Near-maximal contractions with superimposed vibration have been shown to cause greater increases in strength in the acute and chronic time domains than non-vibrated contractions (Issurin et al. 1994; Issurin & Tenenbaum, 1999). Due to the impressive results observed in those studies we wondered whether we could replicate those findings with an alternate but comparable vibrational stimulus. Twelve recreationally active subjects (7 strength + vibration training, 5 strength training only) trained for 5 weeks, three times per week on a leg extension machine. Strength was assessed PRE and POST training by determining the maximum weight the subject could lift for one repetition (1-RM). Each training session involved a warm-up set of eight repetitions at ~50 % 1-RM, followed by three sets of eight repetitions at ~75 % 1-RM. Vibration was applied to the cable of a leg extension machine by a new method which produced a high-frequency braking force driven by the energy produced by the subject lifting the weight. The vibration frequency was dependent upon the rate of contraction (30-45 Hz) in this study, as opposed to Issurin and colleagues’ experiment where the frequency was contraction rate independent (44 Hz). The experiments had ethical approval and subjects gave written informed consent.

Results suggest that strength training with and without additional vibration cause significant increases in strength, but the superimposed vibrations cause trends towards greater strength gains than strength training alone (see Fig. 1). These results provide moderate support for previous studies in which improvement in strength (1-RM) was significantly greater after strength training with superimposed vibration than strength training alone (Issurin et al. 1994). Although we found similar increases in strength after strength training with superimposed vibration to those observed in earlier studies (~40 vs. 49% Issurin et al. 1994), the increases in strength after conventional strength training in our experiments were larger than those reported earlier (~25 vs. 16% Issurin et al. 1994). The results are probably related to subject difference as our subjects were only recreationally active and not strength trained as in the previous experiments, also different muscle groups were used in the previous two studies. Further work is required to test alternate frequencies and amplitudes of vibration during training in different subject groups and in different muscles.

This study was supported by The Wellcome Trust.