The goal of this observational study is to investigate whether ankle evertor muscle fatigue impairs force perception and alters neuromuscular activation patterns during submaximal isometric contractions, and whether these effects differ between individuals with chronic ankle instability (CAI) and individuals without CAI.
Age between 18 and 45 years,
No history of injuries or surgical procedures to the lower limbs,
No peripheral or central neurological impairments.
Age between 18 and 45 years,
None
Participants will be recruited by convenience sampling from the general population and clinical settings.
Case-control
Cross-sectional
Not listed
Constant Error (CE)
Muscle force sense will be assessed by the accuracy of force reproduction during force-matching tasks. Constant Error (CE) will be calculated as the mean difference in force (Nm) between reproduction with and without visual feedback during the middle three seconds, averaged across three repetitions at each load level. Unit of measure: Newton-meters (Nm).
Absolute Error (AE)
Muscle force sense will be assessed by the accuracy of force reproduction during force-matching tasks. Absolute Error (AE) will be calculated as the mean absolute difference in force (Nm) between reproduction with and without visual feedback during the middle three seconds, averaged across three repetitions at each load level. Unit of measure: Newton-meters (Nm).
Variable Error (VE)
Muscle force sense will be assessed by the accuracy of force reproduction during force-matching tasks. Variable Error (VE) will be calculated as the standard deviation of errors across three repetitions at each load level. Unit of measure: Newton-meters (Nm).
Coefficient of Variation (CV) of generated force
Ratio of the standard deviation to the mean force during the middle three seconds of sustained contraction in each trial, calculated separately for trials with and without visual feedback. Unit of Measure: Percentage (%).
Surface EMG root mean square (RMS) amplitude of ankle muscles
RMS amplitude from surface EMG signals of the peroneus longus, tibialis anterior, soleus, and gastrocnemius medialis will be obtained during the fatigue protocol, MVIC and force-matching task. Unit of Measure: millivolts (mV).
Surface EMG median frequency of peroneus longus mucle
Median frequency of EMG signals will be obtained from the peroneus longus during the fatigue protocol, the maximal voluntary isometric contraction (MVIC) and force-matching tasks. Frequency values will be averaged across repetitions. Unit of Measure: Hertz (Hz).
Maximal voluntary isometric contraction (MVIC)
MVIC of the ankle evertors will be measured at the beginning of the protocol to determine the target force for submaximal isometric contractions, and repeated immediately after the fatigue protocol to assess the effectiveness of fatigue, expressed in Newton-meters (Nm).
Ratings of perceived exertion
Description: Ratings of perceived exertion (RPE) will be assessed at the end of each fatigue protocol using the Borg 10 category-ratio scale, with 0 is no effort and 10 is an extreme physical effort.
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