Low Intensity Laser as an Adjuvant to Improve Muscle Strength after Exercise: A Case Report

Muscle fatigue is a limiting factor in prosthetic patients and studies show that low intensity laser can improve performance and increase muscle strength. We tested a concentric exercise protocol comparing a test applied after 10 sessions without and with the use of laser using the Cybex Humac Norm® Test & Rehabilitation System in a patient with left lower limb amputation. First, a test was performed to determine the baseline value of peak torque, average power per repetition and total work performed. Ten exercise sessions and a new test were followed to determine the difference in power gain. Ten more sessions and a new test without laser application were performed to determine whether the torque increment level was reached, followed by ten more sessions with laser application 5 minutes before the exercise and a new test, with laser application, to evaluate the torque increment. An increase in PT was found of 5% for extensors and 7% for knee flexors in the second test in relation to baseline. The increase was 0% for the extensors and 11% for the flexors in the next test. After laser application there was an increase of 8% for the extensors and a deficit of 11% for the flexors. For TTR, the relative values for extenders and flexors were 3% and -3%, -10% and -2% (without laser) and 18% and 17% (with laser). We concluded that, in this protocol, the laser produced a gain in the peak torque of extensor muscles, but not of the flexors as well as a significant increase in the average power per repetition and the total work performed by both the extensors and the knee flexors, which may be of value as an adjuvant in the treatment of prosthetic patients. Keyword Low-level light therapy, Muscle fatigue, Muscle strength, Human Check for updates ated with an exercise program was able to improve postural stability and decrease the risk of falling in elderly patients [4]. One of the ways to promote muscle fatigue is through repeated contraction exercises with maximum endurance (isokinetCitation: Plapler H, Sugawara AT, Montelli RC, et al. (2020) Low Intensity Laser as an Adjuvant to Improve Muscle Strength after Exercise: A Case Report. J Phys Med 2(1):55-59 Plapler et al. J Phys Med 2020, 2(1):55-59 Open Access | Page 56 | not applied before the exercise sessions or before the test. These values were considered as an increase due to the exercises. Ten more exercise sessions were performed twice a week applying the low intensity laser (DMC Ltd, São Carlos, Brazil), at 4 equidistant points along the longitudinal axis of the anterior and the posterior face of the thigh, with a wavelength of 660 nm, continuous mode, nominal power 100 mW, frequency of 50 Hz, spot diameter of 2 mm, power density 32.2 W/ cm2·per point, irradiation time of 60 seconds per point, energy of 6 J per point, energy density of 193.5 J/cm2·per point, keeping the stationary tip in contact with the skin at an angle of 90° and slight pressure. A new test with the same parameters described above followed. To perform the tests, the patient remained seated at an angle of 90° between trunk and hip and with the leg attached to the seat by means of a brace. The patient was verbally encouraged to maintain maximum strength throughout the exercises (Table 1). All measures were submitted to the Kruskal-Wallis test and, in case of statistical significance, validated by the Student-Newman-Keuls test for difference of posts (Figure 1).