The Effects of Acetazolamide on Exercise Performance at Sea Level and in Hypoxic Environments: A Review

Safety and efficacy of electro-thumbtack needle for acute mountain sickness patients: a protocol of a randomized, single-blinded, and placebo-controlled study

BACKGROUND

Acute mountain sickness (AMS) is considered the most common altitude sickness. It can be detrimental to the health of tourists who rapidly ascend high mountains, and can also impair the performance of individuals who move to the plateau for work or education. Acupuncture has been shown to improve AMS as a simple, safe, and effective nonpharmacological method, in case electro-thumbtack needle (ETN) is a more convenient form of acupuncture for both doctor and patient. There are no studies validating the effectiveness of electro-thumbtack needle in improving symptoms in participants with AMS. In this study, we will conduct a randomized controlled trial to evaluate the clinical efficacy and safety of electro-thumbtack needle in participants with AMS. Our hypothesis is that electro-thumbtack needle is safe and effective in treating participants with AMS.

METHODS

This study is a single-center, randomized, single-blinded, and placebo-controlled study involving at least 114 participants who were diagnosed with AMS. The participants randomly assigned in a 1:1 ratio to the electro-thumbtack needle group and the sham acupuncture group. The treatment protocol involved stimulation of seven predefined acupuncture points, including Zhong Wan (RN12), bilateral Nei Guan (PC6), bilateral He Gu (LI4), and bilateral Tai Yang (EX-HN5), for approximately one minute each, with continuous application over 48 h. The primary outcome was improvement in 2018 Lake Louise score (LLS) after 48 h of treatment. Secondary outcome indicators included the incidence of participants with moderate-to-severe AMS (AMS > 5)and AMS, the LLS, visual analogue scale of headache, clinical functioning scores, the Groningen Sleep Quality Survey, the Stanford Somnolence Scale, blood pressure, oxygen saturation, and heart rate, in addition to treatment-related adverse events were also captured.

DISCUSSION

This trial aims to ascertain the therapeutic benefits of ETN in mitigating AMS symptoms, thereby contributing to the evidence base for traditional medical practices, particularly acupuncture, in high-altitude medicine.

TRIAL REGISTRATION

Chinese Clinical Trials Registry: ChiCTR2300073882. Registered on 24 July 2023.

Ketone monoester attenuates declines in cognitive performance and oxygen saturation during acute severe hypoxic exposure under resting conditions

Exogenous ketone supplements are a potential augmentation strategy for cognitive resilience during acute hypoxic exposure due to their capacity to attenuate the decline in oxygen (O2) availability, and by providing an alternative substrate for cerebral metabolism. Utilizing a single-blind randomized crossover design, 16 male military personnel (age, 25.3 ± 2.4 year, body mass, 86.2 ± 9.3 kg) performed tests of cognitive performance at rest in three environments: room air (baseline), normoxia (20 min; 0 m; 20.9% O2) and hypoxia (20 min; 6096 m, 9.7% O2) using a reduced O2 breathing device (ROBD). (R)-3-Hydroxybutyl (R)-3-hydroxybutyrate (R-BD R-βHB) ketone monoester (KME; 650 mg/kg, split dose given at 30 min prior to each exposure) or taste-matched placebo (PLA) was ingested prior to normoxia and hypoxic exposure. Blood R-βHB and glucose concentrations, cognitive performance and O2 saturation (S p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ ) were collected throughout. KME ingestion increased blood R-βHB concentration, which was rapid and sustained (>4 mM 30 min post; P < 0.001) and accompanied by lower blood glucose concentration (∼20 mg/dL; P < 0.01) compared to PLA. Declines in cognitive performance during hypoxic exposure, assessed as cognitive efficiency during a Defense Automated Neurobehavioral Assessment (DANA) code substitution task, were attenuated with KME leading to 6.8 (95% CL: 1.0, 12.6) more correct responses per minute compared to PLA (P = 0.018). The decline inS p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ during hypoxic exposure was attenuated (6.40%S p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ ; 95% CL: 0.04, 12.75; P = 0.049) in KME compared to PLA (KME, 76.8 ± 6.4%S p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ ; PLA, 70.4 ± 7.4%S p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ ). Acute ingestion of KME attenuated the decline in cognitive performance during acute severe hypoxic exposure, which coincided with attenuation of declines in O2 saturation.

The Impact of Acetazolamide and Methazolamide on Exercise Performance in Normoxia and Hypoxia

Doherty, Connor J., Jou-Chung Chang, Benjamin P. Thompson, Erik R. Swenson, Glen E. Foster, and Paolo B. Dominelli. The impact of acetazolamide and methazolamide on exercise performance in normoxia and hypoxia. High Alt Med Biol. 24:7-18, 2023.-Carbonic anhydrase (CA) inhibitors are commonly prescribed for acute mountain sickness (AMS). In this review, we sought to examine how two CA inhibitors, acetazolamide (AZ) and methazolamide (MZ), affect exercise performance in normoxia and hypoxia. First, we briefly describe the role of CA inhibition in facilitating the increase in ventilation and arterial oxygenation in preventing and treating AMS. Next, we detail how AZ affects exercise performance in normoxia and hypoxia and this is followed by a discussion on MZ. We emphasize that the overarching focus of the review is how the two drugs potentially affect exercise performance, rather than their ability to prevent/treat AMS per se, their interrelationship will be discussed. Overall, we suggest that AZ hinders exercise performance in normoxia, but may be beneficial in hypoxia. Based upon head-to-head studies of AZ and MZ in humans on diaphragmatic and locomotor strength in normoxia, MZ may be a better CA inhibitor when exercise performance is crucial at high altitude.

[Ophthalmic drug therapy in professional athletes-what is allowed, what is doping?]

At first sight, ophthalmic drugs are not necessarily suspected of being used as performance-enhancing agents in competitive sports. However, there are some restrictions that must be noted, especially when certain drugs are taken orally. A structured analysis of the doping relevance of ophthalmic drugs was performed on the basis of a literature review, taking into account the current guidelines of the National Anti-Doping Agency of Germany and the World Anti-Doping Agency. Use of the most common ophthalmological drug groups is possible without restrictions, especially in the case of topical application. An exception is the oral use of diuretics, which is prohibited at all times. For glucocorticoids, topical application to the eye is allowed, but oral application is prohibited in competition. A similar restriction applies to the use of epinephrin, for which all forms of systemic application are prohibited in competition. When taking beta-blockers, the sport being played is the determining factor: use is prohibited in billiards, archery, darts, golf, motor sports, shooting sports, skiing/snowboarding, ski jumping, freestyle aerials/half pipe, snowboard half pipe/big air, and underwater sports. For shooting and archery, beta-blockers are also prohibited outside of competitions. Athletes with pre-existing ophthalmological conditions should seek comprehensive advice from an ophthalmologist before using any medication, and together they should choose a permissible active ingredient, consider the appropriate route of application, and, if necessary, apply for a Therapeutic Use Exemption. It is currently not known how many of the national and international athletes have to be treated with eye drops.

Hydration Strategies for Physical Activity and Endurance Events at High (>2500 m) Altitude: A Practical Management Article

A growing number of adventurous athletes are seeking new challenges through endurance events or physical activities held at high altitude (>2500 m). This coincides with a significant increase in the numbers of trekkers who ascend into the world's mountains. Altitude itself influences and complicates the athlete's effective and safe hydration. This article considers the physiology of adaptation to altitude and the effects on hydration at altitude compared with sea level, reviews the "ad libitum versus programmed hydration" controversy in conventional endurance event hydration, examines the evidence for extrapolation of sea level hydration strategies to the high-altitude environment, and synthesizes these disparate factors into a set of practical recommendations for hydration management during high-altitude physical activity. The guidelines will be relevant to participants of physical activity at altitude and health care staff who may care for them in the preparation or performance phases of their adventure.

Voluntary Increase of Minute Ventilation for Prevention of Acute Mountain Sickness

This study evaluated the feasibility and efficacy of voluntary sustained hyperventilation during rapid ascent to high altitude for the prevention of acute mountain sickness (AMS). Study subjects (n=32) were volunteer participants in a 2-day expedition to Mount Leoneras (4954 m), starting at 2800m (base camp at 4120 m). Subjects were randomized to either: 1) an intervention group using the voluntary hyperventilation (VH) technique targeting an end-tidal CO₂ (ETCO₂)<20 mmHg; or 2) a group using acetazolamide (AZ). During the expedition, respiratory rate (28±20 vs. 18±5 breaths/min, mean±SD, P<0.01) and SpO₂ (95%±4% vs. 89%±5%, mean±SD, P<0.01) were higher, and ETCO₂ (17±4 vs. 26±4 mmHg, mean±SD, P<0.01) was lower in the VH group compared to the AZ group - as repeatedly measured at equal fixed intervals during the ascent - showing the feasibility of the VH technique. Regarding efficacy, the incidence of 6 (40%) subjects registering an LLS score≥3 in the VH group was non-inferior to the 3 (18%) subjects in the acetazolamide group (P=0.16, power 28%). Voluntary increase in minute ventilation is a feasible technique, but - despite the underpowered non-inferiority in this small-scale proof-of-concept trial - it is not likely to be as effective as acetazolamide to prevent AMS.

Exogenous Ketone Supplements in Athletic Contexts: Past, Present, and Future

The ketone bodies acetoacetate (AcAc) and β-hydroxybutyrate (βHB) have pleiotropic effects in multiple organs including brain, heart, and skeletal muscle by serving as an alternative substrate for energy provision, and by modulating inflammation, oxidative stress, catabolic processes, and gene expression. Of particular relevance to athletes are the metabolic actions of ketone bodies to alter substrate utilisation through attenuating glucose utilisation in peripheral tissues, anti-lipolytic effects on adipose tissue, and attenuation of proteolysis in skeletal muscle. There has been long-standing interest in the development of ingestible forms of ketone bodies that has recently resulted in the commercial availability of exogenous ketone supplements (EKS). These supplements in the form of ketone salts and ketone esters, in addition to ketogenic compounds such as 1,3-butanediol and medium chain triglycerides, facilitate an acute transient increase in circulating AcAc and βHB concentrations, which has been termed 'acute nutritional ketosis' or 'intermittent exogenous ketosis'. Some studies have suggested beneficial effects of EKS to endurance performance, recovery, and overreaching, although many studies have failed to observe benefits of acute nutritional ketosis on performance or recovery. The present review explores the rationale and historical development of EKS, the mechanistic basis for their proposed effects, both positive and negative, and evidence to date for their effects on exercise performance and recovery outcomes before concluding with a discussion of methodological considerations and future directions in this field.

Altitude, Acute Mountain Sickness, and Acetazolamide: Recommendations for Rapid Ascent

Toussaint, Claudia M., Robert W. Kenefick, Frank A. Petrassi, Stephen R. Muza, and Nisha Charkoudian. Altitude, acute mountain sickness, and acetazolamide: recommendations for rapid ascent. High Alt Med Biol. 22:5-13, 2021. Background: Sea level natives ascending rapidly to altitudes above 1,500 m often develop acute mountain sickness (AMS), including nausea, headaches, fatigue, and lightheadedness. Acetazolamide (AZ), a carbonic anhydrase inhibitor, is a commonly used medication for the prevention and treatment of AMS. However, there is continued debate about appropriate dosing, particularly when considering rapid and physically demanding ascents to elevations above 3,500 m by emergency medical and military personnel. Aims: Our goal in the present analysis was to evaluate and synthesize the current literature regarding the use of AZ to determine the most effective dosing for prophylaxis and treatment of AMS for rapid ascents to elevations >3,500 m. These circumstances are specifically relevant to military and emergency medical personnel who often need to ascend rapidly and perform physically demanding tasks upon arrival at altitude. Methods: We conducted a literature search from April 2018 to February 2020 using PubMed, Google Scholar, and Web of Science to identify randomized controlled trials that compared AZ with placebo or other treatment with the primary endpoint of AMS incidence and severity. We included only research articles/studies that focused on evaluation of AZ use during rapid ascent. Results: Four doses of AZ (125, 250, 500, and 750 mg daily) were identified as efficacious in decreasing the incidence and/or severity of AMS during rapid ascents, with evidence of enhanced effectiveness with higher doses. Conclusions: For military, emergency medical, or other activities involving rapid ascent to altitudes >3,500 m, doses 500-750 mg/day within 24 hours of altitude exposure appear to be the most effective for minimizing symptoms of AMS.

Effects of daily ingestion of sodium bicarbonate on acid-base status and anaerobic performance during an altitude sojourn at high altitude: a randomized controlled trial

Background

The present study investigated the effects of chronic sodium bicarbonate (NaHCO₃) ingestion on a single bout of high-intensity exercise and on acid-base balance during 7-day high-altitude exposure.

Methods

Ten recreationally active subjects participated in a pre-test at sea level and a 7-day hiking tour in the Swiss Alps up to 4554 m above sea level. Subjects received either a daily dose of 0.3 g/kg NaHCO₃ solution (n = 5) or water as a placebo (n = 5) for 7 days. Anaerobic high-intensity exercise performance was assessed using the portable tethered sprint running (PTSR) test under normoxic and hypoxic conditions (3585 m). PTSR tests assessed overall peak force, mean force, and fatigue index. Blood lactate levels and blood gas parameters were assessed pre- and post-PTSR. Urinary pH and blood gas parameters were further analyzed daily at rest in early morning samples under normoxic and hypoxic conditions.

Results

There were no significant differences between the bicarbonate and control group in any of the PTSR-related parameters. However, urinary pH (p = 0.003, ηp² = 0.458), early morning blood bicarbonate concentration (p < 0.001, ηp² = 0.457) and base excess (p = 0.002, ηp² = 0.436) were significantly higher in the bicarbonate group compared with the control group under hypoxic conditions.

Conclusions

These results indicate that oral NaHCO₃ ingestion does not ameliorate the hypoxia-induced impairment in anaerobic, high-intensity exercise performance, represented by PTSR-related test parameters, under hypobaric, hypoxic conditions, but the maximal performance measurements may have been negatively affected by other factors, such as poor implementation of PTSR test instructions, pre-acclimatization, the time course of hypoxia-induced renal [HCO₃⁻] compensation, changes in the concentrations of intra- and extracellular ions others than [H⁺] and [HCO₃⁻], or gastrointestinal disturbances caused by NaHCO₃ ingestion. However, chronic NaHCO₃ ingestion improves blood bicarbonate concentration and base excess at altitude, which partially represent the blood buffering capacity.

Acetazolamide does not alter endurance exercise performance at 3,500-m altitude

Acetazolamide (AZ) is a medication commonly used to prevent acute mountain sickness (AMS) during rapid ascent to high altitude. However, it is unclear whether AZ use impairs exercise performance; previous literature regarding this topic is equivocal. The purpose of this study was to evaluate the impact of AZ on time-trial (TT) performance during a 30-h exposure to hypobaric hypoxia equivalent to 3,500-m altitude. Ten men [sea-level peak oxygen consumption (VO₂peak): 50.8 ± 6.5 mL·kg^-1·min^-1; body fat %: 20.6 ± 5.2%] completed 2 30-h exposures at 3,500 m. In a crossover study design, subjects were given 500 mg/day of either AZ or a placebo. Exercise testing was completed 2 h and 24 h after ascent and consisted of 15-min steady-state treadmill walking at 40%-45% sea-level VO₂peak, followed by a 2-mile self-paced treadmill TT. AMS was assessed after ~12 h and 22 h at 3,500 m. The incidence of AMS decreased from 40% with placebo to 0% with AZ. Oxygen saturation was higher (P < 0.05) in AZ versus placebo trials at the end of the TT after 2 h (85 ± 3% vs. 79 ± 3%) and 24 h (86 ± 3% vs. 81 ± 4%). There was no difference in time to complete 2 miles between AZ and PL after 2 h (20.7 ± 3.2 vs. 22.7 ± 5.0 min, P > 0.05) or 24 h (21.5 ± 3.4 vs. 21.1 ± 2.9 min, P > 0.05) of exposure to altitude. Our results suggest that AZ (500 mg/day) does not negatively impact endurance exercise performance at 3,500 m.NEW & NOTEWORTHY To our knowledge, this is the first study to examine the impact of acetazolamide (500 mg/day) versus placebo on self-paced, peak-effort exercise performance using a short-duration exercise test in a hypobaric hypoxic environment with a repeated-measures design. In the present study, acetazolamide did not impact exercise performance after 2-h or 24-h exposure to 3,500-m simulated altitude.

Comparison of blood carbonic anhydrase activity of athletes performing interval and continuous running exercise at high altitude

The effects of high-intensity interval and continuous exercise on erythrocytes carbonic anhydrase (CA, EC 4.2.1.1) activity levels were scarcely investigated up until now. Here we present a study focused on the CA activity from erythrocytes of athletes experiencing interval and continuous training for 6 weeks, during cold weather and at high altitude (> 1600 m). We observed a 50% increase in the blood CA activity at the second week after initiation of the training in both interval and continuos running groups, whereas the control group did not experience any variation in the enzyme activity levels. In the trained individuals a mild decrease in their body mass, BMI and an increased [Formula: see text] were also observed. The CA activity returned at the basal values after 4-6 weeks after the training started, probably proving that a metabolic compensation occurred without the need of an enhanced enzyme activity. The unexpected 50% rise of activity for an enzyme which acts as a very efficient catalyst for CO2 hydration/bicarbonate dehydration, such as the blood CA, deserves further investigations for better understanding the physiologic basis of this phenomenon.