Marcelo Papoti

We investigated the acute effects of local and/or systemic hypoxia on performance and psycho‐physiological responses during repeated cycle sprints. Eleven physically active young adults (six men, five women) performed four sessions on separate days, each involving three sets of five 5‐s all‐out efforts on a cycle ergometer (25 seconds rest between efforts and 5 minutes rest between sets). Sessions were conducted under four conditions, combining blood flow restriction [BFR; 45% of arterial occlusion pressure (AOP)] or control (CON; 5% of AOP) applied bilaterally to the legs during sprints, with inter‐effort recovery hypoxia [IEH; inspired oxygen fraction (FiO ₂ ) = 13.5%] or normoxia (NOR; FiO ₂ = 20.9%). Power output decreased across sprints and heart rate increased over sets, with no differences between conditions (Δ = −9.18%). IEH resulted in lower peripheral oxygen saturation (Δ = −8.0%) but higher oxygen uptake (Δ = 6.7 mL·kg ⁻¹ min ⁻¹ ) and minute ventilation (Δ = 6.1 L·kg ⁻¹ min ⁻¹ ), compared to normoxic conditions. Blood lactate concentration increased (Δ = 6.5 mM) post‐session similarly across all conditions. Vastus lateralis muscle oxygenation during sprints and inter‐set recovery was comparable across conditions, although the mean tissue saturation index during inter‐set recovery was lower in BFR + IEH versus CON + NOR conditions (Δ = −4.0%). Ratings of perceived exertion (Δ = 22.5%), limb discomfort (Δ = 34.2%), and breathing difficulty (Δ = 43.7%) increased throughout the sets, independently of conditions. Despite physiological and perceptual adjustments across sprint repetitions, neither BFR during sprints nor systemic hypoxia during recovery altered mechanical output in physically active individuals.

Background: Physiological adaptations associated with chronic exposure to hypoxia have been suggested as potential factors contributing to reduced COVID-19 severity in high-altitude populations. Therefore, hypoxic exercise training has emerged as a potential strategy to enhance recovery following COVID-19 infection. Hypothesis: Moderate-intensity training associated with continuous hypoxia (HYP) or intereffort recovery hypoxia (IEH) could induce additional stimulus to cardiorespiratory capacity in COVID-19 rehabilitation. Study Design: Randomized controlled clinical trial. Level of Evidence: Level 2. Methods: Sixty-one adults recovered from COVID-19 (35.9 days after diagnosis, on average) were randomly assigned to a no-exercise control group (CON, n = 18) or moderate-intensity training groups under normoxia [NOR, n = 12; fraction of inspired oxygen (FiO ₂ ) = 20.9%], HYP (n = 16; FiO ₂ = 13.5%), or IEH (n = 15; efforts at 20.9% and the recovery periods at 13.5%). Ventilatory and lactate thresholds (VT and LT, respectively), peak power output (PPO) determined during a graded exercise cycling test to exhaustion, forced expiratory volume in 1 second (FEV1), and forced vital capacity (FVC) were accessed before and after an 8-week cycling training program (3-6 efforts of 5 min at 90% to 110% of LT interspersed with 2.5 min of recovery, 3 times per week). Group × time effects were assessed using generalized mixed-effects models. Results: VT increased in all groups (all P ≤ 0.013), with no group × time interaction (all P > 0.15). VT ventilation increased only in the training groups (all P ≤ 0.013), and there was a group × time effect for IEH versus CON ( P = 0.036). PPO increased only in the training groups ( P < 0.001), with group × time interactions for all training groups versus CON (all P ≤ 0.002). Maximal ventilation increased in NOR ( P = 0.016) and HYP ( P = 0.012), both differing from CON ( P = 0.005). FEV1 decreased in NOR only ( P < 0.001), with group × time interactions versus HYP ( P < 0.001) and IEH ( P = 0.035). Conclusion: Moderate-intensity training promoted benefits in the indicators of aerobic capacity and PPO of COVID-19 convalescents. The additional exposure to hypoxia in the training sessions did not result in differences compared with NOR. Clinical Relevance: This training protocol can be used in COVID-19 rehabilitation. In addition, HYP and IEH can achieve similar results compared to NOR, with probably lower intensity.

Background: High-intensity interval training (HIIT) is known to improve insulin sensitivity, glycemic control, and body composition in people with type 2 diabetes mellitus (T2DM). Intermittent hypoxia (i.e., reduced oxygen availability) combined with HIIT may enhance glycemic control through convergent insulin-independent molecular pathways, including AMP-activated protein kinase activation and GLUT 4 translocation. Objective: To evaluate whether 8 weeks of intermittent hypoxia and HIIT, both isolated and combined, improve glucose homeostasis and related health outcomes in individuals with T2DM. Methods: This single-blind, randomized controlled trial will recruit 64 individuals (18-65 years) with T2DM. Participants will be randomly assigned to one of four groups: 1) HIIT with inter-effort recovery hypoxia (inspired oxygen fraction, FiO₂, of 0.135), 2) HIIT in normoxia (FiO₂ = 0.209), 3) passive intermittent hypoxia (FiO₂ = 0.135) or 4) control. Interventions will last 8 weeks, with three sessions per week. HIIT will be performed on a cycle ergometer at intensities based on the heart rate corresponding to the respiratory compensation point and peak power output, as determined by baseline cardiopulmonary exercise testing. The primary outcome is glycated hemoglobin, while secondary measures include glucose homeostasis, cardiorespiratory fitness, cardiovascular health, body composition, and hematological, metabolic, and behavioral outcomes. Generalized linear mixed models (α = 0.05) will be used for statistical analysis. Discussion: This study explores a novel non-pharmacological approach to T2DM management by applying intermittent hypoxia only during recovery periods of HIIT sessions. This method aims to elicit adaptations comparable to conventional intermittent hypoxia, while preserving training quality and offering a more practical, ecologically valid intervention.

This study examined the effects of sprint duration and blood flow restriction due to cuff pressure applied only during exercise on sprint cycling performance and psychophysiological responses. On separate days, 12 physically active young adults (9 men and 3 women) performed six ‘all‐out’ cycling sprints (5, 10, 15, 20, 25 and 30 s) in a randomised order under three cuff pressure conditions (0%, 40% and 60% of arterial occlusion pressure [AOP]). BFR was applied exclusively during exercise bouts, with passive rest periods of 5–15 min between sprints depending on sprint duration. Power output, peripheral oxygen saturation, vastus lateralis muscle oxygenation, heart rate and ratings of perceived exertion were measured. Mean and peak power output and total work done decreased with longer sprints (i.e., 20–30 s) than shorter efforts (i.e., 5–15 s), with no differences observed between cuff pressure conditions. Ventilatory responses, heart rate and muscle oxygenation variables increased with longer sprints. Peripheral oxygen saturation remained unaffected. BFR at 40% and 60% AOP increased limb discomfort for 15‐, 25‐ and 30‐s sprints compared to 0% AOP. In conclusion, increasing the sprint duration decreased mechanical output (external load) and increased physiological strain (internal load), with these effects largely unaffected by moderate‐to‐high (40%–60% AOP) external limb compression.

This study aimed to investigate the effects of the “living high–training low” (LHTL) model, in which mice were housed under hypoxic conditions but trained in normoxia to maintain training quality. We analyzed key proteins involved in cellular metabolism and oxidative stress, including hypoxia‐inducible factor 1α (HIF‐1α), peroxisome proliferator‐activated receptor gamma coactivator 1 alpha (PGC‐1α), and oxidation resistance protein 1 (OXR1). Forty male isogenic C57BL/6J mice were divided into nontrained (N) and trained (T) groups living in normoxic (NOR) or hypoxic (HYP) environments. HYP mice were housed 18 h/day for 8 weeks in a normobaric tent supplied with oxygen‐depleted air (FiO ₂ = 14.5%). Animal handling, including training, was conducted in normoxia (FiO ₂ = 19.5%). Training occurred 5 times/week (40 min/session) at ~80% of individual critical velocity. All mice were euthanized to extract the soleus, white gastrocnemius, and hypothalamus for protein analysis. Compared with training alone, LHTL did not lead to significantly greater HIF‐1α, PGC‐1α, or OXR1 expression across tissues; however, induced behavioral changes—such as reduced spontaneous physical activity and diminished ability to complete training—may indicate that the demands of the LHTL model were not trivial.

Exercise training in hypoxia enhances physiological adaptations improving exercise performance. However, acute hypoxia generally reduces high-intensity exercise tolerance, limiting its application in sports training. Here, we investigated whether oxygen consumption and exercise tolerance are affected during a session of an emerging high-intensity intermittent training (HIIT) model in hypoxia. This model involves efforts in normoxia with inter-effort hypoxia (IEH) recoveries. Young active males were recruited and completed a graded exercise test in normoxia, followed by HIIT sessions under three conditions: normoxia, continuous normobaric hypoxia (FIO ₂ : ~0.13), and IEH recovery, in different days and random order. Oxygen consumption, ventilatory variables and muscle oxygenation in the vastus laterali were assessed during HIIT sessions consisting of ten 1-min efforts (at 120% of maximal treadmill running speed from the graded test), with 2-min passive recoveries. Compared to normoxia, IEH recovery caused significant hemoglobin desaturation (between 95% and 88%) and a ~ 14% decrease in V̇O ₂ during recoveries. During efforts, particularly in the first 30 s, VO ₂ was significantly increased by approximately 7% in the IEH condition compared to normoxia. Notably, exercise task completion was nearly identical between normoxia (87 ± 24%) and IEH recovery conditions (87 ± 18%), but significantly lower in continuous hypoxia (44 ± 27%), along with impaired indexes of O ₂ metabolism. Additionally, IEH recovery resulted in a significantly lower pulmonary O ₂ diffusion gradient at a given V̇O ₂ , suggesting a compensatory increase in blood flow. In conclusion, IEH recovery preserved muscle oxygenation and exercise performance while enhancing V̇O ₂ during efforts.

Intermittent hypoxia combined with physical training may enhance performance and health parameters but can impair session quality, limiting adaptations. To address these drawbacks, inter-effort recovery hypoxia has been proposed. This study investigated the effects of a 5-week inter-effort recovery hypoxia protocol followed by a 1-week tapering period in recreational runners. Twenty-four men were allocated to an inter-effort recovery hypoxia group (n = 11) or a normoxia group (n = 13) and assessed for body composition, hematological profile, running economy, maximum velocity, and peak oxygen uptake before training (W0), after training (W6), and after tapering (W8). Training consisted of 3 weekly sessions for 5 weeks: a 5-minute warm-up at 60% of maximum velocity, ten 1-minute effort at 120% (wk 1–3) or 130% (wk 4 and 5) of maximum velocity with 2-minute passive recovery, and 5-minute cool-down at 60% of maximum velocity. The inter-effort recovery hypoxia group inhaled hypoxic air (fraction of inspired oxygen=0.136) during warm-up, recovery bouts, and cool-down. Outcomes were analyzed using generalized linear mixed models. Peak oxygen uptake increased in the inter-effort recovery hypoxia group at W6 (+7%) and W8 (+10%), while the normoxia group improved at W8 (+7%), without group differences; running economy improved in the normoxia group at W8 (+10%). No significant changes occurred in erythropoietin, erythrocytes, hemoglobin, reticulocytes, or body composition. The 5-week inter-effort recovery hypoxia protocol enhanced peak oxygen uptake without hematological changes, indicating a feasible and non-erythropoietic strategy for improving aerobic fitness.

Introduction: Recent evidence suggests that the combination of exercise and photobiomodulation therapy (PBMT) enhances muscle performance, including improvements in strength, hypertrophy, and fatigue resistance. As muscle tissue changes after training, a dose progression over time may show additional effects. However, there needs to be more clarity regarding the optimal physical parameters for enhancing muscle performance. Thus, the aim was to evaluate the impact of strength training combined with PBMT at fixed or progressive doses on strength performance, metabolic activity, and clinical outcomes in healthy individuals. Methods: This was a double-blind, randomized clinical trial. Fifty-six male participants were randomly allocated into four groups: Sham, minimal dose (60 J), maximal dose (300 J), and incremental dose (60–300 J). Baseline assessments included body composition analysis and isokinetic dynamometry (peak torque and total work of the quadriceps femoris and hamstring muscles), followed by ten sessions of strength training combined with PBMT applied before each exercise session, which consisted of three sets of stiff and squats. PBMT irradiation was applied to the quadriceps and hamstrings. Training loads and psychophysiological responses were monitored throughout the intervention. Participants were reassessed at the end of the training period and followed up for a total duration of seven days. Results: No significant differences were observed between the groups in isokinetic strength parameters (P>0.05), although small to moderate effect sizes favored the Incremental and Maximal Dose groups. Similar patterns were found for psychophysiological responses and training loads across the groups. Conclusion: In the context of this research model, PBMT combined with strength training did not yield superior outcomes in muscle strength, psychophysiological, or metabolic parameters compared to the different dosing strategies evaluated.

Objetive: To propose a specific test to assess the physical fitness of Krav Maga (KM) practitioners, determine the correlation of this specific test with other physical fitness tests, and assess the sensibility of this specific test to a KM training protocol. Methods: The participants were 24 adolescents of both sexes (17.0 ± 0.5 years old) who were high school students at a Military College and who underwent a 12-week training protocol, 3 times a week. Flexibility, muscular strength/resistance, and cardiorespiratory fitness were measured to assess health related physical fitness (HRPF), and the Krav Maga Combat Test (KMCT) was proposed to assess the specificity of KM. The t-test was used for dependent samples, while a multiple linear regression model was used to determine how the physical fitness test explains the variance of the KMCT, with all tests adopting a p-value of <0.05. Results: The results showed that 12 weeks of training improved general (p < 0.05) and specific HRPF (KMCTpre = 18.37 ± 4.00 reps; KMCTpost = 30.54 ± 11.03 reps, p < 0.05), and the KMCT showed moderate-strong correlations (0.42 – 0.72) with HRPF, with these variables explaining 49% of the test. Conclusions: It is concluded that the training program proposed in this study is effective in improving the general and specific physical fitness of KM practitioners, and that the KMCT proposed for the modality presented correlation with physical fitness tests and sensitivity to training.

This investigation attempts to elucidate power density's interplay with observed outcomes subsequent to a training regimen. Forty-two participants were stratified into three groups (Sham, Cluster, LED-Blanket), with irradiated groups receiving 300 J of energy under distinct parameters. Photobiomodulation irradiation was applied to the quadriceps and hamstrings before each of the ten prescribed training sessions, which consisted of three sets of stiff and squats. Participants underwent assessment during sessions, encompassing blood lactate measurements and psychophysiological scales (Numerical Rating Pain Scale for Pain and Rate of Perceived Effort). Additionally, pre-intervention, post-intervention, and follow-up evaluations on an isokinetic dynamometer measured peak torque. Two-way repeated measures ANOVA for intra- and inter-group comparisons. No significant inter-group differences or group-time interactions were discerned in lactate concentration or psychophysiological indices. Solely, a difference surfaced in the peak torque of the dominant limb during knee flexion, manifesting across pre-, post, and follow-up intervals (p = 0.003 and p < 0.001) with an effect size of n² = 0.080. Within the outlined methodological framework, photobiomodulation was ineffective in eliciting performance enhancements, with divergent parameters evincing equivocal efficacy.