Both increased net Ca absorption and increased net bone mineral formation will cause the Ca isotope composition of blood and urine (d44Ca) to shift in a positive direction. This is the natural Ca isotope composition, not anything involving tracers. See, for example:

Channon M, Gordon GW, Morgan JLL, Skulan, JL, Smith, SM, Anbar AD. Using natural, stable calcium isotopes of human blood to detect and monitor changes in bone mineral balance. Bone 2015; 77: 69-74; DOI: 10.1016/j.bone.2015.04.023.

I think this article is available here.

Yes, Shanaz, there are several articles that support calcium absorption after load-bearing exercise (or resistance training). Kodkararan et al (2014) reported that  intake of calcium and phosphor supplement along with resistance exercise led to more increase of osteocalcin, parathyroid, alkaline phosphatase, calcium and phosphor of the body compared with the resistance exercise alone. These measures are indices of bone density and are important in understanding treatment for osteoporosis (see link, below). Calcium in blood is not an indicator of calcium absorption so measures of ostocalcin, parathyroid hormone, and alkaline phosphatase are better indicators of calcium absorption.

http://pelagiaresearchlibrary.com/european-journal-of-experimental-biology/vol4-iss5/EJEB-2014-4-5-72-75.pdf

Both increased net Ca absorption and increased net bone mineral formation will cause the Ca isotope composition of blood and urine (d44Ca) to shift in a positive direction. This is the natural Ca isotope composition, not anything involving tracers. See, for example:

Channon M, Gordon GW, Morgan JLL, Skulan, JL, Smith, SM, Anbar AD. Using natural, stable calcium isotopes of human blood to detect and monitor changes in bone mineral balance. Bone 2015; 77: 69-74; DOI: 10.1016/j.bone.2015.04.023.

I think this article is available here.

With our patients we routinely monitor fasting calcium, phosphorus, total protein, albumin and globulin. I have found chronic infections [in the mouth], chronic inflammation [from different sources] and digestion problems [that lower the amino acid pool quantity] - all can pull bone minerals out.. We use the ionized calcium, albumin corrected formula to verify a reduction in ionized calcium that reflects a lowering of the free calcium risk, responsible for so many pathology.

Thank you to set an interesting question, well documented answers that might serve many useful things to learn!