Photobiomodulation Therapy on Performance in Successive Cycling Tests

Effects of Photobiomodulation Therapy on Performance in Successive Time-to-Exhaustion Cycling Tests: A Randomized Double-Blinded Placebo Controlled Trial

The goal of this study was to investigate the effects of Photobiomodulation therapy (PBMT) on performance, oxygen uptake (VO2 kinetics), and lower limb muscle oxygenation during three successive time-to-exhaustion tests (TTEs) in cyclists. This was a double blind, randomized, crossover, placebo-controlled trial study. Sixteen cyclists (~23 years old), with a cycling training volume of ~460 km/week, volunteered for this study. In the first session, cyclists performed a maximal incremental test to determine maximal oxygen uptake and maximal power output (POMAX). In the following sessions, cyclists performed three consecutive TTEs at POMAX. Before each test, PBMT (135 J/thigh) or a placebo (PLA) PBMT was applied to both thighs. VO2 amplitude, O2 deficit, time delay, oxyhemoglobin (O2Hb), deoxyhemoglobin (HHb), and total hemoglobin (tHb) were measured during tests on the right vastus lateralis. The PBMT, applied before three successive TTE, increased performance of the first and second TTE (~10-12%) tests, speed of VO2 and HHb kinetics during the first test, and increased peripheral muscle oxygenation (increase in HHb and tHb) in the first and second exhaustion tests. However, the PBMT effects were attenuated in the third TTE, as performance and all the other outcomes were similar to the ones from the PLA intervention. In summary, PBMT application increased the first and second successive TTEs, speed of VO2, and muscle oxygenation.

The goal of this study was to investigate the effects of Photobiomodulation therapy (PBMT) on performance, oxygen uptake (VO2 kinetics), and lower limb muscle oxygenation during three successive time-to-exhaustion tests (TTEs) in cyclists. Our study was characterized as a crossover, randomized, double-blind trial (blinding of the cyclists and the researcher responsible for evaluations). All protocols were explained to the participants, who voluntarily provided their consent to participate in the investigation through an informed consent document. This study received approval from the Research Ethics Committee for Human Subjects Studies at the institution where the research was conducted (number 708.362). Inclusion criteria involved cyclists aged 18-30 years, with a competitive history and no history of musculoskeletal injuries in the lower limbs in the last two years. Exclusion criteria included chronic disease, smoking, metabolic disorders, use of steroids in the last six months, chronic disease, physical disabilities, and use of antibiotic drugs in the previous week. The cyclists participating in the present study had ~6.5 years of regular training/competition and no history of lower limb muscular and/or skeletal injuries. Each cyclist visited the laboratory on three occasions. At the first visit, cyclists performed a maximum incremental test and familiarization to three successive TTEs. At the two subsequent visits, participants performed a standard protocol of three successive TTEs at maximal power output (POMAX) with preferred cadence, and PBMT or placebo (PLA) treatments were applied before each trial. The three testing days were performed with a 72h interval apart. A single therapist was involved with the random allocation of the PBMT and PLA interventions. This therapist received instructions not to disclose the treatment modality employed during each assessment session to either the cyclists or other researchers involved with data collection and data analysis. Furthermore, cyclists utilized opaque eyewear to shield their eyes and obstruct their visual access (visual blinding) during the PBMT or PLA intervention. The therapist was explicitly advised against revealing the treatment modality to both the cyclists and the other researchers. PBMT did not elicit any thermal or tactile sensations, thereby ensuring that athletes remained unaware of the specific application on their thigh area. The random assignment was determined through a basic drawing of lots during the first testing session, determining the allocation of either active PBMT or inactive PLA.

Inclusion Criteria:

• Cyclists aged 18-30 years;
• Competitive history;
• No history of musculoskeletal injuries in the lower limbs in the last two years.

Exclusion Criteria:

• Chronic disease;
• Smoking;
• Metabolic disorders;
• Use of steroids in the last six months;
• Physical disabilities;
• Use of antibiotic drugs in the previous week.