A pacemaker with patient effort-controlled stimulation frequency that responds to a control parameter. Accelerometers (1) with capacity variation are placed on a substratum. Each of the accelerometers is sensitive in one direction of a Cartesian coordinate system. The output of the accelerometers are combined and integrated over a small time constant to produce a signal representative of the patient's metabolic power exerted. The signal is then used to control the stimulation frequency of the pacemaker. The integration may be based on the sum of the absolute value of the acceleration signals or the square root of the sum of the squares of the acceleration signals.