In:
Medicine & Science in Sports & Exercise, Ovid Technologies (Wolters Kluwer Health), Vol. 55, No. 3 ( 2023-3), p. 469-481
Abstract:
Voluntary activation (VA) determined by interpolation-twitch technique could be affected by the characteristics of the in-series elastic components. To overcome this possible bias, a novel approach based on the mechanomyographic (MMG) signal to detect voluntary activation (VA MMG ) has been proposed. We examined the changes in VA and VA MMG after passive stretching to check the influence of neural and mechanical factors in the force output. Methods Twenty-six healthy men underwent VA assessment using the interpolated-twitch technique before and after unilateral passive stretching of the plantarflexors (five 45-s on + 15-s off). In addition to the force signal, the MMG signal was detected on gastrocnemius medialis, gastrocnemius lateralis, and soleus. From the force and MMG signal analysis, VA and VA MMG were calculated in the stretched and contralateral nonstretched limbs. Joint passive stiffness was also defined. Results In the stretched limb, passive stretching increased dorsiflexion range (mean ± SD = +18% ± 10%, P 〈 0.001, ES = 1.54) but reduced joint passive stiffness (−22% ± 8%, P 〈 0.001, ES = −1.75), maximum voluntary contraction (−15% ± 7%, P 〈 0.001, ES = −0.87), VA (−7% ± 3%, P 〈 0.001, ES = −2.32), and VA MMG (~−5% ± 2%, P 〈 0.001, ES = −1.26/−1.14). In the contralateral nonstretched limb, passive stretching increased dorsiflexion range (+10% ± 6%, P 〈 0.001, ES = 0.80) but reduced joint passive stiffness (−3% ± 2%, P = 0.041, ES = −0.27), maximum voluntary contraction (−4% ± 3%, P = 0.035, ES = −0.24), VA (−4% ± 2%, P 〈 0.001, ES = −1.77), and VA MMG (~− 2% ± 1%, P 〈 0.05, ES = −0.54/−0.46). The stretch-induced changes in VA correlated with VA MMG ( R ranging from 0.447 to 0.583 considering all muscles) and with joint passive stiffness (stretched limb: R = 0.503; contralateral nonstretched limb: R = 0.530). Conclusions VA output is overall influenced by both neural and mechanical factors, not distinguishable using the interpolated-twitch technique. VA MMG is a complementary index to assess the changes in VA not influenced by mechanical factors and to examine synergistic muscles.
Type of Medium:
Online Resource
ISSN:
1530-0315
,
0195-9131
DOI:
10.1249/MSS.0000000000003076
Language:
English
Publisher:
Ovid Technologies (Wolters Kluwer Health)
Publication Date:
2023
detail.hit.zdb_id:
603994-7
detail.hit.zdb_id:
2031167-9
SSG:
31
Permalink