Photobiomodulation (PBM) Therapy on Muscle Performance in Elderly Women
Condition: Lasers; Resistance Training; Muscle Strength; Aged; Performance
Study type: Interventional

Summary: 
      The present project aims to investigate the acute and chronic effects of laser
      photobiomodulation (PBM) at 808 nm on muscle performance in physically active elderly women.
      The hypothesis of this study is that laser PBM would improve muscle strength (i.e., MVIC and
      1RM) and endurance (i.e., repetitions-to-failure, blood lactate levels), functional capacity
      (i.e., short physical performance battery score), and rating of perceived exertion when
      compared with placebo laser.
    

Detailed description: 
      The purpose of this study will be to investigate the acute and chronic effects of laser PBM
      (λ: 808 nm) on muscle performance in physically active elderly women. For this purpose, the
      participants will be enrolled in two trials: Trial 1: Initially, all participants (n =
      20/group) will be submitted for a 1-wk familiarization period (3 non-consecutive sessions) of
      functional tests (i.e., standing balance, gait speed, and chair stand tests) from short
      physical performance battery (SPPB), knee flexion-extension exercise (3 sets of 10-12
      repetitions), maximum voluntary isometric contraction (MVIC), balance test on a force
      platform, and one-repetition maximum (1RM) test for knee extension exercise. Thereafter,
      participants will be randomized to receive 1 of 2 treatments (active or placebo laser) on two
      occasions (T1 and T2), separated by a 7-day washout period. During T1 and T2, participants
      will receive their respective treatments and then perform the muscle performance tests,
      separated by 10 minutes, in the following order: SPPB, MVIC, and repetitions-to-failure.
      After the last test, the participants will be instructed to reported the perceived exertion
      by OMNI scale, and a blood sample will be collected for measurement of blood lactate levels.
      Differences between groups will be assessed using a 2-tailed paired t-test. The significance
      level will be 0.05. Trial 2: participants will be randomized into two groups (n = 20/group):
      active laser or placebo laser. Both groups will be submitted for a 10-wk resistance training
      program (2 x/week) involving unilateral knee extension exercise. The following variables will
      be assessed from pre-to post-training: anthropometric, muscle thickness from vastus lateralis
      muscle using ultrasound, MVIC, 1RM, repetition-to-failure, and balance variables on a force
      platform. Shapiro-Wilk and Levine tests will be used to test the normality and homogeneity of
      the measurements, respectively. Two-way ANOVA (group x time) tests for repeated measures will
      be performed to assess changes over time and between groups for all dependent variables.
      Violation of sphericity will adjust using Greenhouse-Geser correction. The Bonferroni
      post-hoc test will detect specific differences between groups. When appropriate, the
      percentage of change (∆%) will be reported according to the following equation: ∆% =
      [(pre-average post average) / pre-average mean] × 100. Values will be express as mean ±
      standard deviation. O significance level α will be 0.05.
    

Intervention name(s): Active laser; Placebo laser
Intervention type(s): Radiation; Radiation
Intervention description(s): Participants will receive laser irradiation on the rectus femoris muscle of both legs immediately before the test (trial 1) and training (trial 2) sessions. A researcher blinded to the treatment conditions will apply the irradiation on eight points distributed over the muscle belly, using a gallium arsenide aluminum (Ga-As-Al) laser (λ: 808 nm) equipment. The points will placed at 25, 35, 50 and 75% of the total distance between the anterior superior iliac spine and superior border of the patella, bilaterally, with 2 cm of distance between each point.; Participants will receive placebo irradiation on the rectus femoris muscle of both legs immediately before the test (trial 1) and training (trial 2) sessions. A researcher blinded to the treatment conditions will apply the placebo irradiation on eight points distributed over the muscle belly. The points will placed at 25, 35, 50 and 75% of the total distance between the anterior superior iliac spine and superior border of the patella, bilaterally, with 2 cm of distance between each point.
Other intervention name(s): Active laser therapy; Placebo laser therapy
Allocation: Randomized
Intervention model: Factorial Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Basic Science
Keywords: Photobiomodulation; Muscle function; Elderly; Resistance exercise; Balance