The First Council of Nicea 325 a.d. in the 20th canon forbade kneeling
HAMMOND: Although kneeling was the common posture for prayer in the primitive Church, yet the custom had prevailed, even from the earliest times, of standing at prayer on the Lord's day, and during the fifty days between Easter and Pentecost. Tertullian, in a passage in his treatise De Corona Militis, which is often quoted, mentions it amongst other ohservances which, though not expressly commanded in Scripture, yet were universally practised upon the authority of tradition. "We consider it unlawful," he says, "to fast, or to pray kneeling, upon the Lord's day; we enjoy the same liberty from Easter-day to that of Pentecost." De Cor. Mil. s. 3, 4. Many other of the Fathers notice the same practice, the reason of which, as given by Augustine; and others, was to commemorate the resurrection of our Lord, and to signify the rest and joy of our own resurrection, which that of our Lord assured. This canon, as Beveridge observes, is a proof of the importance formerly attached to an uniformity of sacred rites throughout the Church, which made the Nicene Fathers thus sanction and enforce by their authority a practice which in itself is indifferent, and not commanded directly or indirectly in Scripture, and assign this as their reason for doing so: "In order that all things may be observed in like manner in every parish" or diocese.
HEFELE: All the churches did not, however, adopt this practice; for we see in the Acts of the Apostles(xx. 36 and xxi. 5) that St. Paul prayed kneeling during the time between Pentecost and Easter. This canon is found in the Corpus Juris Canonici. Decretum, Pars III, De Cone. Dist. III. c.
x.
http://www.fordham.edu/halsall/basis/nicea1.txt
Well, perhaps.
The Canon is cited in its entirety, along with commentary--names of commentators are in caps.
Clearly, although Nicea decided that "for uniformity" standing was preferable (thus enjoined,) the practice was sanctioned by such as St. Paul.
Evidently many followed the practice of kneeling, (some regardless of Nicea's command) and the practice returned.
We can conclude that the "Sensus Fidelium" was in favor of kneeling, as it is today.