Abstract
The purpose of this study was to investigate the influence of a 6‐week proprioceptive neuromuscular facilitation (
PNF
) stretching training program on the various parameters of the human gastrocnemius medialis muscle and the Achilles tendon. Therefore, 49 volunteers were randomly assigned into
PNF
stretching and control groups. Before and after the stretching intervention, we determined the maximum dorsiflexion range of motion (
RoM)
with the corresponding fascicle length and pennation angle. Passive resistive torque (
PRT
) and maximum voluntary contraction (
MVC
) of the musculo‐articular complex were measured with a dynamometer. Muscle‐tendon junction (
MTJ
) displacement allowed us to determine the length changes in tendon and muscle, and hence to calculate stiffness. Mean
RoM
increased from 31.1 ± 7.2° to 33.1 ± 7.2° (
P
= 0.02), stiffness of the tendon decreased significantly in both active (from 21.1 ± 8.0 to 18.1 ± 5.5 N/mm) and passive (from 12.1 ± 4.9 to 9.6 ± 3.2 N/mm) conditions, and the pennation angle increased from 18.5 ± 1.8° to 19.5 ± 2.1° (
P
= 0.01) at the neutral ankle position (90°), only in the intervention group, whereas
MVC
and
PRT
values remained unchanged. We conclude that a 6‐week
PNF
stretching training program increases
RoM
and decreases tendon stiffness, despite no change in
PRT
.