## 3 Results
### Cr(VI) Altered Grip Strength in Older Age Groups  
We assessed the effects of Cr(VI) on grip strength after 1 and 7 weeks of drinking water exposure (Figure 2). One geriatric control rat was identified as a statistical outlier (698 g) and was removed from comparisons at 7 weeks. When only considering Cr(VI) effects, not accounting for age groups, Cr(VI) had no effect on grip strength after either 1 or 7 weeks of exposure (Figure 2A,B). We then considered the effects of Cr(VI) across multiple age groups (Figure 2C,D). We observed no change in grip strength of young (3 months old), middle-aged (7 months old), or geriatric rats (18 months old) after 1 week of Cr(VI) exposure, and no differences due to age. After 7 weeks, we observed slightly decreased grip strength in young rats exposed to both Cr(VI) concentrations and a decrease in middle-aged rats exposed to 0.1 mg Cr(VI)/L: 415.2, 377.3, and 315.4 g for middle-aged control, 0.05, and 0.1 mg Cr(VI)/L, respectively. We observed significantly increased grip strength in geriatric rats after 7 weeks of exposure to 0.05 mg Cr(VI)/L (\(p\) = 0.01): 271.5, 359.5, and 323.1 g for control, 0.05, and 0.1 mg Cr(VI)/L, respectively (Figure 2D). Cr(VI) Altered Locomotor Coordination in Middle-Aged Rats, Exploratory Behavior in Young Rats during the Open-Field Assay  
Rats performed the open-field assay during weeks 2 and 8 of Cr(VI) exposure. We assessed exploratory behavior as the percentage of time spent exploring the center area of the open-field chamber (Figure 3), locomotor coordination as rearing behavior (Figure 4), and locomotor function as distance traveled (Figure 5). We assessed center area exploration after 2 and 8 weeks of Cr(VI) exposure. One young control rat was identified as a statistical outlier (32.26%) and was removed from comparisons at 8 weeks. When considering the effects of Cr(VI) alone on exploratory behavior, we observed no change in center area exploration (Figure 3A,B). We then considered center area exploration across age groups (Figure 3C,D). After 2 weeks, we observed significantly increased center area exploration in young rats exposed to 0.1 mg Cr(VI)/L (\(p=0.05\)) and slightly increased exploration in middle-aged rats exposed to 0.05 mg Cr(VI)/L, but we observed a slight decrease in geriatric rats exposed to Cr(VI) (Figure 3C). After 8 weeks,  
Figure 2: **Cr(VI) Impacted Grip Strength in Older Age Groups. ** We considered the effect of Cr(VI) exposure on female rat grip strength after 1 or 7 weeks of exposure to Cr(VI) in drinking water. (**A,B**) Data were compared across Cr(VI) groups ((**A**), \(n=25\), \(26\), and \(26\), respectively; (**B**), \(n=25\), \(25\), and \(25\), respectively). (**C,D**) Data were then compared across ages ((**C**), young \(n=8\), \(8\), and \(8\), respectively; mid-aged \(n=8\), \(7\), and \(7\), respectively; geriatric \(n=9\), \(11\), and \(11\), respectively; (**D**), young \(n=8\), \(8\), and \(7\), respectively; mid-aged \(n=8\), \(6\), and \(8\), respectively; geriatric \(n=8\), \(11\), and \(10\), respectively). One outlier removed from 7 week control (geriatric, 698 g); other missing data points are due to rats refusing to grasp the horizontal bar in the grip strength test or due to early death in geriatric rats as indicated in the Methods. Data represent the mean \(\pm\) SEM. Blue circles are control groups, orange squares are 0.05 mg Cr(VI)/L, and red triangles are 0.1 mg Cr(VI)/L. we observed increased center area exploration in young rats exposed to 0.05 mg Cr(VI)/L, whereas middle-aged rats exhibited a slight concentration-associated decrease and geriatric rats exhibited no effect (Figure 3D). We assessed the effects of Cr(VI) on rearing behavior with no effect after 2 weeks of exposure but a slight decrease after 8 weeks of exposure to 0.05 mg Cr(VI)/L (Figure 4A,B). We then considered rearing behavior across age groups (Figure 4C,D). Rearing was not affected in young rats in either week.