Author(s): DAMICO, A., BOURANIS, C., NICOLAY, K., SILVA, K., GALLO, J., Institution: SALEM STATE UNIVERSITY, Country: UNITED STATES, Abstract-ID: 888

INTRODUCTION:
Photobiomodulation (PBM), sometimes referred to as low-level laser therapy, has been shown to improve aerobic endurance performance, along with muscular endurance during single joint resistance exercises targeting smaller muscles. It is unclear whether this benefit extends to compound exercises targeting larger muscles, such as the barbell bench press.
METHODS:
In a within-group design, 10 collegiate athletes (mean±sd; age 20.1±1.1 yrs; BMI 25.3±3.9 kg.m-2) received PBM or a sham treatment both six hours prior and then immediately preceding a bench press protocol. Photobiomodulation dosage was 30 Joules per site using an 850 nm wavelength nine diode cluster applicator with five infrared laser diodes (6 J/diode) at 200 milliwatts each and four 650 nm wavelength LED diodes at 10 milliwatts each. Two treatment sites each on the pectoralis major, triceps, and deltoids were irradiated. Bench press one repetition maximum (1RM), volume load (VL) lifted during five sets to failure at 60% 1RM, and soreness immediately after and in the three days following were compared between PBM and sham conditions. Testing was conducted over three sessions separated by a week each, with a baseline testing day occurring first, and the PBM and sham condition testing days following in a counterbalanced fashion to control for order effects. Two-tailed paired t-tests were used to compare the change from baseline between conditions (alpha level = 0.05). Cohen’s d was used to calculate effect size.
RESULTS:
No significant differences were observed between groups for bench press 1RM (p=0.48), VL (p=0.19), or soreness (p=0.90). No effect was observed for 1RM (d=.18) or soreness (d=.08). A moderate effect (d=.50) was observed for VL, where sham condition change from baseline was 710±518 lbs versus 459±484 lbs in the PBM condition.
CONCLUSION:
These findings suggest that muscular performance during compound, large muscle group exercises such as the bench press may not benefit from PBM at moderate loads relative to 1RM. Photobiomodulation is thought to exert its effects via mitrochondrial biogenesis and increased electron transport chain activity; therefore, ergogenic benefits may be limited to longer-duration exercise. Further, while a significant result was not observed, the moderate effect observed in the volume load assessment, where more weight was lifted over five sets in athletes in the placebo condition versus the PBM condition, suggests that the specific treatment used in this study may have inhibited performance. It is unclear whether there is an upper limit at which point PBM becomes ergolytic, but the findings of this study may indicate that such a threshold exists.