fNIR for Muscle Oxygenation

This is one of many ADVANCED FEATURES for the selected Application. Scroll down for hardware options.

Sample Setup to Record Muscle Oxygenation Activity from the Biceps

Hardware

Imager: FNIR203C with Sensor: RXFNIR-2000-5 5ch sensor pad → see all fNIR Systems for Research
EMG: BN-EMG2 wireless EMG amp with transmitter
Electrodes EL504 x 2 and Lead Set BN-EL30-LEAD2
WRAP1 Self-adhesive stretch wrap

Participant

Place NIRS sensor and EMG electrodes in the direction of muscle fibers on the biceps brachii, symmetrical with the line between medial acromion and fossa cubit at 1/3 from fossa cubit.

Sensor: Place the sensor pad on the anterior side of muscle (muscle belly) and use WRAP1 to secure the placement of the sensor pad on the participant’s arm.

Electrodes: Place electrode approximately 10 cm apart along the medial side of the muscle’s short head and connect Vin⁺ and Vin^– leads.

 Experimental Procedure

Record baseline (~120 sec): Participant begins in a standing, relaxed position with arms down next to the body.

Record muscle activation (~60 sec): After baseline, instruct the participant to flex his/her biceps for about 60 seconds and return to initial relaxed position. Manually insert an event marker to indicate the onset of the flexing motion.

Alternate protocol: Record 30 sec baseline. Pull up against resistance with the biceps at 50% MVC until exhaustion. After 20 minutes, perform semi-dynamic contraction alternating for 4 sec each at 20% and 60% MVC until exhaustion.

Analysis

COBI Studio Modern was used to record the light intensity graph from the fNIRS sensor pad. The automated calculation of oxy and deoxy hemoglobin trails was performed with the use of fNIRSoft.

Figure 1: Oxy (red) and deoxy (blue) hemoglobin trail on CH1 of RXFNIR-2000-5 Sensor
Marker 1 was inserted manually to indicate the onset of the flexing motion.

The oxygenated hemoglobin data was exported from fNIRSoft as a .csv file and subsequently imported into AcqKnowledge.

Figure 2: CH1 raw EMG, CH2 imported oxy hemoglobin trail, CH3 Root Mean Square (RMS) of the EMG signal

The experiment showed an initial decrease in the oxy hemoglobin and increase in the deoxy hemoglobin concentration in the muscle tissue during the muscle flexing part of the experiment. A slow recuperation of the HbO was observed during the flexing stage. After the active part of the experiment, the HbR returned almost immediately to pre-flexing concentration levels, whereas the HbO concentration exceeded the resting period levels and gradually returned to resting state levels over time.

All concentration levels and changes indicated are relative with respect to initial baseline recorded prior to the start of the actual experiment.

Application Notes

Knowledge Base