Table 3.
Behavioral and Functional Characteristics
| B6 |
MIN |
|||
|---|---|---|---|---|
| Sedentary |
Wheel |
Sedentary |
Wheel |
|
| Behavior | ||||
| Food Intake (g) | ||||
| 12 wk | 3.7 ± 0.1 | 3.7 ± 0.1 | 3.8 ± 0.2 | 3.7 ± 0.1 |
| 18 wk | 4.0 ± 0.1$ | 4.3 ± 0.2$ | 3.7 ± 0.2* | 3.9 ± 0.1* |
| Δ | 0.33 ± 0.13 | 0.54 ± 0.22 | −0.16 ± 0.33* | 0.18 ± 0.13* |
| Cage Activity (x1000 counts) | ||||
| 12 wk | 19.5 ± 1.3 | 19.6 ± 1.4 | 22.0 ± 2.7 | 23.4 ± 2.8 |
| 18 wk | 26.4 ± 2.0$ | 29.8 ± 2.6$ | 12.6 ± 3.4*$ | 14.1 ± 2.0*$ |
| Δ | 6.9 ± 2.7 | 10.2 ± 2.6 | −9.4 ± 2.9* | −9.4 ± 3.0* |
| Whole-body Function | ||||
| Grip Strength (mN/g) | ||||
| 12 wk | 106.2 ± 0.9 | 103.4 ± 2.5 | 108.4 ± 2.9 | 103.5 ± 2.1 |
| 18 wk | 113.1 ± 3.8 | 112.7 ± 1.1$ | 100.0 ± 2.0* | 107.4 ± 2.0* |
| Δ | 6.9 ± 3.9 | 9.3 ± 3.0^ | −8.4 ± 4.0* | 3.9 ± 3.0*^ |
| Fall Latency (sec) | ||||
| 12 wk | 61.5 ± 4.6 | 62.1 ± 5.9 | 61.3 ± 4.4 | 56.4 ± 8.4 |
| 18 wk | 76.7 ± 5.7 | 68.1 ± 5.2 | 69.0 ± 9.7 | 72.2 ± 3.4 |
| Δ | 15.2 ± 5.1 | 6.1 ± 6.2 | 7.8 ± 9.6 | 15.8 ± 7.2 |
| Time to Fatigue (min) | ||||
| 12 wk | 77.9 ± 4.1 | 79.7 ± 6.0 | 78.8 ± 6.7 | 74.2 ± 6.1 |
| 18 wk | 86.6 ± 3.6 | 150.3 ± 11.7$^ | 40.8 ± 6.9$* | 99.9 ± 15.2*^ |
| Δ | 8.7 ± 4.1 | 70.7 ± 13.7^ | −38 ± 7.3 | 25.7 ± 15.2*^ |
| Skeletal Muscle Function | ||||
| Twitch Properties | ||||
| 1/2 RT (ms) | 7.3 ± 0.2 | 7.5 ± 0.1 | 9.4 ± 0.8* | 10.3 ± 1.2* |
| TPT (ms) | 15.1 ± 0.2 | 14.8 ± 0.2 | 16.2 ± 0.4* | 17.6 ± 1.3* |
| Force Production | ||||
| Po (mN) | 1544 ± 42 | 1647 ± 36 | 1300 ± 82* | 1356 ± 87* |
| sPo (kN/m2) | 285 ± 9 | 309 ± 8 | 271 ± 12* | 279 ± 9* |
| Contraction Rates | ||||
| + dP/dtmax (N/s) | 24.0 ± 1.0 | 23.2 ± 1.0 | 20.6 ± 1.9 | 20.9 ± 1.7 |
| − dP/dtmax (N/s) | 17.5 ± 1.3 | 19.7 ± 1.0 | 12.5 ± 1.3* | 13.1 ± 1.6* |
Values are means ± SEM. Average daily food intake measured over 3 days in grams (g). Average daily cage activity measured over 3 days in beams crossed (counts). Relative grip strength given in milliNewtons force /grams of body weight (mN/g). Time on the rotorod (fall latency) given in seconds (sec). Time to fatigue during a graded exercise treadmill test given in minutes (min). All behavior and whole-body function outcomes were measured at 12 and 18 weeks (wk). Delta (Δ) between 12 and 18 weeks. Properties of skeletal muscle function were measured at ~18 wks prior to sacrifice. 1/2 Relaxation time (RT) and time to peak twitch (TPT) given in milliseconds (ms) measured during an isolated twitch contraction. Absolute (Po) and specific (sPo) maximal force production given in milliNewtons (mN) and kiloNewtons/meters2 (kN/m2), respectively, measured at 200 hz. Rate of contraction (+dP/dtmax) and rate of relaxation (−dP/dtmax) given in newtons/second (N/s) measured at 200 hz. C57BL/6 (B6; sedentary n=10, wheel n=9). ApcMin/+ (MIN; sedentary n=10, wheel n=10). Two-way ANOVA.
Main effect of genotype.
Main effect of treatment.
Repeated measures, effect of time. Significance was set a p≤0.05