Chapter 6 Muscle Balance, Posture and Spinal Stability
The Importance of Muscle Balance
O
ptimal functioning of the human body depends on the
relationship between muscular strength, muscular flexibil-
ity, and neural excitation of the muscles. A muscle must
be two things: flexible enough to allow for normal range of motion
and strong enough to provide adequate joint stability.Muscle balance should exist across the joint between prime
movers and antagonist muscles, between synergist muscles
that are working together to produce a movement, and between
prime movers and stabilizers. Muscle imbalance exists when the
relationship between muscular strength, muscular flexibility, and
neural excitation of the muscles is not balanced. Therefore, one
muscle is weaker or less flexible.Muscle imbalance is typically described as feelings of fatigue,
reports of discomfort, or noticeable and reported tightness. Mus-
cle imbalance typically presents as faulty movement patterns,
improper posture, isolated weakness, inflexibility, increased joint
load, or improper recruitment or lacking the ability to recruit or
turn on specific muscles.How Muscle Balance Relates to Posture
The key to proper posture and structural balance is the equal pull
of the opposing muscles over the joint. It is safe to assume that
inflexible muscles are typically strong, therefore holding the oppos-
ing muscle in a lengthened position. On the contrary, it is assumed
that muscles that are excessively flexible are typically weak.Causes of Muscle Imbalance
Constant Workload
Stabilizer muscles are responsible for stabilizing or holding the
joint in a static position. These muscles are typically slow twitch,
inflexible, and held in one position for extended periods of time.
Stabilizers present as tight and inflexible when overused (e.g. a
joint posture is held for an extended period of time).Insufficient Activation
With reduced activation or usage of the stability or postural mus-
cles, the muscles become weak with neuromuscular inefficiency
(e.g. inability to properly engage the transverse abdominals).Tight Muscles lead to Muscle Imbalance
The tight muscle will overpower the lengthened, passive oppos-
ing muscle group compromising joint stability.Weak Muscles lead to Muscle Imbalance
The strong muscle will overpower the weak opposing muscle