When RI is employed, the reduction in tone relies on the physiological inhibiting effect of antagonists on the contraction of a muscle. When the motor neurons of the contracting agonist muscle receive excitatory impulses from the afferent pathway, the motor neurons of the opposing antagonist muscle receive inhibitory impulses at the same time,

The TVA appears to be the key muscle of the inner unit. Richardson et al. (1999) found that in people without back pain, the TVA fired 30 milliseconds prior to shoulder movements and 110 milliseconds before leg movements. This corroborates the key role of the TVA in providing the stability necessary to perform movements of the appendicular

Let’s look at it from another angle. We know that the function of the muscles inserting into the ITB (TFL) is to abduct the leg. The Gmed, which inserts into the femur, is also an abductor; if this muscle is weak, the ITB will assist in the role of abducting and consequently become overworked. The ITB, however, does not have an insertion that

If the adductors receive more neural stimulus from the obturator nerve (as when the adductors have become the main stabilizing muscle instead of the Gmed), this compensation pattern will naturally take the hip into an increased medial rotation, adduction, and hip flexion. As a result, the knee drifts medially (valgus position) because of the

When you are standing, the weak muscles show themselves; when you are lying, the short muscles show themselves.

The weight of the head is approximately 7% of total body weight (shoulders and arms are around 14%). This means that for a person weighing 176 lb. (80 kg), the head will weigh around 11 to 13 lb. (5 to 6 kg). If the head and shoulders move forward, out of ideal alignment, the activation of the neck extensors will increase dramatically, resulting in

Tip: Overactivity of the adductors will result in a weakness inhibition of the abductors, in particular the gluteus medius. This can result in a Trendelenburg pattern of gait as explained in chapter 6

Bilateral hypertonicity of the rectus femoris will cause the pelvis to adopt an anterior tilt, resulting in lower back pain due to the fifth lumbar vertebra facet joints being forced into a lordotic position.

Osar (2012) mentions that nutation is the anterior inferior motion of the sacral base, while counternutation is the posterior superior motion of the sacral base. Nutation is necessary for the locking of the SIJ during unilateral stance. The inability to nutate the sacrum is a leading cause of unilateral stance instability and one of the causes of