Table 1.

Comparison of subject characteristics. There were no significant group differences in resting ankle angle (expressed in degrees of plantarflexion) or tendon thickness, but middle-aged adults exhibited slightly smaller pennation angles (p < 0.05) in a resting ankle posture.

	Young adults	Middle-aged adults
Age:	25 ± 4 years	49 ± 4 years
Gender:	8 M, 7 F	5 M, 5 F
Height:	69 ± 3 inches	70 ± 5 inches
Weekly exercise:	11 ± 5 hours	10 ± 5 hours
Resting ankle angle:	25 ± 5 deg.	25 ± 6 deg.
Tendon thickness:	4.2 ± 0.6 mm	4.7 ± 0.9 mm
Resting pennation angle:	22 ± 4 deg.	19 ± 3 deg.