Research Paper Volume 8, Issue 4 pp 620—635

Figure 2. Influenza infection induced functional decrements in voluntary locomotor activity and gait kinematics that is more pronounced in the hind limbs and in the aged mice. Young and aged C57BL/6 mice were intranasally infected with 500 EID₅₀ of PR8 influenza. On days 0, 3, 7, 11, 15, and 20 mice were tested for functional performance. (A) Spontaneous voluntary activity was assessed via the open field test on a photobeam activity system. Beam breaks were recorded as mice traveled at 16”x16” open field and locomotor activity was assessed as beam breaks per minute. Gait parameters were assessed utilizing DigiGait, a ventral plane videography treadmill system. Postural gait parameters (Stance width of the fore (B) and hind (E) limbs and midline distance of the fore (C) and hind (F) limbs) were altered during flu infection with more prominent differences in the hind limbs of aged mice. Kinematic gait parameters were also altered with flu infection. Gait symmetry of the fore/hind limbs (D) was increased. Stride length variability of the fore limb (G) did not change, however the aged mice had increased stride length variability in the hind limbs later in the infection (J). Maximal rate of change of paw area contact during the breaking phase (Max dA/dt) and propulsion phase (Min dA/dt) is altered in the fore (H and I, respectively) and hind limbs (K and L, respectively) with more dramatic results in the hind limbs. All data analyzed via two-way ANOVA with Bonferroni post hoc corrections with effect of flu infection over time (compared to day 0, p<0.05) indicated by brackets above data and differences between young and aged mice (p<0.05) at time points indicated by asterisk.