The objective of this study was to assess the electromyographic activity of the rectus abdominis (upper and lower part) and external oblique during sit-ups performed on BOSU ball(s). Twenty-four men participated in a familiarization session, and in the next session, they performed the experimental tests in randomized order. The sit-ups were performed with 10 repetitions with body weight and with 10 repetition maximum (10RM) using elastic bands as external resistance under 4 different conditions: (a) on a stable surface, (b) with the BOSU ball under their feet (dome side down, lower-body instability), (c) BOSU ball under the low back (dome side up, upper-body instability), and (d) with BOSU balls under both feet and the low back (dual instability). The feet were not attached to the surface. We observed that with body weight, external oblique activation was decreased by upper-body instability and dual instability by 22-24% (p = 0.002-0.006), whereas the rectus abdominis was not affected by the surface. Using 10RM loads, the upper and lower rectus abdominis activities were increased by upper body and dual instability by 21-24% compared with that for a stable surface (P ≤ 0.001-0.036). Further, lower-body instability did not affect muscle activities significantly with either load for any condition. Hence, BOSU balls under the low back can increase and decrease abdominal muscle activation depending on the load, whereas placing a BOSU ball under the feet with the dome side down had little impact.
Efferent neural drive during strong muscle contractions is attenuated with age, even after life-long strength training. However, it is unknown if this deterioration may impede contralateral neural plasticity, and limit the clinical value of unilateral strength training. We assessed muscle force-generating capacity, evoked potentials recordings (V-wave and H-reflex normalized to M-wave; V/M-ratio and H/M-ratio) and voluntary activation (VA) in the plantar flexors of the contralateral limb following unilateral maximal strength training (MST) with the dominant limb for 3 weeks (nine sessions). Twenty-three 73 ± 4(SD) year old males were randomized to a MST group (N = 11), exercising with an intensity of ~90% of maximal strength, or a control group (CG, N = 12). MST improved contralateral maximal strength (107.6 ± 27.0 to 119.1 ± 34.8 Nm; 10%) and rate of force development (197.3 ± 54.1 to 232.8 ± 77.7 Nm s-1; 18%) (both p < .05). These strength gains were associated with (r = 0.465-0.608) an enhanced soleus V/M-ratio (0.12 ± 0.09 to 0.21 ± 0.17) and VA (79.5 ± 5.1 to 83.3 ± 5.2%) (all p < .05). H/M-ratio (10% maximal strength) remained unaltered after MST, and no changes were apparent in the CG. In conclusion, cross-limb effects in older adults are regulated by efferent neural drive enhancement, and advocate the clinical relevance of MST to improve neuromuscular function in individuals with conditions that results in unilateral strength reductions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.