The Use of Thermal Infra-Red Imaging to Detect Delayed Onset Muscle Soreness

The overall goal of this procedure is to identify and measure delayed onset muscle soreness or DOMS in its initial stages using a thermal infrared camera. The first step is to take baseline images of both arms. Pain measurements are done using a visual analog scale, and blood is drawn to measure serum myoglobin.

Next muscle strength is measured in the arm that will be exercised. The appropriate weight needed for the exercise is calculated as a percentage from this muscle strength measurement. Then the subject does four sets of 25 repetitions using the calculated weight.

The final step is to take images of both the exercised and non-exercise arms at 24 and 48 hours. After the exercise, blood is collected and the visual analog scale is administered at several time points after the exercise to verify the pain intensity. Ultimately, the acquired IR images are analyzed using the Thermo Vision Examiner software showing a significant increase of the skin temperature above the exercise muscle.

The main advantage of this technique is that unlike visual analog scales, which are kind of a subjective measure of whether someone's sore or not, this technique gives you quantifiable absolute data. This method has the additional advantage of being able to detect delayed onset muscle soreness are DOMS in its early stages. This allows more detailed studies of the micro physiology of exercise and muscle soreness, rather than using simple subjective scales demonstrating this technique will will be ha Ley Hani is a PhD candidate earning his doctorate in rehabilitation science here in the School of Allied Health at Loma Linda University.

To prepare for infrared imaging set a temperature controlled room to a constant temperature to minimize any external bias from differences in room temperature, which could lead to false thermal readings. A room with darker colored paint is preferred to minimize any infrared interference. It is also critical that the room lighting doesn't emit infrared waves, which can give false high readings.

Uniform LED lights are preferred over fluorescent or tungsten lighting as LED lights produce little infrared interference prior to exercise of the elbow flexors set the camera at a distance of one meter away and at a perpendicular angle to the skin being measured. Here, a FLIR six 60 IR camera is used. The intended target should be isolated as body heat from sources other than the target could disrupt the thermal image and give false readings.

After the camera is set up, advise the subjects to stand still until the image has been taken. Imaging should take no more than a couple of seconds, but it is very critical to minimize movement to ensure the accuracy of the acquired image acquire an IR image of the arm to be exercised. An image of the non exercised arm should also be obtained for comparison purposes.

Record image numbers from the IR camera immediately on a separate spreadsheet to correlate the subject arm time points and the image numbers. A visual analog scale is used to assess subjective soreness of the arm before and after exercise. The scale is characterized by a 10 centimeter long line marked no pain at one end and extremely sore at the opposite end.

Direct each participant to make a mark along the 10 centimeter line to indicate their response to soreness before the exercise. Also before exercise, obtain peripheral blood from the subjects to measure myoglobin concentration levels in the blood as described in the written procedure. Centrifuge the blood at 4, 000 RPM for 10 minutes to separate the serum from the cells.

Store the samples at minus 80 degrees Celsius until myoglobin analysis is performed prior to beginning the exercise. The resistance maximum or RM should be tested for each participant to do so, use a strain gauge device interfaced with a computer through a BioPack bioelectric amplifier module to measure muscle strength. The module is connected to an MP 100 analog to digital converter, sampling at a frequency of 1000 hertz per second, and at a resolution of 24 bits.

The strain gauge device is fixed to a bench at a 45 degree angle. Instruct the subjects to sit behind the device and rest their elbows on the padded area so that the exertion force is through their wrists. This is the best way to ensure that the subject will not recruit any muscle other than the biceps determine strength on three occasions with each contraction being three seconds in duration with approximately 45 seconds separating the contractions.

The average of the three measurements is the rm. After determining the RM for the biceps muscle of each participant, the intended session of exercise should be carried out with 35%of their RM by using the appropriate weighted dumbbells to induce muscle soreness. Participants carry out the exercise by doing a set of 25 repetitions of biceps concentration curls while seated on a chair and with the elbows supported on their thighs.

Instruct subjects to do the full set of 25 repetitions, but stop them if they fail to steadily control the weight during the exercise. Following the exercise, give each subject a 92nd resting period. Repeat the exercise and resting period three more times for a total of four sets of 25 repetitions.

30 minutes following exercise. Collect peripheral blood samples as done before blood collection should also be performed. 48 hours post-exercise at 24 and then 48 hours post-exercise.

Take IR images of the exercised muscle and control muscle. Also administer the VAS at these times. Process the acquired IR images using the Thermo Vision Examiner software.

After selecting the required image for analysis, identify four regions of interest on the acquired image of the arm using statistical boxes on the software interface. When the required regions across the arm have been located, the software shows the means and standard deviations of the temperatures for each of the selected regions. At this point, each individual region can be cross compared, or an average temperature of the whole arm can be obtained.

The results of IR thermal images taken during this investigation are clearly represented here. Images taken at three time periods for the exercised arms of 41 subjects showed a statistically significant increase in average skin temperature at 24 hours post-exercise when compared to pre-exercise temperatures and temperatures taken at 48 hours. However, for the non-exercise arm changes amongst the three time periods were not evident.

The difference in average skin temperature over the three days was not significant shown. Here are the results of the pain readings from the VAS. The reported pain of the exercised muscle had a dramatic increase on days two and three.

The results of the myoglobin concentration levels indicate that there was little change between the two myoglobin concentrations on day one, taken pre-exercise and 30 minutes post-exercise. But on day three, there was a very large increase in myoglobin of 147 nanograms per milliliter of blood when compared to the first two concentrations on day one. While attempting this procedure, one of the most important steps is to keep the room temperature constant and to use the LED lighting throughout the data collection period.

The reason for that is to minimize any bias, any temperature related bias that the camera will pick up.