification requests. Prior to section 598.21(8A), "Iowa courts had historically recognized society's mobility and had not fixed or changed custody based on one party's move from an area where both parents resided absent other circumstances." In re Marriage of Crotty, 584 N.W.2d 714, 717 (Iowa App. 1998) (citing In re Marriage of Vrban, 359 N.W.2d 420, 425 (Iowa 1984), and Frederici, 338 N.W.2d at 161). After section 598.21(8A), a court may consider a move of 150 miles or more, by itself, to be a substantial change in circumstances. Crotty, 584 N.W.2d at 717. Thus, the statute tempers the ability of a parent who is responsible for his or her children's physical care to relocate. Williams, 589 N.W.2d at 762. Section 598.21(8A) does not change the burdens of proof applicable to custody modification requests. As is clear on its face, section 598.21(8A) does not eliminate the requirement a parent requesting either a visitation modification or physical-care modification must prove the requisite change in circumstances. Nor does it eliminate the requirement a parent requesting a physical-care modification must also prove he or she has the ability to minister more effectively to the well-being of the parties' children. After stating "the court shall modify the custody order" if the court determines a move of 150 miles or more is a substantial change in circumstances, section 598.21(8A) states "if modified, the order may include a provision for extended visitation during summer vacations and school breaks and scheduled telephone contact between the nonrelocating parent and the minor child." Thus, if a party proves only a substantial change in circumstances, section 598.21(8A) explicitly contemplates only a visitation modification. This does not mean section 598.21(8A) is not applicable to physical-care modification requests. Rather, it confirms the statute is consistent with modification cases like Frederici that require a parent requesting a physical-care modification to prove a substantial change of circumstances and an ability to minister more effectively to his or her children's well-being. In other words, by implication section 598.21(8A) preserves the second element of the burden of proof applicable to physical-care modification requests.