Effects of Photobiomodulation Therapy and Restriction of Wrist Extensor Blood Flow on Grip: Randomized Clinical Trial

To evaluate the influence of two different photobiomodulation therapy (PBMT) protocols (red 660 nm vs. infrared 830 nm) combined with a blood flow restriction (BFR) training protocol in wrist extensor muscles on handgrip, wrist extension force, and electromyographic behavior [root mean square (RMS)]. PBMT has been widely used to increase muscle performance and recovery in recent clinical trials. However, there is no evidence whether PBMT (red and/or infrared) can promote better results when combined with BFR, a known method to induce better strength gains. This study was a randomized controlled trial including 58 volunteers allocated into four groups: (1) control (conventional strengthening), (2) BFR (strengthening with BFR), (3) 660 nm (BFR strengthening with 660 nm PBMT-35 mW; 0.05 cm²; 2.10 J, total energy 18.9 J), and (4) 830 nm (BFR strengthening with 830 nm PBMT-32 mW; 0.101 cm²; 1.92 J, total energy 17.2 J). Data were analyzed by using a mixed-effects model, with a 5% significance index. A statistically significant increase was obtained for handgrip strength for the 660 nm group [27.36 ± 2.61 kilogram force (kgF)] compared with the 830 nm group (23.04 ± 3.06 kgF) (p = 0.010) and for wrist extensor strength in the 660 nm (7.77 ± 0.58 kgF) and BFR (7.54 ± 0.92 kgF) groups compared with the control group (5.33 ± 0.61 kgF) (p = 0.001 and p = 0.004, respectively). The RMS value for the 660 nm group was significantly higher than control (p < 0.0001), BFR (p < 0.0001), and the 830 nm group (p = 0.0009). The association of PBMT (660 nm) and BFR was effective for increasing handgrip strength of the wrist extensors, associated with an increase in RMS.