Hypertrophy of the heart muscle may occur as a result of maximum and prolonged physical training. Till now, heart failure has been the delineating marker for determining physiological hypertrophy and the transition period into pathological hypertrophy. The state of the heart muscle is usually evaluated by heart muscle injury markers, one of which is cardiac troponin I (cTnI). Troponin is detectable only in heart tissues and it's concentration in blood increases rapidly in relation to the level of myocardium failure. During this study some sledge dogs had increased concentrations of cTnI concentration in their sera which indicated heart muscle failure as a result of an excessive workload