Suppression of shivering by breath holding, relaxation, mental arithmetic, and warm water ingestion.

Four methods of suppressing cold-induced shivering were evaluated in 26 young male volunteers exposed to 0.0 +/- 1.0 degrees C air for 135 min. Voluntary relaxation of musculature (R), breath holding (BH), warm (50 degrees C) water ingestion (W), and performance of a mental arithmetic task (MA) were applied in a counterbalanced order following 2 h of cold exposure. Surface electromyograms of seven muscles were recorded and converted to root mean square voltage (RMS) as a measure of shivering intensity. Mean skin and rectal temperatures decreased significantly, 4.9 degrees C and 0.3 degrees C, respectively (p < or = 0.01). Mean reduction of EMG activity was 35% during R, 24% during BH, 18% during MA, and 5% during W. R was significantly more effective than BH, MA, and W, and BH and MA were significantly more effective than W in reducing shivering. These results indicate that, at small decreases in rectal temperature, shivering can be voluntarily suppressed to some extent during relaxation, breath holding, and mental arithmetic.