Local exercise based on voluntary contractions produces greater warm-up effects on balance control than electro-induced contractions

2022 ◽  
pp. 136458
Author(s):  
Sacha Zéronian ◽  
Frédéric Noé ◽  
Thierry Paillard
2002 ◽  
Vol 87 (4) ◽  
pp. 1859-1866 ◽  
Author(s):  
Monica Gorassini ◽  
Jaynie F. Yang ◽  
Merek Siu ◽  
David J. Bennett

The main purpose of this study was to examine whether facilitation of human motor unit recruitment by repeated voluntary contractions is mediated, in part, by time and activity-dependent increases in the intrinsic excitability of the parent motoneuron. To do this, pairs of tibialis anterior or soleus motor units were recorded during slowly increasing and then decreasing voluntary contractions. The firing rate of the lower-threshold motor unit of the pair (control unit) was used as a measure of effective synaptic excitation (i.e., drive) to the motoneurons. This rate was used to estimate the recruitment threshold of the higher-threshold unit of the pair (test unit). The test unit was repeatedly recruited and de-recruited in a series of contractions, and the interval between the de-recruitment and re-recruitment of the test unit (interactivation interval) was systematically varied between 0.6 and 60 s. An increase in intrinsic excitability of a unit was considered to have occurred if the level of estimated synaptic input (as measured by the firing rate of the control motor unit) needed to recruit a unit was reduced. At short interactivation intervals (1–2 s), the control unit firing frequency was significantly lower when the test unit was recruited on the second contraction, compared with the first (by 3.9 Hz or a 64% reduction). This suggested that the intrinsic excitability of the test motor unit had increased during the second contraction because it could be recruited at a much lower level of estimated synaptic drive. Longer interaction intervals (2–6 s) produced less recruitment facilitation. At even longer interactivation intervals (>6 s) there was no significant facilitation (time constant of effect was 4.8 s). In some motor units, the effect of this short-term facilitation appeared to be so pronounced that it resulted in reversing the order of de-recruitment with the other initially lower-threshold motor units. Such reversals were occasionally observed for orderly re-recruitment. The time course and behavior of the observed short-term facilitation of motor unit discharge was qualitatively similar to the warm-up phenomenon of plateau potentials seen in motoneurons of reduced preparations (e.g., 4–6 s). The possibility of warm-up contributing to the time and activity-dependent facilitation of human motor unit recruitment is discussed.


2015 ◽  
Vol 40 (3) ◽  
pp. 230-237 ◽  
Author(s):  
Laurent B. Seitz ◽  
Gabriel S. Trajano ◽  
Fabien Dal Maso ◽  
G. Gregory Haff ◽  
Anthony J. Blazevich

The purposes of this study were to determine whether performing dynamic conditioning activities (CAs) contributes to postactivation potentiation (PAP); to examine the potential confounding effects of CAs with different velocity, total contraction duration, and total work characteristics; and to gain a greater understanding of potential peripheral and central mechanisms underlying PAP. Voluntary (isokinetic knee extensions at 180°·s−1) and electrically evoked torques and electromyogram (EMG) data were captured before and 1, 4, 7, 10, and 13 min after 5 different dynamic CAs (4 knee extensions at 60°·s−1, 4 and 12 at 180°·s−1, and 4 and 20 at 300°·s−1), after the participants had completed a full warm-up including extensive task-specific practice to the point where maximal voluntary contractile capacity was achieved. Even after maximal voluntary contractile capacity had been achieved, the imposition of CAs of longer total contraction duration (6 s) and a minimum total work of ∼750–900 J elicited significant increases in both voluntary (for 7 min; up to 5.9%) and twitch (for 4 min; up to 13.5%) torques (i.e., PAP), regardless of the velocity of the CA. No changes in EMG:M-wave were detected after any CA. A dynamic voluntary CA can contribute to improved voluntary and electrically evoked torques even when maximal voluntary contractile capacity has previously been achieved. Furthermore, a minimum CA contraction duration and minimum total work appear important to increase torque production, although movement velocity appears unimportant. Changes in peripheral function but not central drive may have contributed to the observed PAP under the present conditions.


2019 ◽  
Vol 4 (6) ◽  
pp. 1418-1422
Author(s):  
Bre Myers ◽  
J. Andrew Dundas

Purpose The primary aim of the current article is to provide a brief review of the literature regarding the effects of noise exposure on the vestibular and balance control systems. Although the deleterious effects of noise on the auditory system are widely known and continue to be an active area of research, much less is known regarding the effects of noise on the peripheral vestibular system. Audiologists with working knowledge of how both systems interact and overlap are better prepared to provide comprehensive care to more patients as assessment of both the auditory and vestibular systems has been in the audiologists' scope of practice since 1992. Method A narrative review summarizes salient findings from the archival literature. Results Temporary and permanent effects on vestibular system function have been documented in multiple studies. Hearing conservation, vestibular impairment, and fall risk reduction may be more intimately related than previously considered. Conclusions A full appreciation of both the vestibular and auditory systems is necessary to address the growing and aging noise-exposed population. More cross-system studies are needed to further define the complex relationship between the auditory and vestibular systems to improve comprehensive patient care.


2007 ◽  
Author(s):  
David Tod ◽  
Jonathan Baker ◽  
Michael McGuigan
Keyword(s):  

Author(s):  
Mohammed Yahia
Keyword(s):  

2021 ◽  
Vol 141 (1) ◽  
pp. 1-12
Author(s):  
Akira Koide ◽  
Takao Tsuji ◽  
Kazuyuki Tanaka ◽  
Hitoshi Sugimoto

2007 ◽  
Vol 16 (3) ◽  
pp. 281-290
Author(s):  
Eue-Soo Ann ◽  
Jongkyu Kim
Keyword(s):  

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