Reduction of the bilateral deficit following unilateral strength training: A TMS study

Alan Pearce, Dawson Kidgell

Research output: Contribution to journalMeeting Abstractpeer-review


Introduction: Cross-education and bilateral deficit phenomena are well documented within the literature; however, the precise mechanisms are still remaining to be elucidated. The aims of this study were to measure changes in the bilateral deficit following 4 weeks of unilateral (single arm) strength training and associate these with neurophysiological testing using transcranial magnetic stimulation (TMS) at tonic contraction levels between 10% and 40% of MVC. Methodology: Twenty right handed participants (29.5±7.0 years) were randomly allocated into either strength training (n= 10) or a control group (no training, n= 10). Prior to and post-4 week training, all participants undertook maximal strength test (1 repetition maximum) and neurophysiological measures using TMS. The strength training group completed fully supervised, dominant arm, bicep curl training of 4 sets of 8 repetitions at 80% of their measured 1RM, at a speed of 3s concentric/4s eccentric, with a 3 min recovery between sets. The principle of progressive overload was employed, when participants were able to complete the 8 repetitions comfortably, the training weight was increased by 5%. Results: No differences in strength and the bilateral deficit were observed between groups prior to the training intervention. Similarly, no differences were observed between groups in corticospinal measures of latency and excitability before the training intervention. Following the training period, the training group increased strength in the trained arm by 26.4% with a cross-education transfer effect to the untrained left arm of 16.3%, and a reduction in bilateral deficit 12.9%. The training group showed increased corticospinal excitability projecting from the contralateral motor cortices projecting to the biceps at 20%, 30% and 40% of MVC. No changes in strength, bilateral deficit or corticospinal excitability were observed in the control group. Correlations at 20%, 30%, and 40%showed moderate (−0.70,−0.65,−0.66) inverse correlations with increased corticospinal excitability to the reduction in bilateral deficit. Discussion: Increases in strength to the trained arm, improvement in cross-education to the untrained arm and reduction in bilateral deficit occurred following the period of unilateral strength training. Further, the observation of increased corticospinal excitability and association to the reduction in bilateral deficit suggests that neurophysiological mechanisms may underpin these findings following unilateral strength training.
Original languageEnglish
Pages (from-to)e88-e88
Number of pages1
JournalJournal of Science and Medicine in Sport
Issue numberS1
Publication statusPublished - Dec 2010
Externally publishedYes
EventASICS Conference of Science and Medicine in Sport 2010 - Port Douglas, Port Douglas, Australia
Duration: 3 Nov 20106 Nov 2010

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