30-s Cycle Research Articles

Neural Activity for Uninvolved Knee Motor Control After ACL Reconstruction Differs from Healthy Controls

Recovery from anterior cruciate ligament reconstruction (ACLR) induces bilateral functional and physiological adaptations. Neurophysiologic measures of motor control have focused on the involved knee joint, limiting understanding regarding the extent of bilateral neural adaptations. Therefore, the aim of this study was to investigate differences in neural activity during uninvolved-limb motor control after ACLR compared to healthy controls. Methods: Fifteen participants with left ACLR (8 female and 7 male, 21.53 ± 2.7 years, 173.22 ± 10.0 cm, 72.15 ± 16.1 kg, Tegner 7.40 ± 1.1, 43.33 ± 33.1 mo. post-surgery, 2 patellar tendon, and 13 hamstring) and 15 matched controls (8 female, 23.33 ± 2.7 years, 174.92 ± 9.7 cm, 72.14 ± 15.4 kg, Tegner 7.33 ± 1.0) participated. Neural activity was evaluated using functional magnetic resonance imaging on a 3T Siemens Magnetom scanner during four 30-s cycles of a right (uninvolved) knee flexion-extension task paced with a metronome (1.2 Hz) and was completed interspersed with 30 s of rest. A significance threshold of p < 0.05 was used for all analyses, cluster corrected for multiple comparisons, and z-thresholds of >3.1 (subject level), and >2.3 (group level). Results: The ACLR group had greater neural activity in one statistically significant cluster corresponding to the left middle frontal gyrus (MFG) (834 voxels, z = 3.81, p < 0.01 multiple comparisons corrected) compared to controls. Conclusions: These data indicate a potential contribution to uninvolved-knee neuromuscular deficits after injury and support the limitations of using the uninvolved side as a clinical reference. Uninvolved knee motor control after ACLR may require greater cognitive demand. Clinicians should be aware that the uninvolved limb might also demonstrate whole brain alterations limiting clinical inference from functional symmetry.

Intermittent Vibration Induces Sleep via an Allatostatin A-GABA Signaling Pathway and Provides Broad Benefits in Alzheimer's Disease Models.

While animals across species typically experience suppressed consciousness and an increased arousal threshold during sleep, the responsiveness to specific sensory inputs persists. Previous studies have demonstrated that rhythmic and continuous vibration can enhance sleep in both animals and humans. However, the neural circuits underlying vibration-induced sleep (VIS) and its potential therapeutic benefits on neuropathological processes in disease models remain unclear. Here, it is shown that intermittent vibration, such as cycles of 30s on followed by 30s off, is more effective in inducing sleep compared to continuous vibration. A clear evidence is further provided that allatostatin A (AstA)-GABA signaling mediates short-term intermittent vibration-induced sleep (iVIS) by inhibiting octopaminergic arousal neurons through activating GABAA receptors. The existence of iVIS in mice is corroborated, implicating the GABAergic system in this process. Finally, intermittent vibration not only enhances sleep but also reduces amyloid-β (Aβ) deposition and reverses memory defects in Alzheimer's disease models. In conclusion, the study defines a central neural circuit involved in mediating short-term iVIS and the potential implications of vibration in treating sleep-related brain disorders.

Physical Fitness Determinants of a Military Casualty Evacuation Test.

Casualty evacuation has been identified as a typical and essential single military task which every soldier should be able to perform rapidly during combat. Previous studies suggest that casualty evacuation is typically conducted by dragging and demands e.g., lean body mass and anaerobic performance. Association of physical fitness with casualty evacuation by dragging has been studied widely but previous studies lack comprehensive assessment of all physical fitness determinants. The purpose of the present study was to examine comprehensively how casualty emergency evacuation (CEE) performance associates with physical fitness and body composition. A total of 25 conscripts (20 men, 5 women) volunteered for measurements of height, weight, waist circumference, body composition, 1-min sit-ups and push-ups, grip strength, isometric bench and leg press, standing long jump, 30-s cycle ergometer test, and 12-min run test. Subjects performed a CEE test in which evacuation time (ET), heart rate, blood lactate concentration, and rate of perceived exertion were measured. In the CEE test, subjects wore combat gear (11.7 ± 1.6 kg) and dragged a doll wearing combat gear (80.2 kg) 28 m while crawling (go round two cones, Z-pattern) and 20 m upright (straightforward). Correlations and backward regression analysis were used for statistical analyses. The level of significance was set to P ≤ .05. Evacuation time lasted on average 87 ± 32 s with a peak heart rate of 184 ± 6 bpm, lactate concentration of 9.4 ± 2.7 mmol/l, and RPE of 17 ± 1. Evacuation time correlated inversely and strongly with anaerobic capacity and power (r = -0.72-0.78, P ≤ .001), but not with aerobic fitness. Inverse and strong correlations were observed between ET and maximal strength variables (r = -0.58-0.69, P ≤ .01), whereas muscular endurance and ET revealed non-significant correlations. Evacuation time correlated moderate to strongly with body fat percentage (r = 0.48, P ≤ .05) and inversely with lean body mass (r = -0.74, P ≤ .001) and body height (r = -0.53, P ≤ .01). The backward regression analysis showed that anaerobic capacity (standardized β = -0.52, P ≤ .001), fat percentage (standardized β = 0.40, P ≤ .001), and isometric leg press (standardized β = -0.25, P ≤ .1) together explained the variance of ET significantly (adjusted R2 = 0.84, P ≤ .001). This study examined thoroughly how different physical fitness dimensions and body composition relate to a CEE test performed by a combination of dragging while crawling and in upright position. Casualty emergency evacuation was discovered as a high-intensity military task, which demands most importantly high anaerobic performance, lean body mass, and maximal strength capabilities. Improving these dimensions of physical fitness should be considered highly important as CEE is essential and possibly one of the most demanding military tasks which every soldier should be able to conduct in combat. From operational perspective, it is relevant that soldiers are able to perform CEE during operations; therefore, further research is needed on how acute operational stress changes the nature of CEE and its physical determinants.

Effects of Dietary Nitrate Supplementation on High-Intensity Cycling Sprint Performance in Recreationally Active Adults: A Systematic Review and Meta-Analysis.

This systematic review and meta-analysis investigated the influence of dietary nitrate supplementation on performance metrics during cycling sprint exercise according to the PRISMA guidelines. Searches were conducted on MEDLINE, PubMed, ScienceDirect, Scopus, and SPORTDiscus databases up to September 2023. Inclusion criteria were healthy recreationally active men and women who consumed nitrate-rich and nitrate-deficient beetroot juice to assess performance outcomes of mean power, peak power, time-to-peak power, and minimum power during 30-s cycling sprints. Risk of bias was assessed using the Cochrane Risk of Bias 2 and TESTEX tools and funnel plots. A random effects model was performed on six studies and showed that dietary nitrate had significant effects on time-to-peak power (SMD: -0.66, 95% CI: -1.127 to -0.192, p = 0.006) but not on mean power, peak power, or minimum power. Subgroup analysis revealed that an acute low nitrate dose improved time-to-peak power (SMD: -0.977, 95% CI: -1.524 to -0.430, p < 0.001) but not after a multiday moderate nitrate dose (SMD: -0.177, 95% CI: -0.619 to -0.264, p = 0.431). These data suggest that acute nitrate supplementation can benefit time-to-peak power during 30-s cycling sprints, but due to the limited availability of data and heterogeneity in methodology, these results should be interpreted with caution. There was insufficient data on women to analyze sex-based differences. Future studies are required to provide insight on how supplementation regimen and population impact the effects of dietary nitrate for enhancing cycling sprint performance.

Interactions Between Carotid Arterial Stiffness, Amplitude of Cerebral Blood Flow Oscillations, and Cerebral Tissue Oxygenation During Simulated Hemorrhage in Humans

Introduction: Inducing 0.1 Hz (10-s cycle) oscillations in cerebral blood flow attenuates the reduction in cerebral tissue oxygenation during simulated hemorrhage in humans. It is unknown, however, how stiffness of the cerebral feed arteries influences the magnitude of cerebral blood flow oscillations, and/or the protection of cerebral tissue oxygenation. When 0.1 Hz oscillations are induced during simulated hemorrhage, we hypothesize that: 1) arterial stiffness of the internal carotid artery (ICA) will increase from rest; 2) the amplitude of 0.1 Hz oscillations in cerebral blood flow will be higher in individuals with stiffer arteries, and; 3) the reduction in cerebral tissue oxygenation will be smaller with higher amplitude of cerebral blood flow oscillations. Methods: 8 healthy human participants (age: 30.1±7.6 y) underwent a 10-min hypovolemic oscillatory lower body negative pressure (OLBNP) protocol, where chamber pressure oscillated every 5-s between -30 mmHg and -90 mmHg (i.e., 0.1 Hz). ICA beta stiffness index was calculated from measurements of ICA diameter (via ultrasound imaging), and arterial pressure (via finger photoplethysmography). Middle cerebral artery velocity (MCAv) was measured using transcranial doppler ultrasound, and cerebral tissue oxygenation (ScO2) was measured with near infrared spectroscopy. Fast Fourier transformation was used to quantify oscillations in mean MCAv at ~0.1 Hz. Results: While Mean MCAv 0.1 Hz oscillations increased from baseline to OLBNP (N=8, 34.0±33.9 (cm/s)2 vs. 104.7±58.1 (cm/s)2, p=0.01), ICA beta stiffness did not increase (N=5, 6.1±0.7 au vs. 8.2±2.7 au, p=0.21). There was no relationship between baseline ICA beta stiffness and the percent change in mean MCAv 0.1 Hz oscillations (N=5; r=0.44, p=0.46). ScO2 decreased from baseline to OLBNP (N=8, 66.5±2.9 % vs. 64.8±2.9 %, p=0.03), but there was also no relationship between the percent change in mean MCAv 0.1 Hz oscillations and the decrease in ScO2 (r=0.28, p=0.50). Conclusions: Based on these data, 0.1 Hz OLBNP does not affect ICA stiffness, and there is no relationship between ICA stiffness, amplitude of induced 0.1 Hz cerebral blood flow oscillations, and the reduction in cerebral tissue oxygenation during simulated hemorrhage. However, as this analysis was performed retrospectively, and arterial stiffness was not initially an outcome measure, there was limited data available for analysis. This limitation will be addressed in a project currently in progress in our laboratory. American Heart Association Grant in Aid. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Pulsatile Perfusion Therapy at 0.1 Hz Improves Survival Following Severe Hemorrhage in Rats

Oscillations in arterial pressure and blood flow at 0.1 Hz are associated with protection of tissue oxygenation during conditions of reduced tissue perfusion. Pulsatile Perfusion Therapy (PPT) is a method we have developed to induce these oscillations, and has been associated with increased tolerance to simulated hemorrhage via lower body negative pressure in humans. However, it is unknown how effective this therapy would be in an actual hemorrhage model. The aim for this study was to test the effcacy of PPT in a rat model of severe hemorrhage. We hypothesized that PPT at 0.1 Hz would protect arterial pressure and cerebral blood flow following severe hemorrhage in rats, subsequently improving survival. Eleven adult Sprague-Dawley rats (six female, five male) were anesthetized via isoflurane, then underwent bilateral carotid artery catheterization for assessment of arterial pressure and carotid artery blood flow, while heart rate was assessed via lead II ECG. Following a 15-min baseline period, all animals were hemorrhaged to 50% of their estimated blood volume over 30-min. Rats were then randomly assigned to the PPT group (3 female, 3 male) or the control group (CON; 3 female, 2 male). PPT was administered via inflatable cuffs attached to both hind limbs, oscillating between 0 mmHg and 250 mmHg every 5-s (10-s cycles or 0.1 Hz) for 30-min immediately following hemorrhage. For the CON group, the leg cuffs were also attached but were not inflated for this 30-min period. All animals were then monitored for an additional 150-min recovery period post-hemorrhage, or until death — defined as the absence of ventricular function on the ECG. Survival time and peak mean arterial pressure (MAP), carotid blood flow, and heart rate were assessed to determine the effectiveness of PPT in protecting hemodynamic responses following hemorrhage. PPT increased survival time ( P = 0.02), with 3 of 6 (50%) rats in the PPT group and 0 of 5 (0%) rats in the CON group surviving the entire 180-min recovery period following hemorrhage. During recovery, PPT protected MAP (PPT: −46.5 ± 12.9% vs. CON: −72.6 ± 19.5% from baseline; P = 0.07) and carotid blood flow (PPT: −61.5 ± 17.7% vs. CON: −83.7 ± 6.7% from baseline; P = 0.04), but did not affect heart rate (PPT: 0.11 ± 6.58% vs. CON: −18.70 ± 29.34% from baseline, P = 0.20), although responses were highly variable between subjects. PPT protected arterial pressure and carotid blood flow in rats following severe hemorrhage, subsequently improving survival. These data add further evidence for the use of 0.1 Hz hemodynamic oscillations as a therapeutic intervention for the treatment of hemorrhage. Physiology and Anatomy Department Seed Grant. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Effect of 0.1 Hz Blood Flow Oscillations on Microvascular Blood Flow Responses Following Severe Ischemia

Background: We have shown that inducing 10 second (0.1 Hz) oscillations in arterial pressure and blood flow protects against reductions in tissue oxygenation during ischemia, independent of changes in macrovascular blood flow. However, it is unknown whether 0.1 Hz hemodynamic oscillations impacts microvascular function and vasodilatory capacity following severe ischemia. To examine this question, we assessed the reactive hyperemic response following a prolonged peripheral limb ischemia protocol with and without induced 0.1 Hz hemodynamic oscillations. Hypothesis: 0.1 Hz oscillations in blood pressure and blood flow will increase microvascular blood flow, assessed via reactive hyperemia following a 10-min period of ischemia. Methods: Thirteen healthy human participants (6M, 7F; 27.3 ± 4.2 y) completed two experimental protocols separated by ≥48 h. In both conditions, ischemia of the forearm was induced with a pneumatic cuff on the upper arm to decrease brachial artery blood velocity by ~70-80% from baseline. In the oscillation condition (OSC), 0.1 Hz oscillations in mean arterial pressure (MAP) and brachial artery blood flow were induced by inflating and deflating bilateral thigh cuffs every 5-s (10-s cycles; 0.1 Hz) throughout the forearm ischemia period. In the control condition (CON), the thigh cuffs were in place, but were inactive throughout the forearm ischemia period. Beat to beat arterial pressure was measured via finger photo plethysmography, and brachial artery diameter and blood velocity were measured via duplex Doppler ultrasound during baseline, ischemia, and the reperfusion period. The maximum mean brachial artery blood velocity, and 3-min area under the curve (AUC) of mean brachial artery blood velocity were used to determine the reactive hyperemia response. Results: The magnitude of forearm ischemia, indexed by the reduction in brachial artery conductance, was matched between conditions (CON: -74.8 ± 10.4% vs. OSC: -75.6 ± 6.7%, p=0.39). Reactive hyperemia was not different between conditions as indexed by maximum mean brachial artery blood velocity (CON: 36.4 ± 12.4 cm/s vs. OSC: 39.3 ± 11.2 cm/s, p=0.53) or 3-min brachial artery blood velocity AUC (CON: 1495 ± 744 (cm/s)2 vs. OSC: 1596 ± 804 (cm/s)2, p=0.74). Conclusion: Inducing 0.1 Hz hemodynamic oscillations during severe ischemia does not affect microvascular function, indexed by reactive hyperemia following release of the ischemic stimulus. A more direct measure of microvascular blood flow is needed to examine whether 0.1 Hz hemodynamic oscillations improves microvascular perfusion during ischemia. NIH Neurobiology of Aging &amp; Alzheimer’s Disease Training Grant (T32 AG02049; KAD); American Heart Association Transformational Project Award (19TPA34910743; CAR); American Heart Association Predoctoral Fellowship (23PRE1018469; KAD); UNTHSC Physiology and Anatomy Seed Grant 2021 (CAR). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Mouth Rinsing and Ingestion of Unpleasant Salty or Bitter Solutions Does Not Improve Cycling Sprint Performance in Trained Cyclists.

The purpose of this study was to investigate the influence of mouth rinsing and ingesting unpleasant salty or bitter solutions on cycling sprint performance and knee extensor force characteristics. Eleven male and one female trained cyclists (age: 34 ± 9years, maximal oxygen uptake 56.9 ± 3.9ml·kg-1·min-1) completed a ramp test and familiarization followed by four experimental trials. In each trial, participants completed an all-out 30-s cycling sprint with knee extensor maximal voluntary contractions before and immediately after the sprint. In a randomized, counterbalanced, cross-over order, the four main trials were: a no solution control condition, water, salty (5.8%), or bitter (2mM quinine) solutions that were mouth rinsed (10s) and ingested immediately before the cycling sprint. There were no significant differences between conditions in mean power (mean ± SD, no solution: 822 ± 115W, water: 818 ± 108W, salt: 832 ± 111W, bitter: 818 ± 105W); peak power (no solution: 1,184 ± 205W, water: 1,177 ± 207W, salt: 1,195 ± 210W, bitter: 1,184 ± 209W); or fatigue index (no solution: 51.5% ± 5.7%, water: 50.8% ± 7.0%, salt: 51.1% ± 5.9%, bitter: 51.2% ± 7.1%) during the sprint. Maximal force and impulse declined postexercise; however, there were no significant differences between conditions in knee extensor force characteristics. The present data do not support the use of unpleasant salty or bitter solutions as an ergogenic aid to improve sprint exercise performance.

Effect of sprint interval training load on maximal oxygen uptake in trained men.

Sprint interval training (SIT) improves maximal aerobic and anaerobic performance, including oxygen uptake (VO2<inf>max</inf>), power output, and sprint performance. This study aimed to investigate the effect of SIT load on V̇O<inf>2max</inf> in trained subjects. SIT was performed twice a week for three weeks by twenty-four trained men (aged: 20.7±2.7, V̇O<inf>2max</inf> 43.6±6.5) and consisted of seven bouts of 10-s cycling sprints followed by a 4-min rest. Subjects were divided into two groups depending on the relative resistance of the load compared to their body mass (BM): 7.5% (S7.5) and 10% (S10). We measured the peak power, mean power, and peak cadence in SIT during the first and final sessions. V̇O<inf>2max</inf>, maximum aerobic power (MAP), heart rate, and lactate (La) concentration were measured before and after SIT using incremental tests. After 3 weeks of SIT, V̇O<inf>2max</inf>, MAP, and La improved significantly in both S7.5 and S10 groups. In addition, changes in V̇O<inf>2max</inf> in S10 were higher than those in S7.5 (2.2±11.2% vs. 9.23±9.57%, P=0.029, adjusted by pre V̇O<inf>2max</inf>). MAP measurements showed the same results (2.2±11.3% vs. 8.3±10.0%, P=0.015, adjusted by pre-MAP). However, there was no significant interaction between time and group. A significant increase in peak cadence from first session to sixth sessions was observed in S7.5 (P=0.01, ES = 0.93, 95% confidence interval [CI]: 0.02-1.78) but not in S10 (P=0.132, ES = 0.22, 95% [CI]: -0.59-1.01). Our results suggest that 3 weeks of SIT improves endurance performance in trained subjects. It seems that SIT at 10% load may tend to be more effective.

Water-Based Microwave-Assisted Extraction of Pigments from Madder Optimized by a Box–Behnken Design

Water is one of the greenest and most accessible solvents. To harness its potential, the water-based microwave-assisted extraction (MAE) of pigments from madder was optimized by the response surface methodology (RSM) using a Box–Behnken experimental design. The extract that presented both the highest extraction yield and the most intense color was obtained after a 30-s cycle at 1000 W using 100 mg of madder for 20 mL of water. This water-based MAE was more efficient than Soxhlet extraction and proved comparable to hydroalcoholic MAE. The optimized extract was further characterized using UHPLC-HRMS/MS to identify its main compounds. Glycosylated flavonoids and anthraquinones were putatively identified, as well as free anthraquinones, generally found in madder. The microwave-assisted extraction extended the range of polarity of the extracted compounds, making the water more versatile.

Hemodynamic responses to oscillatory thigh cuff inflations

Background. In the clinical setting, individuals have varying tolerance to hypovolemia induced by blood loss. Experimental generation of 0.1 Hz oscillations (~10-s cycle) in arterial pressure and cerebral blood flow via oscillatory lower body negative pressure (OLBNP) increases tolerance to this simulated hemorrhage, and protects cerebral tissue oxygenation. However, use of OLBNP as a method of inducing hemodynamic oscillations in the clinical setting is limited as: 1) it is a large and cumbersome technique, and; 2) it induces central hypovolemia, which would only worsen the magnitude of hemorrhage. In this study we evaluated a more clinically applicable method of inducing 0.1 Hz oscillations in arterial pressure and cerebral blood flow, using intermittent inflation of bilateral thigh cuffs. We hypothesized that the amplitude of arterial pressure and cerebral blood flow oscillations at 0.1 Hz would increase in response to repeated thigh cuff inflations at 0.1 Hz when compared with a baseline control condition. Methods. Ten healthy human subjects were tested (6 male, 4 female; 26.8 ± 4.1 y). Middle cerebral artery velocity (MCAv) was measured via transcranial doppler ultrasound, arterial pressure was measured via finger photoplethysmography, and end tidal CO2 (etCO2) was measured via capnography. Following a 10-min baseline period, intermittent thigh cuff inflations at 0.1 Hz and 230 mmHg (5-s inflation, 5-s deflation) were performed for 10-min (“oscillations”). 0.1 Hz oscillatory amplitude of mean arterial pressure and mean MCAv were quantified using Fast Fourier transformation during the last 5-min of baseline and the oscillatory period, and compared via two-tailed paired t-tests. Results. The amplitude of 0.1 Hz oscillations increased during the oscillatory period vs. baseline for mean arterial pressure (baseline: 1.7 ± 1.0 mmHg2 vs. oscillations: 9.0 ± 6.2 mmHg2; P = 0.004) and mean MCAv (baseline: 1.1 ± 0.6 (cm/s)2 vs. oscillations: 3.4 ± 3.1 (cm/s)2; P = 0.04). Absolute mean arterial pressure was similar between baseline and the oscillatory period (baseline: 97.2 ± 8.1 mmHg vs. oscillations: 99.1 ± 15.0 mmHg; P = 0.54), but absolute mean MCAv was lower during the oscillatory period (baseline: 61.7 ± 14.6 cm/s vs. oscillations: 53.2 ± 13.1 cm/s; P = 0.02). This reduction in mean MCAv was most likely due to hypocapnia (indexed by etCO2) induced by pacing the breathing of all subjects at ≥10 breaths/min (baseline: 33.2 ± 4.8 mmHg vs. oscillations 27.2 ± 4.5 mmHg; P = 0.005). Conclusions. Intermittent thigh cuff inflations at 0.1 Hz induced 0.1 Hz oscillations in both arterial pressure and cerebral blood flow when compared to baseline. These findings indicate that intermittent thigh cuff inflations could be developed as a method to induce pulsatile perfusion as a potential new therapy for individuals experiencing major blood loss. American Heart Association (Transformational Project Award) #19TPA34910073 and UNTHSC Physiology and Anatomy Seed Grant 2021 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Foot Cooling between Interval Bouts Enhances Repeated Lower Limb Power Performance: The Role of Delaying Fatigue.

This study aimed to investigate whether interbout foot cooling (FC) may enhance repeated lower limb power performance and the corresponding physiological responses based on interset FC, which has been demonstrated to enhance leg-press performance. In a repeated-measures crossover design, ten active men (aged 21.5 ± 1.5 years, exercising >3 times per week) performed four bouts of 10-s cycle ergometer sprints with interbout FC at 10°C water for 2.5 min or non-cooling (NC) with a 5-day interval. The results indicated that FC elicited higher total work (27.57 ± 5.66 kJ vs. 26.55 ± 5.76 kJ) and arousal scores than NC (p < 0.05). Furthermore, under the NC condition, participants decreased mean power (p < 0.05) with no alteration of vastus lateralis (VL) electromyography (EMG) activities after the second bout; whereas under the FC condition, participants maintained steady mean power accompanied by increased VL EMG activities in the last two bouts (p < 0.05). Jointly, participants had higher mean power ([3rd = 10.14 ± 1.15 vs. 9.37 ± 1.30; 4th = 9.79 ± 1.22 vs. 9.23 ± 1.27] W/kg) and VL EMG activities in the last two bouts under the FC than NC condition (p < 0.05). However, perceived exertion and the heart rate were comparable between the two conditions (p > 0.05). In conclusion, interbout FC elicited a higher arousal level and repeated lower limb power performance, which could be explained by delaying peripheral fatigue via increasing excitatory drive and recruiting additional motor units to compensate for fatigue-related responses and power decrements.

A humanized anti-cocaine mAb antagonizes the cardiovascular effects of cocaine in rats.

The recombinant monoclonal anti-cocaine antibody, h2E2, sequesters cocaine in plasma increasing concentrations more than 10-fold. The increased levels of cocaine in the plasma could have detrimental peripheral effects, particularly on the cardiovascular system. We investigated the duration and magnitude of the effect of cocaine on the rat heart, and if h2E2 could antagonize that effect. Echocardiography was used to evaluate cardiac function under isoflurane anesthesia, while a tail-cuff was used to measure blood pressure. Cocaine was delivered intravenously and the rats were continuously monitored for a total of 45 min. Echocardiography measurements were recorded every 5min and blood pressure measurements were recorded throughout the duration of the experiment using 30-s cycles. ECG recordings were taken simultaneously with the echocardiography measurements. An increase in ejection fraction was seen after the cocaine push with the maximum change occurring at 25 min. Treatment with h2E2 1 h before the cocaine push did not have any effect on cardiac parameters. Subsequent cocaine treatment had no effect on the ejection fraction, indicating that the antibody-bound cocaine does not affect the heart. This antagonism of cocaine's effects was greatly decreased after 1 week and entirely absent after 1 month. Cocaine in the presence of h2E2 is pharmacologically inert and h2E2 may have additional clinical utility for reversing cocaine effects on the cardiovascular system.

Piezoelectric energy harvesting from extremely low-frequency vibrations via gravity induced self-excited resonance

In this paper, we originally present a gravity induced self-excited vibration generator based on a cantilever piezoelectric resonator. The configuration is composed of a sliding rod, a sleeve, a transduction unit. To estimate output voltage and investigate dynamic responses of the generator, an equivalent model based on mechanical structure was established and numerically solved. The effects of the cantilever length, tip mass and linear coupling factor on the open circuit voltage were discussed. In addition, we also conducted series of experiments to validate the theoretical responses. In a 10s cycle (namely 0.1Hz excitation frequency) scenario, the transduction unit responds with structural resonant frequency of 8.621Hz. The results of the experiments show that the open circuit voltage of the generator increases with increment of the cantilever beam length and the tip mass, which agrees well with simulation estimations. We also conducted impedance matching experiments to examine power response in the load spectrum, of which the results indicate that the prototype peak power reaches maximum 1.897 mW. We also discussed the change of gravity potential energy of the prototype and compared it with electric energy. This work provides a novel approach for piezoelectric energy harvesting from extremely low frequency excitations.

Acute enteric-coated sodium bicarbonate has negligible effect on anaerobic performance but affects metabolomics and attenuates the gastrointestinal response.

Sodium bicarbonate ingestion before exercise has a performance-enhancing effect on high-intensity exercise. However, gastrointestinal symptoms can be a problematic side-effect. Enteric-coated sodium bicarbonate can attenuate gastrointestinal symptoms following acute bicarbonate loading. In addition, the subsequent effects on exercise performance and metabolomics have not been investigated. The purpose of this study was to investigate the acute effect of enteric-coated sodium bicarbonate supplementation on the anaerobic performance, physiological profile, and symptoms of gastrointestinal discomfort after severe-intensity intermittent exercise. At the same time, targeted metabolomics was used to study the changes in urine metabolism after ingestion of enteric-coated sodium bicarbonate and to explore the characteristics of biological metabolism. In a randomized crossover design, twelve male college students completed four Wingate anaerobic 30-s cycling tests (WACT) after consuming a placebo (PL) and two experimental conditions: 0.2 g/kg body mass in enteric-coated sodium bicarbonate pills (ES) or general sodium bicarbonate pills (GS). Blood lactate (BLA), heart rate (HR), ratings of perceived exertion (RPE), and gastrointestinal–symptoms assessment questionnaire (GSAQ) were measured pre-exercise and post-exercise. In contrast, mean power (MP) and peak power (PP) were recorded immediately post-exercise. Urine samples were collected before formal tests and 50 min after the third WACT. Our findings indicate the following: 1) mean power and peak power showed no significant difference among conditions (MP: F2.0, 33 = 0.541, p = 0.587, η2 = 0.032; PP: F2.0, 33 = 0.526, p = 0.596, η2 = 0.031). The PP decline of the ES and GS after the third WACT was lower than that of the PL; 2) There were no significant differences in physiological responses, such as BLA (F2.0, 33.0 = 0.191, p = 0.827, η2 = 0.011) and heart rate (F2, 33 = 0.418, p = 0.662, η2 = 0.025), between the three conditions. Although blood lactate concentration after 10 min of the third WACT was lower with ES and GS than with placebo; 3) Fewer participants experienced gastrointestinal symptoms with enteric-coated than with general sodium bicarbonate; 4) The metabolites with differences among the three conditions 50 min after exercise were 3-phospho-d-glycerate, d-Glucose 6-phosphate, pyruvate, cis-aconitate, oxaloacetate, and citrate. ES had higher levels of 3-phospho-d-glycerate, d-Glucose 6-phosphate, pyruvate, and cis-aconitate than GS. The 3-phospho-d-glycerate, d-Glucose 6-phosphate, pyruvate, and cis-aconitate levels in GS were significantly lower than in PL. In contrast, the citrate level in GS was significantly higher than that in other experimental conditions. Compared to PL, the level of oxaloacetate was higher after exercise in ES. This data suggests that supplementation of enteric-coated and general sodium bicarbonate before exercise can alter energy metabolism following anaerobic exercise, involving the metabolism of 3-phospho-d-glycerate, D-Glucose 6-phosphate, pyruvate, cis-aconitate, oxaloacetate, citrate, and lactate. However, they do not affect anaerobic performance and blood lactate. The supplementation of acute enteric-coated sodium bicarbonate and general sodium bicarbonate can enhance some of the weak effects of blood lactate clearance during anaerobic exercise, which may be beneficial for glycolytic energy supply. In addition, enteric-coated sodium bicarbonate intake mitigates gastrointestinal symptoms compared to general sodium bicarbonate.

The Effects of “Physical BEMER® Vascular Therapy” on Work Performed During Repeated Wingate Sprints

ABSTRACT Purpose: The purpose of this study was to investigate the effects of Bio-Electro-Magnetic-Energy-Regulation (BEMER) on recovery and performance parameters in anaerobic exercise compared to active and passive recovery. Method: Fifteen recreationally active participants completed four sessions separated by 2–5 days between each session. The first visit involved one Wingate Anaerobic Test (WAnT; 30-s cycling sprint on a Monark ergometer) to familiarize participants with testing procedures. The three subsequent sessions involved four repeated WAnTs. Each sprint was followed by 4 min of either passive recovery (laying supine), active recovery (pedaling at 50 rpm at 20% of sprint workload), or BEMER recovery (laying supine on the BEMER body pad at intensity level “5-Plus.”). The same recovery method was used within each testing session, and recovery method order was randomized across participants. Results: There was no difference in peak power, average power, fatigue index, or average work performed between recovery conditions. Active recovery resulted in a statistically significant decrease in ratings of pain intensity (M = −0.767, SD = 0.928) and pain unpleasantness (M = −0.608, SD = 0.915), from the first minute to the fourth minute of recovery, compared to both BEMER (Intensity: M = 0.675, SD = 0.745, Unpleasantness: M = 1.125, SD = 0.862) and passive (Intensity: M = 0.542, SD = 0.774, Unpleasantness: M = 1.018, SD = 0.872) recoveries, where pain ratings increased. Conclusions: Although no recovery method resulted in increased performance, active recovery led to a more comfortable exercise experience while still allowing comparable exercise performance.

Effects of the number of sit-stand maneuver repetitions on baroreflex sensitivity and cardiovascular risk assessments.

Sit-stand maneuvers (SSMs) have increasingly been used for baroreflex sensitivity (BRS) measurement in physiological research, but it remains unknown as to how many SSMs need to be performed to measure BRS and assess its relationship with cardiovascular disease (CVD) risk. Therefore, this study aimed to determine 1) the effect of the number of SSM repetitions on BRS, and 2) the association between BRS and CVD risk factors. Data were collected from 174 individuals during 5 min of spontaneous rest and 5 min of repeated SSMs at 0.05 Hz (i.e., 15 cycles of 10-s sit and 10-s stand). During SSMs, BRS was calculated from the incremental cycles of 3, 6, 9, 12, and 15 SSMs using transfer function analysis of heart rate (HR) and systolic blood pressure (SBP). General CVD risk factors, carotid arterial stiffness, and cardiorespiratory fitness were measured. In result, HR and SBP increased during SSMs (P < 0.05). The BRS remained at a similar level during the resting and SSM conditions, whereas the coherence function reached its peak after 3 cycles of SSMs. BRS with ≥6 cycles of SSMs was strongly correlated with age (r = -0.721 to -0.740), carotid distensibility (r = 0.625-0.629), and cardiorespiratory fitness (r = 0.333-0.351) (all P < 0.001). Multiple regression analysis demonstrated that BRS with ≥6 cycles of SSMs explained >60% of the variance in CVD risk factors. Therefore, our findings suggest that repeated SSMs significantly strengthens the association between BRS and CVD risk factors. Particularly, BRS with ≥6 cycles of SSMs is strongly associated with CVD risk.

Hormonal, metabolic, and angiogenic responses to all-out sprint interval exercise under systemic hyperoxia

ObjectiveHyperoxic gas inhalation during exercise may negatively affect all-out sprint interval exercise (SIE)-induced hormonal, metabolic, and angiogenic responses. We investigated the effects of acute all-out SIE under systemic hyperoxia on hormonal, metabolic, and angiogenic responses. DesignThis was a randomised-crossover trial. Ten healthy males (mean ± standard error of age = 23.1 ± 0.9 years; height = 171.0 ± 1.6 cm; body mass = 66.2 ± 2.0 kg; body mass index = 22.6 ± 0.5 kg/m2) completed the following two experimental regimens: 1) SIE under normoxia and 2) SIE under systemic hyperoxia (FiO2 = 60%). The subjects performed four bouts of 30-s maximal cycling efforts with 4 min recovery between efforts. The circulating levels of hormonal (growth hormone, epinephrine, and norepinephrine), metabolic (glucose, free fatty acid, and lactate), and angiogenic (vascular endothelial growth factor, matrix metalloproteinase-2 and -9, and endostatin) markers were measured before and at 0 (immediately after the regimen), 30, and 120 min after both regimens. ResultsIn response to both SIE regimens, the peak and mean power outputs gradually decreased over the intermittent exercise session compared with those in the first bout (p < 0.01) with no significant differences between the regimens. Both regimens significantly increased the circulating concentrations of all hormonal, metabolic, and angiogenic markers (p < 0.01). However, there were no significant differences in the levels of these markers in response to the two regimens at any time point (p > 0.05). ConclusionThese findings suggest that acute systemic hyperoxia does not influence the hormonal, metabolic, and angiogenic responses to all-out SIE.

Quadriceps Muscle Fatigue Reduces Extension and Flexion Power During Maximal Cycling.

Purpose: To investigate how quadriceps muscle fatigue affects power production over the extension and flexion phases and muscle activation during maximal cycling.Methods: Ten participants performed 10-s maximal cycling efforts without fatigue and after 120 bilateral maximal concentric contractions of the quadriceps muscles. Extension power, flexion power and electromyographic (EMG) activity were compared between maximal cycling trials. We also investigated the associations between changes in quadriceps force during isometric maximal voluntary contractions (IMVC) and power output (flexion and extension) during maximal cycling, in addition to inter-individual variability in muscle activation and pedal force profiles.Results: Quadriceps IMVC (−52 ± 21%, P = 0.002), voluntary activation (−24 ± 14%, P < 0.001) and resting twitch amplitude (−45 ± 19%, P = 0.002) were reduced following the fatiguing task, whereas vastus lateralis (P = 0.58) and vastus medialis (P = 0.15) M-wave amplitudes were unchanged. The reductions in extension power (−15 ± 8%, P < 0.001) and flexion power (−24 ± 18%, P < 0.001) recorded during maximal cycling with fatigue of the quadriceps were dissociated from the decreases in quadriceps IMVC. Peak EMG decreased across all muscles while inter-individual variability in pedal force and EMG profiles increased during maximal cycling with quadriceps fatigue.Conclusion: Quadriceps fatigue induced by voluntary contractions led to reduced activation of all lower limb muscles, increased inter-individual variability and decreased power production during maximal cycling. Interestingly, power production was further reduced over the flexion phase (24%) than the extension phase (15%), likely due to larger levels of peripheral fatigue developed in RF muscle and/or a higher contribution of the quadriceps muscle to flexion power production compared to extension power during maximal cycling.

CYP1A2 Genotype Polymorphism Influences the Effect of Caffeine on Anaerobic Performance in Trained Males.

The purpose was to investigate the effects of CYP1A2 -163C > A polymorphism on the effects of acute caffeine (CAF) supplementation on anaerobic power in trained males. Sixteen trained males (age: 21.6 ± 7.1years; height: 179.7 ± 5.6cm; body mass: 72.15 ± 6.8kg) participated in a randomized, double-blind, placebo (PLA) controlled crossover design. Participants supplemented with CAF (6mg/kg of body mass) and an isovolumetric PLA (maltodextrin) in random order and separated by 7 days, before an all-out 30-s anaerobic cycling test to determine peak, average, and minimum power output, and fatigue index. Genomic deoxyribonucleic acid was extracted to identify each participants CYP1A2 genotype. Six participants expressed AA homozygote and 10 expressed C alleles. There was a treatment by genotype interaction for peak power output (p = .041, η2 = .265, observed power = 0.552) with only those expressing AA genotype showing improvement following CAF supplementation compared with PLA (CAF: 693 ± 108 watts vs. PLA: 655 ± 97 watts; p = .039), while no difference between treatments was noted in those expressing C alleles (CAF: 614 ± 92watts vs. PLA: 659 ± 144watts; p = .135). There were no other interaction or main effects for average or minimum power output, or fatigue index (p > .05). In conclusion, the ingestion of 6mg/kg of CAF improved peak power output only in participants with the AA genotype compared with PLA; however, expression of the CYP1A2 did not influence average or minimum power output or fatigue index.