This is the second phase of a study designed to determine the immunological effects of long-term exercise on risk factors for ischemic heart disease (phase 1) and osteoporosis (phase 2). The results indicate that six months of moderate intensity exercise reduces bone resorption and increases the secretion of anti-osteoclastogenic cytokines by peripheral blood mononuclear cells.

In a before and after trial involving 43 healthy adults the investigators measured the effect of six months of supervised exercise on the spontaneous and phytohemagglutinin-induced production of osteoclastogenic cytokines (interleukin-1α, tumor necrosis factor-α), anti-osteoclastogenic cytokines (transforming growth factor-β, interleukins 4 and10), pleiotropic cytokines with variable effects on osteoclastogenesis (interferon-γ, interleukin-6), and T cell growth and differentiation factors (interleukins 2 and 12) by peripheral blood mononuclear cells. The investigators also measured lymphocyte phenotypes, and serum markers of bone formation (osteocalcin), bone resorption (C-terminal telopeptides of Type I collagen), and bone homeostasis (estradiol, vitamin D2, testosterone, parathyroid hormone, insulin-like growth factor).

Inclusion Criteria:

• Normal exercise treadmill test

Exclusion Criteria:

• Any medical condition that would prevent participation in a six month exercise program