Pre-participation screening is very important for prescribing and practising exercise safely. The aim of this study was to investigate both ratings of perceived exertion (RPE) and blood pressure responses in two different types of exercises with matching duration and indirectly determined working heart rate (HR). Participants were 23 male students, who were generally healthy but sedentary. The time course of their RPE and blood pressure during a 50- minute work-out session on an arm crank ergometer and a cross trainer were compared. RM-ANOVA showed both a higher RPE (p < 0.001) and diastolic blood pressure (DBP) (p < 0.001) response to the arm exercise that were shown significantly correlated (r = 0.883; p = 0.008). Linear regression analysis (p = 0.001) confirmed the ability to predict the time course of DBP by knowing the RPE on the arm crank ergometer. Even if people use the recommended relative intensity, the HR method is not always safe for health without pre-participation screening because exercise characteristics can negatively influence physiological responses. The HR method could be substituted by the RPE method.