The data are recorded from 10 intact subjects repeating 7 grasps 12 times, twice a day for 5 days.
The names are coded as follows:
Subject: 1
Day: 1
Time of the day: 1 (morning, while 2 is afternoon)

Acquisition Protocol
The acquisition protocol is an evolution of the acquisition protocol used to record the previous Ninapro datasets. The researcher explains the experiment to the subject, asks him to respond to a few questions (including age, gender, height, weight and laterality) and measures the length (wrist to elbow) and circumference of the subject’s forearm. Then, the researcher explains the experiment to the subject. The subject sits in front of a table with the forearm leaning on it. The experiment consists of 12 repetitions of 7 grasps performed on a set of 14 objects. The set of hand grasps (figure below) was chosen from the robotics and rehabilitation literature with the goal of covering several hand movements exploited in activities of daily living (ADL). The grasp to be performed is shown to the subject with two videos (in first and third person perspective). Afterwards, a set of audio commands explains the subject the task to be performed (i.e. grasping the object, releasing the object and returning to the rest position).
While performing the experiment, a fixed image representing the grasp is shown on the screen of the laptop. The number of repetitions is equally distributed among two objects I. Each repetition lasts for 4 seconds and is followed by 4 seconds of rest. The data recorded from each subject are uploaded to Ninaweb and publicly available as the 6th Ninapro dataset 3 .

Acquisition Setup
The hardware acquisition setup consists of:
• DELL Latitude E5520: the laptop used to perform the data acquisitions and to record the data.
• Tobii Pro Glasses II: a wearable eye tracking system used to record the eye movements and field of view;
• 14 Delsys Trigno double differential sEMG Wireless electrodes: used to record the muscular activity of the forearm. The electrodes are equally space around the forearm. The first eight at the height of the radio humeral joint, the remaining 6 below. The electrodes were fixed on the forearm using their standard adhesive bands. Moreover, a hypoallergenic elastic latex–free band was placed around the electrodes to keep them fixed during the acquisition. The sEMG signals are sampled at a rate of 2 kHz.

Data Sets
For each exercise, for each subject, the database contains one matlab file with synchronized variables.
The variables included in the matlab files are:
- subj: subject number
- acc (48 columns): three-axes accelerometers of the 12 electrodes (6 columns are empty)
- emg (16 columns): sEMG signal of the 14 electrodes (2 columns are empty)
- stimulus (1 column): the movement repeated by the subject.
- restimulus (1 column): again the movement repeated by the subject. In this case the duration of the movement label is refined a-posteriori in order to correspond to the real movement
- object (1 column): used object.
- reobject (1 column): relabeled used object.
- repetition (1 column): repetition of the stimulus
- rerepetition (1 column): repetition of restimulus
- repetition object (1 column): used object repetition
- daytesting: day of the acquisition (1 to 5)
- time: time of the acquisition (1 to 2)

The 6th Ninapro database is thoroughly described in the paper:
"Francesca Palermo, Matteo Cognolato, Arjan Gijsberts, Barbara Caputo, Henning Müller and Manfredo Atzori, Analysis of the repeatability of grasp recognition for hand robotic prosthesis control based on sEMG data, in: IEEE International Conference on Rehabilitation Robotics, London, UK, 2017"
You must cite this paper for any work related to the 6th Ninapro database and look at it for further details.