Changes in body composition and weight loss frequently occur when humans are exposed to hypoxic environments. The mechanisms thought to be responsible for these changes are increased energy ...expenditure resulting from increased basal metabolic rate and/or high levels of physical activity, inadequate energy intake, fluid loss as well as gastrointestinal malabsorption. The severity of hypoxia, the duration of exposure as well as the level of physical activity also seem to play crucial roles in the final outcome. On one hand, excessive weight loss in mountaineers exercising at high altitudes may affect performance and climbing success. On the other, hypoxic conditioning is presumed to have an important therapeutic potential in weight management programs in overweight/obese people, especially in combination with exercise. In this regard, it is important to define the hypoxia effect on both body composition and weight change. The purpose of this study is to define, through the use of meta-analysis, the extent of bodyweight -and body composition changes within the three internationally classified altitude levels (moderate altitude: 1500-3500 m; high altitude: 3500-5300 m; extreme altitude: >5300 m), with emphasis on physical activity, nutrition, duration of stay and type of exposure.
Endurance and strength training are established as distinct exercise modalities, increasing either mitochondrial density or myofibrillar units. Recent research, however, suggests that mitochondrial ...biogenesis is stimulated by both training modalities. To test the training "specificity" hypothesis, mitochondrial respiration was studied in permeabilized muscle fibers from 25 sedentary adults after endurance (ET) or strength training (ST) in normoxia or hypoxia fraction of inspired oxygen (Fi(O(2))) = 21% or 13.5%. Biopsies were taken from the musculus vastus lateralis, and cycle-ergometric incremental maximum oxygen uptake (VO(2max)) exercise tests were performed under normoxia, before and after the 10-wk training program. The main finding was a significant increase (P < 0.05) of fatty acid oxidation capacity per muscle mass, after endurance and strength training under normoxia 2.6- and 2.4-fold for endurance training normoxia group (ET(N)) and strength training normoxia group (ST(N)); n = 8 and 3 and hypoxia 2.0-fold for the endurance training hypoxia group (ET(H)) and strength training hypoxia group (ST(H)); n = 7 and 7, and higher coupling control of oxidative phosphorylation. The enhanced lipid oxidative phosphorylation (OXPHOS) capacity was mainly (87%) due to qualitative mitochondrial changes increasing the relative capacity for fatty acid oxidation (P < 0.01). Mitochondrial tissue-density contributed to a smaller extent (13%), reflected by the gain in muscle mass-specific respiratory capacity with a physiological substrate cocktail (glutamate, malate, succinate, and octanoylcarnitine). No significant increase was observed in mitochondrial DNA (mtDNA) content. Physiological OXPHOS capacity increased significantly in ET(N) (P < 0.01), with the same trend in ET(H) and ST(H) (P < 0.1). The limitation of flux by the phosphorylation system was diminished after training. Importantly, key mitochondrial adaptations were similar after endurance and strength training, regardless of normoxic or hypoxic exercise. The transition from a sedentary to an active lifestyle induced muscular changes of mitochondrial quality representative of mitochondrial health.
Background
For future experimental studies or the development of targeted pharmaceutical agents, a deeper insight into the pathophysiology of migraine is of utmost interest. Reliable methods to ...trigger migraine attacks including aura are desirable to study this complex disease in vivo.
Methods
To investigate hypoxia as a trigger for migraine and aura, we exposed volunteers diagnosed with migraine, with (n = 16) and without aura (n = 14), to hypoxia utilizing a hypoxic chamber adjusted to a FiO2 of 12.6%. The occurrence of headache, migraine, aura, and accompanying symptoms were registered and vital signs were collected for 6 hours under hypoxia and 2 hours of follow-up. A binary logistic regression analysis examined the probability of triggering headaches, migraines, aura, photo- and phonophobia.
Findings
Of 30 participants, 24 (80.0%) developed headaches and 19 (63.3%) migraine, five (16.7%) reported aura. Two patients that developed aura never experienced aura symptoms before in their life. The increase of mean heart frequency was higher in patients developing headaches or migraine. Mean SpO2 during hypoxia was 83.39%.
Conclusion
Hypoxia was able to trigger migraine attacks and aura independently of any pharmacological agent.
Cold weather exercise is common in many regions of the world; however, it is unclear whether respiratory function and symptom worsen progressively with colder air temperatures. Furthermore, it is ...unclear whether high-ventilation sport background exacerbates dysfunction and symptoms.
Seventeen active females (measure of the maximum volume of oxygen VO(2max): 49.6±6.6 mL·kg⁻¹·min⁻¹) completed on different days in random order 5 blinded running trials at 0°C, -5°C, -10°C, -15°C, and -20°C (humidity 40%) in an environmental chamber. Distance, heart rate, and rating of perceived exertion (RPE) were measured within each trial; forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), forced expiratory flow at 25%-75% (FEF₂₅₋₇₅), and forced expiratory flow at 50% (FEF₅₀) were measured pre- and post-test (3, 6, 10, 15, and 20 minutes). Respiratory symptoms and global effort were measured post-test spirometry.
Mean decreases were found in FEV1 (4%-5% at 0°C, -5°C, -10°C, and -15°C; 7% at -20°C). FEF₂₅₋₇₅ and FEF₅₀ decreased 7% and 11% at -15°C and -20°C, respectively. Post-exertion spirometry results were decreased most at 3 to 6 minutes, recovering back to baseline at 20 minutes. Respiratory symptoms and global effort significantly increased at -15°C and -20°C with decreased heart rate. High-ventilation sports decreased function more than low-ventilation participants but had fewer symptoms.
These results indicate that intense exercise at cold air temperatures up to -20°C is achievable; however, greater effort along with transient acute bronchoconstriction and symptoms of cough after exercising in temperatures colder than -15°C are likely. It is recommended that individuals cover their mouth and reduce exercise intensity to ameliorate the effects of cold weather exercise.
Athletes often experience poor sleep quality due to stress, altitude exposure, travel across different time zones, and pre-competition nervousness. Coaches use daytime naps to counteract the negative ...effects of fragmented nighttime sleep. Napping before competitions has also been used to enhance performance in athletes without sleep problems, with mixed results in previous studies, particularly for endurance performance. Thus, we investigated the effects of napping after partial sleep deprivation (PSD) on endurance performance and wakefulness in athletes.
We recruited 12 healthy and trained participants (seven female and five male) for a randomized crossover study design. The participants underwent two test sessions: a five-hour night of sleep without a nap (noNap) and a five-hour night of sleep with a 30-min nap opportunity (Nap30). Participants recorded their sleep-wake rhythm one week before and during the study using the Consensus Sleep Diary-Core and the Morningness-Eveningness Questionnaire to examine their circadian rhythm type. We quantified PSD and the nap with pupillography (pupil unrest index, PUI), a subjective level of sleepiness questionnaire (Karolinska Sleepiness Scale, KSS), and polysomnography. After each night, participants performed a maximal cycling ergometry test to determine time to exhaustion (TTE) and maximal oxygen uptake (VO
).
Participants had an average sleep duration of 7.2 ± 0.7 h and were identified as moderately morning types (
= 5), neither type (
= 5), and moderately evening types (
= 2). There was a significant difference in both sleepiness parameters between the two conditions, with the PUI (
= 0.015) and KSS (
≤ 0.01) significantly decreased at 5 h and nap compared with only 5 h of sleep. The PUI (
≤ 0.01) and KSS (
≤ 0.01) decreased significantly from before to after the nap. However, there was no significant difference in physical exercise test results between the conditions for TTE (
= 0.367) or VO
(
= 0.308).
Our results suggest that napping after light PSD does not significantly influence endurance performance. We conclude that aerobic performance is a multidimensional construct, and napping after PSD may not enhance it. However, napping is an effective method to increase wakefulness and vigilance, which can be beneficial for sports competitions.
This systematic review aimed to evaluate the effects of upper body endurance training (UBET) on oxygen uptake (VO
) in healthy persons and derive evidence-based recommendations to improve upper body ...fitness and performance.
: Databases were systematically searched in accordance with PRISMA guidelines until 1 February 2023. Eligibility criteria included healthy male and female adults and older adults who underwent an UBET intervention. Outcomes of interest included physical fitness (VO
and/ or VO
) and transfer effects (i.e., effects from trained (VO
) to untrained (VO
) musculature).
: The search identified 8293 records, out of which 27 studies reporting on 29 interventions met our eligibility criteria. The average duration of interventions was 6.8 ± 2.6 weeks with 3.2 ± 0.8 training sessions per week. For 21 of 29 interventions, significant increases in VO
were reported following UBET (+16.4% ± 8.3%). Three of the nine studies that analyzed transfer effects of untrained legs after upper body training exhibited significant increases in VO
(+9.3% ± 2.6%).
: This review showed that UBET is a beneficial and useful training modality to increase the oxygen utilization in the upper body. Although UBET is an uncommon form of endurance training in healthy individuals, transfer effects to the untrained muscles can be observed in isolated cases only, rendering transfer effects in UBET inconclusive. Further research should focus on the peripheral changes in muscle morphology of the trained muscles and central changes in cardiovascular function as well as when transfer effects can occur after UBET in healthy people.
Hypoxia, Oxidative Stress and Fat Netzer, Nikolaus; Gatterer, Hannes; Faulhaber, Martin ...
Biomolecules,
06/2015, Volume:
5, Issue:
2
Journal Article, Book Review
Peer reviewed
Open access
Metabolic disturbances in white adipose tissue in obese individuals contribute to the pathogenesis of insulin resistance and the development of type 2 diabetes mellitus. Impaired insulin action in ...adipocytes is associated with elevated lipolysis and increased free fatty acids leading to ectopic fat deposition in liver and skeletal muscle. Chronic adipose tissue hypoxia has been suggested to be part of pathomechanisms causing dysfunction of adipocytes. Hypoxia can provoke oxidative stress in human and animal adipocytes and reduce the production of beneficial adipokines, such as adiponectin. However, time-dose responses to hypoxia relativize the effects of hypoxic stress. Long-term exposure of fat cells to hypoxia can lead to the production of beneficial substances such as leptin. Knowledge of time-dose responses of hypoxia on white adipose tissue and the time course of generation of oxidative stress in adipocytes is still scarce. This paper reviews the potential links between adipose tissue hypoxia, oxidative stress, mitochondrial dysfunction, and low-grade inflammation caused by adipocyte hypertrophy, macrophage infiltration and production of inflammatory mediators.
The present study determined the association between body fluid variation and the development of acute mountain sickness (AMS) in adults.
Forty-three healthy participants (26 males and 17 females, ...age: 26 ± 6 yr, height: 174 ± 9 cm, weight: 68 ± 12 kg) were passively exposed at a FiO2 of 12.6% (simulated altitude hypoxia of 4500 m, PiO2 = 83.9 mmHg) for 12-h. AMS severity was assessed using the Lake Louise Score (LLS). Food and drink intakes were consumed ad libitum and measured; all urine was collected. Before and after the 12-h exposure, body weight and plasma osmolality were measured and whole-body bioimpedance analysis was performed.
The overall AMS incidence was 43% (38% males, 50% females). Participants who developed AMS showed lower fluid losses (3.0 ± 0.9 vs. 4.5 ± 2.0 ml/kg/h, p = 0.002), a higher fluid retention (1.9 ± 1.5 vs. 0.6 ± 0.8 ml/kg/h, p = 0.022), greater plasma osmolality decreases (-7 ± 7 vs. -2 ± 5 mOsm/kg, p = 0.028) and a larger plasma volume expansion (11 ± 10 vs. 1 ± 15%, p = 0.041) compared to participants not developing AMS. Net water balance (fluid intake--fluid loss) and the amount of fluid loss were strong predictors whether getting sick or not (Nagelkerkes r(2) = 0.532). The LLS score was related to net water balance (r = 0.358, p = 0.018), changes in plasma osmolality (r = -0.325, p = 0.033) and sodium concentration (r = -0.305, p = 0.047). Changes in the impedance vector length were related to weight changes (r = -0.550, p<0.001), fluid intake (r = -0.533, p<0.001) and net water balance (r = -0.590, p<0.001).
Participants developing AMS within 12 hours showed a positive net water balance due to low fluid loss. Thus measures to avoid excess fluid retention are likely to reduce AMS symptoms.
The aim of this study was to determine alterations of the metabolome in blood plasma in response to concentric-eccentric leg exercise performed at a simulated altitude of 3,500 m. To do so, we ...recruited 11 well-trained subjects and performed an untargeted metabolomics analysis of plasma samples obtained before, 20 min after as well as on day 8 after five sets of maximal, concentric-eccentric leg exercises that lasted 90 s each. We identified and annotated 115 metabolites through untargeted liquid chromatography-mass spectrometry metabolomics and used them to further calculate 20 sum/ratio of metabolites. A principal component analysis (PCA) revealed differences in-between the overall metabolome at rest and immediately after exercise. Interestingly, some systematic changes of relative metabolite concentrations still persisted on day 8 after exercise. The first two components of the PCA explained 34% of the relative concentrations of all identified metabolites analyzed together. A volcano plot indicates that 35 metabolites and two metabolite ratios were significantly changed directly after exercise, such as metabolites related to carbohydrate and TCA metabolism. Moreover, we observed alterations in the relative concentrations of amino acids (e.g., decreases of valine, leucine and increases in alanine) and purines (e.g., increases in hypoxanthine, xanthine and uric acid). In summary, high intensity concentric-eccentric exercise performed at simulated altitude systematically changed the blood metabolome in trained athletes directly after exercise and some relative metabolite concentrations were still changed on day 8. The importance of that persisting metabolic alterations on exercise performance should be studied further.
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