112 Flexibility
The quadriceps muscle is quickly stretched, and the muscle spindles react by contracting
the quadriceps muscle causing the knee-jerk response. The greater or more rapid the
stretch, the greater the response of the muscle spindles and the resultant muscle contraction.
Signals are high in frequency at the beginning of a stretch, but then slow down as they adapt
to the new length.The lengthening reaction engages GTOs, which are located in the muscle-tendon
junctions, and activates them when the tension in a tendon is increased as a result of either
muscular contraction, stretching the muscle beyond its resting length, or a combination of
the two. When muscular tension increases, the GTOs respond by sending inhibitory signals
to the muscle; this causes the muscles to relax, and protects the muscles and tendons from
tearing due to tension overload. Knowledge of the stretch reflex and the lengthening
reaction is useful for effective stretching.The most effective stretches are performed
slowly, and held for 15 - 30 seconds.
Performing the stretch slowly avoids excessive activation of the muscle spindles
and resultant muscular contraction. Holding the stretch allows time for the muscle spindles
to adapt to the new muscle length, and eventually, to achieve greater lengths. The length
and duration of the stretch should also be sufficient to activate the GTOs so that they
override the muscle spindles and induce muscular relaxation.Flexibility Training Methods
There are several training methods used to develop flexibility; however, most fall
under the following general categories:" Dynamic
" Static
" Ballistic
" Proprioceptive neuromuscular facilitation (PNF)
Dynamic Stretching
Dynamic stretching (sometimes referred to as active stretching) consists of
controlled movements which increase in range and/or speed so that you gradually reach
your full range and speed of movement (e.g., slow, controlled leg swings or kicks,
controlled arm swings, back bends). This type of stretching often mimics the activity that
is to be performed and prepares the muscles for that activity.