Effect of dance on multi-muscle synergies in older adults: a cross-sectional study

Abstract

Background: The purpose of this study was to investigate the efficacy of dance in the experienced older dancers compared to the inexperienced older adults. We explored the effect of dance on the composition of muscle groups and multi-muscle synergies stabilizing the center of pressure (COP) displacement in preparation to take a step during support surface translation.

Methods: Eight dance experienced elderly participants were asked to take a step in response to support surface perturbations. Uncontrolled manifold analysis was used to identify muscle modes (M-modes) as factors in the muscle activation space. Variance components in the M-mode space and indices of M-mode synergy stabilizing COP displacement were computed.

Results: The reciprocal M-modes were observed more frequently in the dance group than in the control group prior to the step initiation. Dance led to higher indices of multi-muscle synergies and earlier anticipatory synergy adjustments during preparation for making a step in response to the support surface translations.

Conclusions: Dance appeared to be associated with adjustments in both the composition of M-modes and M-mode co-variation patterns resulting in stronger synergies stabilizing COP coordinate in older adults. The results reported here could have clinical relevance when offering a dance approach to balance training for impaired individuals.

Keywords: Anticipatory adjustments; Dance; Older adults; Perturbation; Synergy.

Fig. 1

Typical EMG patterns averaged across trials for representative dance and control subjects for the normal stepping (NS; dark line) and perturbation stepping (PS; gray line) conditions, respectively. Time zero (t₀) corresponds to the alignment time, which is the time of toe-off. The EMGs were recorded in muscles on the right side of the body. The EMG scales are in arbitrary units and time is in ms (TA tibialis anterior, GM medial head of gastrocnemius, RF rectus femoris, BF biceps femoris)

Fig. 2

Onsets of EMG activity averaged across subjects, plotted for the normal stepping (NS) and perturbation stepping (PS) conditions in the dance and control groups. Onset of muscle activation is plotted in ms and the mean ± SD is shown (TA tibialis anterior, SOL soleus, GL lateral head of gastrocnemius, GM medial head of gastrocnemius, RF rectus femoris, VL vastus lateralis, VM vastus medialis, BF biceps femoris, ST semitendinosus, RA rectus abdominis, ES erector spinae). The asterisks ‘*’ indicate statistical significance

Fig. 3

Representative loading coefficients for the PCA of the dance and control subjects (TA tibialis anterior, SOL soleus, GL lateral head of gastrocnemius, GM medial head of gastrocnemius, RF rectus femoris, VL vastus lateralis, VM vastus medialis, BF biceps femoris, ST semitendinosus, RA rectus abdominis, ES erector spinae). Loading magnitudes over 0.5 are shown in gray (significant loadings)

Fig. 4

Time profiles of the ∆V_Z index for representative dance and control subjects in the normal stepping (NS; dark line) and perturbation stepping (PS; gray line) conditions. The two ∆V_Z profiles started with positive values and included a transient drop in ∆V_Z during the early postural adjustment (EPA) time interval followed by another drop during the anticipatory postural adjustment (APA) time interval (gray-shaded area).The arrows represent drops of anticipatory synergy adjustment (ASA). Time zero (t₀) corresponds to the alignment time, which is the time of toe-off

Fig. 5

Timing indices for the early postural adjustment (EPA) and anticipatory postural adjustment (APA) averaged across subjects are shown for the normal stepping (NS) and perturbation stepping (PS) conditions for the dance and control groups. The asterisks ‘*’ indicate statistical significance