Force variability depends on core and muscle temperature

Brazaitis, Marius; Skurvydas, Albertas; Vadopalas, Kazys; Daniusevičiūtė, Laura

doi:10.1016/j.jtherbio.2010.08.002

Cited by 8 publications

(7 citation statements)

References 24 publications

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“…The electrical stimulation (TT-100 Hz) superimposed on the voluntary contraction was used to distinguish between central and peripheral mechanisms during continuous 2-min MVC [53,54]. In agreement with Racinais et al (2008), Brazaitis et al (2010), and Todd et al (2005), our data shows that passive hyperthermia induces an additional decrease in voluntary activation (i.e., greater central fatigue) [1,8,17]. This additional decrease is not due to interference with the peripheral transmission of the neural drive and is likely to be associated with the supraspinal failure [1].…”

Section: Discussionsupporting

confidence: 82%

“…It is well established that whole-body hyperthermia impairs neuromuscular [1,2,3], cognitive performance [4,5], the ability to activate skeletal muscles [1,6], and increases central fatigue during exercise [1,2,7,8]. The results of numerous experiments have proven that work output decreases when the core temperature increases up to a critical point (i.e., rectal temperature > 38.6 °C) [9], especially when intensive activation of the thermoregulatory and cardiovascular systems takes place [10,11,12].…”

Section: Introductionmentioning

confidence: 99%

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Pre-Exercise Rehydration Attenuates Central Fatigability during 2-Min Maximum Voluntary Contraction in Hyperthermia

et al. 2019

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Background and objectives: Hyperthermia with dehydration alters several brain structure volumes, mainly by changing plasma osmolality, thus strongly affecting neural functions (cognitive and motor). Here, we aimed to examine whether the prevention of significant dehydration caused by passively induced whole-body hyperthermia attenuates peripheral and/or central fatigability during a sustained 2-min isometric maximal voluntary contraction (MVC). Materials and Methods: Ten healthy and physically active adult men (21 ± 1 years of age) performed an isometric MVC of the knee extensors for 2 min (2-min MVC) under control (CON) conditions, after passive lower-body heating that induced severe whole-body hyperthermia (HT, Tre > 39 °C) with dehydration (HT-D) and after HT with rehydration (HT-RH). Results: In the HT-D trial, the subjects lost 0.94 ± 0.15 kg (1.33% ± 0.13%) of their body weight; in the HT-RH trial, their body weight increased by 0.1 ± 0.42 kg (0.1% ± 0.58%). After lower-body heating, the HT-RH trial (vs. HT-D trial) was accompanied by a significantly lower physiological stress index (6.77 ± 0.98 vs. 7.40 ± 1.46, respectively), heart rate (47.8 ± 9.8 vs. 60.8 ± 13.2 b min−1, respectively), and systolic blood pressure (−12.52 ± 5.1 vs. +2.3 ± 6.4, respectively). During 2-min MVC, hyperthermia (HT-D; HT-RH) resulted in greater central fatigability compared with the CON trial. The voluntary activation of exercising muscles was less depressed in the HT-RH trial compared with the HT-D trial. Over the exercise period, electrically (involuntary) induced torque decreased less in the HT-D trial than in the CON and HT-RH trials. Conclusions: Our results suggest that pre-exercise rehydration might have the immediate positive effect of reducing physiological thermal strain, thus attenuating central fatigability even when exercise is performed during severe (Tre > 39 °C) HT, induced by passive warming of the lower body.

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Section: Discussionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Pre-Exercise Rehydration Attenuates Central Fatigability during 2-Min Maximum Voluntary Contraction in Hyperthermia

et al. 2019

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“…In contrast to our expectation, even though HWI-45 °C caused neuromuscular modulation, it did not seem to increase additional peripheral or central fatigue during the 2-min MVC. This contrasts with evidence that WBH decreases the neural drive transmission at both the level of the peripheral nervous system and spinal cord, and decreases the capacity to sustain voluntary activation of exercising muscles for more than a few seconds (Nybo and Nielsen, 2001;Todd et al, 2005;Racinais et al, 2008;Brazaitis et al, 2010;Périard et al, 2014).…”

Section: Discussioncontrasting

confidence: 69%

Modulation of neuromuscular excitability in response to acute noxious heat exposure has no additional effects on central and peripheral fatigability

et al. 2022

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Background: Whole-body hyperthermia (WBH) has an adverse effect on the nervous system and neurophysiological performance. In the present study, we examined whether short-duration whole-body immersion in 45°C water (HWI-45°C), which produces a strong neural and temperature flux without inducing WBH, can increase or impair neurophysiological performance in humans.Methods: Fifteen men (aged 25 ± 6 years) were enrolled in this study and participated in three experiments: 1) a brief (5-min) immersion of the whole body in 37°C water (WI-37°C); 2) a brief (5-min) HWI-45°C; and 3) a control trial in a thermoneutral condition at an ambient temperature of 24°C and 60% relative humidity. Before and after the immersions, neuromuscular function (electromyographic activity, reflexes, electrically and voluntary induced torque production, voluntary muscle activation level) were tested. To provoke central inhibition, the participants performed a sustained 2-min maximal voluntary contraction (MVC).Results: Thermophysiological strain was greater after HWI-45°C than after WI-37°C. Electrophysiological modulations of motor drive transmission and peripheral modulations of muscle contractility properties in response to HWI-45°C seemed to have little effect on central activation of the exercising muscles and no effect on MVC production.Conclusion: Although exposure to acute noxious heat was effective in evoking neuromuscular excitability, the increases in core temperature (∼0.2°C) and muscle temperature (∼0.6°C) did not induce moderate or severe WBH. These changes did not seem to affect central structures; that is, there were no additional increases in central and/or peripheral fatigue during a sustained 2-min MVC.

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“…The method to measure subjective ratings for the whole-body has been described elsewhere [18] , [8] . Briefly, ratings of thermal sensation ranged from 1 (very cold) to 9 (very hot), with 5 being neutral.…”

Section: Methodsmentioning

confidence: 99%

Time Course of Physiological and Psychological Responses in Humans during a 20-Day Severe-Cold–Acclimation Programme

et al. 2014

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The time course of physiological and psychological markers during cold acclimation (CA) was explored. The experiment included 17 controlled (i.e., until the rectal temperature reached 35.5°C or 170 min had elapsed; for the CA-17 session, the subjects (n = 14) were immersed in water for the same amount of time as that used in the CA-1 session) head-out water immersions at a temperature of 14°C over 20 days. The data obtained in this study suggest that the subjects exhibited a thermoregulatory shift from peripheral-to-central to solely central input thermoregulation, as well as from shivering to non-shivering thermogenesis throughout the CA. In the first six CA sessions, a hypothermic type of acclimation was found; further CA (CA-7 to CA-16) led to a transitional shift to a hypothermic–insulative type of acclimation. Interestingly, when the subjects were immersed in water for the same time as that used in the CA-1 session (CA-17), the CA led to a hypothermic type of acclimation. The presence of a metabolic type of thermogenesis was evident only under thermoneutral conditions. Cold-water immersion decreased the concentration of cold-stress markers, reduced the activity of the innate immune system, suppressed specific immunity to a lesser degree and yielded less discomfort and cold sensation. We found a negative correlation between body mass index and Δ metabolic heat production before and after CA.

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Force variability depends on core and muscle temperature

Cited by 8 publications

References 24 publications

Pre-Exercise Rehydration Attenuates Central Fatigability during 2-Min Maximum Voluntary Contraction in Hyperthermia

Pre-Exercise Rehydration Attenuates Central Fatigability during 2-Min Maximum Voluntary Contraction in Hyperthermia

Modulation of neuromuscular excitability in response to acute noxious heat exposure has no additional effects on central and peripheral fatigability

Time Course of Physiological and Psychological Responses in Humans during a 20-Day Severe-Cold–Acclimation Programme

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