Background and purpose: The control of balance is vital in many sporting activities as well as in activities of daily life. In order to treat deficiencies properly valid and reliable methods are needed to evaluate different aspects of stability. Muscle fatigue has been proposed to cause a change in postural control strategy, and the use of different tools and variables might therefore elucidate these changes. The aims of the present study were: to investigate if forceplate and accelerometer measurements about postural control during one-legged stance indicate changes in postural control strategy after fatiguing exercise; and to investigate the correlation between forceplate and accelerometer measurements obtained before and after fatiguing exercise.
Method: The study used an experimental design. Twenty-three healthy women (mean age 26.8 years; range 20-34 years) were studied. Forceplate and accelerometer data were obtained simultaneously and consisted of measures of centre of pressure movements and horizontal trunk acceleration in medio-lateral and antero-posterior directions. The calf muscles of the right leg were fatigued by repeated heel rises.
Results: The average amplitude of centre of pressure movements and trunk acceleration increased, whereas the average velocity of centre of pressure movements decreased during fatigue. These changes indicate a change of movement strategy. Moderate correlation between trunk acceleration and centre of pressure movements was seen, confirming the link between the variables, but indicating that different aspects of the ability to control balance were measured.
Conclusions: Calf muscle fatigue has a short-lasting effect on body balance, with measurements indicating a change in postural control strategy. Different tools and variables are needed to identify different balance control strategies. The procedures used in the present study may be modified to identify subjects with inadequate capacity to choose between balance control strategies; they are also applicable in clinical settings outside a laboratory environment.