- Clarify the interaction between strength and dexterity training after stroke, see especially table 5.1
Motor problems resulting from lesions of the central nervous system can be characterized as:
-negative impairments: those that represents a loss of pre-existing function, such as a loss of strength and dexterity
-positive impairments: additional, such as abnormal postures, increased proprioceptives reflexes (spasticity) and increased cutaneus reflexes.
Decreasing spasticity and contracture after stroke is a focused approach to be considered. Contracture is more prevalent than spasticity. Moreover, mild to moderate spasticity has been shown not to be related to with, function and it can probably be ignored in most situations.
Therefore, clinical guidelines in order to decrease the risk of muscle shortening and prevent contracture suggests:
-20-30 minutes of stretch in outer range every day. This can be facilitated by incorporing passive positioning part of routine ward protocols (ex: affected foot behind the knee provide passive dorsi flexion).
When considering negative impairments, studies indicate that there is no correlation between loss of dexterity and strength after stroke. These factors are major contributors to loss of ability. However, loss of strength is a more significant contributor to physical disability than loss of dexterity.
- Loss of dexterity: a loss of both the spatial and temporal accuracy needed to make a movement according to environmental demands.
- Assessment: It is often difficult to assess this factor, due to presentation of weakness (requires tests that utilize precise coordination but minimal strength).
- Clinical practice: Dexterity can only be trained once some strength is present.
- Weakness/Loss of strength: an inability to achieve high levels of torque regardless accuracy.
- Neural consequences: This is due to results of loss of descending excitation to spinal segments reducing the number of motor units activated. Functional motor unit are halved within the first 6 months after stroke.
- Assessment: It can be difficult because of the nature of the condition (afasia).
- Clinical practice: It is important to stimulate maximum excitation of motor units early after stroke to prevent loss of motor units.
Additionally, a study has demonstrated that the stroke subjects are relatively stronger in their lengthened range and relatively weaker in their shortened range. This study suggests that as soon as some muscle activity is present, strengthening should include exercises that focus on the shortened range.
- Therapeutic intervention, to increase strength and dexterity after stroke, has to include strengthening exercises:
-focusing on the mid-range of the muscle length when it is usually the strongest
-decreasing the effect of gravity (e.g by changing body position)
-decreasing friction
-decreasing the lever arm of the limb
Furthermore, therapeutic intervention has to include goals and using efficient measurement tools (ex: PBCS) in order to quantify the improvement.
Jehanne Crouzier 