Effect of Low-Level Laser Therapy and Strength Training Protocol on Hand Grip by Dynamometry.

The purpose of this study was to investigate the effect of low-level laser therapy (LLLT) - 660 nm and 904 nm - before grip strength protocol in healthy subjects. The study included 45 healthy volunteers with an average age of 22.7 (±1.4) years, subdivided into the following groups, control group: grip strength training associated with placebo LLLT; 660 nm group: LLLT (660 nm, 20 J/cm, power of 30 mW, and beam area of 0.06 cm, continuous, energy 1.2 J, and exposure time 40 seconds per point) before grip strength training and 904 nm group: LLLT (904 nm, 10 J/cm, peak power of 70 W and 0.13 cm beam area, with pulsed beam 9.500 Hz and 30 seconds of exposure time per point and emitted energy 1.2 J) before grip strength training. The LLLT was timed to contact 10 points located in the region of the superficial and deep flexor muscles of the fingers, with a total energy of 12.0 J per session. For the strength training protocol, the volunteer exercised their fingers with the dominant hand on a small table, elbow flexed at 90°, forearm in neutral, using a light extension handle. The Oxford protocol was performed during four weeks. The grip strength was assessed using a dynamometer (Jamar™). The data were evaluated by the analysis of variance (ANOVA) statistical method. In the comparison of intragroup evaluation, only the 904 nm group showed a difference compared to the baseline assessment after 4 weeks ( < 0.05), in the final intergroup evaluation, a difference was observed in the comparison between the control and 904 nm groups In conclusion, LLLT (904 nm) applied before resistance training was effective in gaining grip strength when compared to LLLT (660 nm) and isolated strength training after 4 weeks.