Fig. 6.

The effects of resistance training (RT) on myofiber group size, submaximal motor unit activation (MUA), and acetylcholine receptor (AChR) are dependent on type I myofiber grouping prevalence. A and B: only those older adults (OA) with the highest type I myofiber grouping (OA-H, PD-H), as defined by K-means cluster analysis, displayed reductions in type I myofiber group size (A) and MUA post-RT (B). However, both OA-L/M and PD-L/M displayed a trend for MUA reduction post-RT. C: both PD-L/M and PD-H increased AChR-β subunit protein levels post-RT, whereas OA-H displayed a trend toward increase. There were no other RT-induced differences in denervation-associated transcript or protein expression. *Different from pre-RT, P < 0.05; †trend toward difference from pre-RT, P < 0.07. Values are means + SE.