Vol. 16 Issue 5
The Motor Control Model
Treatment applications and research considerations
Motor control allows our bodies to "regulate or direct the mechanisms essential to movement" (Crepeau, Cohn, & Boyt Schell, 2003, p. 1031). In short, it allows our bodies to move when we need them to go, without ever having to think about it. When one exhibits "normal" motor control, we can assume that he has normal muscle tone, normal postural tone and postural mechanisms, selective movement and coordination. Abnormal motor control can occur instantaneously with the occurrence of a stroke, brain injury or disease such as Parkinson's or multiple sclerosis. These are all disorders that damage the central nervous system, thus affecting voluntary movement (Pedretti & Early, 2001).
When motor control is lost, therapeutic intervention is absolutely necessary to restore normal movement patterns. A possible first step is to work toward rehabilitating the structures of the brain that control movementthe sensorimotor system.
There are three popular sensorimotor approaches used to treat poor motor control: the neurodevelopmental approach (NDT), the proprioceptive neuromuscular approach (PNF) and the Rood Approach. These approaches are theoretically based on the Reflex and Hierarchical Model of Motor Control, which makes two assumptions:
• Reflexes are the basic units of motor control.
• Motor control is arranged hierarchically (Pedretti & Early, 2001).
These assumptions state that in order to relearn normal movement patterns, it is necessary to go back to infantile responses (reflexes) and build on them until one achieves conscious, volitional movement.
Neurodevelopmental Treatment (NDT), also known as the Bobath approach, developed during the 1940s by a husband and wife who were hoping to restore normal movement to children with cerebral palsy to those with hemiplegia.
NDT uses the sensorimotor-sensory feedback loop to describe the development of motor skills. Postural control develops through sensation and provides a foundation for functional skills. When someone has poor postural control, he uses compensatory methods in his everyday activity, which ultimately disrupts the sensorimotor-sensory feedback loop, creating abnormal movement (Miles Breslin, 1996).
NDT focuses on regaining postural control and selective movement control, and also works to normalize muscle tone. Intervention is broken into two phases. The first, or preparatory, stage helps increase the joint mobility and facilitates postural alignment. In the second phase (facilitation of active movement), the occupational therapist provides sensory input and uses key points of control to help facilitate movement. Techniques may include handling; inhibition of spastic muscles and facilitation of flaccid muscles; weight bearing and weight shifting; integration of functional tasks; and positioning (Miles Breslin, 1996).
Although NDT is popular, there is very little evidence to show its effectiveness (Miles Breslin, 1996; Mudie, Winzeler-Mercay, Radwan, & Lee, 2002). Mudie et al. (2002) compared NDT with task-specific reach and balance-performance-monitor feedback training to assess training symmetry of weight distribution after stroke. The most significant changes were in those patients in the Bobath treatment group.
NDT treatment has been shown to be most effective when NDT techniques are used in conjunction with activities that are meaningful to the patient (DeGangi, 1994, as cited in Miles Breslin, 1994).
Proprioceptive Neuromuscular Facilitation
Herman Kabat developed proprioceptive neuromuscular facilitation (PNF) in the 1940s; in the following decade Dorothy Voss and Margaret Knott expanded upon it.
PNF focuses on the developing sequence of movement and how the agonist and antagonist muscles work together to produce volitional movement (Pedretti & Early, 2001). Like NDT, the goal is to help restore normal movement, but PNF uses the developmental sequence in relearning. Whereas NDT tries to prohibit reflexive movement, PNF uses those reflexes as a basis for learning more volitional movement. The idea is that one must be able to roll before he can crawl and crawl before he walks.
PNF focuses on mass movement patterns that are diagonal and resemble functional movement. The body does not work in parts, but instead as a whole. As an OT, it is necessary to assess what patterns a patient still has and what needs to be remedied or compensated for. In order to promote these mass movement patterns, PNF uses a multi-sensory approach, incorporating the auditory, visual and tactile systems. Like NDT, PNF allows the patient to understand what normal movement feels like through the use of various senses and with the help of an occupational therapist (Pedretti & Early, 2001).
The two approaches also use some similar treatment methods. Much like the handling technique used it NDT, PNF uses manual contacts to cue the patient and facilitate movement. PNF also uses similar facilitation/inhibition techniques such as stretch, traction and approximation.
Primarily, however, PNF treatment techniques focus on three things:
• Increase the motor learning of the agonist through repetition of an activity (repeated contractions) and rhythmic initiation.
• Reverse the motor patterns of the antagonist. Two techniques are slow reversal and rhythmic stabilization, which both use isometric contraction.
• Finally, learning to relax muscles helps to increase range of motion and decrease spasticity (Pedretti & Early, 2001).
Several studies have been conducted to prove the effectiveness of PNF. Ferber, Gravelle, and Osternig (2002) examined the effect of PNF stretch techniques on older adults and found that active PNF stretches produced increases joint range of motion, specifically knee-joint range of motion.
Klein, Stone, Phillips, Gangi, and Hartman (2002) also examined how PNF affected range of motion and isometric strength in the assisted-living population. They found significant increases in ROM for ankle flexion and shoulder flexion, as well as isometric strength for ankle flexion and extension and hip extension. They also found significant increases in balance and mobility for sit-to-stand. These results are consistent with other findings by Sady (1982) and Godges (1989, as cited in Klein et al., 2002) of the effectiveness of PNF.
The Rood Approach
The final sensorimotor approach, developed by Margaret Rood in the 1950s, is the "Rood Approach."
Before treatment can begin, the therapist must apply facilitation and inhibition techniques to help normalize muscle tone. Stretch, tapping, resistance, vibration, traction, approximation, inhibitory tendon pressure, fast brushing, light touch, neutral warmth and slow stroking are all examples of these techniques (Metcalfe & Lawes, 1998). Many of these also appear in both NDT and PNF to get the body ready to work.
Rood suggested four components of motor control:
• Reciprocal inhibition, an early motor pattern developed as a protective mechanism, is a quick motion that contracts the agonist muscles and relaxes the antagonistic muscles.
• Co-contraction provides stability to the body by contracting both the agonists and antagonists.
• In heavy work, the third component, the distal portion of the body provides stability, and the proximal portion provides mobility.
• Finally, skill is the highest level of motor control and allows the distal portion of the body to be mobile while the proximal portion serves as stability.
This line of thinking has been beneficial to other motor control treatment approaches that are applied today (Pedretti & Early, 2001).
Like PNF, the Rood Approach focuses on developmental sequence in treatment and the understanding that flexion and extension patterns will affect each other. Rood believed that motor control could be inhibited or facilitated by positioning children into ontogenetic patterns of development. While in these patterns, it was most effective to have patients participating in functional activities that had meaning to them. Through repetition and in a real-life context, they could achieve occupational functioning. (Metcalfe & Lawes, 1998).
According to Pedretti and Early (2001) and Metcalf and Lawes (1998), Rood's approaches are not commonly used in practice. However, elements of her work are important to study because they could have therapeutic use, and she gives a good understanding of motor control and developmental sequence. These authors found little information as to the efficacy of Rood's approach through an exhaustive literature review. Although her work is of interest, it is not as widely accepted as NDT or PNF.
These three sensorimotor approaches have provided a foundation for treatment of many neurological and orthopedic disorders. Most individuals take for granted normal movement patterns until they are no longer able to do things that once came so simple to them. Theorists such as Bobath, Knott, Voss, and Rood have provided insight into the human condition and given people the opportunity to regain function and live normal lives. Although few studies have proven the efficacy of these approaches, research has shown their benefits when used in conjunction with meaningful occupations (Miles Breslin, 1996; Metcalfe & Lawes, 1998; Shapero Sabari, 1991).
Erin Stroup, OTS, is a MSOT student at Milligan College. Jeff Snodgrass, MPH, OTR/L, CEES, CWCE, ABDA, is an assistant professor of occupational therapy at Milligan College.