Background: Barriers to physical activity in transgender youth often center on social and psychological factors, but the effects of puberty blocking treatment that some youth receive on physical activity have yet to be explored. This study investigated the effects of puberty blocking treatment on physical activity in young female and male rats. Methods: Four week old female (F, n=19) and male rats (M, n=19) received the gonadotropin releasing hormone agonist (GnRHa) triptorelin as a puberty blocker (F-PB, n=10; M-PB, n=10) or saline as a control (F-CON, n=9; M-CON, n=9) for 4 weeks. Animals were then housed in voluntary wheel running (VWR) cages and activity was recorded during treatment period. Results: Main drug (p<0.0001) and sex (p=0.045) effects with a significant drug x sex interaction (p=0.0095) was observed with total 4 week running distance with F-PB having a lower VWR activity than F-CON (240 ± 23 km vs 67 ± 9 km, respectively, p<0.0001) and M-PB having lower VWR activity than M-CON (165 ± 15 km vs. 77 ± 14 km, respectively, p<0.001). Significant differences in daily wheel running distance were first detected on day 5 for F-PB when compared to F-CON (p=0.036) and on day 11 for M-PB when compared to M-CON (p=0.034). Conclusions: Treatment with a GnRHa reduced voluntary running wheel activity in young female and male rats. Social and psychological factors are important variables impacting physical activity in transgender youth, but puberty blocker treatment may be an additional factor to consider when addressing physical activity.