What is "CRF"?
There seems to be increasing suggestion that overdoing it may be harmful. Probably better to do moderate excercise more regularly:
http://news.health.com/2010/05/11/st...ellular-death/
Quote:
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Strenuous exercise appears to stop the body’s cells from killing themselves as they’re programmed to do, a new study suggests.
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Br J Sports Med. 2008 Jan;42(1):11-5. Epub 2007 May 15.
Deleterious effects of short-term, high-intensity exercise on immune function: evidence from leucocyte mitochondrial alterations and apoptosis.
Tuan TC,
Hsu TG,
Fong MC,
Hsu CF,
Tsai KK,
Lee CY,
Kong CW.
Dr C-W Kong, Division of Cardiology, Taipei Veterans General Hospital, No 201, Sec 2, Shih-Pai Road, Taipei, 11217, Taiwan.
Abstract
BACKGROUND: Although moderate exercise can benefit health, acute and vigorous exercise may have the opposite effect. Strenuous exercise can induce alterations in the physiology and viability of circulating leucocytes, which have a causal relationship with exercise-induced immune distress. OBJECTIVES: To investigate the use of mitochondrial transmembrane potential (MTP), a functional marker of the energy and viability status of leucocytes, for monitoring the immunomodulating effects of short-term, high-intensity exercise. METHODS: 12 healthy volunteers with a mean Vo(2)max of 70.4 ml/kg/min carried out 3 consecutive days of high-intensity exercise (85% of Vo(2)max for 30 min every day). Blood samples were collected at multiple time points immediately before and after each exercise session and at 24 and 72 h after the completion of exercise. Leucocyte MTP, apoptosis and circulatory inflammation markers were measured by flow cytometry and enzyme-linked immunosorbent assays. RESULTS: MTP of peripheral blood leucocytes had declined immediately after the first exercise session and remained subnormal 24 h later. It did not normalise until 72 h after exercise. The sequential changes in MTP were consistent among the three leucocyte subpopulations (polymorphonuclear neutrophils, lymphocytes and monocytes) and were significant (p<0.05). Leucocytes displayed a gradual and incremental change in their propensity for apoptosis during and after exercise. Similarly, plasma concentrations of tumour necrosis factor-alpha and soluble Fas ligand were raised during the exercise sessions and had not normalised by 72 h after the completion of exercise. Correlation between changes in leucocyte MTP and plasma concentrations of tumour necrosis factor-alpha and soluble Fas ligand was variable, but significant for polymorphonuclear neutrophils and lymphocytes (p<0.05). CONCLUSIONS: Short-term, high-intensity exercise can lead to a significant and prolonged dysfunction of the mitochondrial energy status of peripheral blood leucocytes, which is accompanied by an increased propensity for apoptosis and raised pro-inflammatory mediators. These results support the immunosuppressive effects of excessive exercise and suggest that MTP is a useful marker of these effects.
PMID: 17504785 [PubMed - indexed for MEDLINE]