The effect of wrist orthoses on forearm muscle activity.
A general hypothesis is that a wrist orthosis reduces the wrist extensor muscle load. The aim of this study was to investigate the effects of a completely stiff wrist orthosis (SO) and a commercially available wrist orthosis (CO) on flexor and extensor electromyographic (EMG)-activity in a standardised intermittent gripping task and during standardised manual work tasks. Surface EMG from two forearm flexor and two extensor muscles was recorded. The target grip forces were 5%, 20% and 40% of maximal voluntary contraction (MVC). During the grip contraction phase CO had no effect on the EMG-readings. SO resulted in higher EMG activity than when gripping with CO and with no orthosis (NO), especially when gripping with 40% MVC. During the relaxation phase neither CO nor SO had any effect on the extensors. For the flexors the SO gave higher EMG-readings than when gripping with CO and NO, especially at 40% MVC. In conclusion the wrist orthoses tested did not reduce the EMG-activity from the flexors or the extensors during gripping or manual tasks.
Johansson
Lena
L
Department for Work and Health, National Institute for Working Life, Stockholm SE-113 91, Sweden. lena.johansson@arbetslivsinstitutet.se
Björing
Gunnar
G
Hägg
Göran M
GM
D004576:Electromyography; D005260:Female; D005542:Forearm / Q000502:physiology*; D018737:Hand Strength; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D009989:Orthotic Devices; D013548:Sweden; D014953:Wrist / Q000502:physiology*