Photobiomodulation Therapy on Performance in Successive Cycling Tests
Condition: Photobiomodulation Therapy; Cyclists; Performance
Study type: Interventional

Summary: 
      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.
    

Detailed description: 
      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.
    

Intervention name(s): Photobiomodulation Therapy; Placebo Photobiomodulation
Intervention type(s): Device; Device
Intervention description(s): Phototherapy treatment (Photobiomodulation therapy or placebo) was performed using a Photobiomodulation therapy device (Vectra Genisys Systems, Chattanooga Group, Dallas, TX, USA). The cluster probe consisted of five low-level laser therapy diodes (850 nm) and 28 light emitting diodes therapy (670 nm, 880 nm, and 950 nm). Photobiomodulation therapy was applied in nine sites of each quadriceps femoris muscle
. A dosage of 15 J per site led to a total energy of 135 J per thigh, effectively increasing cycling performance in a previous study. We chose to apply Photobiomodulation therapy specifically to the quadriceps femoris because this muscle group is of utmost significance in generating torque and propelling the pedaling cycle. Its pivotal role in cycling performance made this muscle a prime target for the Photobiomodulation therapy intervention in our study.; The placebo treatment was performed in exactly the same manner as the Photobiomodulation therapy treatment, but with the device switched off, and the cluster was held stationary in contact with the skin at a 90° angle, with light pressure on the skin. The total application time of Photobiomodulation therapy or placebo was ~5 min for both limbs (9 points per thigh = 18 points × 16 s per point) before each time-to-exhaustion test.
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Crossover Assignment
Crossover, randomized, double-blind trial (blinding of the cyclists and the researcher responsible for evaluations)
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Other
Keywords: Phototherapy; VO2 response; muscle oxygenation; cyclists; performance