Advances in Physiology Education

John Greenleaf's life of science

Donald E. Watenpaugh


This article summarizes the life and career of John E. Greenleaf, PhD. It complements an interview of Dr. Greenleaf sponsored by the American Physiological Society Living History Project found on the American Physiological Society website. Dr. Greenleaf is a “thought leader” and internationally renowned physiologist, with extensive contributions in human systems-level environmental physiology. He avoided self-aggrandizement and believed that deeds rather than words define one's legacy. Viewed another way, however, Greenleaf's words define his deeds: 48% of his 185 articles are first author works, which is an unusually high proportion for a scientist of his stature. He found that writing a thorough and thoughtful discussion section often led to novel ideas that drove future research. Beyond Greenleaf's words are the many students, postdocs, and collaborators lucky enough to have worked with him and thus learn and carry on his ways of science. His core principles included the following: avoid research “fads,” embrace diversity, be the first subject in your own research, adhere to rules of fiscal responsibility, and respect administrative forces–but never back down from them when you know you are right. Greenleaf's integrity ensured he was usually right. He thrived on the axiom of many successful scientists: avoid falling in love with hypotheses, so that when unexpected findings appear, they arouse curiosity instead of fear. Dr. Greenleaf's legacy will include the John and Carol Greenleaf Award for prolific environmental and exercise-related publication in the Journal of Applied Physiology.

  • National Aeronautics and Space Administration
  • environmental physiology
  • exercise
  • weightlessness
  • human

this article presents some highlights of John E. Greenleaf's life and scientific career. It follows a 2007 interview of Dr. Greenleaf sponsored by the American Physiological Society (APS) Living History Project, found on the APS website ( His curriculum vitae is there as well. This article does not rehash all of his many scientific findings; those are easily found in the literature. Those fortunate enough to know and work with Dr. Greenleaf will hopefully enjoy this recollection of his exploits. Those who didn't know him may benefit from his experiences and lessons learned during a prolific career in exercise and environmental physiology.

Family History and Early Years

The ancestors of the American Greenleafs were Edmond, his wife Sarah Dole, and their nine children. They crossed the Atlantic from England to settle in Newbury, MA, in 1635. Edmond was a Huguenot: French protestant refugees whose motto was “Every man's work shall be manifest, for the day shall declare it.” This motto certainly presaged John's work ethic. Julia Flint Greenleaf gave birth to John Edward in Joliet, IL, in September 1932. She was a girls' physical education (PE) teacher, and John's father, John Simon Greenleaf, was a mechanical engineer who worked in auto service. Because jobs were scarce in the 1930s, the family moved multiple times until settling in Springfield, IL, where John started first grade. His sister Sandra was born there, 5 yr his junior.

Bs and Cs in elementary school offered little indication of Greenleaf's eventual scholarship. Grades were somewhat higher in conduct, spelling, music, and physical skills, yet lower in reading and math. Early teacher comments noted that he “runs, skips, and bounces a ball with certain amount of freedom” and that he “shows special interest and ability in handiwork and drawing.” John was a fine young athlete and often gathered blue ribbons at county field days in broad jump and sprint events.

He displayed early interest in history and later credited this appreciation for his habit of exhaustively reviewing scientific literature before designing studies. Young John visited California in 1939 on a train trip with his maternal grandmother. This visit first piqued his interest in the Golden State. He exhibited an early interest in aviation and once cut class to go to an airplane show at Springfield Airport's grass runways after being denied school permission to attend.

In gradeschool, John was small for his age and became a target of bullies. These encounters both created and revealed a strength of character that served him well later in life. The bullies, including sons of town leaders, twisted his arm and rubbed snow in his face to make him say “uncle” (surrender). But John Greenleaf never said “uncle,” and the recalcitrance encouraged further bullying. The schoolboy terrorism perhaps also contributed to the stutter John carried through life. One day at recess, a tough got him down enough to trigger a reaction, but it still wasn't “uncle”: in a flash of anger, John rose to his knees and knocked the boy out with a right jab to the jaw. The bullying stopped after this decisive incident. As he put it later, these formative encounters helped John “learn when to charge, when to retreat, and when to stand and fight.”

John's father believed that idle hands got into trouble and therefore encouraged work. At age 12, John's first paying job was as a shoeshine boy at a local barbershop. He charged 15 cents per shine, but they usually gave him a quarter. He always appreciated earning and having his own money thereafter. Academic performance at Springfield High School (1946–1950) remained average. His higher grades in English, drafting, and band compensated for lower grades in math, chemistry, and Latin. In some ways, John's scientific career began during this time. Classroom experiments often failed due to poorly controlled conditions. So, he bought his own chemistry sets and attempted experiments at home, often with greater success. Only once did a smoke-filled basement alarm the family. John played saxophone (like his father) and increasingly enjoyed music during high school. Another interest was riflery. He made the high school team and carried his rifle on the bus to the YMCA range to practice. Tennis became a priority: John and his doubles partner eventually won the Illinois state championship in 1950.

Family and peers pressured John toward college preparatory classes, but he also took vocational courses, which caused friction. John's father became convinced that his son's stubbornness would get him in trouble. John's mediocre grades distressed the family to the extent that his father arranged for occupational and intelligence testing at a local hospital. The results revealed an IQ score sufficient to attend medical school, high interests in mechanics, science, and music, and low interests in literature and the arts. Thus, academic problems stemmed from application rather than capability. To boost grades, John's parents kept him home on school nights, and his bedtime was 9:00 PM. He graduated in 1950, 60th in a class of 237.

College and National Guard Service

Greenleaf enrolled at the University of Illinois, Urbana-Champaign (UIU-C), due to its proximity, convenience, and low cost. Tuition was $80/semester. Soon after he matriculated, his fraternity was placed on probation: it was the senior year for many World War II veterans, which led to raucous partying and low grades. This probation helped with John's academic discipline.

John applied to the Naval Reserve Officers Training Corps in hopes of becoming a Marine Corps fighter pilot, but substandard eyesight led to rejection. As a fallback option, he joined the Illinois National Guard, which was called to service in 1951 during the Korean War. He played saxophone in the 44th Infantry Division Band based at Camp Cooke near Lompoc, CA, and soon became drum major. He regretted not having the honor of serving in combat, but he made the best of his time in the Guard. His duties included playing for military brass and other notables going to Korea, including Bob Hope and his troupe. When on leave, John hitchhiked down Highway 1 to play tennis at a posh country club in Santa Barbara, CA. In those days, truckers in particular stopped to pick up servicemen and buy them lunch as well. Corporal Greenleaf made $100/mo, of which roughly half was sent home and half was spent on tennis. He was discharged after a year of active duty.

His service entitled him to 2.5 years of the G.I. Education Bill, which was sufficient to see him complete undergraduate studies. So, he returned to UIU-C and majored in PE. He became interested in human research, which the PE program emphasized. The Army year significantly reorganized John's outlook on life and college: the focus was now academics. His name thereafter remained on the Dean's list. One pivotal course was human anatomy and physiology. He said later: “How do you keep them down on the farm after taking physiology!?”

John also continued to enjoy and excel at tennis (Fig. 1) as well as the self-defense courses taught by Prof. Armand Seidler. Seidler and a colleague, Harold “Heck” Kenney (a wrestling coach and former National Collegiate Athletic Association champion), reportedly prowled the south side of Chicago at night hoping to be accosted by muggers so they could practice their self-defense skills for real. In 1955, Seidler took a position as Chairman of the PE Department at New Mexico Highlands University in Las Vegas, NM. Seidler asked Greenleaf to accompany him after John graduated.

Fig. 1.

John Greenleaf (5 ft. 11 in., 160 lb) on the tennis court at the University of Illinois, Urbana-Champaign, in 1955.

Highlands' student body of 800 provided an interesting contrast to UIU-C with its 25,000 students. Greenleaf's duties as a graduate assistant included teaching personal defense and tennis, coaching the tennis team, and helping operate the Las Vegas summer recreation program. Most of the tennis team members were novices at best, so they lost frequently. One problem was lack of conditioning, so John started a team running program at the school track. This quickly became unpopular, because the track went around the football practice field and the football players took to deriding the jogging tennis team. Therefore, a compromise was reached whereby the team ran in a nearby park. The hilly park provided a much harder workout, so the compromise served both purposes well. While at Highlands, John considering teaching tennis professionally. His Masters thesis was titled The Development of the Lawn Tennis Racket (4).

After completing his Masters degree in 1956, John returned home to Springfield to take a junior drafting position at Allis-Chalmers, a company that made tractors. It was there that he first observed goldbricking in a workplace. As John put it, “After a few weeks of observing the older engineers draw one line, look out the window, take a coffee break, wander around to chat to colleagues, etc., our novice group decided to earn our money. We turned out drawings like machine guns and quickly became grossly unpopular.” Shortly thereafter, in September 1957, he decided to return to graduate studies in PE at UIU-C, with a Physiology minor.

John enjoyed his return to academics because the environment allowed and encouraged him to work hard and independently. He enjoyed it for other reasons as well, as his fellow students proved to be more interesting company than the tractor company engineers. One particular coed in his Physical Anthropology class caught his eye. Carol Johnson was hard to miss in part because she was routinely last to arrive. It turned out that the only empty seat left by the time she got there usually just happened to be next to John. Everyone in the class knew what was going on except her. By the end of the semester, John and Carol knew each other more than well.

After completing all the required courses for the PE doctoral program, the lure of physiology became too great, and John transferred to the Physiology graduate program in 1959. This committed him to 4 more years of graduate school. Learning was becoming a hobby. Two other PE doctoral candidates, Charlie “Tip” Tipton and Dan Zaharko, also transferred to physiology. Shortly after “marrying” physiology, John married Carol in 1960.

John's prior PE coursework included substantial training in how to conduct human research. This nicely complemented his transfer to physiology, which was deficient in such courses. On the other hand, his new major required that he take basic courses such as biochemistry, genetics, cellular physiology, and histology. His lower interest in these subjects made them tough for him. Even so, he felt as though he never fully understood physiology until learning these fundamentals.

One particularly stimulating course was “Physiology for Space Travel,” which was designed and taught by John's mentor, Robert E. Johnson (of Harvard Fatigue Laboratory fame). Greenleaf's interest was great because the United State (US)-Soviet Space Race had just started and he completely enjoyed Johnson's teaching methods. Johnson would pose problems and create teams from diverse disciplines (physiologist, engineer, psychologist, statistician) to solve them. One challenge was to design a spacecraft to take humans from Earth to the Moon and back; another was to design a “moon suit” to provide life support for a trek from a lunar lander to a distant hill and back. This class essentially prescribed John's eventual career path.

John was able to support his graduate studies with teaching and research stipends. He enjoyed teaching, yet he emphasized to students that they were ultimately responsible for their own education; the teacher shared responsibility only as a guide. To drive the point home, he required students to calculate the cost of their education per credit hour: tuition, fees, books, etc. divided by total course hours. He encouraged them to get their money's worth. John received National Science Foundation and National Institutes of Health predoctoral fellowships, which allowed him to spend full time in preparation for written and oral exams and on his dissertation. Rumor held that if a candidate did well on written exams, the orals went much easier. John passed both without problems and received his PhD in 1963 with a graduate grade point average of 4.53/5.00.

The next step was a postdoctoral fellowship; the dilemma was where to apply for one in human research. The National Aeronautics and Space Administration (NASA) conducted human physiology research at Johnson Space Center (JSC) in Houston, TX, and Ames Research Center (ARC) in Moffett Field, CA. Dr. Greenleaf applied to both in 1963 when the Apollo Program was in full swing. JSC did not respond, but Don Young called from ARC. He said that no fellowships were available, but to Greenleaf's surprise, Young offered John a regular research position based only on his fellowship application. Fond memories of California and its good weather for tennis made ARC irresistible.


John and Carol Greenleaf drove to California in October 1963. It was a rocky first few weeks. He started work immediately, and they looked for a house during his off hours. They settled on a home in Sunnyvale due to its pink kitchen and 10% ($2,500) downpayment. This depleted their ready cash. Although ARC paid every 2 wk, new employees didn't get their first check until 4 wk after they started. To complicate matters, John contracted intestinal flu and missed several days of work. He of course had not yet worked enough to accrue sick leave. His division chief suggested they attribute his sick time to visits to the Stanford Library, which was apparently a common practice. Dr. Greenleaf balked at this subterfuge and so took leave without pay for his days spent ill. He and Carol ended up eating one hotdog per day for the week before his first paycheck–an inauspicious beginning.

One of Dr. Greenleaf's first desires was to visit the Ames Library. However, his co-workers advised against it: they told him employees often went there to nap! In fact, the center director declared that the library was off limits to employees during work hours, a policy that seemed inappropriate for a purported research institution. Greenleaf found the library dark, dirty, and disorganized. It was disgusting and prompted him to start his own collection of scientific books, journals, and journal articles. Little did he know at the time how valuable this collection would become to his students and collaborators in the years ahead.

Greenleaf's first official task was to read the thick and tedious Ames Management Manual and pay close attention to the regulations that applied to his work. His first research assignment was to assist Dr. Young. For 3 days, Greenleaf sat in Young's laboratory awaiting instructions. Shortly thereafter, Greenleaf requested a laboratory for himself. He was given a small space in an adjacent building in which he constructed a two-level research facility composed of an office and small test room above and a biochemical laboratory on the ground floor. Greenleaf acquired a large gray metal government-issue desk plus a table to spread out papers when writing manuscripts. However, his large desk was soon confiscated. He was innocently unaware that the larger desks were reserved for more senior government workers. To avoid further “desk drama,” Greenleaf bought his own large walnut desk, one they still use in their den.

Greenleaf's first publication came out in 1964 … in the journal Nature (1)! An ancillary but interesting observation from his dissertation suggested that exercise training imparts heat acclimation because exercise produces metabolic heat. He wrote it up as a long abstract, but there weren't that many places to publish works of such length. So, he sent it off as a solo letter to Nature because the format fit the finding. Greenleaf's earliest work also documented the phenomenon of involuntary dehydration, which is the insufficient and delayed drinking response to exercise and environmentally induced dehydration in humans (2, 10).

Studies from Greenleaf's first few years at ARC included the first NASA-funded study using female test subjects (9). Conducted in 1965, the study explored how dehydration impacted orthostatic and exercise performance of exercise-trained women. He dutifully submitted the manuscript for NASA internal review. This started with the Ames branch, division, and directorate chiefs, a legal officer, and the center director. Manuscripts then went to NASA headquarters in Washington, DC, for multilevel review there and thereafter to the journal. With some hesitation, the Ames division chief approved the article and chuckled at the consternation sure to blossom when the manuscript reached headquarters.

In those early days of the US space program, NASA leadership quashed any talk of women as astronauts. Testing female research subjects was considered akin to authorizing women to apply to the astronaut program. Female pilots lobbied for entry into the program, which seemed reasonable, since throughout history women accompanied or followed men on virtually all explorations. Also, the Soviets sent Valentina Tereshkova into space in 1963. Greenleaf heard the article did cause significant heartburn at NASA headquarters, but it was ultimately approved: they did not want to set a precedent for suppressing bona fide research on policy grounds.

NASA JSC asked Ames to investigate the orthostatic intolerance occurring in astronauts during upright (sitting) posture after landing in the ocean in a hot Gemini capsule. This request led to the first bedrest simulation of spaceflight conducted at ARC, with Greenleaf as principal investigator (PI) (6). The all-male subject group underwent bedrest in trailers in the parking lot over the Christmas holidays in 1964, when college students were available. Working on Christmas day marked the research team as peculiar. Another early study (7) assessed the effects of dehydration on acceleration (centrifugation) tolerance. ARC offered many unique research facilities, including a human-rated centrifuge capable of producing accelerations of up to 20 g (Fig. 2). In those early days, staff rode the centrifuge without much, if any, red tape. The ARC medical monitor in the 1960s, Dr. Milton Matter, and Dr. Greenleaf had an ongoing competition regarding +Gz (head to foot) acceleration tolerance. Greenleaf always lost.

Fig. 2.

The National Aeronautics and Space Administration (NASA) Ames Research Center (ARC) 20-g human-rated centrifuge early in its career and configured with a minialtitude chamber cab.

ARC boasted one of the best collections of aeronautical engineering and technical support personnel in the country. Then and now, Ames architecture is best characterized as “Wind Tunnel City.” Expertise included design and fabrication in metal, wood, electrical, and instrumentation shops plus a publications branch that provided editorial and graphics services. Greenleaf found early that admixing biologists with aeronautical engineers “was like combining oil and water without emulsification.” Regardless, he often needed their help to construct experimental hardware and instrumentation. Once they found out his team's work involved human research in support of the astronaut program, their doors opened readily. He further enhanced cooperation by “closing the loop” and giving them reprints of the studies they facilitated.

Greenleaf tended to evade the Ames public relations office. With the space program steaming full speed in the 1960s and ‘70s, space-related human research was a media magnet. Greenleaf learned early that journalists often glamorize a story to the detriment of scientific findings. He turned down requests for interviews if they didn’t guarantee him some editorial control over the journalistic product. This policy, in turn, discouraged requests for interviews.

By 1966, life sciences personnel were to move into their new building, N-239. The floorplan showed office and laboratory space for everyone except Greenleaf. Substantial space remained vacant in the large, warehouse-like building next door, N-239A. So, he asked his division chief for construction of a laboratory in N-239A. This was of course initially rejected, as were all new ideas. One morning soon thereafter, Dr. Greenleaf went to the chief's office to discuss the matter but was denied a meeting. Greenleaf then sat and waited outside the office: he knew the chief had to pass him to go home. At the end of the day the chief emerged, amused and impressed by Greenleaf's persistence, and requested his plan for the new laboratory. Dr. Greenleaf designed a 372-m2 facility modeled after the Environmental Physiology Laboratory at UIU-C. To his surprise and delight, it was approved for construction.


Dr. Greenleaf's original interest in NASA was to undertake a postdoctoral fellowship, yet they hired him into a permanent position. Thus, in 1965, he asked management for permission and support to study elsewhere for a year. They failed to grasp the academic postdoctoral concept or the value to the home institution of external training and experience. They ultimately approved his request, but as leave without pay. Greenleaf garnered an invitation and senior postdoctoral fellowship from the Swedish Medical Research Council to work at the Karolinska Institute in Stockholm, Sweden. The fellowship plus wife Carol's salary for part-time laboratory support covered most of the loss of John's NASA salary. (Subsequently, other NASA scientists received full pay and benefits while away on such sabbaticals.)

Dr. and Mrs. Greenleaf were received at Karolinska Institute by Prof. Christensen. Once he learned of Carol's Swedish ancestry, the welcome became emphatic. Christensen's laboratory personnel saw him as a tyrant, but Greenleaf found him cordial, and they held many enlightening teatime discussions. Christensen's knowledge of the scientific literature was encyclopedic, which appealed to Greenleaf's predilections.

Greenleaf proposed to measure the heat acclimation capability of Swedes with no prior exposure to hot climates. However, Christensen stipulated that the research must proceed from previous work at their laboratory, and they had not studied heat acclimation. As an alternative, Greenleaf built on earlier work by Bengt Saltin by studying thermoregulation during exercise at altitude (5). This was the only manuscript Greenleaf ever submitted that was accepted without revision, which revealed to him the value of situations that emphasize research and minimize distractions.

The Greenleafs returned to the States with their 1963 Volvo Amazon on the Swedish Liner Kungsholm and then drove from New York back to Sunnyvale. Awaiting Greenleaf at ARC was his new laboratory. A small environmental/altitude chamber was installed nearby, and a much larger such chamber was under construction (Figs. 3 and 4). Greenleaf was flabbergasted and eager to get to work to earn the new digs. However, the Swedish experience whetted his appreciation and appetite for international collaboration.

Fig. 3.

Large environmental/altitude chamber at NASA ARC.

Fig. 4.

Interior of the large environmental/altitude chamber with a treadmill built into its floor.

Operating Tenets

Dr. Greenleaf established a few basic operating tenets early in his Ames career, and he refined these and developed others along the way (Table 1). He considered two as most important and unbending. First, money matters would be conducted in strict conformance with all rules and regulations. Second, he extended the Hippocratic oath to science: never harm anyone. This was well before Nobel Laureate Sir Joseph Rotblat's 1995 proposal of the idea, yet well after abuses like the Tuskegee experiment.

View this table:
Table 1.

Dr. John Greenleaf's human research tenets

John put this tenet into practice by almost always being the first test subject in his research. This allowed his research team to fine-tune procedures, and it gave him insight to the challenges their protocols imposed on subjects. The primary exception was prolonged bedrest, which he never undertook as a subject because this would prevent his participation as investigator for these long and complex studies.

Greenleaf's personal experience from the subjects' perspective often led to protocol refinements that protected subjects and/or improved data quality. As one example, he once lost consciousness during centrifugation. The next day, he experienced malaise and a severe headache. His responses led to a policy that prevented subjects from undergoing tests on a day after loss of consciousness during testing.

Still another benefit from his participation as a subject was improved understanding of findings and inspiration for new research ideas. As one example, Greenleaf noted that water immersion relieved the profound thirst he experienced from dehydration. A typical naïve subject would not be able to interpret this observation physiologically, but Greenleaf certainly was. This immersion-induced amelioration of thirst fed future hypotheses and study designs.

Early in his career, Greenleaf adopted running as another tool to generate new research ideas as well as to help solve problems and relieve stress. He found that running cleared his mind in a way he couldn't otherwise achieve. He termed the practice “turning the corner,” because new ideas and solutions to problems often emerged as he turned around at the 1-mi. point to start back. The physical health rewards were a side benefit. Go try it, right now!

Dr. Greenleaf believed that taxpayer-funded research should help resolve human and animal problems to enhance health and well-being, the applied versus basic research dichotomy. He once heard a professor lecture that every time he discovered a practical application for his work, he dropped it immediately and did something else. That riled Greenleaf. He contended that basic research hypotheses can usually be reformulated to an applied purpose and should be if funded by the government.

Greenleaf designed and conducted studies “to be defensible in a court of law under questioning from a sharp prosecutor.” This required unassailable experimental design, routine instrument calibration, well-controlled, repeatable protocols, precise data acquisition, proper analytic techniques, and careful, double-checked data processing. He held that good research demands meticulous attention to detail.

When designing a study, all proposed measurements underwent intense scrutiny; if no hypothesis-related reason existed to measure a variable, then it wasn't measured. Also, no more data were collected than necessary to answer the question. Most of Dr. Greenleaf's career was well before our modern luxuries of computer data acquisition with effectively unlimited data storage. He rarely allowed add-on measurements, usually based on intuition that they might lead to new hypotheses. However, he required that such add ons show relevance to and not interfere with collection of primary data (Table 1).

Another basic tenet was that the harder way now results in an easier way later. The hard way implies taking sufficient time and effort to do the job right the first time, because repeating work wastes time and resources presuming that you even get a second chance. For example, it is not always possible to retest a subject if things go wrong, especially during and after bedrest studies. This was sometimes a difficult concept for young people, who had no previous similar experiences. That was why Dr. Greenleaf preferentially hired athletes as laboratory assistants and test subjects; they had already acquired self-discipline and a strong work ethic.

Greenleaf's other operating tenets sought to optimize research novelty, quality, and productivity. He chose to investigate less popular (but still relevant) questions because, by definition, many others were studying the more popular areas. Test subjects would be treated as guests in your home with a smiling, friendly attitude, because he understood the importance of subject and investigator morale and mutual respect to data quality. He preferentially used tests and measurements that were easy to perform accurately, in part because his assistants were often relatively inexperienced students. Greenleaf required immediate reporting of all errors in data collection, with no penalty. Conversely, any team member found to conceal errors would face discipline and possible termination.

Two team members verified all raw data and then entered reduced data onto spreadsheets with a no. 2 pencil (with its graphite being impervious to liquids). This laborious process allowed them to know the data well and further screen for errors. Data were then entered into computers for statistical analyses and preparation of graphs and tables. Greenleaf continued to handwrite drafts of manuscripts with pencil on legal pads long after most authors transitioned to typing into computers. This mode forces an author to more thoroughly organize ideas in their head before even starting to write.

John believed there were always better ways to do everything, and staff were encouraged to discuss options anytime. However, formal meetings were discouraged and rare. Instead, the workday, and especially lunchtime, offered daily opportunity for informal discussion of new ideas. Greenleaf resented and spurned midmorning and midafternoon meetings called by management, as these time slots broke up prime productive time in the laboratory.

Because Greenleaf's laboratory received adequate and continuous funding, it would have been easy to conduct studies faster than the ability to publish. However, this was not his way. He practiced and inculcated in others a culture of prompt publication, yet he also felt need to suspend data collection roughly one of every 5 yr to catch up on writing. He knew scientists who complained of accumulated unpublished data yet continued to conduct studies instead of taking time to publish completed data sets. Greenleaf understood early that writing up data sets drove the research process forward inexorably by leading to ideas for the next project.

It was the discussion section of articles that fostered innovation. A properly crafted discussion requires its author to interpret their current findings with prior related work, be it theirs or others. Did our findings confirm or refute expectations? How and why did results agree or differ from prior related work? Furthermore, data sets often present surprises, and the receptive scientist will embrace those departures and see where they go. How do we explain this unusual and unexpected result? Put another way, the reference list from a thoughtful discussion section may differ substantially from the reference list of the proposal that led to the study. You truly know your results only after you've discussed them in context of the relevant literature, and new research ideas often spring from this process.

Last, but definitely not least, Greenleaf thrived on collaboration. At meetings you would find him at the poster sessions talking with people in depth about their research and his as well as related work of others, common interests, surprising observations, open questions, etc. These discussions sometimes led to invitations to collaborate, either by Greenleaf visiting their laboratory or they his. He developed a national and international reputation as a creative, reliable, hard-working, productive, and fun co-worker, which, in turn, fed repeat as well as new invitations to collaborate. This article describes a few of these opportunistic partnerships.


John and Carol Greenleaf first met Dr. Stanislaw Kozlowski in the early 1970s at a conference in Cambridge, United Kingdom (UK). He was director of the Laboratory of Applied Physiology at the Polish Academy of Sciences in Warsaw, Poland. Greenleaf was immediately drawn to Kozlowski's happy, pleasant manner as well as his diverse interests, with an emphasis on the control of fluid metabolism in dogs. At that time, the US National Research Council ran an exchange program with Soviet and Eastern European institutions. The sending institution covered travel costs, and the host institution provided room and board. Between 1973 and 1989, the program funded five visits by Greenleaf to Warsaw, totaling about 1 yr. Therefore, Greenleaf's visits spanned from before Pope John Paul II's 1979 visit to Poland, which sparked the founding of Solidarity under Lech Walesa, to the 1989 Round Table Talks, which led to a free Poland and ultimately to disintegration of the Soviet Union.

In 1973, the “Iron Curtain” strongly divided Europe. Greenleaf flew from London to Warsaw in a worn-out Russian medium bomber refitted for Polish Airlines civilian use. The bombardier's nosecone was still in place! Greenleaf dozed inflight, but he woke to a loud announcement over the speaker, repeated in multiple languages: “Attention, attention–you have just crossed into the Peoples' Republic of Poland!” They landed awhile later in darkness and heavy snow. From the tarmac, the airport seemed deserted. What did he get himself into? To Greenleaf's relief, Kozlowski and colleagues greeted him warmly inside the terminal and then kindly took him to dinner at the famous duck restaurant in Old Town.

On the way to the restaurant, it continued to snow huge, beautiful flakes. They walked through King's Castle Square past a large and unguarded Plexiglas box filled with cash donated for rebuilding the Castle. It remained demolished since Hitler ordered it razed in 1944. Greenleaf commented on the unguarded box, and his hosts said that no one would think of pilfering those donations. This was when most Poles lived in poverty.

Before this first trip to Poland, Greenleaf mailed care packages ahead. He suspected that he may not be able to get certain things there. Sent items included aluminum foil, personal hygiene products, a Swiss Army knife, and popcorn. The boxes arrived before Greenleaf, and a graduate student went to the airport to pick them up. Polish customs agents inventoried the contents to determine import tariffs. They noticed baby powder and said items for babies were tax exempt. The graduate student responded that all of the items were for babies, so duty was waived.

Greenleaf stayed in a small apartment loaned to him by a laboratory technician, which was a significant hardship for the tech. His new Polish labmates arranged for John to have a name day celebration, when all Catholics with the same first name hosted a party. In addition to supplying the Johnny Walker Black Label whiskey, Greenleaf popped some corn. No one there had seen popcorn before, even those from farming communities. They ate even unpopped kernels, and they all took the popcorn home to show to their families. If all else failed, Greenleaf's ultimate legacy would be the man who introduced Poland to popcorn.

Kozlowski and colleagues organized the studies to start testing immediately upon Greenleaf's arrival. This minimized his absence from Ames. The institute had few modern conveniences and relatively archaic equipment. The huge iron key to the building appeared medieval. As with Prof. Christensen, Kozlowski and Greenleaf held many delightful conversations over afternoon tea, an almost universal repast in European institutes.

Kozlowski's primary obstacle to running the institute was the “colleague” who also served as liaison to the Communist Party. All major decisions required his approval. Since everyone in this socialist country had to have a job, there were many laboratory technicians and assistants. Most did very good work. The poorly paid support staff worked only 4 h/day; they spent the remainder of their day standing in long lines at shops. Many of these institute workers eventually joined Solidarity.

Greenleaf was in Poland during the summer of 1980 when the Olympic Games were held in Moscow. The Russians confiscated Polish food to send there, or at least tried: hungry Polish railway workers stopped food trains at the Russian border. The Russians responded by lining up tanks on their side. The US State Department contacted Carol and assured her that they planned to evacuate John if trouble erupted. Fortunately, he dodged the situation by flying to Berlin to visit Prof. Karl Kirsch.

In addition to his personal scientific growth and worldly experience, Greenleaf hoped his tenure in Poland boosted their morale and productivity during that pivotal time in Eastern Europe. His initial 3-mo stay generated nine peer-reviewed articles. Publications from the entire fellowship totaled 24 papers, 12 abstracts, and 4 chapters. One of the few perks offered by the Polish government was to pay honoraria to publish in Acta Physiologia Polonia–completely opposite the Western system, where authors pay page charges.

Collaborators and Students

All research emanating from Dr. Greenleaf's laboratory resulted from the integrated expertise and efforts of the staff. This included an ever-changing and diverse mix of paid and volunteer (including Carol) technicians, Ames scientist collaborators, university faculty visiting international scholars, postdocs, and graduate and undergraduate students. The only constant, of course, was John Greenleaf.

Greenleaf's many sabbaticals demonstrated his eagerness to explore the world of science, but the world was also eager to come to him. While most of his students and co-workers naturally came from California institutions, he also hosted collaborators from Colorado, Kentucky, Missouri, New Mexico, Pennsylvania, Australia, Austria, Canada, Italy, France, New Zealand, Norway, and the UK. These many and multicultural connections led to the cross-fertilization of ideas that fed Greenleaf's scientific imagination. The sheer number of collaborations he fostered drove his considerable productivity.

Greenleaf enjoyed the opportunity to work with many very intelligent people. Two Stanford students, Steve Raymond and his fiancé Sandy Corsialia, were exceptional. Raymond's IQ was about 180, and Corsialia's was higher and unmeasurable. Greenleaf wondered how to supervise such people and eventually decided: you don't. He purchased a state of the art infrared spectrophotometer, but Sandy and Steve could not get it to work by following the directions. They eventually set up and ran the spectrophotometer and, in the process, identified many errors in the operating manual. They shared their findings with Beckman, the manufacturer, which led to complete revision of the manual.

One day, commotion erupted among Ames aeronautical engineers. A Mr. Raymond was coming to visit, who was in fact Steve's grandfather, the chief engineer for Douglas Aircraft, and the driving force behind the venerable C-47 transport. The C-47 stands among the most important implements for our victory in World War II. The senior Mr. Raymond arrived by limousine and then had a genial 30-min chat with John. After the visit, Mr. Raymond seemed satisfied with his grandson's situation at Ames, and Greenleaf's status among Ames' engineers increased significantly.

Greenleaf hosted many students in his laboratory over the years that went on to successful independent careers. Vic Convertino stands out as one of the most prolific and successful. He certainly absorbed, applied, and appreciated Greenleaf's tutalage. When asked about the most important lessons, Convertino shared: “John used to drill into us that all the work you do is worth nothing if it doesn't get published and get out to the scientific community.” Convertino also admired the practice of investigators being subjects first. However, Greenleaf recalled that Convertino was rather hemophobic, so his participation in invasive protocols was challenging.

For any human environmental physiologist, it was a great pleasure to visit Dr. Greenleaf's office and browse through his vast collection of articles. You looked for an excuse, and you were always welcome. He organized the articles logically by topic in a bank of filing cabinets. Many reprints were original, and some were signed with a salutation from the author. The Ames library eventually developed support services, such as document translation. Extensive and growing European, Soviet/Russian, and Japanese contributions to the aerospace biomedical literature made accurate to-English translation increasingly important over Greenleaf's career. His reprint library was well stocked with these unique translations, which made the collection even more singular.

Bedrest Studies

During Greenleaf's career, bedrest emerged as the method of choice to simulate existence in weightlessness, in some part due to the bedrest studies he conducted, the quality of the studies, and the findings that they generated. Water immersion was also used for acute studies, and Greenleaf conducted many studies with this model, particularly in collaboration with Dr. Helmut Hinghofer-Szalkay of Austria. However, water immersion was unsuitable for longer than several hours unless the Russian “dry immersion” modification was implemented.

Greenleaf's early experience with housing bedrest subjects in trailers led him to conceptualize an ideal bedrest research facility. He and management knew that such a facility would be necessary to address the biomedical questions raised by spaceflights lasting weeks. This need led to the construction of the Human Research Facility (HRF) at ARC in 1970. Designed by Greenleaf, the HRF had bedrooms to house up to eight subjects (2 subjects/room), beds configured for head-down tilt, overhead televisions, a metabolic kitchen, a large living room/common area, a horizontal shower, testing rooms with space for experimental and monitoring equipment as well as sample collection and processing, and plenty of space to roll subjects around on gurneys.

Bedrest studies tend to be complex, multidisciplinary endeavors that require substantial planning as well as the coordination of effort from management, co-investigators, extended support staff, and subjects. Attention to detail is necessary both in planning and in the moment, and some stages are more critical than others. Depending on the measurement, there exists little, if any, margin for error during the postbedrest data collection. Dr. Greenleaf excelled at running these studies, and none was more challenging than the 1986 30-day Ames bedrest study.

The overall goal of the project was to assess exercise countermeasures against bedrest-induced deconditioning. The original study design called for ARC to contribute the supine cycling intervention and for JSC to contribute a supine running intervention by configuring a treadmill vertically with a horizontal subject suspension system and bungee cords for footward loading. As planning proceeded, however, the Challenger disaster occurred. JSC withdrew from participation in the study, and ARC management offered Greenleaf the option of cancelling or delaying the project. The loss of the Challenger and its crew stunned and devastated the entire NASA community and the nation as well. In Greenleaf's view, the questions to be answered by the study remained, substantial resources had already been spent in preparation, and he saw no reason to hesitate. So, ARC continued with a simplified experimental design including the cycling intervention plus leg isokinetic exercise. JSC's departure cut the number of investigators down to 14, representing 6 institutions.

The study remained quite full of personalities and priorities. The subjects certainly created their own ways to make things interesting. Among the personalities Greenleaf worked with was Dee O'Hara, the legendary NASA nurse to the astronauts. As manager of the HRF, she was sometimes more free with medications for subjects than he and the other investigators preferred, and she initially left investigators out of such decision making. He later lamented that “Nurses are used to handling sick people, but bedrest subjects aren't sick!” They soon found a middle ground that met everyone's needs, including the subjects.

Thanks to Greenleaf and the research team assembled around him, the 1986 Ames 30-day bedrest study proceeded smoothly through all phases (Fig. 5). It generated over 10 peer-reviewed publications and multiple ancillary works.

Fig. 5.

Dr. Greenleaf in his office at ARC.

Japan (Kitakyushu)

Dr. Greenleaf met Dr. Keizo Shiraki and Dr. Taketoshi Morimoto at a meeting in Las Vegas in the 1980s. Greenleaf and Morimoto had crossed paths once earlier, when Morimoto started a postdoc with Dr. Johnson at Illinois in 1963, as Greenleaf was leaving. In Las Vegas, they discussed how water immersion attenuates the intense thirst caused by dehydration. The discussions led Shiraki to invite Greenleaf to Japan to investigate this and related questions.

Shiraki hosted Greenleaf and wife Carol with typical and appreciated Japanese hospitality. They easily walked to the laboratory and to grocery stores, which had many American products. Japanese shoppers would politely ask to speak with them to work on English skills. Neighborhood children would wave from afar shouting “herro” (hello), due to their difficulty in pronouncing “L”s.

Shiraki oversaw a well-organized and well-funded research team with superlative facilities. Each team member carried out a specific role during data collection. Greenleaf's assignment was to carry blood samples from the immersion room to the chemical laboratory upstairs, which he performed without mishap. Work from the two visits led to four articles and five abstracts. One spin off of their investigations into the mechanism of the Gauer-Henry reflex involved the assertion that fluid volume shifts from the lower extremities headward instigated the immersion-induced diuretic response (11, 13). Data from Shiraki's laboratory indicated that normal and quadriplegic men exhibit similar diuresis during head-out immersion. Therefore, one loses the same amount of fluid volume during immersion regardless of peripheral innervation.

In 1964, Greenleaf's early mentor R. E. Johnson postulated that “the ideal astronaut would be a cool, slow breathing, hyperosmotic dwarf” (12). The collective findings and operational considerations suggested to Greenleaf that astronauts without lower extremities might physiologically cope better with microgravity in addition to being more energy efficient. When he later brought up this idea at a conference, some attendees excoriated him because they assumed (incorrectly) that he recommended leg amputation for existing astronauts.

Defending and Quantifying Research and Productivity

In 1991, the center direction of ARC asked Dr. Greenleaf and two other ARC scientists “to evaluate the process of scientific publication as it pertains … to the overall NASA research effort” and to justify why ARC personnel should publish their work. That the director of a research center would ask why publication is important illustrates the sometimes bizarre world of NASA management that Greenleaf endured. Greenleaf and co-authors dutifully wrote a booklet entitled Facilitation and Measurement of Research Publication Productivity (15). They stated that

Publishing research results is an essential aspect of being a scientist … Scientific achievements are rarely created in a vacuum from a sudden and dramatic insight, but are built upon accumulated published data.

The authors also laid out “several reasons why it is in the best interest of NASA management to encourage and facilitate research and publishing”–as if any such “reverse cheerleading” should be necessary!

One controversial inclusion in this booklet was a means to quantify the productivity of a scientist based on her/his publications produced per resources used. This Publication Efficiency Index (PEI) was calculated as follows: PEI=(Number of publication)×(Publication quality)(Grant dollars/2yr)×(Available research time) Where “number of publications” is self-explanatory; “publication quality” is a numerical weighting based on scientific import, similar to journal impact factor; “grant dollars/2 yr” is the average funding available over the preceding 2 yr; and “available research time” is the time left for research after subtracting the time required for administrative and other nonscience duties.

The PEI integrated conducting science with the economics of science funding, at least in a superficial way. In addition to answers for Dr. Charlie Tipton's perennial question, “What have you done for science today?,” Greenleaf and co-authors were concerned with addressing “What have you done for (or to!) the taxpayer?” One obvious bugaboo with the index was exactly how to quantify the ultimate importance of an article. This simply can't be known for years.

Greenleaf and co-authors thought that the PEI would be used mainly as a basis for discussion, but NASA headquarters reportedly applied it to compare ARC and JSC research programs. This was perhaps unfair, because JSC's flight experiments were very expensive and sometimes too operationally oriented or limited to be publishable. Should operational relevance factor into publication quality in NASA-funded research? Nevertheless, this booklet strongly defended the need and value of publication, and the PEI it introduced provided provocative food for thought about how to quantify research productivity.

Japan (Kyoto)

In 1997, Greenleaf worked with Prof. Takatoshi Morimoto in Kyoto, Japan, as a visiting professor funded by the Japan Society for Promotion of Science Fellowship. He and Carol stayed within walking distance of the Prefectural University of Medicine. The walk took them across the grounds of the Imperial Palace. Dr. Morimoto kindly arranged for the Greenleafs to visit the old Shogun's compound with him as a translator. Japanese nationals were not usually allowed to visit these palaces. Levels of defense for the Shogun included gravel pathways outside that crunched underfoot, squeaky wood “nightingale floors” inside, an adjacent room full of samurai during political meetings, and finally a group of young women who served the Shogun and guests tea with elegant ceremony. Those women were also most proficient at kenjutsu (swordplay). Greenleaf speculated that this “cut down” on complaints about tea quality.

Investigators began to notice that human aging exhibits physiological correlates with bedrest and thus perhaps with weightlessness. The primary hypothesis tested during the Kyoto visit was whether older men preserve the ability to increase blood volume and respond to a thermal dehydration challenge after 6 days of acclimation to exercise in the heat (14). The hypothesis was negated in that the acclimated older men showed a reduced ability to recover from acute dehydration relative to younger men, which appeared to have been due to decreased ad libitum fluid intake and blood volume. The older subjects exhibited attenuated neuroendocrine responses of volume-retaining hormones and reduced subjective thirst. One implication of these results is that older people should consciously focus on drinking more during and after activity in the heat. This brief but productive visit led to two manuscripts, one abstract, and one chapter.


In the mid-1990s, Dr. Greenleaf submitted a proposal to NASA to study the mechanism of orthostatic syncope. The proposal focused on the time course of hormonal and physiological events that precede fainting as a way to predict ensuing syncope. Reviewers rejected the proposal, but Greenleaf (like many proposal authors) disagreed with the critique. At a scientific meeting, he discussed the proposal with Dr. Peter Norsk, then director of the Danish Aerospace Medical Centre of Research (DAMEC Research). Norsk became convinced the project was worthwhile and invited John to Copenhagen, Denmark, to perform the study.

Greenleaf visited Copenhagen twice in the late 1990s to cordial welcomes. DAMEC Research resided in an early 1900s building whose age did not diminish the institution's world-class research. The Norsk laboratory imposed meticulous control over subjects' prestudy diet as well as all aspects of data collection. The testing team was superb, including co-investigators who performed hormone assays. This was another example of how minimizing extraneous distractions increases research quality. The findings suggested that attenuated plasma renin activity, and thus angiotensin II, precipitates presyncope, with elevated plasma vasopressin as a possible cofactor (8). Baseline data suggested that low resting plasma renin activity may predict lower orthostatic tolerance. Greenleaf ranked this study as among the best he ever conducted, which is certainly high praise. The Denmark collaboration led to two papers, one abstract, and one chapter. It also “closed the loop” on Greenleaf's career of international collaboration, with his first and final such sabbaticals in Scandinavia.

Greenleaf and Management

Some of the above vignettes allude to persistent conflicts between Greenleaf and ARC management (Table 2). As noted above, he steadfastly adhered to safety and fiscal regulations. Over time, however, it became clear that little would be accomplished if one followed all managerial rules all the time. For instance, his superiors sometimes took months to approve a manuscript. In science, prompt publication is important: if others publish work similar to yours before you, it dilutes the originality and importance of your work. Therefore, Greenleaf learned to submit manuscripts for NASA and journal review simultaneously. He incorporated any changes required by management (usually nil or insignificant) when responding to journal referees. To his knowledge, management never knew of this practice.

View this table:
Table 2.

Dr. John Greenleaf's approach to management

Greenleaf's sole interest was always science, but it became clear that the primary goal of management was to obtain and spend money. At the end of one fiscal year, Greenleaf had excess money and asked his division chief to return it to NASA headquarters. The stunned and angry chief threatened to fire him if he ever made the suggestion again. A visiting headquarters manager once offered Greenleaf $100,000 of additional funding, which he rejected because he was already sufficiently funded. Managerial prestige and opportunity for advancement were tied not to research productivity, but instead to budget size. Greenleaf treated research funding as if it were his own money, yet this frugality directly opposed his leadership's goals. This schism continued throughout his career.

Controversies involving the allocation of authority and responsibility between principal investigators and administrators vexed Dr. Greenleaf throughout his tenure at ARC. Management consistently dodged requests for clear guidelines. Assignment of authorship constituted one major ongoing problem: what criteria must one satisfy to be included as co-author of a work, and who is the ultimate decision maker? Greenleaf adhered to formal, accepted definitions. He included individuals as co-authors if a study's success depended in some way on their specific participation and contributions. This left out administrators and other bystanding co-authors.

Another repeated challenge was who held authority to terminate a study, and for what reasons. Greenleaf's superiors occasionally sought to cancel a study (one suspects to divert the funds elsewhere). They would question hypotheses or methods after the protocol received the many necessary formal approvals, including their own as well as other merit, ethical, and safety reviews. Greenleaf challenged them to produce relevant literature to support their fresh concerns, which usually ended the matter. During one forceful and fateful discussion of a specific study, the chief threatened to present his “file” on Greenleaf to higher-ups. John then offered to similarly open his file on the chief. Threats of “file sharing” never emerged again, and that particular study went forward as planned. Greenleaf always wore a white laboratory coat to avoid being mistaken for a manager (Table 2).

As Greenleaf puts it: “People are people, so there will be similar problems everywhere. The major question is whether and how they can be resolved: fight is generally better than flight.” He advises finding a workable and stable position and staying there. This worked well for him overall and contradicts more modern ideas of career mobility. Given the time and other resources that Dr. Greenleaf spent overcoming administrative hindrance over the years, one wonders how productive he would have been with consistently facilitating and supportive oversight. Put another way, how much was scientific progress slowed, and how much did it cost us, for him to be opposed instead of helped by his “leadership?” How much are similar situations costing science today?

Retirement and Epilogue

John Greenleaf retired from ARC in 2002 (Fig. 6). His decision resulted primarily from the increasingly frequent movement of his office and laboratory by management. Without this harassment, he would probably have continued working another few years.

Fig. 6.

John and Carol Greenleaf at their home in California.

John remains busy during retirement with scientific consulting, his many hobbies, and of course enjoying retirement with his wife Carol. They've continued their tradition of going on a date every Friday, although now it's for lunch and not dinner. Greenleaf's peer-reviewed work includes 185 articles, 127 abstracts, and 26 chapters and books. He's also authored or co-authored 75 other publications, many of them NASA technical reports. He helped launch a sports hydration beverage, “The Right Stuff,” adapted from the citrate-based astronaut rehydration beverage “AstroAide” he invented while at ARC (3). History remains a strong interest, as indicated by reading tomes like Gibbon's six-volume The History of the Decline and Fall of the Roman Empire. As in high school, Greenleaf still enjoys riflery. (However, he no longer carries his gun on the bus to the local shooting range.) He continues to accrue honors recognizing his career.

John and Carol Greenleaf will endow funds to the APS for a future annual award in their name through the Environmental and Exercise Section. The award will reward first author publication in the Journal of Applied Physiology; Dr. Greenleaf had 25 such articles. They also fund a bequest to a local clinic for the purchase of medical instrumentation. John's desired epitaph is “He published, but alas, he perished.” Before this happens, we hope he writes his memoirs, because this article is too short to do his life and career justice.


The APS Living History Project funded the interview of Dr. Greenleaf that led to this biography.


No conflicts of interest, financial or otherwise, are declared by the author(s).


Author contributions: D.E.W. conception and design of research; D.E.W. analyzed data; D.E.W. prepared figures; D.E.W. drafted manuscript; D.E.W. edited and revised manuscript; D.E.W. approved final version of manuscript.


The author thanks Carol Greenleaf, Jenna, Kendra, and Shannon Watenpaugh, Dr. Vic Convertino, and Dr. Charlie Tipton for respective contributions. The author of course thanks the subject of this work, Dr. John Greenleaf, for a highly productive, educational, and inspirational career.


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