Table 1 Phenotypic characterization and muscle weights standardized to tibia length for male and female C57BL/6J mice at middle age (15-month SED), old age (23-month SED), and following 34 weeks of RWE intervention (23-month EXE)

 Abdominal fat pad (% BW)

1.0 ± 0.3

2.8 ± 0.4*

1.8 ± 0.3

0.8 ± 0.1

2.0 ± 0.4*

1.3 ± 0.2

 Blood glucose (mmol/L)

10.7 ± 0.3

9.2 ± 0.4

8.7 ± 0.5

11.6 ± 1.0

9.9 ± 0.4*

9.6 ± 0.3

 Tibia length (cm)

1.80 ± 0.01

1.80 ± 0.01

1.82 ± 0.2

1.82 ± 0.01

1.81 ± 0.01

1.83 ± 0.01

 Heart weight (mg)

174.6 ± 7.2°

165.3 ± 6.2°

187.3 ± 7.0°^♦

135.4 ± 7.1

145.0 ± 5.0

169.3 ± 7.0^♦

 Quadriceps (g)/tibia (cm)

119.1 ± 3.6°°°

101.6 ± 2.6*°°°

112.4 ± 2.9°^♦

87.7 ± 2.3

76.7 ± 2.0*

84.6 ± 1.6^♦

 Gastrocnemius (g)/tibia (cm)

93.8 ± 3.3°°°

83.1 ± 2.0*°°°

89.2 ± 2.7°^♦

67.4 ± 1.3

66.2 ± 2.3

69.9 ± 1.5

 Soleus (g)/tibia (cm)

5.5 ± 0.3 °

4.5 ± 0.2*

6.6 ± 0.3^♦♦♦

4.7 ± 0.2

4.5 ± 0.2

5.7 ± 0.4^♦♦♦

 TA (g)/tibia (cm)

28.0 ± 1.7°°°

24.1 ± 0.7*°°°

26.5 ± 1.7°

20.5 ± 1.0

18.3 ± 0.3

20.1 ± 1.2

 EDL (g)/tibia (cm)

6.8 ± 0.4°°°

6.3 ± 0.3°°°

7.3 ± 0.1°^♦

5.6 ± 0.2

4.9 ± 0.2

5.9 ± 0.5^♦

 Triceps (g)/tibia (cm)

72.6 ± 2.2°°°

68.2 ± 1.2°°°

68.5 ± 2.5°

52.2 ± 1.0

52.0 ± 2.3

53.2 ± 1.2