Low-Level Laser Therapy Facilitates Postcontraction Recovery with Ischemic Preconditioning

Area of Science:

• Exercise Physiology
• Biomedical Engineering
• Rehabilitation Science

Background:

• Ischemic preconditioning is increasingly used in strength training, particularly with low-load resistance exercise, to enhance performance and combat early muscle fatigue.
• Understanding adjunct therapies that can further optimize recovery in this training paradigm is crucial for athletes and clinicians.

Purpose of the Study:

• To investigate the efficacy of low-level laser (LLL) therapy in accelerating postcontraction recovery when combined with ischemic preconditioning during low-load resistance exercise.
• To determine the effects of LLL on muscle force production, force control, and motor unit (MU) activation patterns during recovery.

Main Methods:

• Forty healthy adults were randomized into LLL and sham groups, both undergoing ischemic preconditioning and wrist extension exercise at 40% maximal voluntary contraction (MVC).
• The LLL group received 808 nm laser (60 J) on working muscles during recovery, while the sham group received no laser therapy.
• Measurements included MVC, force fluctuations, and MU discharge variables during trapezoidal contractions at baseline, postcontraction, and post-recovery.

Main Results:

• The LLL group demonstrated significantly higher normalized MVC (86.22%) compared to the sham group (71.70%) post-recovery (P=0.001).
• LLL treatment resulted in reduced normalized force fluctuations (94.76% vs. 121.37%, P=0.002) and increased normalized electromyography amplitude (94.33% vs. 73.57%, P<0.001).
• These improvements in the LLL group were associated with lower MU interspike interval variability and higher recruitment thresholds.

Conclusions:

• Low-level laser therapy significantly accelerates postcontraction recovery when combined with ischemic preconditioning.
• LLL enhances force generation capacity and improves force precision through optimized motor unit recruitment and reduced discharge variability.