A portable arrangement in connection with a fitness exercise of a person, the arrangement comprising: means for measuring (602, 604, 606, 608, 610, 622, 624, 626, 628, 630) multidimensional electrocardiographic data of the person by at least three measuring electrodes (602, 604, 622, 624; 102, 104, 106, 108) positioned in spatially different positions on the person; means for processing the multidimensional electrocardiographic data of the person, the multidimensional electrocardiographic data comprising at least two spatially separately measured electrocardiographic signal components; and means for forming a vectorcardiographic measure on the basis of the multidimensional electrocardiographic data; characterized in that the portable arrangement further comprises: means for applying the vectorcardiographic measure in determination of a fitness exercise related parameter, the fitness exercise related parameter comprising exercise instructions for the person to carry out the fitness exercise; and means for providing (646, 660, 674) the exercise instructions for the person by using sound and/or visual indication, the exercise instructions indicating at least one of the following: it is appropriate to start the fitness exercise, it is appropriate to continue the fitness exercise, it is not appropriate to start the fitness exercise, it is not appropriate to continue the fitness exercise, it is appropriate to reduce stress of the fitness exercise, an appropriate exercising level of the fitness exercise. means for measuring (602, 604, 606, 608, 610, 622, 624, 626, 628, 630) multidimensional electrocardiographic data of the person by at least three measuring electrodes (602, 604, 622, 624; 102, 104, 106, 108) positioned in spatially different positions on the person; means for processing the multidimensional electrocardiographic data of the person, the multidimensional electrocardiographic data comprising at least two spatially separately measured electrocardiographic signal components; and means for forming a vectorcardiographic measure on the basis of the multidimensional electrocardiographic data; characterized in that the portable arrangement further comprises: means for applying the vectorcardiographic measure in determination of a fitness exercise related parameter, the fitness exercise related parameter comprising exercise instructions for the person to carry out the fitness exercise; and means for providing (646, 660, 674) the exercise instructions for the person by using sound and/or visual indication, the exercise instructions indicating at least one of the following: it is appropriate to start the fitness exercise, it is appropriate to continue the fitness exercise, it is not appropriate to start the fitness exercise, it is not appropriate to continue the fitness exercise, it is appropriate to reduce stress of the fitness exercise, an appropriate exercising level of the fitness exercise. means for applying the vectorcardiographic measure in determination of a fitness exercise related parameter, the fitness exercise related parameter comprising exercise instructions for the person to carry out the fitness exercise; and means for providing (646, 660, 674) the exercise instructions for the person by using sound and/or visual indication, the exercise instructions indicating at least one of the following: it is appropriate to start the fitness exercise, it is appropriate to continue the fitness exercise, it is not appropriate to start the fitness exercise, it is not appropriate to continue the fitness exercise, it is appropriate to reduce stress of the fitness exercise, an appropriate exercising level of the fitness exercise.