Sildenafil does not improve performance in 16.1 km cycle exercise time-trial in acute hypoxia

Decreased Work Capability Related to High-Altitude Exposure

Background

The unique environment of high altitude can affect the work capacity of those not accustomed to it, and in some cases, it can even endanger their lives. Studying the effect of high-altitude exposure on work capacity is important. Still, there are few reviews on this topic. We aimed to summarize the parameters used to evaluate work capability in a high-altitude environment, the potential pathophysiological mechanisms, and the available pharmacological and non-pharmacological strategies for improvement.

Methods

We conducted searches on PubMed, Google Scholar, and China National Knowledge Infrastructure to explore the existing literature including basic and clinical studies from 1968 to 2023, using keywords such as "work capability/performance and high-altitude hypoxia" or "work/exercise at high altitude". Conference proceedings, notes, and case reports were excluded. The CiteSpace 6.1.R3 was used for de-duplication.

Results

A total of 727 papers were identified through search terms from the database. 486 papers were eliminated following the de-duplication process, lacking full text and deemed irrelevant to this article. Among the remaining 241 papers, 21 investigate the underlying mechanisms of reduced work capability due to altitude exposure, and 94 papers discuss measures to improve work capability when exposed to high altitudes.

Conclusion

In conclusion, this review summarizes the evaluation of indicators, pathomechanisms, and improvement measures for high-altitude exposure-related changes in work capability. More basic research on its mechanisms and large-sample, randomized controlled clinical studies to validate its effects are needed.

Exploring the Potential Benefits of Interventions When Addressing Simulated Altitude Hypoxia during Male Cyclist Sports: A Systematic Review

Training in hypoxic environments enhances endurance, but the various influences of training protocols and supplementation for efficient performance are not yet clear. This systematic review explored the effects of different supplementations and interventions used to optimize the aerobic and anaerobic performance of cyclists. Data were collected from the following sources: PubMed, Google Scholar, EMBASE, WOS, Cochrane Central Register of Controlled Trials, and randomized controlled trials (RCTs). Studies that explored the effects of supplementation or intervention during cycling were selected for analysis. Five studies (67 male cyclists; mean age, 23.74–33.56 years) reported different outcomes from supplementation or intervention during the acute hypoxia of cyclists. Three studies (42 male cyclists; mean age, 25.88–36.22 years) listed the benefits of beetroot juice in preserving SpO2 (pulse oxygen saturation) and enhancing high-intensity endurance performance, effectively preventing the reduction in power output. This systematic review provided evidence that the different effects of ischemic preconditioning (IPC), sildenafil, and beetroot (BR) supplementation and intervention did not present a statistically greater benefit than for normoxia groups, but BR supplementation promoted the benefits of SpO2. Future research should evaluate the duration and higher FiO2 (simulated altitude, hypoxia) levels of hypoxia in training protocols for cyclists. This is important when determining the effectiveness of supplements or interventions in hypoxic conditions and their impact on sports performance, particularly in terms of power output.

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.

EFFECT OF CREATINE AND SILDENAFIL CITRATE ON THE PHYSICAL PERFORMANCE OF MICE

ABSTRACT Introduction: The use of substances to enhance sports performance among professional and amateur athletes is increasing. Such substances may either be included in the group of dietary supplements or fall into pharmacological classes. Every substance used for this purpose is called an ergogenic agent. The number of ergogenic options available increases every day, favoring overuse and use without proper guidance. Among the dietary supplements, we highlight the use of creatine, a substance widespread in sports. Among the pharmacological groups, many drugs are used. Recently the use of sildenafil citrate by professional athletes from various predominantly aerobic sports modalities was reported in the media. Objective: To compare and demonstrate the responses caused by physical training associated with the use of creatine and sildenafil citrate in mice. Methods: A swim training protocol was applied and then an electrophysiograph was used in order to obtain parameters related to contraction intensity, the area under the curve and the percentage drop. Results: The responses obtained demonstrated the ergogenic action of creatine because it altered the parameters used for measurement. The use of sildenafil citrate did not yield satisfactory results to frame the drug as an ergogenic agent. Conclusion: Creatine has an ergogenic effect, reducing the percentage drop after 10 seconds, while sildenafil demonstrated no ergogenic potential and, interestingly, resulted in weaker responses when compared to the exercise groups. Evidence level II; Comparative prospective study .

Is the healthy respiratory system built just right, overbuilt, or underbuilt to meet the demands imposed by exercise?

In the healthy, untrained young adult, a case is made for a respiratory system (airways, pulmonary vasculature, lung parenchyma, respiratory muscles, and neural ventilatory control system) that is near ideally designed to ensure a highly efficient, homeostatic response to exercise of varying intensities and durations. Our aim was then to consider circumstances in which the intra/extrathoracic airways, pulmonary vasculature, respiratory muscles, and/or blood-gas distribution are underbuilt or inadequately regulated relative to the demands imposed by the cardiovascular system. In these instances, the respiratory system presents a significant limitation to O₂ transport and contributes to the occurrence of locomotor muscle fatigue, inhibition of central locomotor output, and exercise performance. Most prominent in these examples of an "underbuilt" respiratory system are highly trained endurance athletes, with additional influences of sex, aging, hypoxic environments, and the highly inbred equine. We summarize by evaluating the relative influences of these respiratory system limitations on exercise performance and their impact on pathophysiology and provide recommendations for future investigation.

Perfusion of Intrapulmonary Arteriovenous Anastomoses Is Not Related to VO2max in Hypoxia and Is Unchanged by Oral Sildenafil

Background: Perfusion of intrapulmonary arteriovenous anastomoses (IPAVA) is increased during exercise and in hypoxia and is associated with variations in oxygen saturation (S_PO₂), resulting in blood bypassing the pulmonary microcirculation. Sildenafil is a pulmonary vasodilator that improves S_PO₂ and endurance performance in hypoxia. The purpose of this study was to determine if 50 mg sildenafil would reduce IPAVA perfusion (Q_IPAVA) and if the decrement in maximal exercise capacity (VO_2max) in hypoxia is related to Q_IPAVA. We hypothesized that during progressive levels of hypoxia at rest (F_IO₂ = 0.21, 0.14, 0.12), sildenafil would increase S_PO₂ and reduce bubble score (estimate of Q_IPAVA) compared to placebo, and that the decrement in VO_2max in hypoxia would be positively correlated with bubble score at rest in hypoxia. Materials and Methods: Fourteen endurance-trained men performed a graded maximal exercise test at sea level and at a simulated altitude of 3000 m, followed by two experimental visits where, after randomly ingesting sildenafil or placebo, they underwent agitated saline contrast echocardiography during progressive levels of hypoxia at rest. Results: All participants experienced a decrement in power output in hypoxia that ranged from 9% to 19% lower than sea level values. Compared to normoxia, bubble score increased significantly in hypoxia (p < 0.001) with no effect of sildenafil (p = 0.580). There was a negative correlation between S_PO₂ and bubble score (p < 0.001). The decrement in peak power output at VO_2max in hypoxia was unrelated to IPAVA perfusion in resting hypoxia (p = 0.32). Several participants demonstrated Q_IPAVA greater than zero in room air, indicating that arterial hypoxemia may not be the sole mechanism for Q_IPAVA. Conclusion: These results indicate that the VO_2max decrement caused by hypoxia is not related to Q_IPAVA and that sildenafil does not improve VO_2max in hypoxia through modulation of Q_IPAVA.

Sildenafil does not reliably improve exercise performance in hypoxia: a systematic review

Objective

Sildenafil is a pulmonary vasodilator that may reduce the decrement in endurance performance in moderate hypoxia. We assessed the efficacy of sildenafil to improve performance in hypoxia.

Data sources/eligibility Criteria

We systematically searched electronic databases (until August 2018) for randomised trials comparing sildenafil with placebo. We also examined the effect of sildenafil on pulmonary artery pressure (PAP), cardiac output (CO) and pulse oxygen saturation (S_PO₂) compared with placebo in hypoxia. Fourteen studies were included; 210 subjects received sildenafil 40, 50 or 100 mg/day.

Results

Sildenafil showed a large effect for decreasing PAP during exercise and at rest, a small effect for increasing CO during exercise and a moderate effect at rest, a moderate effect for increasing S_PO₂ and a small effect for improving performance. In a subgroup analysis, there was no statistically significant difference between 100 and 50 mg sildenafil dose on S_PO₂. Sildenafil had a moderate effect on increasing S_PO₂ and performance at terrestrial hypobaric altitude but only a small effect on both in normobaric hypoxia. Regression analysis showed that hypoxic dose (PO₂) and metabolic rate do not account for a significant portion of the variance in effect size for sildenafil on PAP, CO, S_PO₂ and performance.

Conclusion

This meta-analysis indicates that sildenafil reduces PAP, has a moderate to small effect on CO and S_PO₂, and no effect on performance.