Search Results (35)

This study investigated whether the addition of nitrate (from beetroot) to an isotonic drink provided over 5 days would affect sprint interval exercise (SIE) performance and muscle oxygenation. Twenty (seven female) physically active participants (mean ± SD; age 28 ± 6 years, BMI 22.6 ± 2.0 kg/m²) completed a double-blind, randomized, crossover study where they consumed 570 mL of either isotonic drink (ISO-C) or isotonic beetroot juice drink (ISO-BR) for 5 days before performing SIE (six 10 s maximal effort, interspersed with 50 s active recovery) on a cycle ergometer. Both drinks contained equal osmolality (290 mOsm/kg) but differed in the nutrients from beetroot extract, particularly the nitrate content (ISO-C: 0 mmol, ISO-BR: 12.9 mmol). ISO-BR significantly reduced the average time to peak power (ISO-C: 2.0 ± 0.18 s vs. ISO-BR: 1.6 ± 0.37 s; main effect of drink, p = 0.003, partial η² = 0.04) and increased muscle deoxygenation (ΔHHb) (main effect of drink, p = 0.002, partial η² = 0.021) compared to ISO-C. Five-day supplementation with ISO-BR improved the time to peak power but not the peak or mean power output for SIE compared with ISO-C. Full article

Adequate exercise prescription requires a deep understanding of the body’s response to exercise. This study explored the responses of heart rate (HR), muscle oxygen saturation (SmO₂), and perceived exertion (RPE) during six body-weight squat exercise variations. A total of 15 recreationally active participants (age: 28.2 ± 8.0 years; body mass: 71.1 ± 11.2 kg; height: 1.73 ± 0.08 m) were recruited. Six body-weight squat variations (deep, jumping, single-leg, uneven, unstable, and wall-sit) were randomly performed for 90 s. Results revealed that the jumping squat promoted a higher average and peak HR (165.3 ± 14.5 and 146.1 ± 14.8 bpm, respectively), and a lower average SmO₂ and higher deoxygenation SmO₂ in the soleus muscle (40.3 ± 15.4 and 46.0 ± 11.4%, accordingly). No differences were observed in recovery time or in the same SmO₂ derived-parameters in the vastus lateralis muscle. The jumping variation promoted a greater response at a physiological level, both centrally, related to cardiovascular response, and peripherally, related to soleus SmO₂. It was also the more demanding variation at both the overall and lower limb muscular level of RPE. This holistic view allows a precise identification of the response patterns in body-weight squat exercise variations to an acute session, with a training intervention providing additional information. Full article

Background: This investigation aimed to examine sex-based differences in deoxy[heme] (HHb), tissue saturation (StO₂), and force-deoxygenation ratio (FD) of the forearm flexor muscles during a maximal-effort intermittent fatiguing handgrip protocol. Methods: Thirty-three healthy males (n = 15) and females (n = 18) completed a fatiguing handgrip protocol consisting of 60 4 s contractions separated by a 1 s rest. Near-infrared spectroscopy was used to measure muscle oxygenation before, during, and after the protocol. Results: Sex differences in HHb (p = 0.033) and StO₂ (p = 0.021) were observed with significantly greater values for females (HHb: 110.204 ± 12.626% of baseline; StO₂: 72.091 ± 5.812%) in comparison to males (HHb: 101.153 ± 12.847% of baseline; StO₂: 66.978 ± 7.799%). Females (0.199 ± 0.081 AU) also demonstrated significantly (p = 0.001) lower FD in comparison to males (0.216 ± 0.094 AU). However, males (b = −0.023 ± 0.008 AU) demonstrated a significantly (p < 0.001) greater rate of decline in FD in comparison to females (b = −0.017 ± 0.006 AU). Conclusions: Prior to, during, and after a maximal-effort intermittent fatiguing handgrip fatiguing protocol, males demonstrate significantly lower StO₂ than females and a faster rate of decline in FD. Moreover, females demonstrate greater HHb values than males when assessed relative to a resting baseline. Full article

Background: Impaired systemic tissue oxygenation and microvascular perfusion are associated with adverse outcomes in patients with acute respiratory distress syndrome (ARDS). Tissue oxygenation and microvascular reactivity, assessed by using near-infrared spectroscopy (NIRS), are correlated with disease severity in critically ill populations. This study aimed to detect alterations in these factors and their ability to predict outcomes in patients with ARDS. Methods: We performed NIRS measurements on the first (Day 1) and third (Day 3) days after ARDS diagnosis in 29 patients. We recorded the baseline forearm muscle oxygen saturation (StO₂) and calculated the deoxygenation slope (Deoxy) and reoxygenation (Reoxy) slope. We divided the subjects into 28-day survival and non-survival subgroups to compare microcirculatory and oxygenation status differences. Results: The Day 1 StO₂ values were significantly higher for the survival subgroup (60.1 ± 13.5%) than the non-survival subgroup (47.2 ± 6.9%) (p = 0.025). The ROC curve showed that Day 1 StO₂ was a significant predictor of 28-day mortality (p = 0.025). There was no significant difference between the Deoxy and Reoxy slopes of the two groups (p > 0.05). The ROC of the Day 1 Reoxy slope for survival prediction (AUC0.74) was not statistically significant (p = 0.074). Conclusions: Our study showed poor survival outcomes in patients who had lower skeletal muscle StO₂ values in early-stage ARDS. NIRS measurements may provide prognostic value for the survival outcomes in patients with this syndrome. Full article

This study aimed to monitor the oxygenation and blood supply in three quadriceps muscles [the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF)] during squatting exercise to exhaustion. Eighteen young resistance-trained males performed five sets of 15 back squats in a Smith machine, with two warm-up sets [at 14% and 45% of the 15-repetition maximum (15RM)] and three main sets at 100% of the 15RM. Three near-infrared spectroscopy devices were attached to the VL, VM, and RF to record the muscle oxygen saturation (SmO₂) and total hemoglobin (tHb, an index of muscle blood supply). The blood lactate concentration was measured after each set with a portable analyzer. The SmO₂ and tHb data were analyzed by repeated-measures two-way ANOVA (muscle × set). Lactate data were analyzed by repeated-measures one-way ANOVA. The statistical significance was set at α = 0.05. The SmO₂ dropped during each set (hitting zero in many instances) and was reinstated during recovery. The three main sets caused severe deoxygenation in the VL and VM, as opposed to moderate deoxygenation in the RF. From one set to the next, the initial value and the drop in the SmO₂ increased, whereas the final SmO₂ value decreased. The tHb increased in the VL, did not change considerably in the VM, and decreased in the RF during each set. The blood lactate concentration increased gradually from one set to the next, reaching about 10 mmol/L. These findings show pronounced differences in the physiological and metabolic responses of three quadriceps muscles to squatting exercise, thus highlighting the importance of studying such responses at multiple sites. Full article

Background: We tested whether gene polymorphisms for angiotensin-converting enzyme (ACE, rs1799752) and tenascin-C (TNC, rs2104772) are associated with variability in fatigue resistance and metabolic strain during static lumbar exercise through interactions with chronic nonspecific lower back pain and habitual physical exercise levels (PA). Methods: Forty-eight patients and matched controls performed an isometric endurance test for lumbar extensors. Metabolic strain to longissimus muscle (oxygen saturation, lactate) and cardiovascular system (muscle hemoglobin, blood pressure) and holding time were monitored. Subjects were genotyped for rs1799752 (II, ID, DD) and rs2104772 (AA, AT, TT). Associations of variance with group, genotype, and PA were analyzed under a 5% false discovery rate. Results: The holding time was lower in patients than in controls (150.9 vs. 188.6 s). This difference was associated with both genotypes, as patients with DD-rs1799752-genotype (p = 0.007) and TT-rs2104772-genotype (p = 0.041) showed lower fatigue resistance. Muscle deoxygenation during exercise varied in positive association with the rs2104772-genotype and PA (p = 0.010, η2 = 0.236). Mean arterial blood pressure (p = 0.028, η2 = 0.108) and recovery of hemoglobin concentration (p = 0.003, η2 = 0.907) demonstrated complex group x rs2104772 interactions. Conclusions: Polymorphisms rs1799752 and rs2104772 influence back pain-related variability in lumbar fatigue resistance. rs2104772 was linked to cardiovascular strain during isometric exercise and recovery via muscle perfusion. Full article

Endothelial dysfunction decreases exercise limb blood flow (BF) and muscle oxygenation. Acute L-Citrulline supplementation (CIT) improves muscle tissue oxygen saturation index (TSI) and deoxygenated hemoglobin (HHb) during exercise. Although CIT improves endothelial function (flow-mediated dilation [FMD]) in hypertensive women, the impact of CIT on exercise BF and muscle oxygenation (TSI) and extraction (HHb) are unknown. We examined the effects of CIT (10 g/day) and a placebo for 4 weeks on blood pressure (BP), arterial vasodilation (FMD, BF, and vascular conductance [VC]), and forearm muscle oxygenation (TSI and HHb) at rest and during exercise in 22 hypertensive postmenopausal women. Compared to the placebo, CIT significantly (p < 0.05) increased FMD (Δ−0.7 ± 0.6% vs. Δ1.6 ± 0.7%) and reduced aortic systolic BP (Δ3 ± 5 vs. Δ−4 ± 6 mmHg) at rest and improved exercise BF (Δ17 ± 12 vs. Δ48 ± 16 mL/min), VC (Δ−21 ± 9 vs. Δ41 ± 14 mL/mmHg/min), TSI (Δ−0.84 ± 0.58% vs. Δ1.61 ± 0.46%), and HHb (Δ1.03 ± 0.69 vs. Δ−2.76 ± 0.77 μM). Exercise BF and VC were positively correlated with improved FMD and TSI during exercise (all p < 0.05). CIT improved exercise artery vasodilation and muscle oxygenation via increased endothelial function in hypertensive postmenopausal women. Full article

Background: Venous occlusion plethysmography (VOP) non-invasively measures forearm blood flow (FBF), whereas near-infrared spectroscopy (NIRS) assesses skeletal muscle oxygenation. Using these techniques has revealed sex differences in microvascular responses. However, it is not clear if NIRS and VOP results are interchangeable under various conditions like reactive hyperemia (RH). Our purpose was to evaluate sex-specific associations between FBF and NIRS-derived parameters: oxygenated hemoglobin, deoxygenated hemoglobin, total hemoglobin, and hemoglobin difference (O₂Hb, HHb, tHb, and HbDiff). Methods: In total, 29 adults (15 men) participated, and a strain-gauge was placed on the forearm for VOP and a NIRS device was distally attached. Slopes for FBF and NIRS parameters were quantified during venous occlusion intervals at rest and during RH. Pearson’s correlations were assessed between VOP and NIRS slopes. Intraclass correlation coefficients (ICC_2,1) examined the sex-specific consistency of the slopes at rest. p ≤ 0.05 was considered significant. Results: During RH, FBF was not correlated with O₂Hb (r = −0.126), HHb (r = 0.228), tHb (r = 0.061), or HbDiff (r = 0.046). Seemingly, there were no sex differences. Resting FBF and NIRS-derived variables, except for HbDiff, displayed suitable consistency as suggested by the reliability results (ICC_2,1 = 0.115–0.577). Conclusions: The NIRS values collected did not match the strain-gauge slopes. Individuals should practice caution when generating blood flow inferences from NIRS-based data during VOP. Full article

Background and Objectives: Fibromyalgia, a chronic condition, manifests as widespread musculoskeletal pain, fatigue, sleep disturbances, autonomic and cognitive dysfunction, hypersensitivity to stimuli, and various somatic and psychiatric symptoms. This study, a controlled and randomized experiment, aimed to evaluate and compare the immediate effects of different treatments on fibromyalgia patients. Materials and Methods: The treatments included the EXOPULSE Mollii suit, a combination of the EXOPULSE Mollii suit with a virtual reality (VR) protocol, and a physical exercise regimen. A cohort of 89 female fibromyalgia patients was randomly assigned to one of four groups: Control (n = 20), Suit only (n = 22), Suit combined with VR (n = 21), and Exercise (n = 26). Results: This study found notable differences across the groups in several key parameters. In the Control group, significant changes were observed in Forced Expiratory Volume (FEV 1/FEV 6), the Numeric Rating Scale (NRS) for pain, Pressure Pain Threshold (PPT) at the epicondyle, cortical arousal levels, the 10 m up-and-go test, and in all measured variables related to temperature and muscle oxygenation. For the group using the suit alone, there were significant differences noted in the NRS, the chair stand test, palm temperature, and all muscle oxygenation parameters. The Suit + VR group showed significant changes in the NRS, PPT at the knee, handgrip strength test, the 10 m up-and-go test, one-leg balance test with the right leg, muscle oxygen saturation (SmO₂), deoxygenated hemoglobin (HHb), and oxygenated hemoglobin (O₂Hb). Finally, the Exercise group exhibited significant differences in FEV 1/FEV 6, chest perimeter difference, NRS, PPT at both the epicondyle and knee, cortical arousal, the chair stand test, the 10-m up-and-go test, and in SmO₂, HHb, and O₂Hb levels. Conclusions: combining neuromodulation with VR and targeted exercise regimens can effectively alleviate fibromyalgia symptoms, offering promising avenues for non-pharmacological management. Full article

It is not known whether different gait modes, or movement patterns, at the same speed elicit differences in muscle oxygen oxygenation, expressed as muscle oxygen saturation (SmO₂). Thus, the aim of this study was to compare the oxygenation of two leg muscles (vastus lateralis and gastrocnemius medialis), as well as the heart rate, respiratory gases, and blood lactate between two gait modes (walking and running) of the same speed and duration. Ten men walked and ran for 30 min each at 7 km/h in a random, counterbalanced order. SmO₂, heart rate, and respiratory gases were monitored continuously. Blood lactate was measured at rest, at the end of each exercise, and after 15 min of recovery. Data were analyzed by two-way (gait mode × time) or three-way (gait mode × muscle × time) ANOVA, as applicable. Heart rate and oxygen consumption were higher when running compared to walking. SmO₂ was lower during exercise compared to rest and recovery, in gastrocnemius medialis compared to vastus lateralis, and in running compared to walking. Blood lactate increased during exercise but did not differ between gait modes. In conclusion, running caused higher deoxygenation in leg muscles (accompanied by higher whole-body oxygen uptake and heart rate) than walking at the same speed (one that was comfortable for both gait modes), thus pointing to a higher internal load despite equal external load. Thus, preferring running over walking at the same speed causes higher local muscle deoxygenation, which may be beneficial in inducing favorable training adaptations. Full article

Exercise increases the cost of breathing (COB) due to increased lung ventilation ($\dot{\mathrm{V}}$E), inducing respiratory muscles deoxygenation ($\nabla$SmO₂), while the increase in workload implies $\nabla$SmO₂ in locomotor muscles. This phenomenon has been proposed as a leading cause of exercise intolerance, especially in clinical contexts. The use of high-flow nasal cannula (HFNC) during exercise routines in rehabilitation programs has gained significant interest because it is proposed as a therapeutic intervention for reducing symptoms associated with exercise intolerance, such as fatigue and dyspnea, assuming that HFNC could reduce exercise-induced $\nabla$SmO₂. SmO₂ can be detected using optical wearable devices provided by near-infrared spectroscopy (NIRS) technology, which measures the changes in the amount of oxygen bound to chromophores (e.g., hemoglobin, myoglobin, cytochrome oxidase) at the target tissue level. We tested in a study with a cross-over design whether the muscular desaturation of m.vastus lateralis and m.intercostales during a high-intensity constant-load exercise can be reduced when it was supported with HFNC in non-physically active adults. Eighteen participants (nine women; age: 22 ± 2 years, weight: 65.1 ± 11.2 kg, height: 173.0 ± 5.8 cm, BMI: 21.6 ± 2.8 kg·m⁻²) were evaluated in a cycle ergometer (15 min, 70% maximum watts achieved in ergospirometry ($\dot{\mathrm{V}}$O₂-peak)) breathing spontaneously (control, CTRL) or with HFNC support (HFNC; 50 L·min⁻¹, fiO₂: 21%, 30 °C), separated by seven days in randomized order. Two-way ANOVA tests analyzed the $\nabla$SmO₂ (m.intercostales and m.vastus lateralis), and changes in $\dot{\mathrm{V}}$E and $\nabla$SmO₂·$\dot{\mathrm{V}}$E⁻¹. Dyspnea, leg fatigue, and effort level (RPE) were compared between trials by the Wilcoxon matched-paired signed rank test. We found that the interaction of factors (trial × exercise-time) was significant in $\nabla$SmO₂-m.intercostales, $\dot{\mathrm{V}}$E, and ($\nabla$SmO₂-m.intercostales)/$\dot{\mathrm{V}}$E (p < 0.05, all) but not in $\nabla$SmO₂-m.vastus lateralis. $\nabla$SmO₂-m.intercostales was more pronounced in CTRL during exercise since 5′ (p < 0.05). Hyperventilation was higher in CTRL since 10′ (p < 0.05). The $\nabla$SmO₂·$\dot{\mathrm{V}}$E⁻¹ decreased during exercise, being lowest in CTRL since 5′. Lower dyspnea was reported in HFNC, with no differences in leg fatigue and RPE. We concluded that wearable optical biosensors documented the beneficial effect of HFNC in COB due to lower respiratory $\nabla$SmO₂ induced by exercise. We suggest incorporating NIRS devices in rehabilitation programs to monitor physiological changes that can support the clinical impact of the therapeutic intervention implemented. Full article

Exercise therapy as part of the clinical management of patients with neuromuscular diseases (NMDs) is complicated by the limited insights into its efficacy. There is an urgent need for sensitive and non-invasive quantitative muscle biomarkers to monitor the effects of exercise training. Therefore, the objective of this systematic review was to critically appraise and summarize the current evidence for the sensitivity of quantitative, non-invasive biomarkers, based on imaging and electrophysiological techniques, for measuring the effects of physical exercise training. We identified a wide variety of biomarkers, including imaging techniques, i.e., magnetic resonance imaging (MRI) and ultrasound, surface electromyography (sEMG), magnetic resonance spectroscopy (MRS), and near-infrared spectroscopy (NIRS). Imaging biomarkers, such as muscle maximum area and muscle thickness, and EMG biomarkers, such as compound muscle action potential (CMAP) amplitude, detected significant changes in muscle morphology and neural adaptations following resistance training. MRS and NIRS biomarkers, such as initial phosphocreatine recovery rate (V), mitochondrial capacity (Q_max), adenosine phosphate recovery half-time (ADP t_1/2), and micromolar changes in deoxygenated hemoglobin and myoglobin concentrations (Δ[deoxy(Hb + Mb)]), detected significant adaptations in oxidative metabolism after endurance training. We also identified biomarkers whose clinical relevance has not yet been assessed due to lack of sufficient study. Full article

This study aimed to elucidate whether muscle blood flow restriction during maximal exercise is associated with alterations in hemodynamics, cerebral oxygenation, cerebral activation, and deterioration of exercise performance in male participants. Thirteen healthy males, cyclists (age 33 ± 2 yrs., body mass: 78.6 ± 2.5 kg, and body mass index: 25.57 ± 0.91 kg·m⁻¹), performed a maximal incremental exercise test on a bicycle ergometer in two experimental conditions: (a) with muscle blood flow restriction through the application of thigh cuffs inflated at 120 mmHg (with cuffs, WC) and (b) without restriction (no cuffs, NC). Exercise performance significantly deteriorated with muscle blood flow restriction, as evidenced by the reductions in $\dot{V}$O_2max (−17 ± 2%, p < 0.001), peak power output (−28 ± 2%, p < 0.001), and time to exhaustion (−28 ± 2%, p < 0.001). Muscle oxygenated hemoglobin (Δ[O₂Hb]) during exercise declined more in the NC condition (p < 0.01); however, at exhaustion, the magnitude of muscle oxygenation and muscle deoxygenation were similar between conditions (p > 0.05). At maximal effort, lower cerebral deoxygenated hemoglobin (Δ[HHb]) and cerebral total hemoglobin (Δ[THb]) were observed in WC (p < 0.001), accompanied by a lower cardiac output, heart rate, and stroke volume vs. the NC condition (p < 0.01), whereas systolic blood pressure, rating of perceived exertion, and cerebral activation (as assessed by electroencephalography (EEG) activity) were similar (p > 0.05) between conditions at task failure, despite marked differences in exercise duration, maximal aerobic power output, and $\dot{V}$O_2max. In conclusion, in trained cyclists, muscle blood flow restriction during an incremental cycling exercise test significantly limited exercise performance. Exercise intolerance with muscle blood flow restriction was mainly associated with attenuated cardiac responses, despite cerebral activation reaching similar maximal levels as without muscle blood flow restriction. Full article

Objectives: This study describes the effects of interval hypoxic training and electrical muscle stimulation (EMS) technology on human productivity with the following metrics: biochemical indices, cognitive abilities, changes in oxygenated (HbO) and deoxygenated (Hb) hemoglobin concentrations over the prefrontal cortex, and functional connectivity via electroencephalography (EEG). Methods: All measurements according to the described technology were made before the start of training and one month later, right after it ended. The study involved middle-aged Indo-European men. Specifically, there were 14, 15, and 18 participants in the control, hypoxic, and EMS groups, respectively. Results: EMS training improved reactions and nonverbal memory but decreased attention scores. Functional connectivity decreased in the EMS group while it increased in the hypoxic group. A result of the interval normobaric hypoxic training (IHT) was significantly improved contextual memory, with a p-value = 0.08. Conclusions: It was found that EMS training is more likely to cause stress on the body than positively affect cognitive functions. At the same time, interval hypoxic training can be considered a promising direction for increasing human productivity. The data obtained during the study can also help in the timely diagnosis of insufficient or overestimated indicators of biochemistry. Full article

Ischemic preconditioning (IPC) is a non-invasive protective maneuver that alternates short periods of occlusion and reperfusion of tissue blood flow. Given the heterogeneity in the magnitude and frequency of IPC-induced improvements in physical performance, here we aimed to investigate, in a well-controlled experimental set-up, the local effects of IPC in exposed muscles in terms of tissue oxygenation and muscle fatigue. Nineteen subjects were enrolled in one of the two groups, IPC (3 × 5/5 min right arm ischemia/reperfusion; cuff inflations 250 mmHg) and SHAM (3 × 5/5 min pseudo ischemia/reperfusion; 20 mmHg). The subjects performed a fatiguing contraction protocol before and 30 min after the IPC treatment, consisting of unilateral intermittent isometric elbow flexions (3 s ON/OFF, 80% of maximal voluntary contraction) until exhaustion. While muscle strength did not differ between groups, post- vs. pre-treatment endurance was significantly reduced in the SHAM group (4.1 ± 1.9 vs. 6.4 ± 3.1 repetitions until exhaustion, p < 0.05) but maintained in IPC (7.3 ± 2.0 vs. 7.1 ± 4.3, n.s.). The decrease in tissue oxygenation and the increase in deoxygenated hemoglobin were significantly reduced post- vs. pre-IPC (p < 0.05), but not post- vs. pre-SHAM. The results suggest that IPC delays the onset of fatigue likely through improved metabolic efficiency of muscles. Full article