Re: Scapegoat for Iowa Hawkeye Rhabdomyolysis Scandal
Even exercise can kill you.
I want to learn more about why some of players were more susceptible than others.
It is interesting that some people are more prone than others. This is true for animals as well, and is of particular importance to horse breeders. There have been some experimental studies on why some individual horses are more prone to exertional rhabdomyolysis (studies that would be unethical if performed on people). Apparently, the incidence of rhabdo in these horses is affected by diet:
Finno CJ, McKenzie E, Valberg SJ, Pagan J.
Effect of fitness on glucose, insulin and cortisol responses to diets varying in starch and fat content in Thoroughbred horses with recurrent exertional rhabdomyolysis. Equine Vet J. 2010;42:323-328.
Reasons for performing study:
Recurrent exertional rhabdomyolysis (RER) occurs in fit, nervous Thoroughbreds fed high nonstructural carbohydrate (NSC) diets. Clinical signs are diminished by feeding low NSC, high fat diets; however, the mechanism is unclear.
Objective: To determine if the glucose, insulin and cortisol response to isocaloric diets varying in fat and NSC availability differ in fit vs. unfit Thoroughbreds with RER.
Materials and methods: Four fit (10 weeks treadmill training) RER Thoroughbred mares were exercised and fed 3 isocaloric (121 MJ/day) diets in a 5 day/diet block design. Two high NSC concentrates, sweet feed (SF) and a processed pelleted feed (PL) and a low starch high fat feed (FAT) were used. After 24 h of rest and a 12 h fast, horses ate half their daily concentrate. Blood sampled for [glucose], [insulin] and [cortisol] was obtained before, immediately after and at 30–60 min intervals for 420 min. After 3–6 months detraining period, the block design was repeated.
Results: Results for SF and PL were similar. Regardless of diet, cortisol was higher in fit vs. unfit horses. Fit horses on SF/PL had higher post prandial [insulin] and insulin:glucose ratio than unfit horses. FAT resulted in lower post prandial [glucose] and [insulin] vs. SF/PL. Higher [insulin] in fit vs. unfit horses was not seen on the FAT diet.
Conclusions:
Increased post prandial glucose, insulin and cortisol induced by high NSC, but not high fat, feeds are enhanced by fitness in RER horses. This combination may trigger rhabdomyolysis through increased excitability in RER Thoroughbreds.
Valberg S, Häggendal J, Lindholm A.
Blood chemistry and skeletal muscle metabolic responses to exercise in horses with recurrent exertional rhabdomyolysis. Equine Vet J. 1993;25:17-22.
Summary
Six horses with a history of recurrent exertional rhabdomyolysis (RER) and 7 control horses performed both a 55-min submaximal and later a 10-min near-maximal exercise test on a treadmill. Blood samples were obtained during exercise and gluteus medius muscle biopsies were obtained before and immediately after each exercise test and at 24 h after completion of the submaximal test. Rhabdomyolysis was developed by 3 of 6 RER horses during submaximal exercise and in 1 of the RER horses during near-maximal exercise. Concentrations of potassium, glucose, free fatty acids, ammonia, lactate, cortisol, adrenaline and noradrenaline in the blood were measured. None of these variables appeared useful in predicting which RER horses would develop rhabdomyolysis.
The RER horses that developed rhabdomyolysis (RERa) had higher Cortisol and blood glucose concentrations but otherwise had blood chemistry and muscle metabolic responses during submaximal and near-maximal exercise similar to those of RER horses which did not develop rhabdomyolysis (RERb) and to controls. At rest, muscle glycogen concentrations were significantly higher (>650 mmol/kg dry wt) in RERa and RERb horses than in controls. Lactate concentrations in muscle after submaximal and near-maximal exercise were similar or lower, respectively, in RERa horses compared with controls.
The results of this study indicate that, although horses with RER had high resting intramuscular glycogen concentrations, rhabdomyolysis did not appear to be caused by an excessively rapid rate of anaerobic glycolysis with lactate accumulation.
