Physiological Measurements

Technology

Electromyography (EMG) is a technique dedicated to the generation, recording and analysis of myoelectric signals. Myoelectric signals are generated by physiological state variations of the muscle fiber membrane due to action potentials. The focus of the kinesiological EMG is on the recording and analysis of voluntary muscle activation in functional movements and postural activities.

A portable TeleMyo 2400 G2 device from Noraxon and the Captiv measurement system are used for EMG recording. The myoelectric signals are recorded using surface electrodes.

Application

The EMG as an analysis of muscular activity is used primarily for stress analyses during physical work or ergonomic product design. However, increased activity of “resting” muscles can also be detected during emotional or informational excitement. Yet, the EMG alone is difficult to interpret for informational activities.

Technology

Electrocardiography (ECG) is the most reliable and most frequently used method in occupational science to determine the heart rate and the measured variables derived from it.

The recording of the heart rate is usually carried out by means of a Varioport device via three measuring electrodes or alternatively by means of a chest strap from Polar, which is worn underneath the chest. These systems measure the heart rate or R-pulses, which are emitted through the skin, via the skin electrodes. In order to keep skin resistance low, the skin area must be prepared by a local shave.

Application

As an integrating stress measure, HSF reacts to a variety of physical and predominantly non-physical stresses. While the HSF is constant at low physical stress levels, it shows a continuous increase at stress levels. The heart rate increases significantly under informational stress, such as information intake or decision-making processes, if this effect is not masked by energetic components (e.g. physical activity). The heartbeat variability derived from the heartbeat frequency and the frequency band analysis are further indicators for occurring mental stress. If the heart beat variability decreases while the heart beat rate is relatively low, it can be assumed that the user's workload increases. To analyze heart beat variability, a minimum recording rate of 500 Hz is required, which is only achieved with the Varioport system. The analysis of the heartbeat variability is performed by the Kubios HRV Premium software.

Technology

Two electrodes are attached to the skin at a certain distance and the electrical resistance is measured. From the level and duration of the stimulus response, conclusions can be drawn about the psychological activity and the timing and intensity of an emotion experienced. A Varioport system from Becker Meditec is used for the measurement.

Application

Skin conductance determination is used for the objective, continuous or successive recording of skin conductance as a measure for psychological processes. If sweat is produced, e.g. during emotional stress, the skin's ability to act as an electrical conductor increases and so does the skin conductance value. It is therefore well suited to draw conclusions about this as well as about psychological activity.