Laser research: Muscular system sports medicine


Photomedicine and Laser Surgery Volume 31, Number 10, 2013

Protective Effect of Laser Phototherapy on Acetylcholine Receptors and Creatine Kinase Activity in Denervated Muscle

Shimon Rochkind, MD,1,2 and Asher Shainberg, PhD1

Objective: This study was designed to assess the status of skeletal muscles after laser treatment during long-term denervation processes, by investigating changes in the level of acetylcholine receptors (AChR) and creatine kinase (CK) activity in the denervated gastrocnemius muscle of the rat.

Background data: Progressive muscle atrophy is common in patients with severe peripheral nerve injury. Denervated muscles can account for significant differences in the extent of AChR and CK activity during the denervation period.

Methods: The study was conducted on 96 rats: 48 that received laser treatment and 48 untreated controls. The gastrocnemius muscle was denervated by removing a 10mm segment of the sciatic nerve. Low power laser irradiation was delivered transcutaneously to the right gastrocnemius muscle (HeNe continuous wave [CW] laser, 632.8 nm, 35mW, 30 min) for 14 consecutive days. Under general anesthesia, the rats were euthanized at seven time points: day 7 (n = 10), day 14 (n = 10), day 21 (n = 10), day 30 (n = 5), day 60 (n = 4), day 120 (n = 5), and day 210 (n = 4), with and without laser treatment, respectively. AChR was quantified by the 125I-a-bungarotoxin. CK activity was measured by a specific spectrophotometric method.

Results: Laser treatment had a significant therapeutic effect on the denervated muscle during the first 21 days for AChR and the first 30 days for CK activity.

Conclusion: In the early stages of muscle atrophy, laser phototherapy may preserve the denervated muscle by maintaining CK activity and the amount of AChR.

Photomedicine and Laser Surgery Volume 31, Number 10, 2013

Effect of Low-Level Laser Therapy (808 nm) in Skeletal Muscle After Resistance Exercise Training in Rats

Tatiane Patrocinio, PhD,1 Andre Cabral Sardim,2 Livia Assis, PhD,2 Kelly Rossetti Fernandes, MS,2
Natalia Rodrigues, PhD,1 and Ana Claudia Muniz Renno, PhD1

Objective: The aim of this study was to evaluate the effects of 808nm laser applied after a resistance training protocol, on biochemical markers and the morphology of skeletal muscle in rats.

Background Data: Strenuous physical activity results in fatigue and decreased muscle strength, impaired motor control, and muscle pain. Many biochemical and biophysical interventions have been studied in an attempt to accelerate the recovery process of muscle fatigue. Among these, low-level laser therapy (LLLT) has been demonstrated to be effective in increasing skeletal muscle performance in in vivo studies and in clinical trials. However, little is known about the effects of LLLT on muscle performance after resistance training.

Methods: Thirty Wistar rats were randomly divided into three groups: control group (CG), trained group (TG), and trained and laser-irradiated group (TGL).

The resistance training program was performed three times per week for 5 weeks, and consisted of a climbing exercise, with weights attached to the tail of the animal. Furthermore, laser irradiation was performed in the middle region of tibialis anterior (TA) muscle of both legs, after the exercise protocol.

Results: Analysis demonstrated that TGL demonstrated significantly reduced resting lactate level and decreased muscle glycogen depletion than the animals that were exercised only, and significantly increased the cross-section area of TA muscle fibers compared with thoseo in the other groups.

Conclusion: These results suggest that LLLT could be an effective therapeutic approach in increasing muscle performance during a resistance exercise protocol.

Effect of 655-nm Low-Level Laser Therapy on Exercise-Induced Skeletal Muscle Fatigue in Humans

Ernesto Cesar Pinto Leal Junior, M.Sc.,1,2,3 Rodrigo Álvaro Brandão Lopes-Martins, Ph.D.,4, Dalan, P.T.,5 Maurício Ferrari, P.T.,5 Fernando Montanari Sbabo, P.T.,5, Rafael Abeche Generosi, P.E.,6 Bruno Manfredini Baroni, P.T.,5, Sócrates Calvoso Penna, Ph.D.,4 Vegard V. Iversen, Ph.D.,8 and Jan Magnus Bjordal, Ph.D.3,7

Objective: To investigate if development of skeletal muscle fatigue during repeated voluntary biceps contractions could be attenuated by low-level laser therapy (LLLT).

Background Data: Previous animal studies have indicated that LLLT can reduce oxidative stress and delay the onset of skeletal muscle fatigue.

Methods: Twelve male professional volleyball players were entered into a randomized doubleblind placebo-controlled trial, for two sessions (on day 1 and day 8) at a 1-wk interval, with both groups performing as many voluntary biceps contractions as possible, with a load of 75% of the maximal voluntary contraction force (MVC). At the second session on day 8, the groups were either given LLLT (655 nm) of 5 J at an energy density of 500 J/cm2 administered at each of four points along the middle of the biceps muscle belly, or placebo LLLT in the same manner immediately before the exercise session. The number of muscle contractions with 75% of MVC was counted by a blinded observer and blood lactate concentration was measured.

Results: Compared to the first session (on day 1), the mean number of repetitions increased significantly by 8.5 repetitions ( 1.9) in the active LLLT group at the second session (on day 8), while in the placebo LLLT group the increase was only 2.7 repetitions ( 2.9) (p  0.0001). At the second session, blood lactate levels increased from a pre-exercise mean of 2.4 mmol/L ( 0.5 mmol/L), to 3.6 mmol/L ( 0.5 mmol/L) in the placebo group, and to 3.8 mmol/L ( 0.4 mmol/L) in the active LLLT group after exercise, but this difference between groups was not statistically significant.

Conclusion: We conclude that LLLT appears to delay the onset of muscle fatigue and exhaustion by a local mechanism in spite of increased blood lactate levels.