THE RACING CAMEL (CAMELUS-DROMEDARIUS) - PHYSIOLOGY, METABOLIC FUNCTIONS AND ADAPTATIONS

1. Studies were performed on the one humped camel (Camelus dromedarius ) bred and trained to perform in races over distances of 4-10 km. Came l racing has become popular in several Gulf Arab countries, but is wel l established in the United Arab Emirats. The studies were performed i n Al Ain, Abu Dhabi. 2. Few changes occurred in haematology and serum biochemistry associated with season or training. This stability of val ues provides a useful basis for monitoring the health of camels during racing and training. However, resting haematology and serum biochemis try does not provide information on changes in training status. 3. The re is considerable variation in the fibre type composition of the m. g luteus medius when repeated biopsy samples were analysed from the same camels. Some variation was also found between camels, although consis tent trends were evident for all muscles sampled. Most of the major lo comotor muscles have a predominance of type I fibres with few or no ty pe IIb fibres. 4. Energy metabolic enzymes both of the glycolytic and oxidative pathways were high, with a surprisingly low ratio of beta-ox idation to Krebs cycle enzymes. Some triglycerides were present in the muscle but the glycogen content was much more dominant. 5. Type I fib res were recruited preferentially during prolonged low intensity exerc ise. In contrast type IIa fibres were preferentially recruited during high intensity exercise of short duration. However, the glycogen deple tion patterns indicated that both fibre types were recruited during mo derate and high intensity exercise. 6. Camels have a low resting oxyge n uptake and a high locomotor efficiency, with a low relative oxygen c ost per kg per km travelled, compared with the horse, burro, donkey an d man. Over speeds ranging from 2 to 8 m s-1, the oxygen cost of exerc ise was around 75 ml kg-1 km-1. 7. The maximal oxygen uptake was aroun d 55-60 ml kg-1 min-1 in most camels. These values are much lower than racehorses of comparable bodyweights because of lower [Hb] and lower heart rates during maximal exercise. The small increase in [Hb] during exercise was coincident with some water movement out of the circulati on as reflected by an increase in total protein. 8. Moderate and high intensity exercise were characterised by pronounced carbohydrate rathe r than fat utilisation. However, the onset of blood lactate accumulati on in racing camels did not occur until exercise intensities were abov e 90% of maximal oxygen uptake. During prolonged, moderate intensity e xercise, there appeared to be expansion of the plasma volume, rather t han contraction as is common in other species. 9. Camels have an unexp ectedly high anaerobic capacity, given their traditional background as a beast of burden. During very high intensity exercise (above maximal oxygen uptake), substantial concentrations of lactate are produced in skeletal muscle. Over the distances and speeds used in camel racing, lactate was also used as a substrate. 10. During a simulated 8 km race on the treadmill, there was a substantial decrease in creatine phosph ate and a small decline in muscle ATP in the early part of the race. L actate in muscle and blood showed a gradual decline as the exercise co ntinued. In contrast, when the race was run at an even pace, these cha nges were not seen until the end of the race, when the exercise intens ity was increased. 11. Low intensity training, although of long durati on, resulted in few changes in the metabolic capacity of muscle or in maximal oxygen uptake. High intensity training was not only needed to obtain some effect on the anaerobic but also on the aerobic capacities .