Effects of intermittent pneumatic compression on the recovery of cardiovascular parameters after repeated sprint exercise.

PURPOSE: Intermittent pneumatic compression (IPC) applies gradual pressure to facilitate lymph and blood flow movement to reduce exercise-induced tissue fluid accumulation and plasma volume loss. This study aimed to evaluate the cardiovascular system response during the recovery with IPC compared with passive recovery (Sham). METHODS: Sixteen volunteers (7 females and 9 males) executed a cycling-based exhausting sprint interval exercise (8 × 20 s all out), followed by a 30-min IPC or Sham condition. Participants performed two trials in a randomised, counterbalanced, and crossover design. Several cardiovascular parameters (blood pressure, heart function, and peripheral vascular resistance) were recorded at baseline (5'), through the recovery protocol (30'), and afterwards (5'). RESULTS: The use of IPC during the recovery phase led to a faster recovery, stated in relative values to pre-exercise, in mean blood pressure (102.5 ± 19.3% vs. 92.7 ± 12.5%; P < 0.001), and cardiac output (139.8 ± 30.0% vs. 146.2 ± 40.2%; P < 0.05) in comparison to Sham condition. Furthermore, during the IPC-based recovery, there was a slower recovery in cardiac pressure change over time (92.5 ± 25.8% vs. 100.5 ± 48.9%; P < 0.05), and a faster return to pre-exercise values in the peripheral vascular resistance (75.2 ± 25.5% vs. 64.8 ± 17.4%; P < 0.001) compared to Sham. CONCLUSION: The application of IPC after high-intensity exercise promotes the recovery of the cardiovascular system, reducing cardiovascular strain. Future investigations should consider the effects on the sympathetic-parasympathetic balance, such as heart rate variability, to assess further bonds between the use of IPC and autonomous control.

Oxygen Saturation Curve Analysis in 2298 Hypoxia Awareness Training Tests of Military Aircrew Members in a Hypobaric Chamber.

We aim to provide reference values for military aircrews participating in hypoxia awareness training (HAT). We describe several parameters with potential biomedical interest based on selected segments and slopes of the changes in oxygen saturation (SatO2) during a standard HAT. A retrospective analysis of 2298 records of the SatO2 curve was performed, including 1526 military men aged 30.48 ± 6.47 years during HAT in a hypobaric chamber. HAT consisted of pre-oxygenation at 100% and an ascent to 7620 m, followed by O2 disconnection starting the phase of descent of SatO2 until reaching the time of useful consciousness (TUC), and finally reconnection to 100% O2 in the recovery phase. Using an ad hoc computational procedure, the time taken to reach several defined critical values was computed. These key parameters were the time until desaturation of 97% and 90% (hypoxia) after oxygen mask disconnection (D97/D90) and reconnection (R97/R90) phases, the time of desaturation (TUC-D97) and hypoxia (TUC-D90) during disconnection, the total time in desaturation (L97) or hypoxia (L90), and the slopes of SatO2 drop (SDSAT97 and SDSAT90) and recovery (SRSAT97). The mean of the quartiles according to TUC were compared by ANOVA. The correlations between the different parameters were studied using Pearson's test and the effect size was estimated with ω2. Potentially useful parameters for the HAT study were those with statistical significance (p < 0.05) and a large effect size. D97, D90, R97, and R90 showed significant differences with small effect sizes, while TUC-D97, TUC-D90, L97, L90, and SDSAT97 showed significant differences and large effect sizes. SDSAT97 correlated with TUC (R = 0.79), TUC-D97 (R = 0.81), and TUC-D90 (R = 0.81). In conclusion, several parameters of the SatO2 curve are useful for the study and monitoring of HAT. The SDSAT97 measured during the test can estimate the TUC and thus contribute to taking measures to characterize and protect the aircrew members.

Simulated altitude is medicine: intermittent exposure to hypobaric hypoxia and cold accelerates injured skeletal muscle recovery.

Muscle injuries are the leading cause of sports casualties. Because of its high plasticity, skeletal muscle can respond to different stimuli to maintain and improve functionality. Intermittent hypobaric hypoxia (IHH) improves muscle oxygen delivery and utilization. Hypobaria coexists with cold in the biosphere, opening the possibility to consider the combined use of both environmental factors to achieve beneficial physiological adjustments. We studied the effects of IHH and cold exposure, separately and simultaneously, on muscle regeneration. Adult male rats were surgically injured in one gastrocnemius and randomly assigned to the following groups: (1) CTRL: passive recovery; (2) COLD: intermittently exposed to cold (4°C); (3) HYPO: submitted to IHH (4500 m); (4) COHY: exposed to intermittent simultaneous cold and hypoxia. Animals were subjected to these interventions for 4 h/day for 9 or 21 days. COLD and COHY rats showed faster muscle regeneration than CTRL, evidenced after 9 days at histological (dMHC-positive and centrally nucleated fibre reduction) and functional levels after 21 days. HYPO rats showed a full recovery from injury (at histological and functional levels) after 9 days, while COLD and COHY needed more time to induce a total functional recovery. IHH can be postulated as an anti-fibrotic treatment since it reduces collagen I deposition. The increase in the pSer473Akt/total Akt ratio observed after 9 days in COLD, HYPO and COHY, together with the increase in the pThr172AMPKα/total AMPKα ratio observed in the gastrocnemius of HYPO, provides clues to the molecular mechanisms involved in the improved muscle regeneration. KEY POINTS: Only intermittent hypobaric exposure accelerated muscle recovery as early as 9 days following injury at histological and functional levels. Injured muscles from animals treated with intermittent (4 h/day) cold, hypobaric hypoxia or a simultaneous combination of both stimuli regenerated histological structure and recovered muscle function 21 days after injury. The combination of cold and hypoxia showed a blunting effect as compared to hypoxia alone in the time course of the muscle recovery. The increased expression of the phosphorylated forms of Akt observed in all experimental groups could participate in the molecular cascade of events leading to a faster regeneration. The elevated levels of phosphorylated AMPKα in the HYPO group could play a key role in the modulation of the inflammatory response during the first steps of the muscle regeneration process.

An Igor Pro 8.01 Procedure to Analyze Pulse Oximetry during Acute Hypoxia Test in Aircrews.

The recognition of hypoxia symptoms is a critical part of physiological training in military aviation. Acute exposure protocols have been designed in hypobaric chambers to train aircrews to recognize hypoxia and quickly take corrective actions. The goal of the acute hypoxia test is to know the time of useful consciousness and the minimal arterial oxygen saturation tolerated. Currently, there is no computer system specifically designed to analyze the physiological variables obtained during the test. This paper reports the development and analytical capabilities of a computational tool specially designed for these purposes. The procedure was designed using the Igor Pro 8.01 language, which processes oxygen saturation and heart rate signals. To accomplish this, three functional boards are displayed. The first allows the loading and processing of the data. The second generates graphs that allow for a rapid visual examination to determine the validity of individual records and calculate slopes on selected segments of the recorded signal. Finally, the third can apply filters to generate data groups for analysis. In addition, this tool makes it possible to propose new study variables that are derived from the raw signals and can be applied simultaneously to large data sets. The program can generate graphs accompanied by basic statistical parameters and heat maps that facilitate data visualization. Moreover, there is a possibility of adding other signals during the test, such as the oxygenation level in vital organs, electrocardiogram, or electroencephalogram, which illustrates the test's excellent potential for application in aerospace medicine and for helping us develop a better understanding of complex physiological phenomena.

Histomorphological and functional contralateral symmetry in the gastrocnemius muscles of the laboratory rat.

It is usual in anatomical and physiological research to assess the effects of some intervention on extremities (e.g., training programmes or injury recovery protocols) using one muscle for the intervention and its contralateral as control. However, the existence of laterality (left-handedness or right-handedness) in athletes of different specialities is widely recognized. In rats, gastrocnemius is one of the muscles most widely used because of its importance in locomotion and high relative limb mass. Since we have not found studies reporting laterality assessment on the morphology and function in rat gastrocnemius, our study aimed to evaluate the fibre histochemical, morphometrical and muscle force contractile properties between right and left gastrocnemius of the laboratory rat. Fibre-type proportion, fibre morphometrical measurements, muscle capillarization and muscle force properties were analysed in the right and left gastrocnemius of six male rats. No statistically significant differences (p = 0.265) were found in gastrocnemius to body weight ratio (‰) between right (6.55 ± 0.40) and left (6.49 ± 0.40) muscles. The muscles analysed showed a great degree of heterogeneity in fibre type distribution, having three clearly distinguished regions named red, mixed and white. In the three regions, there were no statistical differences in fibre type proportions between right and left gastrocnemius, as is indicated by the p-values (from 0.203 to 0.941) obtained after running t-Student paired tests for each fibre type. When analysing fibre cross-sectional area, individual fibre capillarization and fibre circularity, no significant differences between right and left gastrocnemius in any of these morphometrical parameters were found in any muscle region or fibre type. Most of the p-values (70%) resulting from running t-Student paired tests were higher than 0.400, and the lowest p-value was 0.115. Seemingly, global capillary and fibre densities were not statistically different between right and left sides in all muscle regions with p-values ranging from 0.337 to 0.812. Force parameters normalized to gastrocnemius mass (mN g-1 ) did not show any significant difference between right (PF = 74.0 ± 13.4, TF = 219.4 ± 13.0) and left (PF = 70.9 ± 10.7, TF = 213.0 ± 18.0) muscles with p = 0.623 (PF) and p = 0.514 (TF). Twitch time parameters (ms) also lacked significant differences between the two sides (CT: 43.4 ± 8.6 vs. 45.0 ± 14.3, p = 0.639; HRT: 77.6 ± 15.0 vs. 82.3 ± 25.3, p = 0.475). Finally, both muscles also showed similar (p = 0.718) fatigue properties. We did find an absence of laterality at the morphological and functional levels, which raises the possibility of using right and left gastrocnemius muscles interchangeably for experimental designs where one muscle is used to analyse data after a physiological intervention and its contralateral muscle plays the control role, thus allowing unbiased paired comparisons to derive accurate conclusions.

A comparative analysis of lung function and spirometry parameters in genotype-controlled natives living at low and high altitude.

BACKGROUND: The reference values for lung function are associated to anatomical and lung morphology parameters, but anthropometry it is not the only influencing factor: altitude and genetics are two important agents affecting respiratory physiology. Altitude and its influence on respiratory function has been studied independently of genetics, considering early and long-term acclimatization. OBJECTIVE: The objective of this study is to evaluate lung function through a spirometry study in autochthonous Kichwas permanently living at low and high-altitude. METHODOLOGY: A cross-sectional study of spirometry differences between genetically matched lowland Kichwas from Limoncocha (230 m) at Amazonian basin and high-altitude Kichwas from Oyacachi (3180 m) in Andean highlands. The sample size estimates permitted to recruited 118 patients (40 men and 78 women) from Limoncocha and 95 (39 men and 56 women) from Oyacachi. Chi-square method was used to analyze association or independence of categorical variables, while Student's t test was applied to comparison of means within quantitative variables. ANOVA, or in the case that the variables didn't meet the criteria of normality, Kruskal Wallis test were used to compare more than two groups. RESULTS: The FVC and the FEV1 were significantly greater among highlanders than lowlanders (p value < 0.001), with a proportion difference of 15.2% for men and 8.5% for women. The FEV1/FVC was significantly higher among lowlanders than highlanders for men and women. A restrictive pattern was found in 12.9% of the participants. CONCLUSION: Residents of Oyacachi had greater FVC and FEV1 than their peers from Limoncocha, a finding physiologically plausible according to published literature. Lung size and greater ventilatory capacities could be an adaptive mechanism developed by the highlander in response to hypoxia. Our results support the fact that this difference in FVC and FEV1 is a compensatory mechanism towards lower barometric and alveolar partial pressure of oxygen pressure.

Changes in Lung Diffusing Capacity of Elite Artistic Swimmers During Training.

Artistic swimmers (AS) are exposed to repeated apnoeas in the aquatic environment during high intensity exercise provoking specific physiological responses to training, apnoea, and immersion. This study aimed to evaluate the changes in lung diffusing capacity in AS pre-, mid- and post-training in a combined session of apnoeic swimming, figures and choreography. Eleven elite female AS from the Spanish national team were the study's participants. The single-breath method was used to measure lung diffusing capacity for carbon monoxide (DLCO) and one-way repeated measures ANOVA was utilized to evaluate the statistical analysis. Basal values of DLCO were higher than normal for their age and height (33.6±4.9 mL·min-1·mmHg-1; 139±19%) and there were a significant interaction between DLCO and AS training (ŋ2 p=0.547). After the apnoeic swimming (mid-training) there was an increase in DLCO from basal to 36.7±7.3 mL·min-1·mmHg-1 (p=0.021), and after the figures and choreography (post-training) there was a decrease compared to mid-training (32.3±4.6 mL·min-1·mmHg-1, p=0.013). Lung diffusing capacity changes occur during AS training, including a large increase after apnoeic swimming. There were no differences in lung diffusing capacity from pre- to post-training, although large inter-individual variability was observed.

Earthquake-related stressors associated with suicidality, depression, anxiety and post-traumatic stress in adolescents from Muisne after the earthquake 2016 in Ecuador.

BACKGROUND: The Ecuadorian earthquake in April 16th was the second strongest and deadliest in 2016 worldwide, with approximately one million people affected. In this paper, we analyzed the psychological impact and the relationship between mental health events and various earthquake-related stressors related to the earthquake, 9 months after the event. METHODS: We conducted an analytical cross-sectional study, applying an anonymous survey to 316 adolescents (13-19 years old) from Muisne, Ecuador. Suicidal tendency, depression, anxiety and post-traumatic stress (PTSD) were evaluated via the Child PTSD Symptom Scale (CPSS), Spence Children's Anxiety Scale, Okasha Suicidality Scale, and the Center for Epidemiologic Studies Depression Scale (CES-D) and the adapted seven-questions earthquake-related stressors survey. RESULTS: We found a high prevalence of suicidal ideations and behavior, posttraumatic stress, depression and anxiety compared to international studies. Even though adolescents currently living in shelters had higher levels of anxiety, their suicidal tendency was significantly lower than those living in their own or their relatives' home. Finally, the earthquake-related stressors were not associated with suicidality and mental health events, with the exception of economic damage suffered by the family. CONCLUSIONS: High levels of depression, post-traumatic stress and anxiety among high-school students were found, especially among those who have suffered serious economic damage. The economic impact in their families and high unemployment rates among their parents seems to be related to lack of hope and favorable perspectives for their future, situation that might lead to lead to emotional disturbances and psychological disorders. Although prolonged homelessness experience in shelters may be a stressful occurrence, might also be related with spiritual growth among adolescents, and may work as a protective factor against suicidal ideations and attempts.

Humidity prevents the exercise-induced formation of hydrogen peroxide and nitrite in exhaled breath condensate in recreational cyclists.

PURPOSE: The aerobic exercise affects the respiratory redox-state. The influence of different relative humidity (RH) levels on the formation of respiratory reactive chemical species associated with redox-state altered by exercise has been poorly explored. Our aim was to evaluate the effect of two different RH conditions (40% vs. 90%) on the concentration of hydrogen peroxide and nitrite in exhaled breath condensate ([H2O2]EBC and [NO2-]EBC) and spirometry parameters in recreational cyclists. METHODS: Sixteen men and women (12/4) (mean age ± SD: 23.5 ± 2.2 years) completed 60-min of cycling at 166.3 ± 26.9 watts (70% of maximum load of [Formula: see text]-max. test, 49.3 ± 7.6 mL·min-1·kg-1) at random 40%-RH and 90%-RH conditions separated by 7 days. The two-way RM-ANOVA test was applied to compare [H2O2]EBC, [NO2-]EBC, [NO2-]EBC/[NO2-]Plasma at rest and 80-min post-exercise (80-post); and spirometry parameters at rest, 20-post and 80-post. RESULTS: The interaction of factors (humidity × time) was significant in [H2O2]EBC, [NO2-]EBC, [NO2-]EBC/[NO2-]Plasma (p = 0.005, p = 0.030, p = 0.043, respectively). At 40%-RH conditions, the same parameters were higher in 80-post than at rest (p < 0.001, p = 0.001, p = 0.014, respectively). At the same time, the [H2O2]EBC and [NO2-]EBC/[NO2-]Plasma were higher in 40%-RH than 90%-RH (p = 0.010, p < 0.001, respectively). The interaction was significant in FEV1 (p = 0.013) and FEF25-75% (p = 0.023), but not in FEV1/FVC (p = 0.362). At 80-post, the changes are kept in 90%-RH (p < 0.001), diminishing in 40%-RH being similar to rest. CONCLUSION: In recreational cyclists, 90%-RH prevents the increase of hydrogen peroxide and nitrite in exhaled breath condensate samples observed at 40%-RH and prolonging the bronchodilation until 80-post cycling exercise.

High-intensity interval versus moderate-intensity continuous half-marathon training programme for middle-aged women.

PURPOSE: To test the effectiveness on recreational female middle-aged runners of a programme of high-intensity interval training (HIIT) for a half-marathon race contrasted to a conventional moderate-intensity continuous training (MICT). METHODS: Twenty recreational female runners (40 ± 7 years) followed MICT or HIIT schedules for training a half-marathon. The MICT group trained a mean of 32 km/week at intensities below 80% VO2max. The HIIT group ran 25 km/week at intensities between 80 and 100% VO2max, combined with uphill running and resistance training. Women following HIIT ran 21% less distance and invested 17% less time than those from MICT group. All the women were evaluated at the beginning and end of the training and participated in the same half-marathon run. RESULTS: Women following both schedules reduced their previous finishing times by 2-3%, which for HIIT group would have meant rising up to 90 positions out of 1454 participants in the local half-marathon race. The high intensity performed during series of high power output (200 m and 400 m) and resistance sessions in HIIT programme promoted changes that allowed modifying efficiency at high workloads. At the same time, the HIIT training programme elicited changes in oxygen uptake and transport as indicated the cardiorespiratory parameters obtained during recovery in lab tests. Moreover, HIIT registered a 14% baseline decrease in heart rate contrasting to the not significant 6% decrease in MICT. CONCLUSIONS: Runners following HIIT training obtained similar registers as with a traditional MICT schedule, expending less time and running shorter distances, yet improving their anaerobic and aerobic power.

Reliability of NIRS portable device for measuring intercostal muscles oxygenation during exercise.

This study assessed the intra-individual reliability of oxygen saturation in intercostal muscles (SmO2-m.intercostales) during an incremental maximal treadmill exercise by using portable NIRS devices in a test-retest study. Fifteen marathon runners (age, 24.9 ± 2.0 years; body mass index, 21.6 ± 2.3 kg·m-2; V̇O2-peak, 63.7 ± 5.9 mL·kg-1·min-1) were tested on two separate days, with a 7-day interval between the two measurements. Oxygen consumption (V̇O2) was assessed using the breath-by-breath method during the V̇O2-test, while SmO2 was determined using a portable commercial device, based in the near-infrared spectroscopy (NIRS) principle. The minute ventilation (VE), respiratory rate (RR), and tidal volume (Vt) were also monitored during the cardiopulmonary exercise test. For the SmO2-m.intercostales, the intraclass correlation coefficient (ICC) at rest, first (VT1) and second ventilatory (VT2) thresholds, and maximal stages were 0.90, 0.84, 0.92, and 0.93, respectively; the confidence intervals ranged from -10.8% - +9.5% to -15.3% - +12.5%. The reliability was good at low intensity (rest and VT1) and excellent at high intensity (VT2 and max). The Spearman correlation test revealed (p ≤ 0.001) an inverse association of SmO2-m.intercostales with V̇O2 (ρ = -0.64), VE (ρ = -0.73), RR (ρ = -0.70), and Vt (ρ = -0.63). The relationship with the ventilatory variables showed that increased breathing effort during exercise could be registered adequately using a NIRS portable device.

Swimming versus running: effects on exhaled breath condensate pro-oxidants and pH.

PURPOSE: The respiratory redox-state of swimmers can be affected by chronic exposures to chlorinated pools, and the effects of different exercises on it are unknown. Our aim was to compare two exercises performed at high-intensity and under habitual environmental conditions (swimming indoor vs. running outdoor) on the production of pro-oxidants (hydrogen peroxide and nitrite) and pH in exhaled breath condensate (EBC) and spirometry parameters in competitive swimmers chronically exposed to chlorinated pools. METHODS: Seventeen men and women (mean age ± SD = 21 ± 2 years) swam 3.5 km in an indoor pool treated with Cl2, and after 2-weeks, they ran 10 km outdoors. The pHEBC, [H2O2]EBC, [NO2-]EBC, [NO2-]EBC/[NO2-]Plasma and spirometry parameters were analyzed pre-exercise and 20 min and 24 h after exercise ended. RESULTS: Two mixed models were applied to compare EBC parameters between swimming and running. Lower levels of [H2O2]EBC and [NO2-]EBC (p = 0.008 and p = 0.018, respectively) were found 24-h post-swimming, and the same trend was observed for [NO2-]EBC/[NO2-]Plasma (p = 0.062). Correlations were found in both exercises between pre-exercise levels of pHEBC, [H2O2]EBC, [NO2-]EBC, and [NO2-]EBC/[NO2-]Plasma and their changes (Δ) after 24-h as well as between [H2O2]EBC and [NO2-]EBC for basal levels and for changes after 24 h. A relationship was also found for running exercise between pulmonary ventilation and changes after 24 h in [H2O2]EBC. Spirometry data were unaffected in both types of exercise. CONCLUSION: In competitive swimmers, at 24-h acute post-exercise follow-up, swimming decreased and running increased pro-oxidant biomarkers of pulmonary origin, without changes in lung function.

The disease burden of suicide in Ecuador, a 15 years' geodemographic cross-sectional study (2001-2015).

BACKGROUND: Suicide affects people from different backgrounds, ethnical groups, socio-economic status and geographical locations. In Latin America, suicide reports arescarce, specially in Andean countries. In Ecuador, very few reports have partially described this phenomenon, nonetheless, estimation of the burden of disease (BoD) hasnever been reported in the country. METHODS: A country-wide comparison was performed using the Ministry of Public Health's national databases of overall mortality, Hospital Discharges Database, and the Population Census of the National Institute of Census and Statistics (INEC). The study variables analyzed were age, geographical distribution to provincial level, sex, means of suicide, educational attainment, marital status and mortality. Linear Regression and relative Risk analysis were used to predict outcome and the likelihood that suicide occur among study variables. RESULTS: In the last 15 years, 13,024 suicides were officially reported. Men were 3 times more likely than women to die by suicide. The overall age-adjusted suicide ratio in Ecuador corresponds to 7.1 per 100,000 per year. The sex-specific rates were 5.3 in women and 13.2 in men. The primary mean of suicide was hanging X70 (51.1%), followed by self-poisoning X68-X69 (35.2%) and firearms X72-X74 (7.6%). Provinces located at higher altitude reported higher rates than those located at sea level (9 per 100,000 vs 4.5 per 100.000). The total economic loss due to suicide was estimated to be $852.6 million during the 15 years' analysis. CONCLUSIONS: This is the first geodemographic study exploring the complete burden of suicide in Ecuador and one of the very few in Latin-America. In the last 15 years of available data, Ecuador ranks above the regional average with an adjusted suicide rate of 7.1 per 100,000 inhabitants. An important finding is that Suicide affects rather younger populations, adding more than 10,000 years of premature years of life lost (YYL) between 2001 and 2015, becoming the first and fourth leading cause of death among adolescent women and men respectively. Suicide affects people from different backgrounds, socioeconomic status and educational attainment. The mean of suicide changed over time showing that gun and pesticides related deaths decreased significantly since 2001, while hanging and suffocation increased in more than 50%.

Different training programs decrease blood pressure during submaximal exercise.

OBJECTIVE: Our purpose was to study the effects of aerobic, resistance, and mixed (aerobic and resistance) training programs on blood pressure, both at rest and during submaximal exercise in healthy people. METHODS: We randomized 39 physically active, healthy participants into aerobic, resistance, and mixed (aerobic and resistance) exercise groups, and a control group. The exercise groups trained for 60 min three times/week for 6 weeks, and a submaximal cycle ergometer test was performed before and after training, and 3 weeks after detraining. Continuous blood pressure was determined before and during the test. RESULTS: At the submaximal test, both systolic and diastolic blood pressures decreased significantly (p < 0.05) after detraining in the exercise groups. However, between pre-training and detraining, we found significant reductions at rest only in the mixed exercise group (p < 0.05). CONCLUSION: Although all exercise had similar effects on blood pressure during submaximal exercise, the mixed aerobic and resistance exercise may be optimal for blood pressure reduction, by the addition of diverse physiological pathways.

Differing levels of acute hypoxia do not influence maximal anaerobic power capacity.

OBJECTIVE: The purpose of this study was to determine the effects of different inspired oxygen fractions (Fio2) on average and peak power capacity during consecutive jumps to assess the effectiveness of a hypoxic explosive-strength program. METHODS: Eight physically active subjects (aged 33.62 ± 4.07 years; height, 1.77 ± 0.05 m; weight, 74.38 ± 6.86 kg) completed a Bosco jump test, consisting of a series of 15-second "all-out" jumps with 3 minutes of recovery, performed in a normoxia condition (N [Fio2 = 21%]) and in two hypoxic conditions: moderate hypoxia (MH [Fio2 16.5% o2]) and high hypoxia (HH [13.5% o2]). A force platform provided the average and the maximal power output (W) generated during consecutive jumps. Measurements were also taken of lactate, creatine kinase, arterial oxygen saturation, and perceived exertion using the Borg fatigue scale. RESULTS: The average power outputs throughout the entire sets were similar between N (3187 ± 46) and MH (3184 ± 15; P > .05), but slightly greater with HH (3285 ± 43) compared with N (P < .05). Values for lactate during N (7.5 ± 3.0), MH (7.7 ± 4.0), and HH (7.9 ± 3.0; P > .05), and for creatine kinase (values before, 69.8 ± 15; and 24 hours after in N [79.4 ± 15.60], MH [85.2 ± 26.7], and HH [84.3 ± 47.2]; P > .05) were similar for all conditions. Only during exercise in hypoxia were moderate and severe hypoxemia induced as the sets increased and Fio2 was lower (P < .05). At the same time, the perceived exertion reported by subjects was substantially higher at HH (8.9 ± 1.1) than at N (7.1 ± 1.9; P < .05). CONCLUSIONS: Jumping power output was not negatively affected by mild or high hypoxia in comparison with normoxia during an anaerobic workout despite having higher hypoxemia and a greater perception of exertion.

Circadian and Sex Differences After Acute High-Altitude Exposure: Are Early Acclimation Responses Improved by Blue Light?

OBJECTIVE: The possible effects of blue light during acute hypoxia and the circadian rhythm on several physiological and cognitive parameters were studied. METHODS: Fifty-seven volunteers were randomly assigned to 2 groups: nocturnal (2200-0230 hours) or diurnal (0900-1330 hours) and exposed to acute hypoxia (4000 m simulated altitude) in a hypobaric chamber. The participants were illuminated by blue LEDs or common artificial light on 2 different days. During each session, arterial oxygen saturation (Spo2), blood pressure, heart rate variability, and cognitive parameters were measured at sea level, after reaching the simulated altitude of 4000 m, and after 3 hours at this altitude. RESULTS: The circadian rhythm caused significant differences in blood pressure and heart rate variability. A 4% to 9% decrease in waking nocturnal Spo2 under acute hypoxia was observed. Acute hypoxia also induced a significant reduction (4%-8%) in systolic pressure, slightly more marked (up to 13%) under blue lighting. Women had significantly increased systolic (4%) and diastolic (12%) pressures under acute hypoxia at night compared with daytime pressure; this was not observed in men. Some tendencies toward better cognitive performance (d2 attention test) were seen under blue illumination, although when considered together with physiological parameters and reaction time, there was no conclusive favorable effect of blue light on cognitive fatigue suppression after 3 hours of acute hypobaric hypoxia. CONCLUSIONS: It remains to be seen whether longer exposure to blue light under hypobaric hypoxic conditions would induce favorable effects against fatigue.

Combined intermittent hypobaric hypoxia and muscle electro-stimulation: a method to increase circulating progenitor cell concentration?

BACKGROUND: Our goal was to test whether short-term intermittent hypobaric hypoxia (IHH) at a level well tolerated by healthy humans could, in combination with muscle electro-stimulation (ME), mobilize circulating progenitor cells (CPC) and increase their concentration in peripheral circulation. METHODS: Nine healthy male subjects were subjected, as the active group (HME), to a protocol involving IHH plus ME. IHH exposure consisted of four, three-hour sessions at a barometric pressure of 540 hPa (equivalent to an altitude of 5000 m). These sessions took place on four consecutive days. ME was applied in two separate 20-minute periods during each IHH session. Blood samples were obtained from an antecubital vein on three consecutive days immediately before the experiment, and then 24 h, 48 h, 4 days, 7 days and 14 days after the last day of hypoxic exposure. Four months later a control study was carried out involving seven of the original subjects (CG), who underwent the same protocol of blood samples but without receiving any special stimulus. RESULTS: In comparison with the CG the HME group showed only a non-significant increase in the number of CPC CD34+ cells on the fourth day after the combined IHH and ME treatment. CONCLUSION: CPC levels oscillated across the study period and provide no firm evidence to support an increased CPC count after IHH plus ME, although it is not possible to know if this slight increase observed is physiologically relevant. Further studies are required to understand CPC dynamics and the physiology and physiopathology of the hypoxic stimulus.

Muscle Tone, Stiffness, and Elasticity in Elite Female Cyclists after Consecutive Short Competitions.

Background: For professional road cyclists, most overload injuries affect the lower limbs. They are mostly represented by contractures or muscle shortening, characterised by a variation of muscular tone, stiffness, and elasticity. This real-life study aimed to assess specific mechanical parameters in top-class female cyclists who participated in 3 races a week. Hypothesis. Muscle tone, stiffness, and elasticity will be affected immediately after competition and at the end of the week due to accumulated fatigue. Methods: Six professional cyclists were evaluated. This pilot study consisted of a controlled trial and three days of competition, with rest days between them. MyotonPRO was used to measure tone, stiffness, and elasticity in six leg muscles: vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF), biceps femoris (BF), lateral gastrocnemius (LG), and medial gastrocnemius (MG). Daily basal and pre- and postrace measures were carried through to the 3 races in a week. Results: The muscular tone of VL, VM, LG, and MG and the stiffness of VL, VM, RF, BF, LG, and MG decreased after races. VL and RF were mostly affected by (p=0.05) and (p=0.009), respectively. Basal elasticity improved over time until the last day. Conclusions: Muscle tone and stiffness decreased after a very intense and exhausting cycling endurance competition. Basal elasticity improved immediately after the race and continued this trend until the end of the week. More research is needed on changes in mechanical properties in competition and risk prevention of injuries.

Reduced Violence-Related Burden and Mortality at Higher Altitudes: Examining the Association between High Altitude Living and Homicide Rates in Ecuador.

Esteban Ortiz-Prado, Juan Sebastian Izquierdo-Condoy, María G. Dávila-Rosero, Jorge Vásconez-González, Ana M. Diaz, Carla E. Moyano, Vanessa Arcos-Valle, Ginés Viscor, and Joshua H. West. Reduced Violence-Related Burden and Mortality at Higher Altitudes: Examining the Association between High Altitude Living and Homicide Rates in Ecuador. High Alt Med Biol. 00:000-000, 0000. Background: Homicides are a major public health concern and a leading cause of preventable deaths worldwide. The relationship between altitude and homicides remains unclear, and evidence of the possible effects of living at high altitudes on homicide rates is limited. This research aimed to investigate the mortality rates resulting from various types of aggression that culminated in homicides in Ecuador and to explore potential differences associated with altitude. Methods: An ecological analysis of homicide rates in Ecuador was conducted from 2001 to 2022. Homicide cases and the population at risk were categorized based on their place of residence according to two altitude classifications: a binary classification of low (<2,500 m) and high altitude (>2,500 m), and a detailed classification according to criteria by the International Society for Mountain Medicine, which includes low (<1,500 m), moderate (1,500-2,500 m), high (2,500-3,500 m), and very high altitude (3,500-5,500 m) categories. Both crude and directly age-sex standardized mortality rates were calculated for each altitude category. Results: We analyzed a total of 40,708 deaths attributed to aggressions (ICD-10 codes X85-Y09). The total homicide rate for men was 21.29 per 100,000 (95% confidence interval [CI]: 9.55-32.37), whereas for women, it was 2.46 per 100,000 (95% CI: 1.44-3.27). Average rates across the 22 analyzed years were higher at low altitudes (men: 13.2/100,000 and women: 1.33/100,000) as compared with high altitudes (men: 5.79/100,000 and women: 1.05/100,000). Notably, the male-to-female rate difference was more pronounced at low altitudes (898%) than at high altitudes (451%). Conclusions: Our study revealed a higher prevalence of homicides in certain provinces and significant disparities in mortality rates between men and women. Although we cannot establish a direct relationship between altitude and homicide rates, further research is needed to explore potential confounding factors and a better understanding of the underlying causes for these variations.