Adaptations to high-intensity intermittent exercise in rodents

Bexfield, Nathan A.; Parcell, Allen C.; Nelson, W. Bradley; Foote, Kristopher M.; Mack, Gary W.

doi:10.1152/japplphysiol.91446.2008

Cited by 18 publications

(10 citation statements)

References 36 publications

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“…Our results cannot conclusively determine the precise mechanisms leading to increased endurance capacity, but the differences in endurance were associated with corresponding differences in haematocrit and SO fibre CSA in two key locomotor muscles. The higher haematocrit in endurance-trained lizards is consistent in its directional change to studies of humans and other mammals (reviewed in Bexfield et al, 2009;Connes et al, 2013), as well as birds (Riera et al, 1983), crocodilians (Eme et al, 2009) and fishes (Beamish, 1978), and locomotor endurance in lizards is related to haematocrit (Garland, 1984;. The increased oxygen-carrying capacity that comes with higher haematocrit may explain a significant portion of the increase in endurance.…”

Section: Discussionmentioning

confidence: 59%

Making Olympic lizards: the effects of specialised exercise training on performance

Husak

Keith

Wittry

2015

Journal of Experimental Biology

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Exercise training is well known to affect a suite of physiological and performance traits in mammals, but effects of training in other vertebrate tetrapod groups have been inconsistent. We examined performance and physiological differences among green anole lizards (Anolis carolinensis) that were trained for sprinting or endurance, using an increasingly rigorous training regimen over 8 weeks. Lizards trained for endurance had significantly higher posttraining endurance capacity compared with the other treatment groups, but groups did not show post-training differences in sprint speed. Although acclimation to the laboratory environment and training explain some of our results, mechanistic explanations for these results correspond with the observed performance differences. After training, endurance-trained lizards had higher haematocrit and larger fast glycolytic muscle fibres. Despite no detectable change in maximal performance of sprint-trained lizards, we detected that they had significantly larger slow oxidative muscle fibre areas compared with the other treatments. Treatment groups did not differ in the proportion of number of fibre types, nor in the mass of most limb muscles or the heart. Our results offer some caveats for investigators conducting training research on non-model organisms and they reveal that muscle plasticity in response to training may be widespread phylogenetically.

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Section: Discussionmentioning

confidence: 59%

Making Olympic lizards: the effects of specialised exercise training on performance

Husak

Keith

Wittry

2015

Journal of Experimental Biology

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“…Both LE and SD rats trained on running wheels had significantly elevated levels of %fluid compared with sedentary rats. It has been shown that rats subjected to repeated exercise training undergo an increase in plasma volume (2). The well-known expansion in plasma volume with exercise in humans is attributed to an increase in plasma content of albumin that acts to retain water (2,4,7).…”

Section: Discussionmentioning

confidence: 99%

“…It has been shown that rats subjected to repeated exercise training undergo an increase in plasma volume (2). The well-known expansion in plasma volume with exercise in humans is attributed to an increase in plasma content of albumin that acts to retain water (2,4,7). With significantly elevated %fluid levels in wheel-trained rats, we expected that recovery from an injected bolus of normal or hypertonic saline would differ from that of sedentary animals.…”

Section: Discussionmentioning

confidence: 99%

A noninvasive method to study regulation of extracellular fluid volume in rats using nuclear magnetic resonance

Gordon

Phillips

Johnstone

2016

American Journal of Physiology-Renal Physiology

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Gordon CJ, Phillips PM, Johnstone AF. A noninvasive method to study regulation of extraceullular fluid volume in rats using nuclear magnetic resonance. Am J Physiol Renal Physiol 310: F426-F431, 2016. First published December 23, 2015 doi:10.1152/ajprenal.00405.2015.-Timedomain nuclear magnetic resonance (TD-NMR)-based measurement of body composition of rodents is an effective method to quickly and repeatedly measure proportions of fat, lean, and fluid without anesthesia. TD-NMR provides a measure of free water in a living animal, termed %fluid, and is a measure of unbound water in the vascular and extracellular spaces. We hypothesized that injecting a bolus of fluid into the peritoneal cavity would lead to an abrupt increase in %fluid and the rate of clearance monitored with TD-NMR would provide a noninvasive assessment of the free water homeostasis in an awake rat. Several strains of laboratory rats were injected intraperitoneally with 10 ml/kg isotonic or hypertonic saline and %fluid was monitored repeatedly with a Bruker "Minispec" TD-NMR body composition system. Following isotonic saline, %fluid increased immediately by 0.5% followed by a recovery over ϳ6 h. Injecting hypertonic (3 times normal saline) resulted in a significantly greater rise in %fluid and longer recovery. Intraperitoneal and subcutaneous fluid injection led to similar rates of clearance. The Wistar-Kyoto rat strain displayed significantly slower recovery to fluid loads compared with LongEvans and Sprague-Dawley strains. Rats exercised chronically showed significant increases in %fluid, but the rate of clearance of fluid was similar to that of sedentary animals. We conclude that this technique could be used to study vascular and extracellular volume homeostasis noninvasively in rats. fluid homeostasis; rodent; noninvasive; unanesthetized; deydration NONINVASIVE MEASUREMENT OF body composition of laboratory rodents is becoming an increasingly popular method to measure body fat as well as other components of body composition without the need for anesthesia or terminating the animal. Magnetic resonance-based systems are used to rapidly measure body composition in awake animals (10, 11). Time-domain nuclear magnetic resonance (TD-NMR) measures the percentages of fat, lean, and fluid of unanesthetized mice and rats (5). The %fluid parameter is a measure of water in a liquid, unbound state and does not include water that is bound in tissue. Hence, %fluid measured by TD-NMR is primarily a measure of unbound fluid in blood and other extracellular fluid compartments. TD-NMR measures of %fluid of rats and mice are typically 7-8% (5).We speculated that the TD-NMR measure of %fluid could be used to study the homeostatic regulation of free water in an awake rodent. That is, if a bolus of saline were to be injected into a mouse or rat, one should be able to measure an abrupt increase in the %fluid. The magnitude of the rise in fluid volume and the rate of clearance of the excess could reflect the capacity of homeostatic processes involved in regulating e...

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“…In our study, 1 month of exercise increased liver iron stores and blood Hb and enhanced iron absorption. The increased Hb, without changes in Hct, in the exercising rats' blood reflect a much greater amount of Hb, and a greater circulating erythrocytes mass than in sedentary animals, most likely as a result of the expanded blood volume induced by exercise [33]. This increased erythrocyte mass with accelerated Hb synthesis and erythrocyte turnover [1,19,20] implied that erythropoiesis must be extremely active and requires more iron for Hb synthesis.…”

Section: Discussionmentioning

confidence: 99%

Changes of Iron Stores and Duodenal Transepithelial Iron Transfer During Regular Exercise in Rats

Lilong

Xiao

et al. 2010

Biol Trace Elem Res

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It is unclear whether regular exercise depletes body iron stores and how exercise regulates iron absorption. In this study, growing female Sprague-Dawley rats were fed a high-iron diet (300 mg iron/kg) and subjected to swimming for 1, 3, or 12 months. Their body weight, liver nonheme iron content (NHI), spleen NHI, blood hemoglobin (Hb) concentration, hematocrit (Hct), and kinetics of 59Fe transfer across isolated duodenal segments were then compared with sedentary controls. The main results were as follows: exercise for 1 month enhanced the transepithelial 59Fe transfer and increased liver NHI content and Hb concentration; exercise for 3 months inhibited transepithelial 59Fe transfer without affecting the liver and spleen NHI content, Hb concentration, and Hct; exercise for 12 months did not affect these parameters as compared with the corresponding sedentary controls; and the changes in transepithelial iron transfer were not associated with basolateral iron transfer. Our findings demonstrated that chronic, regular exercise in growing rats with a high dietary iron content does not deplete iron stores in the liver and spleen and may possibly enhance or inhibit duodenal iron absorption and even maintain duodenal iron absorption at the sedentary level, at least, in part depending on growth.

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Adaptations to high-intensity intermittent exercise in rodents

Cited by 18 publications

References 36 publications

Making Olympic lizards: the effects of specialised exercise training on performance

Making Olympic lizards: the effects of specialised exercise training on performance

A noninvasive method to study regulation of extracellular fluid volume in rats using nuclear magnetic resonance

Changes of Iron Stores and Duodenal Transepithelial Iron Transfer During Regular Exercise in Rats

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