Q2. What is the role of the inverted pendulum in balance control?
During balance control, the muscle action appears to be an anticipatory feed-forward mechanism that is determined by an internal model of the inverted pendulum and acts in the long-term.
Q3. How many trials yields acceptable reliability for all COP parameters?
it has been stated that averaging two [35], three [24], four [38] or seven [17] trials yields acceptable reliability for the majority of COP parameters.
Q4. What is the main reason for the reliability of a COP test?
The test-retest reliability depends primarily on factors such as the number of trial recordings and duration rather than the selection of particular COP parameters.
Q5. Why is inter-rater reliability unlikely to be of concern?
While intra-trial and inter-trial reliability needs to be discussed, inter-rater reliability is unlikely to be of concern due to the simplicity of the apparatus, task and instructions.
Q6. What was the common statistical method used for describing the reliability of the force plate?
The statisticsAs with the general experimental setups, an equally heterogeneous selection of statistics for describing the reliability was used, including the coefficient of variation (CV), generalizability coefficient (GC) as well as Pearson’s correlation coefficient (PCC).
Q7. What is the trend for higher reliability estimates under eyes closed conditions?
In addition, the trend by recent papers to report higher reliability estimates under eyes closed conditions may at least partially be attributed to improved technicalequipment, a more rigorous scientific procedures in conducting the studies or a higher true score variability.
Q8. What is the reason for the variation in COP reliability?
In the literature, sampling frequencies ranging from 10-200Hz have been reported [9,16,17,22,27,37-41] and it seems that the reported variations in COP reliability across similar experimental setups are at least partially due to the different frequencies chosen.
Q9. What is the common method of measuring postural stability?
While the evaluation of COP excursions is a commonly used method for measuring postural stability [21-38] no standardization of this method exists.
Q10. What is the commonly used tool to investigate this complex balance system?
Of these, one of the most commonly used tools to investigate this complex balance system is the stabilogram, which is a measure of the time behaviour of the COP of a person positioned on top of a force platform consisting of a rigid plate supported by force transducers.
Q11. What is the role of the feed-forward control in stabilizing the body?
The complementation of this mechanism by the feed-forward control is necessary as the muscle stiffness itself is not sufficient to stabilize the body if the critical level of displacement is reached [2]
Q12. What criteria were used to exclude studies that used dynamic task conditions?
In addition, papers that were anecdotal, speculative or editorial in nature or studies that employed dynamic task conditions such as one-leg hopping, walking or some form of translation of the force platform were excluded.
Q13. How many trials are required to reach an acceptable reliability?
In addition to trial duration, the number of repetitions needed to gain acceptable reliability (r≥0.75) also varies with the COP parameter under investigation and conflicting results have been reported.
Q14. How many trials were required to reach a COP2?
For COP mean velocity for example, just two 120sec trials were required to reach an ICC2,1 >0.90, whereas COP range and RMS needed four 120sec trials to reach similar reliability levels [22].
Q15. How long does it take to reach acceptable reliability for a COP?
The authors recommend the following methods should be employed: Regarding the data acquisition duration, the results suggest that a minimum of 90sec is required to reach acceptable reliability for all traditional COP parameters in healthy subjects.