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Chapter 2 – Literature Review
including those with ET (Adkins, Boychuk, Remple, & Kleim, 2006; Beck,
et al., 2007; Bilodeau, et al., 2000). The cross-over (cross-education)
effect refers to occurrences of strength gains in an untrained limb or
muscle group (Folland & Williams, 2007). Lee, Gandevia and Carroll
(2009) found that after a four week period of RT the maximum voluntary
contraction (MVC) of the untrained limb significantly improved by 8.2%,
which was lower than the trained limb but greater than the control
group which showed no significant change. An improvement in cortical
drive was suggested to be behind the improvements due to a smaller
superimposed twitch used during the post intervention testing
compared to that used at baseline. This finding was similar to the
significant cross-over effect in the untrained limb reported in a pilot
study by Kidgell and Pearce (2010c) who found a strength increase of
26.4% in the trained limb and a 16.3% increase in the untrained limb.
From this study it was suggested that improved activation of the primary
motor cortex seen, via an increase in motor evoked potential amplitude,
may have been one mechanism underlying this change.
Other mechanisms behind such neuromuscular changes may include
increased neural drive, motor unit changes and muscle activation
(Bruton, 2002; Engardt, et al., 1995; Hakkinen, et al., 1998). Reeves,
Narici and Maganaris (2006) examined the effect of a RT programme on
healthy older adults and found significant increases in maximal
concentric and isometric force in the RT group. The authors also
suggested that in the RT group, there was evidence of increased neural
drive in the agonist muscle group, with increases seen in EMG activity
after training. Similar strength and neural drive increases of the agonist
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