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This study assessed the effect of 1-year regular Tai Chi (TC) on neuromuscular reaction in elderly women. A total of 41 elderly women (55 years–68 years) completed the study. The TC group (n = 21) performed the 24-form TC, while the control group (C, n = 20) was instructed to read newspapers or watch television when the TC group practised. Electromyogram measurements were conducted before and after intervention. After a year-long intervention, the post-test results of between-group neuromuscular reaction time showed significant differences in the rectus femoris (t = 3.607, p = 0.001), semitendinosus (t = 2.678, p = 0.011), anterior tibialis (t = 3.455, p = 0.001), and gastrocnemius muscles (t = 4.061, p = 0.000). Within-group results showed that the TC group had significantly shorter neuromuscular reaction time compared to its baseline value in the rectus femoris (t = 3.066, p = 0.006), semitendinosus (t = 2.485, p = 0.022), anterior tibialis (t = 2.311, p = 0.032), and gastrocnemius muscles (t = 2.462, p = 0.023). Results suggested that year-long regular TC can improve neuromuscular reaction function in elderly women. [ABSTRACT FROM AUTHOR]

The aim of this article was to explore age-related differences in the muscle modes (M-modes) during voluntary body sway (VS). M-modes were defined as trunk and leg muscles organized into groups with parallel scaling of muscle activation level within a group. We hypothesized that, in comparison with young performers, older adults would show changes in the compositions of M-modes stabilizing the anterior-posterior (AP) center of pressure (COP) displacement. Young (27.5 ± 7.3 yr, 164.6 ± 9.7 cm and 58.4 ± 10.6 kg) and older (69.4 ± 6.4 yr, 160.0 ± 7.0 cm and 58.9 ± 7.5 kg) subjects performed the VS task in the AP direction while trying to minimize sway in the medio-lateral direction. EMG signals of 10 postural muscles were recorded and analyzed. Principal component analysis (PCA) was used to identify three M-modes within the space of integrated indices of muscle activity. The main findings were (1) that there were no age-related differences in magnitude of the COP displacement or amount of variance explained by the principal components (m-modes), and (2) that the number of times co-contraction and mixed m-modes were used were significantly higher for older adults, and the number of times reciprocal m-modes were used were significantly higher for young adults. These observations suggest that aging is associated with a reduced ability to unite dorsal and ventral muscles of the body, which may be reflective of the CNS developing a useful strategy when faced with self-triggered perturbations. [ABSTRACT FROM PUBLISHER]

This study explored the trunk and lower limb muscle activity of 15 males during unilateral hockey bag carriage of 10%, 20%, and 30% of one’s body weight (BW) compared with without a load during walking. The electromyography (EMG) activities of the left and right erector spinae, rectus abdominis, gluteus maximus, rectus femoris, vastus medialis, biceps femoris, semitendinosus, and the medial gastrocnemius were studied. A 2-way repeated measures analysis of variance (ANOVA) was used to examine the differences between the load weight and muscle side. Results showed significant increase in peak EMG and iEMG in the carrying side vastus medialis, rectus abdominis, semitendinosus, and gastrocnemii (p < 0.05) at the 30% BW load. The noncarrying side showed a greater peak EMG in the semitendinosus and rectus femoris at the 30% BW load when compared with the carrying side (p < 0.05). It was concluded that unilateral hockey bag carriage is similar to both backpack and side-pack carriage styles. [ABSTRACT FROM PUBLISHER]

Little information exists on how body weight (BW) support influences running biomechanics. The study aim was to determine how reducing BW by 50%–80% influences muscle activity while running at different speeds. Subjects (n = 7) ran at 100%, 115%, 125% of preferred speed at 100%, 50%, 40%, 30%, 20% of BW per speed. Average (AVG) electromyography of the rectified signal was compared (within subject design; 3-speeds × 5-BW, repeated measures ANOVAs; biceps femoris [BF], rectus femoris [RF], tibialis anterior [TA], gastrocnemius [GA]). RF, BF, and GA AVG were not influenced by BW–speed interaction (p> .05) and increased across speeds (p< .05). RF and GA AVG signal was reduced as BW was reduced (p< .05), but BF only tended to be different (p= .08). TA was influenced by BW–speed interaction (p< .05) with EMG decreasing across BW (p< .05) while increasing across speeds except at 100% BW. Overall, muscle activity increased with speed and decreased by BW reductions. [ABSTRACT FROM PUBLISHER]