99% of our body’s calcium is stored in our bones with the other 1% being stored in the muscle. Calcium is critical for muscle contractions, but if our muscles are start to run low on calcium they can simply extract more from the bone. This is why calcium intake is so important for the athlete or bodybuilder – maintaining bone density and strength is crucial for long term health and gains!
Reference: Dressendorfer, R. H., Petersen, S. R., Lovshin, S. E. M., & Keen, C. L. (2002). Mineral metabolism in male cyclists during high-intensity endurance training. International Journal of Sport Nutrition and Exercise Metabolism, 12(1), 63-72.