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-exhaustions (TTEs) in cyclists. This was a double-blind, randomized, crossover, placebo-controlled trial study. Sixteen cyclists (~23 years) 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) 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.

Manipulation of Stroke Rate in Swimming: Effects on Oxygen Uptake Kinetics.

The study aimed to assess the effect of different front crawl stroke rates (SRs) in the oxygen uptake (̇VO2) kinetics and ̇VO2 peak, the total time to exhaustion (TTE), and blood lactate concentration ([La]) at 95% of the 400-m front crawl test (T400) mean speed (S400). Twelve endurance swimmers performed a T400 and four trials at 95% of the S400: (i) free SR, (ii) fixed SR (100% of the average free SR trial), (iii) reduced SR (90% of the average free SR trial), and (iv) increased SR (110% of the average free SR trial). ̇VO2 was accessed continuously with breath-by-breath analysis. The results highlighted: (i) the time constant at increased SR (13.3±4.2 s) was lower than in the reduced SR condition (19.5±2.6 s); (ii) the amplitude of the primary phase of ̇VO2 kinetics in the fixed SR (44.0±5.8 ml·kg-1·min-1) was higher than in the increased SR condition (39.5±6.4 ml·kg-1·min-1); and (iii) TTE was lower in the fixed SR (396.1±189.7 s) than the increased SR condition (743.0±340.0 s). The results indicate that controlled SR could be considered a swimming training strategy, focusing on physiological parameters overload.

Saddle Height and Cadence Effects on the Physiological, Perceptual, and Affective Responses of Recreational Cyclists.

Saddle height influences cycling performance and would be expected to influence cyclists physically, perceptually, and emotionally. We investigated how different saddle positions and cadences might affect cyclists' torque, heart rate, rate of perceived exertion (RPE), and affective responses (Feeling scale). Nine male recreational cyclists underwent cycling sessions on different days under different conditions with a constant load. On Day 1, the saddle was at the reference position (109% of the distance from the pubic symphysis to the ground), and on Days 2 and 3, the saddle was in the "upward position" (reference + 2.5%) and "downward position" (reference - 2.5%) in random order. Each session lasted 30 minutes and was divided into three cadence-varied 10-minute stages without interruption: (a) freely chosen cadence (FCC), (b) FCC - 20%, and (c) FCC + 20%. We assessed all dependent measures at the end of each 10 minute stage. While there was no significant interaction (Saddle × Cadence) for any of the analyzed variables, torque values were higher at lower cadences in all saddle configurations, and the FCC + 20% cadence was associated with faster heart rate, higher RPE, and lower affect compared with FCC and FCC - 20% in all saddle positions. At all cadences, the saddle at "downward position" generated a higher RPE compared with "reference position" and "upward position." The affective response was lower in the "downward position" compared with the "reference position." Thus, while cyclists perceived the downward (versus reference) saddle position as greater exercise effort, they also associated it with unpleasant affect.

Time Response of Photobiomodulation Therapy on Muscular Fatigue in Humans.

Rossato, M, Dellagrana, RA, Sakugawa, RL, Lazzari, CD, Baroni, BM, and Diefenthaeler, F. Time response of photobiomodulation therapy on muscular fatigue in humans. J Strength Cond Res 32(11): 3285-3293, 2018-The aim of this study was to identify the effects of 2 different time responses on fatigue of knee extensor. Sixteen male volunteers (26 ± 6.0 years, 81 ± 12 kg, and 181 ± 7.4 cm) participated in the study. Participants performed the same protocol in 5 sessions {control, placebo (placebo applied both 6 hours before and immediately before the test), 6 hours before + immediately before (photobiomodulation therapy [PBMT] applied both 6 hours before and immediately before the test), 6 hours before (PBMT applied 6 hours before and placebo applied immediately before the test), and immediately before (placebo applied 6 hours before and PBMT applied immediately before the test)}. Photobiomodulation therapy was applied on knee extensor (9 sites; 30 J per site). Maximal isometric voluntary contraction (MIVC) was assessed before and after an isokinetic fatigue (45 flexion-extension concentric at 180°·s), associated with electromyography (root mean square [RMS] and median of frequency [MF]). For MIVC, there was no treatment × time interaction for all variables. Time effect was observed for peak torque (PT), RMS, and MF. Treatment effect was verified for PT, and 6 hours before + immediately before condition presented higher PT during MIVCpre than control (p = 0.004) and placebo (p = 0.044). The immediately before presented higher PT values than control (p = 0.047). Regarding MIVCpost, the PT for 6 hours before + immediately before presented higher values than control (p = 0.001) and placebo (p = 0.004). Peak torque during MIVC (pre to post) was reduced in 6 hours before + immediately before treatment (26%) compared with control (33%), placebo (29%), and immediately before (32%). The application of PBMT 6 hours + immediately before and immediately before exercise protocol is able to reduce the fatigue.

Low-level laser therapy improves the VO2 kinetics in competitive cyclists.

Some evidence supports that low-level laser therapy (LLLT) reduces neuromuscular fatigue, so incrementing sports performance. A previous randomized controlled trial of our group showed increased exercise tolerance in male competitive cyclists treated with three different LLLT doses (3, 6, and 9 J/diode; or 135, 270, and 405 J/thigh) before time-to-exhaustion cycling tests. Now, the present study was designed to evaluate the effects of these LLLT doses on the VO2 kinetics of athletes during cycling tests. Twenty male competitive cyclists (29 years) participated in a crossover, randomized, double-blind, and placebo-controlled trial. On the first day, the participants performed an incremental cycling test to exhaustion to determine maximal oxygen uptake (VO2MAX) and maximal power output (POMAX), as well as a familiarization with the time-to-exhaustion test. In the following days (2 to 5), all participants performed time-to-exhaustion tests at POMAX. Before the exhaustion test, different doses of LLLT (3, 6, and 9 J/diode; or 135, 270, and 405 J/thigh, respectively) or placebo were applied bilaterally to the quadriceps muscle. All exhaustion tests were monitored online by an open-circuit spirometry system in order to analyze the VO2 amplitude, VO2 delay time, time constant (tau), and O2 deficit. Tau and O2 deficit were decreased with LLLT applications compared to the placebo condition (p < 0.05). No differences (p > 0.05) were found between the experimental conditions for VO2 amplitude and VO2 delay time. In conclusion, LLLT decreases tau and O2 deficit during time-to-exhaustion tests in competitive cyclists, and these changes in VO2 kinetics response can be one of the possible mechanisms to explain the ergogenic effect induced by LLLT.

Dose-response effect of photobiomodulation therapy on neuromuscular economy during submaximal running.

The purpose of this study was to verify the photobiomodulation therapy (PBMT) effects with different doses on neuromuscular economy during submaximal running tests. Eighteen male recreational runners participate in a randomized, double-blind, and placebo-controlled trial, which each participant was submitted to the same testing protocol in five conditions: control, placebo, and PBMT with doses of 15, 30, and 60 J per site (14 sites in each lower limb). The submaximal running was performed at 8 and 9 km h-1 during 5 min for each velocity. Muscle activation of the vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF), biceps femoris (BF), and gastrocnemius lateralis (GL) was collected during the last minute of each running test. The root mean square (RMS) was normalized by maximal isometric voluntary contraction (MIVC) performed a priori in an isokinetic dynamometer. The RMS sum of all muscles (RMSLEG) was considered as main neuromuscular economy parameter. PBMT with doses of 15, 30, and 60 J per site [33 diodes = 5 lasers (850 nm), 12 LEDs (670 nm), 8 LEDs (880 nm), and 8 LEDs (950 nm)] or placebo applications occurred before running tests. For the statistical analysis, the effect size was calculated. Moreover, a qualitative inference was used to determine the magnitude of differences between groups. Peak torque and RMS during MIVCs showed small effect sizes. According to magnitude-based inference, PBMT with dose of 15 J per site showed possibly and likely beneficial effects on neuromuscular economy during running at 8 and 9 km h-1, respectively. On other hand, PBMT with doses of 30 and 60 J per site showed possible beneficial effects only during running at 9 km h-1. We concluded that PBMT improve neuromuscular economy and the best PBMT dose was 15 J per site (total dose of 420 J).

Effect of pre-exercise phototherapy applied with different cluster probe sizes on elbow flexor muscle fatigue.

Phototherapy has been used for reducing muscle fatigue. In view of the various types of phototherapy cluster probes available in the market, the purpose of this study was to compare the effects of a similar phototherapy dosage with two different cluster probes on elbow flexor muscle fatigue: small cluster probe (SC = 9 diodes; 7.5 cm(2)) vs. large cluster probe (LC = 33 diodes; 30.2 cm(2)). Ten physically active male aged 18-35 years participate in a randomized, crossover, double-blind, placebo-controlled trial, which each participant was submitted to the same testing protocol in four sessions (separated by at least 48 h) with different treatments: LC-phototherapy, SC-phototherapy, LC-placebo, and SC-placebo. The elbow flexion maximal isometric voluntary contraction (MIVC) was performed before and after a fatigue protocol (60 % of MIVC until exhaustion). Electromyography (EMG) of the biceps brachii muscle was collected during all testing procedure. Phototherapy with dose of 60 J per muscle [LC: 33 diodes = 5 lasers (850 nm), 12 LEDs (670 nm), 8 LEDs (880 nm), and 8 LEDs (950 nm); SC: 9 diodes = 5 lasers (850 nm) and 4 LEDs (670 nm)] or placebo applications occurred before fatigue protocol. Two-way ANOVA (treatment and time factors) and one-way ANOVA were used, followed by LSD post hoc. Time to exhaustion was significantly higher in active LC (15 %; p = 0.031) and SC (14 %; p = 0.038) in comparison with their respective placebo treatments, without differences between LC and SC (p > 0.05) or between placebo conditions (p > 0.05). This larger exercise tolerance in phototherapy conditions was not accompanied by a higher decrement in the volunteers' maximal strength capacity (11-15 %; p > 0.05 for all). EMG signals presented no difference between the four condition tested here. In both large and small cluster probes (according parameters tested in this study) led to reduced fatigue in elbow flexor muscles, without difference between them.