Comparison of murine behavioural and physiological responses after forced exercise by electrical shock versus manual prodding.

New Findings: What is the central question of this study? Forced treadmill exercise using electrical shock is the most common technique in rodent exercise studies. Here, we examined how the use of electrical shock during forced treadmill exercise affects behavioural and physiological responses in comparison to a novel non-electrical shock technique. What is the main finding and its importance? In comparison to mice that underwent traditional treadmill running induced by electrical shock, mice that underwent forced running using a novel technique involving gentle prodding to induce running showed: (i) higher locomotor activity; (ii) less anxiety-like behaviour; and (iii) altered exercise-induced muscle pain immediately after exercise.

Abstract: Animal models of exercise have been useful to understand underlying cellular and molecular mechanisms. Many studies have used methods of exercise that are unduly stressful (e.g., electrical shock to force running), potentially skewing results. Here, we compared physiological and behavioural responses of mice after exercise induced using a prodding technique that avoids electrical shock versus a traditional protocol using electrical shock. We found that exercise performance was similar for both techniques; however, the shock group demonstrated significantly lower locomotor activity and higher anxiety-like behaviour. We also observed divergent effects on muscle pain; the prodding group showed hyperalgesia immediately after exercise, whereas the shock group showed hypoalgesia. Corticosterone concentrations were elevated to a similar extent for both groups. In conclusion, mice that were exercised without shock generated similar maximal exercise performance, but postexercise these mice showed an increase in locomotor activity, less anxiety-like behaviour and altered muscle pain in comparison to mice that exercised with shock. Our data suggest that running of mice without the use of electrical shock is potentially less stressful and might be a better technique to study the physiological and behavioural responses to exercise.