Technical description of Hexoskin data channels

This article provides an overview of the key data channels collected by Hexoskin, including acceleration, activity intensity, heart rate, respiration, ECG, cadence, and breathing metrics, with their specifications and data formats.

Acceleration/acc

Acceleration is the 3D movement data that represents how your Hexoskin (and you) moves in space. The accelerometer is used to detect steps and compute the activity.  

3-axis sensor with 13-bit resolution and +/-16g dynamic range. 64Hz, 0.0039g resolution.

Activity/act1s

The activity is a representation of your movement intensity over the last second. Looking at your activity lets you know when you started and stopped running, for example. The intensity of activity also gives you some insight of your activity efficiency: In general, if you can perform an activity by moving less, you are being more efficient in your movements.

1Hz data that represents the intensity of movement. It is the norm of the 3D acceleration, averaged over the last second.

Annotation

The different annotations and ranges present in the specified time range.

Batt

The battery level. The values should range approximately between 2600 (100%) and 2300 (0%).

Breathingrate/r_rr

Your breathing rate indicates how many times per minute you complete a breathing cycle. Although an increased activity intensity often results in an increase in breathing rate, there are techniques that favour deep, slow breathing even when performing intense activities. Watching this value during exercise will allow you to make sure you breathe like you want to.

The respiration rate in respirations per minute. A respiration is a complete cycle including one inspiration and one expiration. It is computed from the average time to perform the last 7 respiration cycles.

Cadence

The cadence is the number of steps per minute that you perform. Many long-distance runners like hanging around 180 steps per minute, but it’s up to you to find a cadence that you are comfortable with.

Number of steps per minute.

Ecg

The raw values collected from the ECG leads. 256 Hz with 12 bits resolution, so values from 0 to 4095.

Ecgstatus/heart_rate_quality

The ECG status signal represents an interpretation of the data quality. It is reported as an integer value, but the important is the bits forming that integer. Each bit represents a certain flag that has been detected or not within the last second of data. There are 6 bits to read and they are organized as described below :

1st bit: Not used, always 0.

2nd bit: DISCONNECTED : Does it seem like there is no shirt connected or that no one is in it?

3rd bit: 50_60HZ : Is there presence of a significant amount of 50 or 60Hz noise in the signal?

4th bit: SATURATED : Does the signal intensity go beyond the dynamic range?

5th bit: ARTIFACTS : Is any movement artifact detected?

6th bit: UNRELIABLE_RR : Does the rr interval seems suspiciously unreliable? Happens either when the signal quality is low and qrs are not detected correctly, or when the user is suffering from tachycardia or bradycardia.

For example, if you see a value of 40, the bit representation is 0010 1000. That means the rr is unreliable and that the signal is saturating.

Expiration/exp

The timestamp of all detected expirations, along with the value of arbitrary units of the respiration sensor. This value is weighted from 71% of the thoracic sensor, and 29% of the abdominal sensor. Each expiration corresponds to one inspiration.

Heartrate/hr

Your heart pumps blood to provide your muscles with oxygen and remove the CO2. Depending on the heart rate zone in which you are training, you will mostly train your aerobic or anaerobic system. You can maintain low-intensity exercise for a long period of time, burning fat as an energy source. High-intensity exercises can be maintained for shorter periods of time, and build up lactic acid that causes muscle aches.

The 1Hz calculated heart rate in beats per minute.

Inspiration/insp

See expiration, timestamp of detected inspirations, and their arbitrary unit values calculated as for expiration.

Minuteventilation/mv

Minute ventilation represents the number of liters of air breathed in a minute. High intensity activities require more oxygen, so increased minute ventilation is observed.

Estimated air volume breathed in 1 minute, estimated from the last 7 respiration cycles. Unit : mL/min

Qrs/qrs_amp

Position of the detected qrs complexes

Respiration/resp

128 Hz raw data from the respiration sensor, with 16-bit resolution. The sensor returns arbitrary units correlated to the surface of the sensor.

Respstatus/breathing_rate_quality

Breathing rate quality is interpreted in the same manner as for the heart rate quality. The bits forming the value are as follows:

NO_ABDO: No abdominal sensor detected or broken

NO_THOR: No thoracic sensor detected or broken

BASE_AB: baseline change in abdominal measured values

BASE_TH: baseline change in thoracic measured values

NOI_AB: significant noise present on the abdominal band

NOI_TH: significant noise present on the thoracic band

RR_interval

The RR interval represents, for each QRS detection, how long since the last QRS has been detected. The value is reported in hexotimestamps, which represents 1/256th of seconds.

For example, a value of 207 means that 207/256 = 0.8 seconds passed since the last QRS detection.

Status

Various status codes, for internal use

Step

The number of steps you take can be an indicator of how active you were for the day. If monitoring yourself throughout the day, you can set yourself goals and see if you can reach and exceed it.

Timestamp of detected steps, and the total count in the record until then

Tidalvolume/vt

Tidal volume is the volume of air breathed from the last breathing cycle. Use this to determine if your breathing is deep or shallow.

The estimated volume of the last breathing cycle.

For more details about the data channels or datatype, please refer to this API documentation: https://api.hexoskin.com/docs/resource/datatype/.