Diurnal and day-to-day variation of isometric muscle strength in myasthenia gravis.
BACKGROUND
In patients with myasthenia gravis (MG), muscle strength is expected to decrease gradually during the day due to physical activities.


METHODS
Isometric muscle strength at the shoulder, knee, and ankle was determined in 10 MG patients (MGFA class II-IV) who were receiving usual medical treatment and in 10 control subjects. To determine diurnal and day-to-day variation, muscle strength was measured 4 times during day 1 and once at day 2.


RESULTS
Knee extension strength decreased during the day in both patients and controls. Neither diurnal nor day-to-day variation of muscle strength was higher in patients compared with controls.


CONCLUSIONS
Patients with mild to moderate MG did not have increased variation of isometric muscle strength during the day or from day-to-day compared with controls. This suggests that isometric muscle performance can be determined with high reproducibility in similar groups of MG patients without regard to time of day.
Department of Neurology, Aarhus University Hospital, Noerrebrogade 44, Building 10, 8000 Aarhus C, Denmark.
Lotte
L
Vinge
The Neurocentre, Rigshospitalet, Copenhagen, Denmark.
Johannes
J
Jakobsen
Research Unit, Hammel Neurorehabilitation and Research Centre, Hammel, Denmark.
Asger Roer
AR
Pedersen
Department of Neurology, Aarhus University Hospital, Noerrebrogade 44, Building 10, 8000 Aarhus C, Denmark.
Henning
H
Andersen
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002940:Circadian Rhythm / Q000502:physiology*; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D009157:Myasthenia Gravis / Q000473:pathology* / Q000503:physiopathology*; D011788:Quality of Life / Q000523:psychology; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires
day-to-day variation; diurnal variation; dynamometry; muscle strength; myasthenia gravis