urthermore, Kritz and Cronin propose that a body in equilibrium theoretically is capable of doing the most efficient work.
In poor, or faulty, posture (aka postural dysfunction), there is an imperfect relationship among various skeletal structures of the body, and this may produce strain on the body’s supporting framework (Britnell et al. 2005). With faulty posture, the body is balanced less efficiently over its base of support. Therefore, any restriction, imbalance or misalignment of the musculoskeletal structures will have an adverse effect on the efficiency of movement.
Skilled personal trainers seek to assess their clients’ postural patterns and, more importantly, to target abnormal patterns such as lordosis (abnormal inward or forward curvature of the vertebral column) and kyphosis (abnormal curvature of the spine, causing a hunchback). A postural assessment provides an objective means of identifying a client’s postural concerns and establishing a direction for appropriate exercise program design. See Figure 1 for a comparison of common posture types and their resultant muscle imbalances.
Posture can be evaluated statically (stationary position) and dynamically (in motion) (Britnell et al. 2005). In both cases, joint positions and skeletal alignment can be assessed, as well as muscle length (i.e., stretch) and force production capabilities. Kritz and Cronin (2008) note that the relationship between static posture assessment and dynamic movement screening is unclear in the research. Although some fitness professionals use dynamic screening techniques with clients, the research supporting these techniques needs further validation through independent research.
Norris (1995) states that standing side posture should be assessed using the plumb line reference point. Have the client stand with the plumb line just in front of the lateral malleolus (lower end of the fibula that forms the prominent bulge on the outer side of the ankle). In optimal posture, this line passes through the midline of the knee, the lumbar vertebrae, the shoulder joint, the cervical vertebrae and the earlobe (see Figure 1).
Kritz and Cronin (2008) suggest assessing the following checkpoints in standing side posture (this list describes optimal posture):
- head: neutral, with no forward or backward tilt
- cervical spine: slight anterior curve
- scapulae: flat against upper back
- thoracic spine: slight posterior curve
- lumbar spine: modest anterior curve
- pelvis: anterior superior iliac spine in same vertical plane as symphysis pubis
- hip joints: neutral, neither flexed nor extended
- knee joints: neutral, neither flexed nor hyperextended
- ankle joints: neutral, with leg vertical to sole of foot
When standing posture is viewed from the front (with feet approximately 3 inches apart), a vertical line should divide the body into two similar halves. Norris (1995) suggests that the anatomical landmarks to compare for horizontal level on both sides of the body include the lateral malleolus (ankles), patella (knees), anterior superior iliac spine (hips), acromion process (highest point of shoulders) and ears. It is also important to look for muscular or structural differences in this frontal-view assessment. Kritz and Cronin (2008) add that the feet should be in a neutral position with no signs of pronation or supination. They suggest continuing the posture check from behind, observing the following (see Figure 2):
- head: neutral, with no tilt or rotation
- shoulders: level, with no depression or elevation
- scapulae: medial borders parallel and approximately 3–4 inches apart
- thoracic spine: straight with no lateral curve
- lumbar spine: no lateral curve
- pelvis: posterior superior iliac spines in the same plane
- lower extremities: straight, not bowed or knock-kneed
- feet: facing parallel or with toes slightly out; no pronation or supination
If the body segments are out of their optimal alignment for extended periods of time, the muscles eventually adapt by either shortening or lengthening (depending on the position) (Hrysomallis & Goodman 2001). 