Strength training is recommended for slowing age-dependent deterioration of muscular strength and for rehabilitating patients with muscle weakening illnesses. Reliable assessment of muscle strength is important for proper design of strength training regimes for prevention, rehabilitation, and sport. One repetition maximum (1RM) is an established measure of muscular strength and is defined as the value of resistance against which a given movement can be performed only once. Proper assessment of 1RM is time consuming, and may lead to muscle soreness as well as temporary deterioration of the function of the tested muscles. Attempts at indirect 1RM determination based on the maximum number of repetitions performed have predicted 1RM with a variable degree of accuracy. Cardiovascular safety has been neglected in 1RM determination, although arterial blood pressure increases considerably when exercising against maximal or near maximal resistance. From the perspective of cardiovascular safety, favorable 1RM measurement methods should avoid performance of repetitions until failure; movement against high resistance and muscle fatigue both increase blood pressure. Although such techniques are likely less accurate than the current methods, their prediction accuracy be sufficient for therapeutic strength training.