Dynamic Apnea Research Articles

Effects of aerobic and anaerobic training on freedivers' performance.

Freediving is a sport that could be defined as both aerobic and anaerobic. Therefore, this study aimed to evaluate the effect of aerobic-anaerobic training on the performance of moderate and elite freedivers. The sample of participants included 26 freedivers (9 females) (average age of 26.62±3.34 years, body height of 178.95±9.19 cm, and body mass of 74.64±11.97 kg). The sample of variables included: anthropometric indices, relative maximal oxygen consumption (rVO<inf>2max</inf>), Diving anaerobic sprint test (DAST), Swimming anaerobic sprint test (SAST), 100-meter crawl sprint test (100 m), maximal dynamic apnea with monofin (DYN), maximal swimming length for 2 minutes (2 min). The study procedure included a 5-month aerobic-anaerobic training intervention. This intervention was conducted during a 4-phase (5-week each) training period. The results showed that moderate group showed a significant decrease in 100 m (final 83.94±15.68; initial 88.29±16.73; P<0.00), DAST<inf>max</inf> (final 10.91±1.46; initial 12.01±1.38; P<0.00), DAST (final 70.29±8.95; initial 79.40±10.25; P<0.00), SAST<inf>max</inf> (final 16.81±2.24; initial 18.01±2.69; P<0.00), SAST(final 112.87±19.19; initial 122.65±21.55; P<0.00), and increase in 2 min (final 140.56±21.53; initial 128.68±19.33; P<0.00), and DYN (final 130.48±26.89; initial 91.65; P<0.00). Similarly, the elite group experienced a decrease in 100 m (final 72.18±9.77; initial 75.00±11.36; P=0.02), DAST<inf>max</inf> (final 10.14±0.95; initial 10.88±0.99; P=0.03), DAST (final 65.55±6.50; initial 71.24±7.32; P=0.02), SAST<inf>max</inf> (final 14.82±1.84; initial 15.76±1.80; P=0.03), and increase in DYN (final 194.94±27.70; initial 161.11±27.70; P<0.00). The results of this study demonstrate that dynamic apnea, as a main performance factor, had increase in all phases of procedure, with highest increase during anaerobic phases.

Cardiovascular and hematological responses to a dry dynamic apnea in breath hold divers.

The mammalian dive reflex, characterized by bradycardia and peripheral vasoconstriction, occurs in all mammals, including humans, in response to apnea. However, the dive reflex to a single, maximal, dry, dynamic apnea (DYN) and how it compares to a time-matched exercise control trial (EX) or dry static apnea (SA) has not been studied. We examined the hypotheses that, compared with EX and SA, the magnitude of the 1) cardiovascular response and 2) hematological response to DYN would be greater. Cardiovascular parameters [heart rate (HR), systolic (SBP), diastolic (DBP), and mean arterial (MAP) blood pressure] were continuously collected in 23 (F = 6 females) moderate and elite freedivers, first during a maximal DYN, then during a time-matched SA and EX on a swimming ergometer in randomized order. Venous blood draws were made before and following each trial. The change in calculated oxygen saturation (DYN: -17 ± 13%, EX: -2 ± 1%, ΔSA: -2 ± 1%; P < 0.05, all comparisons) was greater during DYN compared with EX and SA. During DYN, ΔSBP (DYN: 104 ± 31 mmHg; EX: 38 ± 23 mmHg; and SA: 20 ± 11 mmHg), ΔDBP (DYN: 45 ± 12 mmHg; EX: 14 ± 10 mmHg; and SA: 15 ± 8 mmHg), and ΔMAP (DYN: 65 ± 17 mmHg; EX: 22 ± 13 mmHg; and SA: 16 ± 9 mmHg) were increased compared with EX and SA, while ΔHR was greater during EX (DYN: -24 ± 23 beats/min; EX: 33 ± 13 beats/min; and SA: -1 ± 10 beats/min) than either DYN or SA (P < 0.0001, all comparisons). Females had a greater pressor response to EX (ΔSBP: 59 ± 30 mmHg; ΔDBP: 24 ± 14 mmHg; and ΔMAP: 35 ± 8 mmHg) than males (ΔSBP: 31 ± 15 mmHg; ΔDBP: 11 ± 6 mmHg; and ΔMAP: 18 ± 8 mmHg; P < 0.01, all comparisons). Together, these data indicate that DYN elicits a distinct, exaggerated cardiovascular response compared with EX or SA alone.NEW & NOTEWORTHY This study performed a dry dynamic apnea with sport-specific equipment to closely mimic the physiological demands of competition diving. We found the cardiovascular and hematological responses to dynamic apnea were more robust compared with time-matched exercise and dry static apnea control trials.

Cardiovascular and Hematological Responses to Simulated Dynamic Apnea in Breath Hold Divers

The mammalian dive reflex, characterized by bradycardia and peripheral vasoconstriction, occurs in all mammals, including humans, in response to apnea or facial submersion in water. However, the dive reflex to a single, maximal effort dynamic apnea (DYN), and how it compares to a time-matched exercise control trial (EX), has not been studied. We examined the hypotheses that, when compared to EX, (a) the magnitude of the cardiovascular response, including reduced heart rate (HR), increased systolic-, diastolic-, and mean arterial- pressure (SBP, DBP, and MAP, respectively) would be greater during DYN, and; (b) red blood cells (RBCs), hemoglobin (Hb), and hematocrit (Hct) would also all be elevated following DYN. Twenty-three (F=6) apnea divers performed a maximal DYN and time-matched EX on a swimming ergometer without facial submersion. For the DYN protocol, participants were instructed to exercise maximally while holding their breath which the EX trial was then time and distance matched. Trial duration was similar between DYN (126±7s [mean±SE]) and EX (126±7s;P&gt;0.3), however the change in venous lactate (DYN 1.8±0.3mmol/l, EX: 0.2±0.2mmol/l) and peripheral oxygen saturation (DYN: -15±3%, EX: -1.8±0.5%;p&lt;0.05, both comparisons) were greater during DYN compared to EX. During DYN ΔSBP (DYN: 107±6mmHg, EX: 45±6 mmHg), ΔDBP (DYN: 46±3mmHg, EX: 17±3mmHg) and ΔMAP (DYN: 66±3mmHg EX: 26±3mmHg) were increased compared to EX, while ΔHR was greater during EX (DYN: -24±5bpm, EX: 36±5bpm;p&lt;0.0001, all comparisons). Similarly, the change in estimated stroke volume was further reduced in DYN (DYN: -15.2±3.3mL, EX: -1.0±3.3m;p&lt;0.005) while Δcardiac output was reduced during DYN (-2.9±0.4l/min) and elevated during EX (2.9±0.4l/min;p&lt;0.0001). The change in RBCs (DYN: 0.20±0.04x106 cells/μL, EX: 0.06±0.04x106 cells/μL) and Hct (DYN:1.7±0.3%, EX:0.5±0.3%) were greater during DYN than EX (p&lt;0.02, both comparisons), whereas ΔHb (DYN: 4.0±0.9g/dL, EX: 1.9±0.8g/dL) and spleen volume (DYN: -9.1±7.4cm3, EX:-8.3±6.4cm3;P&gt;0.1, both comparisons) was comparable between the two trials. There was a main effect of sex for ΔDBP (Female: 36±3mmHg, Male: 27±2mmHg), and ΔMAP (Female: 52±5mmHg, Male: 40±3mmHg) indicating that females overall had a greater blood pressure response to both DYN and EX (p&lt;0.05, both comparisons). Together, these data indicate that DYN elicits a greater cardiovascular and hematological response than EX alone, likely due to the combined activation of the metabo- and chemo-reflex during DYN. The mechanism(s) that may elicit greater changes in blood pressure response to DYN and EX in females when compared to males warrant future investigation. NSERC, University Research Chair. 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.

Effect of dry dynamic apnea on aerobic power in elite rugby athletes: a warm-up method.

Objective: While long-term dynamic breath-holding training has been extensively studied to enhance cardiopulmonary function in athletes, limited research has explored the impact of a single breath-holding session on subsequent athletic capacity. In addition, Dry Dynamic Apnea (DA) has a more immediate physiological response than wet and static breath-holding. This study aims to assess the immediate effects of a single session of DA on the aerobic power and hematological parameters of elite athletes. Methods: Seventeen elite male rugby athletes (average age 23.5 ± 1.8) participated in this study. Two warm-up protocols were employed prior to incremental exercise: a standard warm-up (10min of no-load pedaling) and a DA warm-up (10min of no-load pedaling accompanied by six maximum capacity breath holds, with 30s between each breath hold). Fingertip blood indicators were measured before and after warm-up. The incremental exercise test assessed aerobic parameters with self-regulation applied throughout the study. Results: Compared to the baseline warm-up, the DA warm-up resulted in a significant increase in VO2peak from 3.14 to 3.38L/min (7.64% change, p < 0.05). HRmax increased from 170 to 183 bpm (7.34% change, p < 0.05), and HRpeak increased from 169 to 182 bpm (7.52% change, p < 0.05). Hematocrit and hemoglobin showed differential changes between the two warm-up methods (PHematocrit = 0.674; Phemoglobin = 0.707). Conclusion: This study investigates how DA influences physiological factors such as spleen contraction, oxygen uptake, and sympathetic nerve activation compared to traditional warm-up methods. Immediate improvements in aerobic power suggest reduced vagus nerve stimulation, heightened sympathetic activity, and alterations in respiratory metabolism induced by the voluntarily hypoxia-triggered warm-up. Further research is warranted to comprehensively understand these physiological responses and optimize warm-up strategies for elite athletic performance.

Predictors of Competitive Dynamic Apnea Performance in Elite Free Diving Athletes

Predictors of Competitive Dynamic Apnea Performance in Elite Free Diving Athletes

The concordance game: A simple tool to estimate breath hold swimming performance and to teach dynamic apnea.

Swimming is composed of several phases. One of them is done underwater in apnea. Although this phase takes an important part of the performance, it is not taught much because of the risk it entails. At the same time, learning apnea can reduce the fear of immersion and, thus, reduce the number of drownings. The pedagogy used in this paper comes from game theory. This paper tested an apnea game based on the agreement between self-prediction and realization of the task. Considering the preliminary level of the 33 sports students involved, the game offered two choices: swimming apnea over 15 or 20 m with a distribution of payoffs depending on the actual achievement (15 m estimated and less than 20 m performed = + 3 points; 15 m estimated and at least 20 m realized = + 1 points; 20 m predicted and less than 20 m realized = + 2 points; 20 m estimated and at least 20 m realized = + 4 points). Concordance was favored over discordance, including in the swimmer's comfort zone (15 m). Throughout six apneas the results showed that the structure of this game supports the improvement of the estimation of the distances swum. The "Concordance Game" could be offered in Physical Education or in a sports club to learn to swim a longer distance below the surface without forcing.

Into the Blue: First in Man Data on Diving Physiology in Fontan Patients.

Swimming and diving are popular recreational activities. As congenital heart disease, especially patients with univentricular hearts after Fontan palliation are thought to have reduced physiologic capacities for compensation of submersion-associated physiologic demands, current guidelines put restraints on this group of patients. Although these restrictions on doctoral advice place a significant burden on affected patients, it is especially interesting that these guideline recommendations are merely based on physiologic assumptions, i.e., expert consensus. A recent study by Paech et al. presented the first in vivo data on the effects of immersion in Fontan patients, stating no major adverse events in their study group as well as comparable physiologic adaption as reported in the literature for healthy people. Yet, submersion was not reflected in this study, and the current study therefore aimed to conduct a first study for the evaluation of the effects of submersion and apnea diving in Fontan patients. A control group of healthy adults as well as patients recruited from the Heart Center Leipzig, Department of pediatric cardiology underwent a standardized diving protocol including a static as well as dynamic apnea phase. Physiologic data were recorded. This study presents the first structured data on diving physiology in Fontan patients compared to healthy probands. There were no adverse events. The physiologic response to diving seems to be comparable between healthy probands and Fontan patients. Although, healthy probands did reach a much better performance, the basic mechanisms of physiologic adaption seem comparable.

Acute Cardiovascular and Metabolic Effects of Different Warm-Up Protocols on Dynamic Apnea.

The aim of this study was to evaluate the acute physiological response to different warm-up protocols on the dynamic apnea performance. The traditional approach, including a series of short-mid dives in water (WET warm-up), was compared to a more recent strategy, consisting in exercises performed outside the water (DRY warm-up). Nine athletes were tested in two different sessions, in which the only difference was the warm-up executed before 75m of dynamic apnea. Heart rate variability, baroreflex sensitivity, hemoglobin, blood lactate and the rate of perceived exertion were recorded and analyzed. With respect to WET condition, DRY showed lower lactate level before the dive (1.93 vs. 2.60 mmol/L, p = 0.006), higher autonomic indices and lower heart rate during the subsequent dynamic apnea. A significant correlation between lactate produced during WET with the duration of the subsequent dynamic apnea, suggests that higher lactate levels could affect the dive performance (72 vs. 70 sec, p = 0.028). The hemoglobin concentration and the rate of perceived exertion did not show significant differences between conditions. The present findings partially support the claims of freediving athletes who adopt the DRY warm-up, since it induces a more pronounced diving response, avoiding higher lactate levels and reducing the dive time of a dynamic apnea.

Effect of Apnea-Induced Hypoxia on Cardiovascular Adaptation and Circulating Biomarkers of Oxidative Stress in Elite Breath-Hold Divers.

Given the previous evidence that breath-hold diving is a cause of physiological stress, this study aimed to determine whether a combination static and dynamic apnea would affect total oxidant status, nitric oxide, heat shock proteins and cardiovascular parameters in elite freedivers. Thirteen finalists of the World and European championships in swimming pool breath-hold diving participated in the study. Whole-body plethysmography and electrocardiography was performed to determine the cardiorespiratory variables at baseline and during the simulation static apnea. An assessment of the heart rate, blood oxygen saturation and biochemical variables was performed before and in response to a combination of a static followed by a dynamic apnea. Static and dynamic breath-holding had a significant effect on oxidative stress, as evidenced by an increase in the total oxidant status/capacity (p < 0.001). The post apnea concentrations of heat shock proteins 27 (HSP27) were significantly elevated (p < 0.03, but total antioxidant status (TAS), HSP90, HSP70, and nitric oxide (NO) changes were not significant. levels under the influence of the static and dynamic breath-hold protocol. A significant positive correlation between HSPs and TAS (r = 0.63; p < 0.05) as well as NO levels was associated with beneficial cardiovascular adaptation. An increase in serum HSP27 levels mediated in nitric oxide levels could explain its important role in improving cardiovascular functions in elite freedivers. Further studies are necessary to explain the exact mechanisms of breath holds training of cardiovascular adaptation responsible for maintaining adequate oxygen supply in elite divers.

Effects of dynamic apnea training on diving bradycardia and short distance swimming performance.

Apnea training enhances bradycardia and improves competitive apnea performance and has been proposed as a training method for other sports, such as swimming. We evaluated the effects of apneic underwater swimming, i.e., dynamic apnea (DYN), in 9 competitive swimmers (TR) who completed ten DYN sessions over 2 weeks. TR performed pre- and post-training tests including a static apnea test with continuous heart rate (HR) and peripheral oxygen saturation measurements, all-out 50m and 100m freestyle tests and an all-out DYN test. Control groups were competitive swimmers (SC; N.=10) that trained swimming without DYN, and a non-swimmer group (AC; N.=10) performing only static apnea tests. Post-training, TR mean±SD time for 50 m freestyle improved from 25.51±2.01 s to 24.64±2.02 s (P<0.01) and for 100m from 55.5±4.2 s to 54.1±4.4 s (P<0.05). SC also improved their 100m time from 56.7±3.3 s to 56.0±3.1 s (P<0.01; P=0.07 between groups). Only TR performed DYN tests; DYN distance increased from 62.1±11.5 m to 70.9±18.9 m (P<0.05) while DYN speed decreased from 0.74±0.14m/s to 0.64±0.18 m/s (P<0.01). Static apnea duration did not change in any of the groups, but HR-reduction was enhanced post-training only in TR (24.8±14.8% to 31.1±10.9%, P<0.01; P<0.001 between groups). We conclude that 2 weeks of DYN training enhanced DYN performance, which may be caused by the enhanced apnea-induced diving bradycardia. Further research is required to determine whether DYN training enhances short distance freestyle swimming performance.

The Influence of Functional Abilities and Morphological Characteristics on Success in Apnea

Objectives: The main goal of this research was to determine to what extent the competitors’ functional abilities and morphological characteristics hypothetically explain the results achieved in static and dynamic apnea and offer a prediction. Methods: The study included 35 artistic swimmers, body height of 162.98 ± 5.252 cm and body weight of 51.47 ± 5.578 kg that is in the regular training process and competes in the junior competitions. Morphological characteristic variables were obtained by analyzing the subjects’ body composition by the bioelectric impedance method (BIA). Variables for the functional abilities assessment were determined by two tests: forced vital capacity (FVC) and forced expiratory volume (FEV). The influence of functional abilities and morphological characteristics on the results in static and dynamic apnea was assessed by regression analysis. Results: The results show that functional abilities and morphological characteristics have a significant influence on the diving results. Conclusion: These results are important for the selection and effective training during the training period and can influence the appropriate specific training programs development. They can be used for the optimal preparation of all competitors in water sports (swimmers, water polo players, artistic swimmers and athletes practicing apnea).

Blood lactate accumulation during competitive freediving and synchronized swimming

A number of competitive water sports are performed while breath-holding (apnea). Such performances put large demands on the anaerobic system, but the study of lactate accumulation in apneic sports is limited. We therefore aimed to determine and compare the net lactate accumulation (NLA) during competition events in six disciplines of competitive freediving (FD) and three disciplines of synchronized swimming (SSW). The FD disciplines were: static apnea (STA; n = 14); dynamic apnea (DYN; n = 19); dynamic apnea no fins (DNF; n = 16); constant weight (CWT; n = 12); constant weight no fins (CNF; n = 8); free immersion (FIM; n =10). The SSW disciplines were solo (n = 21), duet (n = 31) and team (n = 34). Capillary blood lactate concentration was measured before and three minutes after competition performances, and apneic duration and performance variables were recorded. In all nine disciplines NLA was observed. The highest mean (SD) NLA (mmol·L-1) was found in CNF at 6.3 (2.2), followed by CWT at 5.9 (2.3) and SSW solo at 5 (1.9). STA showed the lowest NLA 0.7 (0.7) mmol·L-1 compared to all other disciplines (P ⟨ 0.001). The NLA recorded shows that sports involving apnea involve high levels of anaerobic activity. The highest NLA was related to both work done by large muscle groups and long apneic periods, suggesting that NLA is influenced by both the type of work and apnea duration, with lower NLA in SSW due to shorter apneic episodes with intermittent breathing.

The Effect of Beetroot Juice Supplementation on Dynamic Apnea and Intermittent Sprint Performance in Elite Female Water Polo Players.

Nitrate-rich beetroot juice is thought to have ergogenic effects, particularly in conditions where oxygen availability is limited. Whether these effects also apply to elite athletes is currently unknown. The aim of this study was to assess the effects of beetroot juice supplementation on dynamic apnea and intermittent sprint performance in elite female water polo players. In a double-blinded, randomized, crossover manner, the Dutch National female water polo team (N = 14) was subjected to two 6-day supplementation periods (1 and 2), with either 140ml/day of nitrate-rich (BR; ∼800mg/day nitrate) or nitrate-depleted (PLA) beetroot juice. Following blood sampling on Day 6, the athletes performed a maximal-distance front crawl swimming test without breathing (dynamic apnea test). In addition, intermittent sprint performance was assessed by performing 16 swim sprints of 15m, in a 4 × 4 block with 30-s recovery between blocks (intermittent test). Distance covered during the dynamic apnea test did not differ between BR (49.5 ± 7.8m) and PLA (46.9 ± 9.1m, p = .178). However, when correcting for test order, the distance covered was significantly larger in BR versus PLA when BR was ingested in Period 2 (50.1 ± 8.5 vs. 42.8 ± 5.7m, p = .002), whereas no difference was observed when BR was ingested in Period 1 (48.8 ± 7.4 vs. 52.3 ± 10.4m, p = .10). The time to complete the intermittent test was not different between BR and PLA (316.0 ± 7.9 vs. 316.3 ± 6.9s, p = .73). In conclusion, beetroot juice supplementation does not improve intermittent performance in elite female water polo players, but there may be a potential for ergogenic effects during dynamic apnea.

The Effect of a Dietary Nitrate Supplementation in the Form of a Single Shot of Beetroot Juice on Static and Dynamic Apnea Performance.

The purpose of the present study was to assess the effects of acute nitrate ([Formula: see text])-rich beetroot juice (BRJ) supplementation on peripheral oxygen saturation (SpO2), heart rate (HR), and pulmonary gas exchange during submaximal static and dynamic apnea. Nine (six males and three females) trained apneists (age: 39.6 ± 8.2years, stature: 170.4 ± 11.5cm, and body mass: 72.0 ± 11.5kg) performed three submaximal static apneas at 60%, 70%, and 80% of the participant's current reported personal best time, followed by three submaximal (∼75% or personal best distance) dynamic apneas following the consumption of either a 70-ml concentrated BRJ (7.7mmol [Formula: see text]) or a [Formula: see text]-depleted placebo (PLA; 0.1mmol [Formula: see text]) in double-blind randomized manner. HR and SpO2 were measured via fingertip pulse oximetry at the nadir, and online gas analysis was used to assess pulmonary oxygen uptake ([Formula: see text]) during recovery following breath-holds. There were no differences (p < .05) among conditions for HR (PLA = 59 ± 11bpm and BRJ = 61 ± 12bpm), SpO2 (PLA = 83% ± 14% and BRJ = 84% ±9%), or [Formula: see text] (PLA = 1.00 ± 0.22L/min and BRJ = 0.97 ± 0.27L/min). The consumption of 7.7mmol of beetroot juice supplementation prior to a series of submaximal static and dynamic apneas did not induce a significant change in SpO2, HR, and [Formula: see text] when compared with placebo. Therefore, there is no apparent physiological response that may benefit free divers as a result of the supplementation.

Physiological Dynamic Apnea Responses in Relation to Apnea Capacity in Triathletes.

The aim was to assess the cardiac, arterial oxygen saturation, lactate, hormonal and Borg rating of perceived exertion (RPE) responses to acute apnea in relation to apnea capacity in 18 middle-aged triathletes. Subjects were monitored while swimming two 50-m freestyle exercise trials with fins at maximal speed: with normal frequency breathing (NB) and with complete apnea (Ap); the latter was used to assess apnea capacity. The subjects with significant alteration in swimming performance inducing a time increase greater than 2.5% during Ap vs. NB were put in the group: bad apnea capacity (Bad Ap); the others, who showed no significant alteration in performance, were put in the group: Good Ap. Under apnea, both groups showed a decrease in arterial oxygen saturation (p<0.05). In Ap conditions, only Bad Ap had a significant lower maximal heart rate vs. NB (p<0.05), with lower blood lactate (p<0.05) and arm stroke frequency (p<0.01). No change in saliva hormonal concentrations was found during the experiment for both groups, whereas RPE responses were increased in the Good Ap group under Ap vs. NB conditions. In conclusion, a good apnea capacity seems to be associated with lower cardiovascular and metabolic apnea alterations in middle-aged recreationally-trained triathletes.

Dynamic Apnea in Pubertal Male and Female Swimmers

Dynamic Apnea in Pubertal Male and Female Swimmers

Blood biomarkers indicate mild neuroaxonal injury and increased amyloid β production after transient hypoxia during breath-hold diving

Objective: To determine whether transient hypoxia during breath-hold diving causes neuronal damage or dysfunction or alters amyloid metabolism as measured by certain blood biomarkers.Design: Sixteen divers competing in the national Swedish championship in breath-hold diving and five age-matched healthy control subjects were included. Blood samples were collected at baseline and over a course of 3 days where the divers competed in static apnea (STA), dynamic apnea without fins (DYN1) and dynamic apnea with fins (DYN2).Main outcomes: Biomarkers reflecting brain injury and amyloid metabolism were analysed in serum (S-100β, NFL) and plasma (T-tau, Aβ42) using immunochemical methods.Results: Compared to divers’ baseline, Aβ42 increased after the first event of static apnea (p = 0.0006). T-tau increased (p = 0.001) in STA vs baseline and decreased after one of the dynamic events, DYN2 (p = 0.03). Further, T-tau correlated with the length of the apneic time during STA (ρ = 0.7226, p = 0.004) and during DYN1 (ρ = 0.66, p = 0.01).Conclusion: The findings suggest that transient hypoxia may acutely increase the levels of Aβ42 and T-tau in plasma of healthy adults, further supporting that general hypoxia may cause mild neuronal dysfunction or damage and stimulate Aβ production.

Dietary nitrate enhances arterial oxygen saturation after dynamic apnea.

Breath-hold divers train to minimize their oxygen consumption to improve their apneic performance. Dietary nitrate has been shown to reduce the oxygen cost in a variety of situations, and our aim was to study its effect on arterial oxygen saturation (SaO2 ) after dynamic apnea (DYN) performance. Fourteen healthy male apnea divers (aged 33±11years) received either 70 mL of concentrated nitrate-rich beetroot juice (BR) or placebo (PL) on different days. At 2.5h after ingesting the juice, they were asked to perform 2×75m DYN dives in a pool with 4.5-min recovery between dives. Each dive started after 2-min countdown and without any warm-up apneas, hyperventilation, or lung packing. SaO2 and heart rate were measured via pulse oximetry for 90s before and after each dive. Mean SaO2 nadir values after the dives were 83.4±10.8% with BR and 78.3±11.0% with PL (P<0.05). At 20-s post-dive, mean SaO2 was 86.3±10.6% with BR and 79.4±10.2% with PL (P<0.05). In conclusion, BR juice was found to elevate SaO2 after 75-m DYN. These results suggest an oxygen conserving effect of dietary nitrate supplementation, which likely has a positive effect on maximal apnea performance.

Release of erythropoietin and neuron‐specific enolase after breath holding in competing free divers

Free diving is associated with extreme hypoxia. This study evaluated the combined effect of maximal static breath holding and underwater swimming on plasma biomarkers of tissue hypoxemia: erythropoietin, neuron-specific enolase and S100B, C-reactive protein, pro-atrial natriuretic peptide, and troponin T. Venous blood samples were obtained from 17 competing free divers before and 3 h after sessions of static apnea and underwater swimming. The heart was evaluated by echocardiography. Static apnea for 293 ± 78 s (mean ± SD) and subsequent 88 ± 21 m underwater swimming increased plasma erythropoietin from 10.6 ± 3.4 to 12.4 ± 4.1 mIU/L (P = 0.013) and neuron-specific enolase from 14.5 ± 5.3 to 24.6 ± 6.4 ng/mL (P = 0.017); C-reactive protein decreased from 0.84 ± 1.0 to 0.71 ± 0.67 mmol/L (P = 0.013). In contrast, plasma concentrations of S100B (P = 0.394), pro-atrial natriuretic peptide (P = 0.549), and troponin T (P = 0.125) remained unchanged and, as assessed by echocardiography, the heart was not affected. In competitive free divers, bouts of static and dynamic apnea increase plasma erythropoietin and neuron-specific enolase, suggesting that renal and neural tissue, rather than the heart, is affected by the hypoxia developed during apnea and underwater swimming.

Ischemic Preconditioning of One Forearm Enhances Static and Dynamic Apnea

Ischemic preconditioning enhances ergometer cycling and swimming performance. We evaluated whether ischemic preconditioning of one forearm (four times for 5 min) also affects static breath hold and underwater swimming, whereas the effect of similar preconditioning on ergometer rowing served as control because the warm-up for rowing regularly encompasses intense exercise and therefore reduced muscle oxygenation. Six divers performed a dry static breath hold, 11 divers swam underwater in an indoor pool, and 14 oarsmen rowed "1000 m" on an ergometer. Ischemic preconditioning reduced the forearm oxygen saturation from 65% ± 7% to 19% ± 7% (mean ± SD; P < 0.001), determined using spatially resolved near-infrared spectroscopy. During the breath hold (315 s, range = 280-375 s), forearm oxygenation decreased to 29% ± 10%; and in preparation for rowing, right thigh oxygenation decreased from 66% ± 7% to 33% ± 14% (P < 0.05). Ischemic preconditioning prolonged the breath hold from 279 ± 72 to 327 ± 39 s, and the underwater swimming distance from 110 ± 16 to 119 ± 14 m (P < 0.05) and also the rowing time was reduced (from 186.5 ± 3.6 to 185.7 ± 3.6 s; P < 0.05). We conclude that while the effect of ischemic preconditioning (of one forearm) on ergometer rowing was minimal, probably because of reduced muscle oxygenation during the warm-up, ischemic preconditioning does enhance both static and dynamic apnea, supporting that muscle ischemia is an important preparation for physical activity.