Parathyroid hormone concentrations during and after two periods of high intensity exercise with and without an intervening recovery period

The purpose of this study was to examine the effect of a recovery period between two periods of exercise on bone metabolism and related hormones. Concentrations of serum parathyroid hormone (PTH]), plasma ionized calcium (Ca²⁺]) and total calcium were measured. A group of 12 healthy men aged 20–27 years participated in this study. They took part in two exercise protocols (P₁ and P₂) on two separate weeks. The exercise in P₁ comprised two successive periods of 21 min each at 70% and 85% of maximal oxygen uptake; P₂ comprised two periods of exercise at the same intensities but separated by 40 min of recovery. Venous blood samples were collected 1 day before the sessions (control), before each protocol, during (7th and 21st min), at the end (42nd min in P₁ and 82nd min in P₂) and after 24 h of recovery. The PTH] was significantly elevated during the two protocols (P<0.01), remained raised in P₁ after 24 h of recovery (P<0.05) and was significantly lower (P<0.01) at the end of P₂ when compared to P₁. The Ca²⁺] decreased significantly during and at the end of the two protocols (P<0.01) and had returned to control values after 24 h of recovery. Plasma lactate concentration increased during the two protocols (P<0.01) and returned to control values after recovery. These results indicate firstly that Ca²⁺] decreases during continuous exercise as PTH] increases and remains raised after 24 h of recovery, secondly that a recovery period between two periods of exercise attenuates the variations in Ca²⁺] and PTH], and thirdly that recovery may have anabolic effects on bone. However, the small physiological changes observed prevent us from forming any firm conclusion about this. Electronic Publication