Q10 (temperature coefficient)

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The Q₁₀ temperature coefficient is a mathematical parameter that is thought to come from the late 19th century, in the work of van ’t Hoff.^[1] Q₁₀ is a measure of temperature sensitivity based on chemical reaction rates, and it applies to most physiological processes (e.g., respiration, digestion, photosynthesis).^[2][3]

The Q₁₀ is calculated as:

${\displaystyle Q_{10}=\left({\frac {R_{2}}{R_{1}}}\right)^{10\,^{\circ }\mathrm {C} /(T_{2}-T_{1})}}$

where;

R is the rate with a context-dependent unit.

T is the temperature in degrees Celsius or kelvin.

Rewriting this equation, the assumption behind Q₁₀ is that the reaction rate R depends exponentially on temperature:

${\displaystyle R_{2}=R_{1}~Q_{10}^{(T_{2}-T_{1})/10\,^{\circ }\mathrm {C} }}$

Q₁₀ is a unitless quantity, as it is the factor by which a rate changes. In this equation, R₁ represents the rate at the reference temperature T₁. In environmental sciences, the reference temperature for calculating Q₁₀ is often chosen to be 0 °C or 10°C.^[4][5][6][7] If the reference temperature is 10 °C, Q₁₀ represents the factor by which the rate is multiplied for each 10°C increase in temperature. For most biological systems, the Q₁₀ value is ~ 2 to 3 (the rate doubles or triples for every 10 °C increase in temperature).^[8][3]

In muscle performance

The temperature of a muscle has a significant effect on the velocity and power of the muscle contraction, with performance generally declining with decreasing temperatures and increasing with rising temperatures. The Q₁₀ coefficient represents the degree of temperature dependence a muscle exhibits as measured by contraction rates.^[9] A Q₁₀ of 1.0 indicates thermal independence of a muscle whereas an increasing Q₁₀ value indicates increasing thermal dependence. Values less than 1.0 indicate a negative or inverse thermal dependence, i.e., a decrease in muscle performance as temperature increases.^[10]

Q₁₀ values for biological processes vary with temperature. Decreasing muscle temperature results in a substantial decline of muscle performance such that a 10 degree Celsius temperature decrease results in at least a 50% decline in muscle performance.^[11] Persons who have fallen into icy water may gradually lose the ability to swim or grasp safety lines due to this effect, although other effects such as atrial fibrillation are a more immediate cause of drowning deaths. At some minimum temperature biological systems do not function at all, but performance increases with rising temperature (Q₁₀ of 2-4) to a maximum performance level and thermal independence (Q₁₀ of 1.0-1.5). With continued increase in temperature, performance decreases rapidly (Q₁₀ of 0.2-0.8) up to a maximum temperature at which all biological function again ceases.^[12]

Within vertebrates, different skeletal muscle activity has correspondingly different thermal dependencies. The rate of muscle twitch contractions and relaxations are thermally dependent (Q₁₀ of 2.0-2.5), whereas maximum contraction, e.g., tetanic contraction, is thermally independent.^[13]

Muscles of some ectothermic species. e.g., sharks, show less thermal dependence at lower temperatures than endothermic species ^[11][14]

See also

• Arrhenius equation
• Arrhenius plot
• Isotonic (exercise physiology)
• Isometric exercise
• Skeletal striated muscle
• Tetanic contraction

References