Quadriceps strength and timed motor performances in myotonic dystrophy, Charcot-Marie-Tooth disease, and healthy subjects.
OBJECTIVE
The leading hypothesis was that a relation exists between muscular strength and functional abilities. Therefore a study was undertaken to quantify such a relationship in a population of subjects with different muscular strengths. This population consisted of healthy subjects and subjects with slowly progressive neuromuscular disorders.


METHODS
The study included 33 patients with myotonic dystrophy, 29 patients with Charcot-Marie-Tooth disease and 20 healthy subjects. Isokinetic and isometric knee torques were measured on an isokinetic dynamometer at various velocities. The following activities were timed: descending and ascending stairs, rising from a chair, rising from supine, walking at natural speed and walking at maximum speed.


RESULTS
The population covered a wide range of the variables: whereas the healthy subjects performed best (i.e. had the highest knee torques and performed the activities most quickly), the myotonic dystrophy group included the subjects with the lowest knee torques. The natural logarithms (In) of isokinetic extension torque at the highest velocity (120 degrees/s) and those of the time taken to perform the described activities showed the highest levels of correlation. It was found that after correction for age and weight, 56% (walking at natural speed) to 73% (descending stairs) of the variance in the In of the time taken could be attributed to the variance in the In of the torques.


CONCLUSIONS
A strong relation between quadriceps strength and timed motor performances were demonstrated. The impact of strength reduction on time taken was most obvious in subjects with considerably decreased strength. Therefore, it is feasible to try to influence muscle strength in patients with relevant strength reduction in order to achieve better functional ability.
Lindeman
E
E
Department of Rehabilitation, University Hospital Utrecht/Rehabilitation Centre de Hoogstraat, The Netherlands.
Leffers
P
P
Reulen
J
J
Spaans
F
F
Drukker
J
J
D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002607:Charcot-Marie-Tooth Disease / Q000503:physiopathology* / Q000534:rehabilitation; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D007717:Knee / Q000503:physiopathology; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009069:Movement Disorders / Q000503:physiopathology* / Q000534:rehabilitation; D015999:Multivariate Analysis; D009119:Muscle Contraction; D009223:Myotonic Dystrophy / Q000503:physiopathology* / Q000534:rehabilitation; D011597:Psychomotor Performance; D013997:Time Factors; D019415:Torque