Gross and fine neuromuscular performance at cold shivering

Meigal, Alexander

doi:10.3402/ijch.v61i2.17449

Cited by 41 publications

(45 citation statements)

References 32 publications

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“…The clothing for AS and AP was the same and the work rate was calculated by the same method for both. Although muscle tension (thermoregulatory muscle tone) [22] and shivering due to cold were neither observed nor reported, these reactions may explain why measured and predicted metabolic rates differed. Cooling to such a degree promotes performance , then the cooling rate of the subjects could actually have been much quicker or they could have started shivering.…”

Section: Sweatingmentioning

confidence: 97%

Calculation of Clothing Insulation by Serial and Parallel Methods: Effects on Clothing Choice by IREQ and Thermal Responses in the Cold

Kuklane

Gao

Holmér

et al. 2007

International Journal of Occupational Safety and Ergonomics

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Section: Sweatingmentioning

confidence: 97%

Calculation of Clothing Insulation by Serial and Parallel Methods: Effects on Clothing Choice by IREQ and Thermal Responses in the Cold

Kuklane

Gao

Holmér

et al. 2007

International Journal of Occupational Safety and Ergonomics

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“…It is, however, difficult to explain the basis of these findings as muscle motor unit recruitment during combined shivering and exercise is poorly understood. Whether motor units of different types or different motor units of the same type would be involved in the response is unknown (Meigal 2002). Based on the thermogenic potential between LOW SHIV and exercise, the larger contribution of exercise towards V O 2 and heat production could have been the main fuel selection modulator.…”

Section: Physiological Mechanismsmentioning

confidence: 99%

Fuel selection during short-term submaximal treadmill exercise in the cold is not affected by pre-exercise low-intensity shivering

Gagnon

Rintamäki

Gagnon

et al. 2014

Appl. Physiol. Nutr. Metab.

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Exercise and shivering rely on different metabolic pathways and consequently, fuel selection. The present study examined the effects of a pre-exercise low-intensity shivering protocol on fuel selection during submaximal exercise in a cold environment. Nine male subjects exercised 4 times for 60 min at 50% (LOW) or 70% (MOD) of their peak oxygen consumption on a motorized treadmill in a climatic chamber set at 0 °C with (SHIV) and without (CON) a pre-exercise cooling protocol, inducing low-intensity shivering. Thermal, cardiorespiratory and metabolic responses were measured every 15 min whereas blood samples were collected every 30 min to assess serum nonesterified fatty acids (NEFA), glycerol, glucose, β-hydroxybutyrate (BHB) and plasma catecholamine concentrations. Rectal and skin temperatures were lower in the SHIV condition, within LOW and MOD conditions, during the first 45 min of exercise. Norepinephrine (NE) concentration was greater in SHIV vs. CON within LOW (1.39 ± 0.17 vs. 0.98 ± 0.17 ng·mL(-1)) and MOD (1.50 ± 0.20 vs. 1.01 ± 0.09 ng·mL(-1)), whereas NEFA, glycerol and BHB were greater in SHIV vs. CON (1060 ± 49 vs. 898 ± 78 μmol·L(-1); 0.27 ± 0.02 vs. 0.22 ± 0.03 mmol·L(-1); 0.39 ± 0.06 vs. 0.27 ± 0.04 mmol·L(-1), respectively) within MOD only. No changes were observed in fat or carbohydrate oxidation between SHIV and CON during exercise. Despite increases in NE, NEFA, glycerol and BHB from pre-exercise low-intensity shivering, fuel selection during short-term submaximal exercise in the cold was unaltered.

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“…This is not the case during cold exposure, and fuel selection by recruitment of specific fibers within the same muscles has been clearly demonstrated during shivering (Haman et al, 2004b). EMG recordings of shivering muscles show two distinct patterns: continuous, low-intensity shivering at 4-8Hz (which signals the recruitment of type I motor units) and high-intensity, burst shivering at 0.1-0.2Hz (from type II motor units) (Petajian and Williams, 1972;Meigal, 2002). During high-intensity shivering, humans are able to modulate their use of carbohydrates by changing the recruitment level of type II fibers (burst shivering) within muscles used for thermogenesis (Haman et al, 2004b).…”

Section: Mechanisms Of Fuel Selectionmentioning

confidence: 99%

Metabolic fuels: regulating fluxes to select mix

Weber

2011

Journal of Experimental Biology

113

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Animal life depends on the capacity to match metabolic fuel supply to changing rates of energy use. The fluxes of multiple substrates must be modulated to achieve real-time selection of mixtures able to support adequate metabolic rates for variable physiological circumstances: from years of torpor to seconds of sprinting. The regulation of energy metabolism is a complex challenge because the fuels available vary widely in stored quantity, energy density, speed of conversion to ATP and water solubility. Therefore, fuel selection strategies aim to exploit the advantages of individual substrates while minimizing the impact of their disadvantages. The rate of energy expenditure necessary for a particular task determines for how long that task can be maintained. Fig.1A illustrates the relationship between metabolic intensity and duration by plotting record times of human athletes running over different distances vs average speed. This example is used to characterize the shape of the more general relationship between metabolic rate and duration. Fig.1B-E compares lipids and carbohydrates for the main parameters determining whether these fuels tend to support prolonged low-intensity tasks or intense activities of short duration.Lipids show unique characteristics that make them ideally suited for long-lasting physiological work because they contain the most energy per unit mass (Fig.1B) and, therefore, are stored in large amounts (Fig.1C). Lipids pack more joules per gram because they can be stored dehydrated and, to a lesser extent, because they are more chemically reduced than other fuels. Their highly reduced state also allows them to yield more metabolic water than proteins or carbohydrates when they are oxidized. Therefore, organismal dehydration can be avoided by producing metabolic water through the oxidation of lipid stores: a strategy commonly used by birds lacking access to drinking water during long migrations (Carmi et al., 1992;Klaassen, 1996). The low maximal rate of ATP production from lipids ( Fig.1E) is not a limiting factor for prolonged, low-to moderate-intensity tasks. Similarly, the low solubility of lipids in water (Fig.1D) would severely restrict the capacity to transport them from storage sites, but this serious handicap is greatly reduced by the solubilizing action of albumin in the plasma (van der Vusse, 2009) and fatty acid binding proteins (FABPs) in the cytosol (Haunerland and Spener, 2004). These specialized transport proteins ensure that lipids can be shuttled between tissues, at least rapidly enough to support low-to moderate-intensity tasks. This requirement for transport proteins may be partly responsible for limiting maximal rates of lipid oxidation.In contrast to lipids, carbohydrates show high maximal rates of ATP production, especially under anaerobic conditions (Fig.1E), and high solubility in water (Fig.1D). These fundamental characteristics make them essential for intense physiological work. For most animals, carbohydrates also provide the benefit of being the only usable...

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Gross and fine neuromuscular performance at cold shivering

Cited by 41 publications

References 32 publications

Calculation of Clothing Insulation by Serial and Parallel Methods: Effects on Clothing Choice by IREQ and Thermal Responses in the Cold

Calculation of Clothing Insulation by Serial and Parallel Methods: Effects on Clothing Choice by IREQ and Thermal Responses in the Cold

Fuel selection during short-term submaximal treadmill exercise in the cold is not affected by pre-exercise low-intensity shivering

Metabolic fuels: regulating fluxes to select mix

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