Julian of Halicarnassus (d. 527) was condemned at a council in Constantinople in 536. In denying a distinction between ousia (common essence) and physis (particular nature), Julian was faced with the problem of explaining how the one nature of Christ (which was both human and divine) could suffer, since impassibility was a natural property of the divine nature. He argued that since the corruption of sin is the source of suffering and weakness, the Son took on human nature as it was before Adam's sin (a prelapsarian humanity), and therefore His body was incorruptible from the moment of the Incarnation—before as well as after the resurrection. He maintained that it was not the necessity of nature that compelled Christ to suffer the weaknesses of human nature, but that He had subjected Himself to them for the economy of salvation.
Many moderate Monophysites were uncomfortable with his extreme solution to this question, because it strongly suggested that Christ's humanity was only an appearance and seemed to lead to Gnostic docetism. Severus of Antioch, a Miaphysite, became one of Julian's most vocal critics, arguing that Christ's human nature before the resurrection was corruptible and passible because He took on our fallen human nature as it was after Adam's sin from the Theotokos.
In Lutheran and Calvinian Christology, although Christ took on human nature fully, it was a human nature without sin. Whereas Adam became subject to suffering, death and corruption after his sin, Christ was born of the virgin Mary, by taking on human nature as it was before Adam's sin. In this way He was not enslaved by sin, nor was His human body corruptible. From the very beginning of His Incarnation His sinless human nature was perfectly united with His divine nature without confusion or change, and for this reason one in being with God can be said of the Son. After His resurrection, Christ appeared glorified in the flesh. This glorification was not something which was added after the resurrection. Instead, it was only after the resurrection that His perfect humanity, which He had possessed from the very beginning of the Incarnation (and which was revealed to the disciples on Mount Tabor), became apparent to all.
Historically speaking only extreme Monophysites who hold Aphthartodocetism, even Severus a Miaphysite condemned this heresy. The basis of this heresy is not in the incorruptibility of Christ's flesh but in its insistence that He took on human nature as it was before Adam's sin. It's this later view which was held and shared by Luther and Calvin, including all early reformers.
Were Luther and Calvin Aphthartodocetists?
To answer this question I can think of two plausible approaches:
First by arguing to the contrary that they believe Christ took on human nature as it was after Adam's sin (a postlapsarian humanity)
By arguing that a belief in Christ took on a prelapsarian humanity is not Aphthartodocetic. Plausible difficulty one needs to face if choosing the first approach is to explain how from a Lutheran or Calvinian theology a postlapsarian Christology wouldn't make Christ guilty of original sin, while if choosing the second approach I believe it would be even harder to show.
[W]e want to discern what evidence we may find within the history of Christology and soteriology which would found, advance, and confirm our proposition that Jesus was born of the fallen race of Adam and that such a condition was absolutely indispensable for our salvation.
Thomas Weinandy, In the Likeness of Sinful Flesh: An Essay on the Humanity of Christ, 1993, p. 21.