Isometric strength training (IST) can reduce anisometric tremor in healthy individuals and in patients with Essential Tremor (Bilodeau et al. 2000; Tracy et al. 2004). One explanation for this might be a reduction in stretch reflex instability (SRi), a mechanism associated with tremor (Durbaba et al. 2005), as IST is known to alter SR properties (Zehr 2006). Here we investigate the effects of short term IST on SRi in healthy individuals. Fourteen individuals (aged 20-39 years) took part in the study. Ethical approval was obtained and subjects gave written, informed consent. Subjects were seated on a dynamometer (Biodex Medical Systems Inc., New York, USA) with their knee and hip angles at 90 degrees. Contraction force from knee extensors of the dominant leg was recorded to assess maximum voluntary contraction (MVC) and SRi at baseline and after 4 weeks. Following baseline recordings, 7 subjects acted as controls and continued their normal daily activity, whilst 7 undertook a 4-week period of IST involving the knee extensor muscles of the dominant leg; 3 times a week, 45 minutes per session. The IST protocol used was designed by Macaluso et al. (2000) and produces an increase in muscle strength. Tremor was induced with anisometric contractions, at 30% baseline MVC, against spring loading that preferentially activated the long or short latency components of the SR (long=5.35 N mm^-1; short=11.06 N mm^-1). Subjects had visual feedback to help maintain the appropriate force level for the recording and training sessions. Autospectra of force fluctuations were computed for analysis. Statistical significance within and across the two groups was accessed by paired and unpaired t-test as appropriate. The training group showed a significant increase in MVC as compared to baseline (28.6±6.4%, mean±SEM; p<0.01), which was significantly greater (p<0.001) than the minimal change observed for controls (0.7±1.9%). Tremor amplitude was significantly decreased (p<0.01) in the training group (long=-43.2±8.2%; short=-34.8±8.4%) as compared to controls (long=-1.8±4.4%; short=-8.1±3.9%). In each group, tremor frequency was not significantly altered for either spring. The results are consistent with a decrease in SR gain, without altering the system dynamics. Also, they support the idea that reductions in anisometric tremor observed in previous studies may be due to changes in SRi. Thus, isometric strength training could be a useful rehabilitation tool in individuals with exaggerated forms of tremor.