Tremor, effect of physical load and reproducibility.
The effect of three kinds of moderate physical loads on the tremor of the middle finger was studied in eight males: cycling 15 min on an ergometer at a heart rate of 140 beats/min (general dynamic load); lifting a mass of 1 kg by the middle finger at a rate of 30 times/min for 5 min (local dynamic load); and carrying in each hand a 15 kg mass for 5 min. Few effects were observed: 10% decrease of RMS acceleration after local dynamic load and some changes in the power spectrum after general dynamic load. It is concluded that the effect of recent, short time physical load of moderate extent can be neglected as a disturbing factor in the study of the effects of toxic exposure on postural tremor. The inter- and intra-individual variation (over 4 weeks) in nine males and nine females also was studied. The intra-individual variation ranged from 4% for the mean frequency to 35% for the 0-4 Hz band of the power spectrum. The inter-individual variation ranged from 8% for the mean frequency to more than 60% for some frequency bands of the power spectrum. It is concluded that the mean frequency possibly is a sensitive parameter in epidemiologic studies on effects of external toxic exposure on tremor.