4.6. Measurements of shivering

Shivering EMGs were recorded from the pectoral (II–V), gastrocnemius (II–IV) and iliofibularis muscles (III). Measurements were performed using bipolar subcutaneous electrodes made of Teflon-coated multistranded steel wire. The EMG signals picked up with the electrodes were fed into differential amplifiers, displayed on an oscilloscope, converted either to mean rectified values (U_mrv) (II) or to rectified mean square values (U_rms) (III, IV, V) with analog integrators, and were recorded either with a pen recorder (II) or with a Hewlett-Packard 34970A Data Acquisition/Switch unit connected to a PC (III, IV, V). Samples of the unintegrated 1000-fold amplified raw EMGs were stored on C-cassette tapes using a stereo cassette deck (II, IV). Frequency spectra for tape-recorded EMG samples were calculated using the Fast Fourier Transform with a DATA 6000 signal analyser (Data Precision Inc.). In 21-day-old Japanese quails, intramuscular EMGs were recorded 5 mm deep from the thickest part of the breast muscle 5 mm laterally from the keel of the sternum with bipolar electrodes made of Teflon-coated multistranded steel wire (Medwire®, part 316SS7/44T, Mt. Vernon, USA).