UB researchers have designed a new tool to list laboratory rats according to their running style on the treadmill, widely used procedure in research on exercise physiology. This method, published in the journal PLOS ONE, improves the understanding of the studies in this scientific field, since it allows linking the running style –and thus, aspects like real intensity of exercise- to metabolic and physiological data, such as indicators of muscle damage. Led by the professor from the Faculty of Biology Ginés Viscor, the study could increase the number of valid animals to take part in the experiments, therefore allowing a better adjustment with the international principles on animal experimentation.
Adaptation problems for constant running
Laboratory rats are a model used worldwide to do research on the body’s response to exercise. Among the most used techniques in these studies is the constant race in the treadmill, but not all rats adapt the same way, since their running is intermittent.
“A variable fraction of the rats learns how to run constantly easily, but others do not get used to it and run intermittently or do not learn how to run and we have to rule them out”, says Ginés Viscor.
Contamination for experimental design
Diversity in the adaptation to the treadmill has different implications in the study, such as the volume of training or the real intensity being different depending on the adaptation process of the rat to the constant running. Also, the fact that those rats that do not get used to this kind of exercise are ruled out or listed in the group of sedimentary rats ends up twisting the control group with rats that tend to run in another way. “In the studies, the risk of selecting ‘good runner’ rats would equal to selecting human volunteers who were trained sportspeople and make them represent the whole population”, notes the researcher.
In this context, the objective of the study is to list the way the rats run in the treadmill and link this running style to the results of the studies in the physiological aspect, so that all animals can be used, both good and bad at running.
The tool the UB team designed assesses and gives a score to the running style of the rats depending on their features: attitude, resistance and performance. “With this score we can monitor the type of activity of the rat and co-relate the runner level shown by the rat in the experiment with the physiological data, which would clarify the results that were confusing. The methodology would enable having a more precise estimation of the real dose of exercise done by every rat”, notes the researcher.
Researchers applied the tool to a project that analyses the impact of training in the recovery of muscle damage. To do so, the study compares physiological indicators of muscle damage with the exercise done by the rats in the treadmill. Results show the new tool enables distinguishing between healthy animals and animals who suffered a previous exercise-induced muscle damage. Therefore, researchers could identify, for instance, that rats who took longer to get used to the constant running were less tired and took longer to reach muscle damage, or the other way round: rats that were good runners presented higher muscle damage for having ran for a longer period during the test, reaching exhaustion.
Correlations allowed by the new tool enable using better the obtained data for every rat, which contributes to a more responsible use of animals in experiments. “The use of this scoring system increases the number of animals for the experiments, and it fulfils the principle of the Three Rs –reduction, refinement and replacement-, one of the basic pillars of animal experimentation”, concludes the researcher.
J. G. Ríos-Kristjánsson, D. Rizo-Roca, K. Mist Kristjánsdóttir, C. A. Núñez-Espinosa, J. R. Torrella, T. Pagès and G. Viscor “A three-criteria performance score for rats exercising on a running treadmill“. PLOS ONE, July 2019.