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.
The surface ectoderm (or external ectoderm) forms the following structures: 1  Skin (only epidermis; dermis is derived from mesoderm) (along with glands, hair, and nails).2  Epithelium of the mouth and nasal cavity salivary glands, and glands of mouth and nasal cavity. Epithelium of the mouth and nasal cavity salivary glands, and glands of mouth and nasal cavity. 2  Tooth enamel (as a side note, dentin and dental pulp are formed from ectomesenchyme which is derived from ectoderm (specifically neural crest cells and travels with mesenchmyal cells).