The effect of endurance exercise-induced lactacidosis on biochemical markers of bone turnover.
BACKGROUND
Stress fractures are frequent injuries among athletes. In vitro, decreases in pH stimulate osteoclasts and inhibit osteoblasts. We hypothesized that exercise-induced lactacidosis stimulates osteoclasts and reduces osteoblast activity in vivo.


METHODS
A total of 32 volunteers (MA, male athletes; MCo, male controls; female athletes; and female controls) performed three 60-min cycle ergometer tests at 75%, 95% and 110% of their individual anaerobic threshold (IAT). Blood was taken before and at 3 and 24 h after exercise. Osteocalcin (OC), pro-collagen type I N-terminal peptide (PINP), C-terminal telopeptides of collagen I (CTx) and tartrate-resistant acid phosphatase (TRAP) were measured.


RESULTS
At 75% and 95% IAT, pH did not change. At 110% IAT, pH decreased in MA by 0.08 units (p=0.041) and in MCo by 0.03 units (p=0.017). The pH results were substantiated by circulating lactate concentrations. The bone resorption markers TRAP and CTx were not consistently modified by any of the exercise tests. Exercise at 75% decreased OC and PINP in all groups. Exercise at 95% and 110% did not induce homogeneous effects.


CONCLUSIONS
Anaerobic exercise does not systemically affect bone turnover, suggesting that exercise-induced acidosis is not involved in the pathogenesis of stress fractures.
Herrmann
Markus
M
Department of Clinical Chemistry and Laboratory Medicine, University Hospital of Saarland, Homburg/Saar, Germany. markusherr@aol.com
Müller
Miriam
M
Scharhag
Jürgen
J
Sand-Hill
Marga
M
Kindermann
Wilfried
W
Herrmann
Wolfgang
W
D000135:Acid Phosphatase / Q000097:blood; D000140:Acidosis, Lactic / Q000473:pathology*; D000328:Adult; D015415:Biomarkers / Q000097:blood*; D001842:Bone and Bones / Q000378:metabolism*; D024042:Collagen Type I / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000097:blood; D008297:Male; D015675:Osteocalcin / Q000097:blood; D010446:Peptide Fragments / Q000097:blood; D010807:Physical Endurance / Q000502:physiology*; D011347:Procollagen / Q000097:blood; D000071681:Tartrate-Resistant Acid Phosphatase; D013997:Time Factors
D015415:Biomarkers; D024042:Collagen Type I; D007527:Isoenzymes; D010446:Peptide Fragments; D011347:Procollagen; C047202:procollagen Type I N-terminal peptide; D015675:Osteocalcin; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase