If the skin isn't as flexible (it will be in due time) then exercise could cause it to stretch quickly from increased blood flow. This quick stretch could explain the pins and needles feeling because the skin is quickly being pulled on the micro-level.
Definition. During development, most animals form a gastrula. A gastrula is an embryo that has undergone gastrulation, or the process that produces different germ layers. Germ layers are the initial tissue layers of an embryo, and animals can have up to three. 1  Ectoderm is the outermost layer of cells.
Ectoderm and endoderm are the primary embryonic germ layers which induce the two secondary germ layers, mesoderm and neural crest cells. Given the diverse structures made by neural crest cells, some consider it to be a fourth germ layer of the embryo, in addition to ectoderm, endoderm, and mesoderm.HE NEURAL CREST. A unique group of important embryonic cells called neural crest cells were a vertebrate innovation. Neural crest cells develop into a number of cell types including sensory neurons, adrenergic neurons, cholinergic neurons, Rohon-Beard cells, satellite cells, and glial cells.