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During intense exercise, lactic-acid accumulates in skeletal muscle and protons build up which causes a decrease in pH and leads to inhibition of muscle function and eventually fatigue. A family of Monocarboxylate Transporters (MCTs) have been identified in equine skeletal muscle but its function during training has not yet been fully elucidated. We hypothesize an important function of MCT1, 2 and 4 in equine muscle. Six Standardbred geldings were trained for a total of 22 weeks in 2 phases (endurance phase and high intensity phase). Exercise intensity during the training sessions were based on fixed percentages of the peak heart frequency (HRpeak) determined during a Standard Exercise Test (SET). At the beginning and end of each phase a SET was performed. Venous blood was drawn from the jugular vein before the test (t=0 minutes), after the warming up (t=9 minutes), and every 5 minutes during the SET (t=14, 19, 24, 29, 34). Samples were kept on ice until whole blood lactic acid had been analysed. Muscle biopsies were taken approximately 60 minutes before each SET using a modified Bergström biopsy needle. Blood and fat tissue were removed from the biopsy and the biopsy was there after immediately frozen in liquid nitrogen for biochemical analysis and Western-blotting for MCT expression. Training (SET1 vs SET2) resulted in an increase in the total plasma lactic acid accumulation during exercise as measured as the area under the curve during the 20-minute endurance run in the SET. Semi quantative densitometric analysis of the blots showed that MCT1 and MCT4 remain unaltered upon training. MCT2 expression was non-significantly increased by more than 60%. We report the expression of MCT1, MCT2 and MCT4 proteins in skeletal muscle of Standardbred trotters during a physical training regimen. The relative high expression of MCT2 was surprising but fits well with the gastrointestinal function of the horse. The high expression of MCT2 suggests an important function in the absorption of short chain fatty acids although such function needs further investigation.

Int J Sports Med 2001 May;22(4):291-4 Related Articles, Books, LinkOut Validation of a computerized metabolic measurement system (Oxycon-Pro) during low and high intensity exercise. Rietjens GJ, Kuipers H, Kester AD, Keizer HA. Department of Movement Sciences, Maastricht University, The Netherlands. Gerard.Rietjens@bw.unimaas.nl The aim of the study was to validate a new, fast metabolic measurement system (the Oxycon-Pro) during low and high exercise intensities against the Douglas bag method. For this purpose twelve highly trained subjects performed an incremental cycle ergometer test. In the third minute of each exercise step simultaneous measurements of the Douglas bag and the Oxycon-Pro were performed. No significant differences between the Oxycon-Pro and the Douglas bag measurements for minute ventilation (VE), oxygen uptake (VO2) and carbon dioxide expiration (VCO2) were found. Bland and Altman analysis of validity demonstrated minimal bias and low standard deviations. In conclusion, the results show that the Oxycon-Pro is a valid apparatus for determination of minute ventilation (VE), oxygen uptake (VO2) and carbon dioxide expiration (VCO2) during low as well as during maximal exercise intensities. Unlike with the Douglas bag method, this fast metabolic measurement system can be used for accurate and quick determination of ventilatory variables during exercise.

[Long-term intensive athletic training; few adverse effects on later physical health] [Article in Dutch] Kuipers H, Keizer HA, Schep G, Hoogeveen AR. Universiteit Maastricht, vakgroep Bewegingswetenschappen, Postbus 616, 6200 MD Maastricht. harm.kuipers@bw.unimaas.nl In general, physical activity benefits health. However, long-term intensive physical training may have detrimental effects on the health of some individuals. In cyclists, changes in the femoral arteries may occur leading to stenoses that are manifested in claudication type symptoms. Some endurance athletes may experience atrial fibrillations that are possibly related to long-term physical training. Older athletes only have an increased risk of osteoarthritis in joints that have suffered injuries. Menstrual disturbances and premature osteoporosis may occur in women as a consequence of intensive physical training. However, the risk for these adverse consequences of long-term physical training is small