Individual pretrial Baseline (IPB)

Definition

The value where we need to put back the participant before the start of trial. This [term] is important because without instructions participant may hold the sensor too loosely (Nazir & al., 2017)

The term of baseline to name this value can be discussed to have the more appropriate and consensual name. We may also call this value a threshold.

This value was set to 1.5N in previous articles with additional informations that this value tend to decrease (18.62%) over time without instructions (Nazir & al., 2017) and there isn't a gender effect (Blampain & al., 2018).

New approaches

The previous value used for baseline was based on ... This value wasn't modified for each participant. Due to the lack of subjectivity of this value, some questions emerged on the possible need to adjust it for each participant and the way to do it.

Lille

This method is based on a weighted mean with 2 values: comfortable holding and cell droping. The mean of the grip force signal is computed during a 60 seconds record when the only instruction given to the participant is to "hold the cell in a confortable way" following the example of the experimenter on the way to hold the cell according to the Lille setup (see image below (recup photo Olivier)). Next, we ask him to release gradually the pressure on the cell until it drops on a box full of foam (to prevent any damage on the cell). This step is repeated [3] times and we take the mean of the 3 minimum values before the cell drops.

We can compute a baseline / threshold value with 80% of the confort mean and 20% of the drop mean following this calculation:

baseline / threshold = 0.8 x confort + 0.2 x drop

value = 80% confort + 20% drop