Heart Rate Variability, or simply HRV, is becoming more and more used in different fields, from an instrument able to diagnose cardiovascular anomalies, to a tool instrumental in improving high performance sports training. Many of us who are seriously into physical activities and sports practicing are familiar with or even have used one of the many apps available for watches or smart phones. But do we really know what they are?
Well, HRV is simply the variance in the interval between two heat beats. Or to be more precise, the changes in the interval between successive normal heartbeats. Usually, this is assessed through the timing between QRS complexes, which are main spikes as seen in a continuous electrocardiographic recording (ECG). HRV is the result of the balance between the sympathetic and the parasympathetic branches of the autonomic nervous system (ANS), as well as of other non-neural sources of variation. From a practical standpoint, it is as simple as a collection of time intervals, or for those more familiar with mathematical terms, it is a time series (a series of data points indexed by time).
Typically, these time intervals are not fixed or static but can vary widely moment to moment in response to input from the sympathetic and the parasympathetic branches of the autonomic nervous system, which control the contraction and relaxation of the cardiac muscle. Each system is activated by multiple receptors, responding to arterial pressure (baroreceptors), oxygen, and CO2 levels, as well as endogenous substances, emotions, immunological alterations, among other stimuli.
The parasympathetic branch, which regulates your energy and helps your body recover during rest periods, is mediated mainly by acetylcholine and is responsible for maintaining homeostatic heart frequencies and contractility without exhausting. It is responsible for short-term fluctuations of the heart frequency, and it operates in a frequency between 9 to 25 cycles per minute or 0.15Hz to 0.4Hz. Note that Hertz (Hz) is an international metric of frequency and is defined as one cycle per second (cpm).
Conversely, the sympathetic branch, which regulates your “fight or flight” stress impulses, is mediated mainly by norepinephrine, and its activity is triggered by stress, increasing cardiac energy demand by increasing heart rate . This branch is responsible for longer-term fluctuations of the heart frequency, operating in a lower bandwidth of 0.04Hz to 0.15Hz (or 2 to 9 cycles per minute).
HRV is commonly studied in the time and frequency domains, that is as a function of time and frequency. Different HRV indicators have been associated with sympathetic or parasympathetic activity. Additionally, there is an important association between specific frequencies and the baroreflex function, which provides a rapid negative feedback loop to adjust our heart frequency in order to maintain blood pressure at nearly constant levels.
But wait, what do time and frequency domains mean?
Let us start with the simpler one, time domain. In mathematics, the domain of a function is the set into which all of the input of the function is constrained to fall; therefore, when the term time domain is used, it simply means that we are doing our analysis based on time intervals extracted from the ECG recording. There are many indicators that have been created to study the variance in the intervals but here we will discuss only two of them, SDNN and RMSSD.
SDNN is the standard deviation, a measure of variation, of the time interval between heart beats (the R-R interval), and reflects all the cyclic components responsible for variability. The greater the SDNN, that is the variation between beats, the better. RMSSD is the square root of the mean squared differences of successive R-R intervals, or the variance of the variance of our time series, and is considered to be related to the parasympathetic activity. Both, SDNN and RMSSD are powerful indicators of our cardiovascular health, since the loss of variance between intervals is associated with many cardiovascular and/or inflammatory diseases. As shown below in Figure 3, we want our heart rate frequency to fluctuate a lot over time.
Now that the main time domain indicators have been defined, let us move to the frequency domain. But first, we need to understand one important math concept: any function or time series—think of the graph of a curve—can be re-written as a summation of sine and cosine functions, which are used to model phenomena such as sound and light waves. This idea was first introduced by Jean Baptiste Fourier in 1882 in his work Théorie analytique de la chaleur and later became known as Fourier series.
Figure 1 shows an example, using an arbitrarily chosen function:fx=x3+ x2+3x+5, plotted in the interval ]-π to π [. The resulting data shown as a curve can be reconstructed using a summation of sines and cosine functions through a Fourier series. In this case, twenty sine/cosine functions were used to approximate the curve, while in Figure 2, fifty functions were used.
It is easy to see from the diagrams that, the more functions we use, the greater the precision in the reconstruction of the original data. In both cases, we are using the sum of sine and cosine or “wave” functions to approximate the curve fx=x3+ x2+3x+5 in an ordered way. Each of the component sine and cosine functions correspond to a specific frequency. In this way, a curve can be broken down into its constituent frequencies.
Figure 3 shows the intervals between heart beats i.e., the R-R intervals extracted from a ECG recording and plotted against the time domain, which shows the variation of the heart rate frequency over time.
The next step is to approximate the waveform or curve formed by the heart beat data displayed in Figure 3 as a summation of functions through the Fourier series. This enables us to determine all the frequencies that are acting in our system. The frequency domain indicators are thought of as the “power” associated with each frequency—think of it as the relative contribution of that frequency in the re-construction of the curve formed by the data and calculated through a Fourier transform. These are usually plotted in a spectrogram, a graph where the x axis corresponds to the frequencies and the y axis to each frequency’s power or contribution, like the one displayed in Figure 4.
Now we are ready to define each one of the frequency domain indicators, categorized according to its associated frequency. They are:
- Ultra-low and Very-low Frequencies: 0.01 to 0.04 Hz, not relevant in most cases, due to the relatively short ECG recording usually used.
- Low Frequencies (LF): 0.04 to 0.15 Hz
- High Frequencies (HF): 0.15 to 0.4 Hz
In the beginning of this article, we noted that the branches of the autonomic nervous system (ANS), that is the sympathetic and the parasympathetic branches operate in different frequencies. Based on that, we can see that different HRV indicators in the frequency domain might be associated with sympathetic or parasympathetic activity.
High frequencies are highly impacted by the respiratory pattern, while low frequencies are affected by both the sympathetic and the parasympathetic branches of the ANS. Therefore, by analyzing the power or contribution associated with different frequencies, we can make inferences about the activity of each of the branches of the ANS and their interaction with other systems.
So, why does that matter?
Going back to the beginning of this article, most of the applications, i.e., “apps” used by smart phones and watches to track HRV perform their analysis are based on SDNN, which is a simple-to-calculate and powerful HRV indicator. It’s use is based on the idea that after a workout, the activity of the sympathetic branch temporarily prevails, reducing the overall variability and hence the SDNN.
In this sense, the tool can be used to avoid overtraining, adjusting the intensity of the training session according to the monitored HRV, until the measured SDNN returns to its pre-training values. The same concept can be used to measure stress levels. In theory, all other factors being the same, the more stressed we are, the less variability, and therefore a lower SDNN can be expected. In both cases, the exercise and the stress will likely induce a temporary preponderance of the sympathetic branch.
Now that we know how to analyze it and we understand that different systems are likely to be associated with different frequencies, we can understand why historically HRV was seen as a good measure of imbalances in the ANS. Probably the best way to describe HRV would be as a surrogate measure of the complex interaction between the brain and the cardiovascular system.
So how does that relate to diving?
It has been demonstrated by many studies that a reduced HRV is related to decreased life expectancy. A reduction in HRV has been reported in several cardiological and non-cardiological diseases, ranging from diabetes to renal failure, to mention a few [2,3,4]. A reduction in HRV, when analyzed in the frequency domain has also been associated with inflammatory processes [4, 5].
It is interesting to note, however, that due to huge inter-individual variance, it is difficult to establish expected HRV parameters for a population, and although some interesting studies have been published over the years, there is no consensus on standard values for each one of the HRV parameters. On the other hand, intrasubject analysis, that is the variation of HRV for the same individual over time, can offer very important insights.
Scuba diving is known to trigger oxidative and inflammatory processes, causing a variety of alterations in our physiology, ranging from loss of endothelial function , that is the capacity of the vascular endothelium to respond to vasodilator stimulus, to the activation of the innate immune system and production of microparticles  i.e., particles shed by different cells, which carry nuclear components of their originating cells, like RNA and DNA, and are involved in cell signaling and communication.
As one could imagine, scuba diving is also related to alterations in HRV  and by studying the pattern of these alterations we could infer how our bodies are responding to a dive and, in particular, to the decompression. Our recent study demonstrated that HRV is negatively associated with the production of microparticles and that, using a model built with machine learning, it was possible to predict the pre to post dive variation of the HRV, based on the variation of specific inflammatory markers, linking inflammation and oxidative stress to HRV in scuba diving.
In the past decade, many studies have demonstrated that the presence of inflammatory processes are linked to lowering HRV (either in the time or frequency domains). In our study we demonstrated the inflammatory and oxidative process related to diving are also related to changes in HRV and, interestingly enough, to a preponderance of the sympathetic branch in cases where the volunteers presented more intense responses to the decompression. This fact is also probably linked to the loss of endothelial function, long observed to happen after diving, although the mechanisms are, at this point, not completely clear.
There is still a lot to be understood about the relationship of HRV alterations and diving. The hyperoxia, i.e., exposure to pressures of oxygen higher than 0.5 ATA associated with diving, has its own effects on HRV, making interpretation of HRV variations in diving even more complex. The long-term goal of our research is to better understand individual responses to decompression. We believe HRV variations can be a powerful tool to achieve this objective.
Our team has been working in cooperation with DAN Europe, which has a huge database of diving profiles and outcomes, and some interesting models are being created to model the oxidative and inflammatory processes, but there is still a long way to go before these models can be used in any practical application. However, it is a promising field, and its comprehension will surely help in the full understanding of decompression physiology, making this subject certainly something interesting for the diving community. We could even dream about being able to adjust our dive profiles based on individual responses, right? Watch this space.
- Ernst G. Heart-Rate Variability—More than Heart Beats? Front Public Heal. 2017;5(September):1-12. doi:10.3389/fpubh.2017.00240
- Malliani A, Pagani M, Lombardi F, Cerutti S. Cardiovascular neural regulation explored in the frequency domain. Circulation. 1991;84(2):482-492. doi:10.1161/01.CIR.84.2.482
- Appel ML, Berger RD, Saul JP, Smith JM, Cohen RJ. Beat to beat variability in cardiovascular variables: Noise or music? J Am Coll Cardiol. 1989;14(5):1139-1148. doi:10.1016/0735-1097(89)90408-7
- Sloan RP. Heart Rate Variability Predicts Levels of Inflammatory Markers: Evidence for the Vagal Anti-Inflammatory Pathway. 2015;(Bernik 2002):94-100. doi:10.1016/j.bbi.2014.12.017.Heart
- Adam Moser, Kevin Range and DMY. Relationship between Heart Rate Variability, Interleukin-6, and Soluble Tissue Factor in Healthy Subjects. Bone. 2008;23(1):1-7. doi:10.1038/jid.2014.371
- Brubakk AO, Duplancic D, Valic Z, et al. A single air dive reduces arterial endothelial function in man. J Physiol. 2005;566(3):901-906. doi:10.1113/jphysiol.2005.089862
- Thom SR, Bennett M, Banham ND, et al. Association of microparticles and neutrophil activation with decompression sickness. J Appl Physiol. 2015;119(5):427-434. doi:10.1152/japplphysiol.00380.2015
- Schirato SR, El-dash I, El-dash V, Natali JE, Starzynski PN, Chaui-berlinck JG. Heart rate variability changes as an indicator of decompression-related physiological stress. Undersea Hyperb Med. 2018;Mar-Apr 20:173-182.
- Schirato et al. Association between Heart Rate Variability and decompression-induced physiological stress. Front. Physiol. Front. Physiol., 03 July 2020
- Schirato’s Talk at the 2019 GUE Conference: Heart Rate Variability: What it is and Why it Matters
- From GUE’s membership magazine QUEST: Decompression: Revisiting Old Assumptions by S.Rhein Schirato
Brazilian scientist, Sergio Rhein Schirato, is a hedge fund manager and a researcher at the Laboratory of Energetics and Theoretical Physiology of the Biosciences Institute of the University of Sao Paulo (USP). He holds a PhD in Sciences, a Masters in Finance jointly granted by New York University and London School of Economics and post graduation in applied Math. His current research includes the application of neural networks in decompression modeling and heart rate variability. Additionally, he is a GUE Fundamentals and Rec 1, 2 and 3 instructor, as well as GUE Rebreather certified diver.
Twenty-five Years in the Pursuit of Excellence – The Evolution and Future of GUE
Founder and president Jarrod Jablonski describes his more than a quarter of a century long quest to promote excellence in technical diving.
by Jarrod Jablonski. Images courtesy of J. Jablonski and GUE unless noted.
The most difficult challenges we confront in our lives are the most formative and are instrumental in shaping the person we become. When I founded Global Underwater Explorers (GUE), the younger version of myself could not have foreseen all the challenges I would face, but equally true is that he would not have known the joy, the cherished relationships, the sense of purpose, the rich adventures, the humbling expressions of appreciation from those impacted, or the satisfaction of seeing the organization evolve and reshape our industry. Many kindred souls and extraordinary events have shaped these last 25 years, and an annotated chronology of GUE is included in this issue of InDEPTH. This timeline, however, will fail to capture the heart behind the creation of GUE, it will miss the passionate determination currently directing GUE, or the committed dedication ready to guide the next 25 years.
I don’t remember a time that I was not in, around, and under the water. Having learned to swim before I could walk, my mother helped infuse a deep connection to the aquatic world. I was scuba certified in South Florida with my father, and promptly took all our gear to North Florida where I became a dive instructor at the University of Florida. It was then that I began my infatuation with cave diving. I was in the perfect place for it, and my insatiable curiosity was multiplied while exploring new environments. I found myself with a strong desire to visit unique and hard-to-reach places, be they far inside a cave or deep within the ocean.
My enthusiasm for learning was pressed into service as an educator, and I became enamored with sharing these special environments. Along with this desire to share the beauty and uniqueness of underwater caves was a focused wish to assist people in acquiring the skills I could see they needed to support their personal diving goals. It could be said that these early experiences were the seeds that would germinate, grow, mature, and bloom into the organizing principles for GUE.
The Pre-GUE Years
Before jumping into the formational days of GUE, allow me to help you visualize the environment that was the incubator for the idea that became GUE’s reality. By the mid-1990s, I was deeply involved in a variety of exploration activities and had been striving to refine my own teaching capacity alongside this growing obsession for exploratory diving. While teaching my open water students, I was in the habit of practicing to refine my own trim and buoyancy, noticing that the students quickly progressed and were mostly able to copy my position in the water. Rather than jump immediately into the skills that were prescribed, I started to take more time to refine their comfort and general competency. This subtle shift made a world of difference in the training outcomes, creating impressive divers with only slightly more time and a shift in focus. In fact, the local dive boats would often stare in disbelief when told these divers were freshly certified, saying they looked better than most open water instructors!
By this point in my career, I could see the problems I was confronting were more systemic and less individualistic. In retrospect, it seemed obvious that key principles had been missing in both my recreational and technical education, not to mention the instructor training I received. The lack of basic skill refinement seemed to occur at all levels of training, from the beginner to the advanced diver. Core skills like buoyancy or in-water control were mainly left for divers to figure out on their own and almost nobody had a meaningful emphasis on efficient movement in the water. It was nearly unheard of to fail people in scuba diving, and even delaying certification for people with weak skills was very unusual. This remains all too common to this day, but I believe GUE has shifted the focus in important ways, encouraging people to think of certification more as a process and less as a right granted to them because they paid for training.
The weakness in skill refinement during dive training was further amplified by little-to-no training in how to handle problems when they developed while diving, as they always do. In those days, even technical/cave training had very little in the way of realistic training in problem resolution. The rare practice of failures was deeply disconnected from reality. For example, there was almost no realistic scenario training for things like a failed regulator or light. What little practice there was wasn’t integrated into the actual dive and seemed largely useless in preparing for real problems. I began testing some of my students with mock equipment failures, and I was shocked at how poorly even the best students performed. They were able to quickly develop the needed skills, but seeing how badly most handled their first attempts left me troubled about the response of most certified divers should they experience problems while diving, as they inevitably would.
Meanwhile, I was surrounded by a continual progression of diving fatalities, and most appeared entirely preventable. The loss of dear friends and close associates had a deep impact on my view of dive training and especially on the procedures being emphasized at that time within the community. The industry, in those early days, was wholly focused on deep air and solo diving. However, alarmingly lacking were clear bottle marking or gas switching protocols. It seemed to me to be no coincidence that diver after diver lost their lives simply because they breathed the wrong bottle at depth. Many others died mysteriously during solo dives or while deep diving with air.
One of the more impactful fatalities was Bob McGuire, who was a drill sergeant, friend, and occasional dive buddy. He was normally very careful and focused. One day a small problem with one regulator caused him to switch regulators before getting in the water. He was using a system that used color-coded regulators to identify the gas breathed. When switching the broken regulator, he either did not remember or did not have an appropriately colored regulator. This small mistake cost him his life. I clearly remember turning that one around in my head quite a bit. Something that trivial should not result in the loss of a life.
Also disturbing was the double fatality of good friends, Chris and Chrissy Rouse, who lost their lives while diving a German U-boat in 70 m/230 ft of water off the coast of New Jersey. I remember, as if the conversation with Chris were yesterday, asking him not to use air and even offering to support the cost as a counter to his argument about the cost of helium. And the tragedies continued: The loss of one of my closest friends Sherwood Schille, the death of my friend Steve Berman who lived next to me and with whom I had dived hundreds of times, the shock of losing pioneering explorer Sheck Exley, the regular stream of tech divers, and the half dozen body recoveries I made over only a couple years, which not only saddened me greatly, but also made me angry. Clearly, a radically different approach was needed.
Learning to Explore
Meanwhile, my own exploration activities were expanding rapidly. Our teams were seeking every opportunity to grow their capability while reducing unnecessary risk. To that end, we ceased deep air diving and instituted a series of common protocols with standardized equipment configurations, both of which showed great promise in expanding safety, efficiency, and comfort. We got a lot of things wrong and experienced enough near misses to keep us sharp and in search of continual improvement.
But we looked carefully at every aspect of our diving, seeking ways to advance safety, efficiency, and all-around competency while focusing plenty of attention into the uncommon practice of large-scale, team diving, utilizing setup dives, safety divers, and inwater support. We developed diver propulsion vehicle (DPV) towing techniques, which is something that had not been done previously. We mostly ignored and then rewrote CNS oxygen toxicity calculations, developed novel strategies for calculating decompression time, and created and refined standard procedures for everything from bottle switching to equipment configurations. Many of these developments arose from simple necessity. There were no available decompression programs and no decompression tables available for the dives we were doing. Commonly used calculations designed to reduce the risk of oxygen toxicity were useless to our teams, because even our more casual dives were 10, 20, or even 30 times the allowable limit. The industry today takes most of this for granted, but in the early days of technical diving, we had very few tools, save a deep motivation to go where no one had gone before.
Many of these adventures included friends in the Woodville Karst Plain Project (WKPP), where I refined policies within the team and most directly with longtime dive buddy George Irvine. This “Doing it Right” (DIR) approach sought to create a more expansive system than Hogarthian diving, which itself had been born in the early years of the WKPP and was named after William Hogarth Main, a friend and frequent dive buddy of the time. By this point, I had been writing about and expanding upon Hogarthian diving for many years. More and more of the ideas we wanted to develop were not Bill Main’s priorities and lumping them into his namesake became impractical, especially given all the debate within the community over what was and was not Hogarthian.
A similar move from DIR occurred some years later when GUE stepped away from the circular debates that sought to explain DIR and embraced a GUE configuration with standard protocols, something entirely within our scope to define.
These accumulating events reached critical mass in 1998. I had experienced strong resistance to any form of standardization, even having been asked to join a special meeting of the board of directors (BOD) for a prominent cave diving agency. Their intention was to discourage me from using any form of standard configuration, claiming that students should be allowed to do whatever they “felt’ was best. It was disconcerting for me, as a young instructor, to be challenged by pioneers in the sport; nevertheless, I couldn’t agree with the edict that someone who was doing something for the first time should be tasked with determining how it should be done.
This sort of discussion was common, but the final straw occurred when I was approached by the head of a technical diving agency, an organization for which I had taught for many years. I was informed that he considered it a violation of standards not to teach air to a depth of at least 57 m/190 ft. This same individual told me that I had to stop using MOD bottle markings and fall in line with the other practices endorsed by his agency. Push had finally come to shove, and I set out to legitimize the training methods and dive protocols that had been incubating in my mind and refined with our teams over the previous decade. Years of trial and many errors while operating in dynamic and challenging environments were helping us to identify what practices were most successful in support of excellence, safety, and enjoyment.
Forming GUE as a non-profit company was intended to neutralize the profit motivations that appeared to plague other agencies. We hoped to remove the incentive to train—and certify—the greatest number of divers as quickly as possible because it seemed at odds with ensuring comfortable and capable divers. The absence of a profit motive complemented the aspirational plans that longtime friend Todd Kincaid and I had dreamed of. We imagined a global organization that would facilitate the efforts of underwater explorers while supporting scientific research and conservation initiatives.
I hoped to create an agency that placed most of the revenue in the hands of fully engaged and enthusiastic instructors, allowing them the chance to earn a good living and become professionals who might stay within the industry over many years. Of course, that required forgoing the personal benefit of ownership and reduced the revenue available to the agency, braking its growth and complicating expansion plans. This not only slowed growth but provided huge challenges in developing a proper support network while creating the agency I envisioned. There were years of stressful days and nights because of the need to forgo compensation and the deep dependance upon generous volunteers who had to fit GUE into their busy lives. If it were not for these individuals and our loyal members, we would likely never have been successful. Volunteer support and GUE membership have been and remain critical to the growing success of our agency. If you are now or have ever been a volunteer or GUE member, your contribution is a significant part of our success, and we thank you.
The challenges of the early years gave way to steady progress—always slower than desired, with ups and downs, but progress, nonetheless. Some challenges were not obvious at the outset. For example, many regions around the world were very poorly developed in technical diving. Agencies intent on growth seemed to ignore that problem, choosing whoever was available, and regardless of their experience in the discipline, they would soon be teaching.
This decision to promote people with limited experience became especially problematic when it came to Instructor Trainers. People with almost no experience in something like trimix diving were qualifying trimix instructors. Watching this play out in agency after agency, and on continent after continent, was a troubling affair. Conversely, it took many years for GUE to develop and train people of appropriate experience, especially when looking to critical roles, including high-level tech and instructor trainers. At the same time, GUE’s efforts shaped the industry in no small fashion as agencies began to model their programs after GUE’s training protocols. Initially, having insisted that nobody would take something like Fundamentals, every agency followed suit in developing their own version of these programs, usually taught by divers that had followed GUE training.
This evolving trend wasn’t without complexity but was largely a positive outcome. Agencies soon focused on fundamental skills, incorporated some form of problem-resolution training, adhered to GUE bottle and gas switching protocols, reduced insistence on deep air, and started talking more about developing skilled divers, among other changes. This evolution was significant when compared to the days of arguing about why a person could not learn to use trimix until they were good while diving deep on air.
To be sure, a good share of these changes was more about maintaining business relevance than making substantive improvements. The changes themselves were often more style than substance, lacking objective performance standards and the appropriate retraining of instructors. Despite these weaknesses, they remain positive developments. Talking about something is an important first step and, in all cases, it makes room for strong instructors in any given agency to practice what is being preached. In fact, these evolving trends have allowed GUE to now push further in the effort to create skilled and experienced divers, enhancing our ability to run progressively more elaborate projects with increasingly more sophisticated outcomes.
The Future of GUE
The coming decades of GUE’s future appear very bright. Slow but steady growth has now placed the organization in a position to make wise investments, ensuring a vibrant and integrated approach. Meanwhile, evolving technology and a broad global base place GUE in a unique and formidable position. Key structural and personnel adjustments complement a growing range of virtual tools, enabling our diverse communities and representatives to collaborate and advance projects in a way that, prior to now, was not possible. Strong local communities can be easily connected with coordinated global missions; these activities include ever-more- sophisticated underwater initiatives as well as structural changes within the GUE ecosystem. One such forward-thinking project leverages AI-enabled, adaptive learning platforms to enhance both the quality and efficiency of GUE education. Most agencies, including GUE, have been using some form of online training for years, but GUE is taking big steps to reinvent the quality and efficiency of this form of training. This is not to replace, but rather to extend and augment inwater and in-person learning outcomes. Related tools further improve the fluidity, allowing GUE to seamlessly connect previously distant communities, enabling technology, training, and passion to notably expand our ability to realize our broad, global mission.
Meanwhile, GUE and its range of global communities are utilizing evolving technologies to significantly expand the quality and scope of their project initiatives. Comparing the impressive capability of current GUE communities with those of our early years shows a radical and important shift, allowing results equal or even well beyond those possible when compared even with well-funded commercial projects. Coupled with GUE training and procedural support, these ongoing augmentations place our communities at the forefront of underwater research and conservation. This situation will only expand and be further enriched with the use of evolving technology and closely linked communities. Recent and planned expansions to our training programs present a host of important tools that will continue being refined in the years to come. Efforts to expand and improve upon the support provided to GUE projects with technology, people, and resources are now coming online and will undoubtedly be an important part of our evolving future.
The coming decades will undoubtedly present challenges. But I have no doubt that together we will not only overcome those obstacles but we will continue to thrive. I believe that GUE’s trajectory remains overwhelmingly positive, for we are an organization that is continually evolving—driven by a spirit of adventure, encouraged by your heartwarming stories, and inspired by the satisfaction of overcoming complex problems. Twenty-five years ago, when I took the path less traveled, the vision I had for GUE was admittedly ambitious. The reality, however, has exceeded anything I could have imagined. I know that GUE will never reach a point when it is complete but that it will be an exciting lifelong journey, one that, for me, will define a life well lived. I look forward our mutual ongoing “Quest for Excellence.”
Jarrod is an avid explorer, researcher, author, and instructor who teaches and dives in oceans and caves around the world. Trained as a geologist, Jarrod is the founder and president of GUE and CEO of Halcyon and Extreme Exposure while remaining active in conservation, exploration, and filming projects worldwide. His explorations regularly place him in the most remote locations in the world, including numerous world record cave dives with total immersions near 30 hours. Jarrod is also an author with dozens of publications, including three books.
A Few GUE Fundamentals
Similar to military, commercial and public safety divers, Global Underwater Explorers (GUE) is a standards-based diving community, with specific protocols, standard operating procedures (SOPs) and tools. Here are selected InDEPTH stories on some of the key aspects of GUE diving, including a four-part series on the history and development of GUE decompression procedures by founder and president Jarod Jablonski.
GUE Instructor Examiner Guy Shockey explains the thought and details that goes into GUE’s most popular course, Fundamentals, aka “Fundies,” which has been taken by numerous industry luminaries. Why all the fanfare? Shockey characterizes the magic as “simple things done precisely!
Instructor evaluator Rich Walker attempts to answer the question, “why is Fundamentals GUE’s most popular diving course?” Along the way, he clarifies some of the myths and misconceptions about GUE training. Hint: there is no Kool-Aid.
As you’d expect, Global Underwater Explorers (GUE) has a standardized approach to prepare your equipment for the dive, and its own pre-dive checklist: the GUE EDGE. Here explorer and filmmaker Dimitris Fifis preps you to take the plunge, GUE-style.
Instructor trainer Guy Shockey discusses the purpose, value, and yes, flexibility of standard operating procedures, or SOPs, in diving. Sound like an oxymoron? Shockey explains how SOPs can help offload some of our internal processing and situational awareness, so we can focus on the important part of the dive—having FUN!
Like the military and commercial diving communities before them, Global Underwater Explorers (GUE) uses standardized breathing mixtures for various depth ranges and for decompression. Here British wrecker and instructor evaluator Rich Walker gets lyrical and presents the reasoning behind standard mixes and their advantages, compared with a “best mix” approach. Don’t worry, you won’t need your hymnal, though Walker may have you singing some blues.
Is it a secret algorithm developed by the WKPP to get you out of the water faster sans DCI, or an unsubstantiated decompression speculation promoted by Kool-Aid swilling quacks and charlatans? British tech instructor/instructor evaluator Rich Walker divulges the arcane mysteries behind GUE’s ratio decompression protocols in this first of a two part series.
Global Underwater Explorers is known for taking its own holistic approach to gear configuration. Here GUE board member and Instructor Trainer Richard Lundgren explains the reasoning behind its unique closed-circuit rebreather configuration. It’s all about the gas!
Though they were late to the party, Global Underwater Explorers (GUE) is leaning forward on rebreathers, and members are following suit. So what’s to become of their open circuit-based TECH 2 course? InDepth’s Ashley Stewart has the deets.
Diving projects, or expeditions—think Bill Stone’s Wakulla Springs 1987 project, or the original explorations of the Woodville Karst Plain’s Project (WKPP)—helped give birth to technical diving, and today continue as an important focal point and organizing principle for communities like Global Underwater Explorers (GUE). The organization this year unveiled a new Project Diver program, intended to elevate “community-led project dives to an entirely new level of sophistication.” Here, authors Guy Shockey and Francesco Cameli discuss the power of projects and take us behind the scenes of the new program
Decompression, Deep Stops and the Pursuit of Precision in a Complex World In this first of a four-part series, Global Underwater Explorers’ (GUE) founder and president Jarrod Jablonski explores the historical development of GUE decompression protocols, with a focus on technical diving and the evolving trends in decompression research.