Gymnastik- och idrottshögskolan, GIH

Aim

The purpose of this study was to compare resistance-trained (RT) and non-trained (NT) males regarding mechanisms for neural activation during isometric muscle contractions of the soleus muscle. Further the plantar flexor strength of the two groups were compared.

Method

Ten males that had been resistance training for at least 3 years (RT) and 10 who did not train regularly (NT) participated in the study. The participants performed isometric contractions of their right plantar flexors against an isokinetic dynamometer at 15, 25, 50, 80 and 100% of maximal voluntary contraction. Five contractions were performed for each level in two different conditions; one where the participants were stimulated using transcranial magnetic stimulation over the left motor cortex and one in which they were stimulated electrically over the tibial nerve. Stimulations were also delivered at rest. The resulting soleus muscle motor evoked potentials (MEPs) and V-waves were normalized to a maximal M-wave (Mmax). Plantar flexor strength was measured and voluntary activation estimated using the twitch interpolation technique.

Results

No significant difference was found between the RT and the NT group for voluntary activation, V/Mmax ratio or MEP/Mmax at any level of maximal voluntary contraction (MVC). The RT group was significantly stronger than the NT group.

Conclusions

The study showed that the RT group was stronger than the NT group. Despite the difference in strength there was no significant group difference between the two groups in MEPs, V/Mmax or voluntary activation. This indicates that there is no, or a very small difference in corticospinal excitability of the soleus muscle between the chronic RT males and the NT males.