Engendering Species-Appropriate Exercise to Attenuate Sarcopenia in Laboratory-Housed Cynomolgus Macaques (Macaca fascicularis).

Sarcopenia is the decline in skeletal muscle mass and function with age and is observed in both humans and non-human primates. Sarcopenia progression in humans is highly correlated with various pathologies and mortality risks independent of other risk factors. Laboratory-housed non-human primates that do not engage in adequate physical activity are at higher risk of developing sarcopenia. We devised a simple behavioral task to enhance environmental enrichment and increase physical fitness. An aperture allowed vertical movement between two vertically mounted cages. Despite this arrangement, male cynomolgus macaques (approximately 13 years old) still spent the majority of time in the upper cage and were not very active. Therefore, we implemented a new behavioral method using sweetened liquid as a reinforcer. Monkeys could initiate each trial by pressing the touch screen in the upper cage which would light a large red button placed in the lower cage. Pressing the button resulted in immediate delivery of juice in the upper cage for 5 s; thus, the monkey was encouraged to rapidly ascend to the top cage to drink as much of the liquid reinforcer as possible. Increases in exercise behavior (measured via operant testing apparatus and real-time monitoring) and activity (measured via actigraphy monitors) suggest that this highly adaptable method successfully increases strenuous exercise and species-typical climbing behavior, and can potentially provide a novel means of measuring and promoting physical and psychological well-being, as well as potentially attenuating sarcopenia in laboratory-housed primates.