How Upper Neck Muscles Influence Hamstring Length
Below are the abstracts of an interesting research study. The researchers used PNF (or active resistance) stretching to examine the effect of upper neck muscles on hip joint range of motion.
Stretching the hamstrings caused 9% increase in hip extension range of motion as measured with the passive 'straight leg raise' (SLR) manouver. Yet stretching the small suboccipital muscles(which connect the occiput with the upper two vertebrae) resulted in almost twice as much (13%) increase of hamstring length as measured with the same SLR test.
The explanation for this extraordinary finding has probably more to do with the neurological importance of the suboccipital muscles. These small muscles have the highest density of muscles spindles in the whole body (and apparently on the whole planet!) and have a major sensory function for antigravity organization. Via the so called 'Tonic Neck Reflex' (which we share with most other mammals) an extension of these muscles tends to trigger a tonus decrease of the hipjoint extensors.
My suggested conclusion for bodyworkers & movem. therapists: if a client shortens the upper neck, his hamstrings will stay short no matter how much he wants to stretch or lengthen them. Whereas if he lowers the tonus of these upper neck muscles (either passively via myofascial manipulation or via active ideokinetic movement facilitation) lengthening the hamstrings and increasing hip flexion range of motion will be much easier.
This fits also with a verbal report I heard from Hubert Godard about an interesting research in Italy: runners on a treadmill would unconsciously increase their running speed when a bioelectrical device on their neck lowered the tonus of the upper neck muscles. Whereas increasing the tonus of these muscles made them slow down their speed, although they were not aware of this and perceived their speed as constant. So a stiff occiput-neck connection will tend to 'put a break' into the legs via shortening of the hamstrings, and a long and loose occiput-neck connection will take 'the break out' by lengthening the midrange of hamstring length and will make the legs swing much faster and easier.
P.S.: For more info on the suboccipital muscles see: McPartland J M, Brodeur R R, Rectus capitis posterior minor: a small but important suboccipital muscle, Journal of Bodywork and Movement Therapies, January 1996
ABSTRACTS from: Journal of Manipulative and Physiological Therapies, September 1997; 20:443-447. http://www.national.chiropractic.edu/jmpt/abstracts.html
A Study of Two Stretching Techniques for Improving Hip Flexion Range of Motio
Henry Pollard, GradDipChiro,GradDipAppSc,1 and Graham Ward, PhD2
Objectives: To compare the effectiveness of a spinal (suboccipital) stretching technique to a peripheral stretching technique.
Design: Clinical cohort study.
Setting: Macquarie University Centre for Chiropractic Outpatient Clinic.