Dynamic balance control and soleus stretch- and h-reflex responses in young and older individuals before and after progressive strength training

Allonen, J., Walker, S., Linnamo, V., Piirainen, J.M. Faculty of Sports and Health Sciences, University of Jyväskylä, Finland

Aging leads to weaker force properties as well as longer and weaker voluntary and reflex response after balance perturbation (Lin & Woollacott 2002, Piirainen et al. 2013). Present study examined whether progressive strength training (PST) would improve dynamic balance control and reflex responses.

Four OLDER (2 women and 2 men, 68.5 ± 2.5 years) and eight YOUNG (5 women and 3 men, 24.0 ± 3.6 years) participants completed this study. The following measurements were performed before and after a 14-week PST intervention; (1) maximum voluntary isometric contraction (MVC) of knee extensors and ankle plantarflexors, (2) dynamic balance tests on a sliding force-plate (Piirainen et al. 2013), (3) with concomitant soleus short-latency stretch-reflex (SLR) responses and (4) H-reflex responses (timed during SLR) during the dynamic balance tests.

YOUNG improved MVC results of knee extension (8 ± 11%; P ˂0,05) and plantarflexion (14 ± 11%; P ˂0,05), which was not observed in OLDER. SLR responses were higher (0.037 ± 0.015) and latencies (44,75 ± 14,73 ms) longer in OLDER than YOUNG (0.022 ± 0.007, P ˂0.05; 36,25 ± 6,32 ms; P ˂0,05) at baseline. Displacement after perturbation was higher in OLDER (51.9 ± 8.4 mm) than YOUNG (33.6 ± 11.0 mm; P ˂0.05) at baseline. No changes in dynamic balance, H-reflex or SLR were observed in either of the groups.

It was concluded that PST intervention did not improve balance control of subjects during sudden perturbation and it did not have effects on stretch- or H-reflex responses of soleus. Thus PST may not be sufficient to improve balance control properties but the training should probably be more explosive as has been shown earlier (Piirainen et al. 2014).


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