(a) Experimental outline for b-c. (b) Blood (*p = 0.012, ***p = 8.89 × 10−5) and tibial (**p = 0.0053, ***p = 0.00079) leptin concentrations measured by ELISA (n = 9 animals for sedentary and exercise, n = 13 animals for post-exercise-sedentary, 3 independent experiments, with Dunn’s post hoc test). (c) Gene expression of niche factors Cxcl12 (*p = 0.015), Vcam1 (*p = 0.038), Kitl (**p = 0.0037 sedentary versus exercise, **p = 0.0035 exercise versus post-exercise-sedentary) and Angpt1 (*p = 0.027) in whole bone marrow by qPCR (n = 9 animals for sedentary and exercise, n = 13 animals for post-exercise-sedentary, 3 independent experiments, one-way analysis of variance with Sidak’s post hoc test). mRNA levels were normalized to Actb Ct values. (d) Experimental outline for e. The post-exercise-sedentary group had access to exercise wheels for 6 weeks after which the wheels were removed for the following 6 weeks. Sedentary controls had no access, while the exercise group had access to wheels during the last 6 weeks before sacrifice. (e) Circulating leukocyte levels at Zeitgeber time 7 (*p = 0.028 sedentary versus exercise, *p = 0.045 exercise versus post-exercise sedentary) and BrdU incorporation into LSK 22 h after intraperitoneal injection (*p = 0.045 sedentary versus exercise, *p = 0.014 exercise versus post-exercise-sedentary, n = 6 animals per group, with Dunn’s post hoc test). (f) Outline of the competitive bone marrow transplantation experiments. LSK were isolated from CD45.2 donors that either exercised for 6 weeks or were sedentary. These were transplanted in a 1:1 ratio into CD45.1 recipients together with LSK isolated from Ubc-GFP mice that exercised for 6 weeks and had a 3-week post-exercise-sedentary period. Blood chimerism 8 weeks after transplantation (n = 4 animals per group, p = 0.12 for exercise versus post-exercise-sedentary donor chimerism, Wilcoxon matched-pairs signed rank test). Data are mean ± s.e.m. We acknowledge Servier Medical Art (https://smart.servier.com) for providing images of mice and components of the cartoon.