The short term effect of static and cyclic stretch paradigms on stiffness and maximal
joint range of motion was examined in 12 recreational athletes. To assess flexibility,
joint range of motion and resistance to stretch were measured using a dynamometer
during a passive stretch of the hamstring muscle group to the point of pain. The recorded
torque-angle curve allowed for identification of maximal joint range of motion and
calculation of passive muscle-tendon stiffness and energy. Three flexibility assessments
(stretch 1 -3), each 10 min apart, were administered to each leg. A 90 s static stretch
and 10 cyclic stretches were performed after the second stretch on the left and right
side, respectively. Stiffness in a common range for stretch 1-3 was unchanged on both
the left and right side. However, on the left side (static stretch) there was a significant
effect of flexibility assessment (stretch 1 - 3) (p < 0.0001) with an increased maximal
joint angle (p < 0.01) and maximal stiffness (p < 0.05) between all three stretches.
Similarly, on the right side (cyclic stretches) there was a significant effect of
flexibility assessment (p < 0.0001) with an increased maximal joint angle between
stretch 1 and 3 (p < 0.01) and maximal stiffness (p < 0.05) between all stretches.
During the static stretch passive torque declined 35 ± 4 % (p < 0.001). During the
cyclic stretches passive energy and hysteresis both declined 17 % (p < 0.05) while
stiffness increased 12 % (p < 0.05). The results of the present study demonstrate
that static and cyclic stretching, as it is commonly performed by athletes, increases
joint range of motion by increasing stretch tolerance while the viscoelastic characteristics
of the muscle remain unaltered.
Key words
Flexibility - viscoelastic - muscle-tendon - stiffness - hysteresis
