An interview with Patrick L. Jacobs, Ph.D.

Richard A. Passwater

Last month, we chatted with Richard Bloomer, Ph.D., about the role of GPLC (GlycoCarn from SigmaTau) in improving the performance of athletes. We discussed the basics of GPLC and nitric oxide (NO) production and how this, in turn, improves health and performance. Now, we will discuss additional aspects of this nutrient in terms of sports performance.

As we have discussed in previous columns, NO is very important to cardiovascular health and athletic performance. It also serves as an important signaling molecule involved in numerous physiological functions, such as improved blood sugar transport and antioxidant properties. This month, we learn from Patrick L. Jacobs, Ph.D., that GPLC also decreases lactic acid build-up, which allows muscles to perform longer.

Dr. Jacobs earned his Ph.D. in exercise physiology from the University of Miami. He is an associate professor in the department of exercise science and health promotion at Florida Atlantic University. He is a fellow of the American College of Sports Medicine and of the National Strength and Conditioning Association (NSCA) as well as a licensed athletic trainer (FL) and a certified strength and conditioning specialist of the NSCA.

Dr. Jacobs has published many peer-reviewed scientific publications documenting his application of diverse exercise and nutritional interventions in populations ranging from the spinal cord injured to the elite athletic competitor.  He has coordinated the performance programs of collegiate and professional championship athletes including football, baseball, power lifting, bodybuilding, auto racing and sailing. He is an inventor whose name appears on several exercise device patents and is a frequent guest on radio health programs throughout the country. Besides being a researcher and strength coach, Dr. Jacobs has done much research on exercises and whole body vibration for those with spinal cord injuries.

Passwater: Dr. Jacobs, how did you become interested in exercise physiology?

Jacobs: Initially, my interest in the field of exercise physiology was fueled by my passion to enhance sport performance, first as a competitive athlete myself and later as a coach. The concepts of exercise physiology provide a critical basis of sport performance in addition to kinesiology, biomechanics and sport

Passwater: What type of research does an exercise physiologist conduct?

Jacobs: Exercise physiologists examine how the different body systems (muscular, respiratory, circulatory, etc.) function at rest and during different types of exercise. They also research the way body systems change in response to exercise training programs. Thirty years ago, the vast majority of research in this area concentrated on the effects of endurance “cardio” training with an emphasis on such measurements as VO2max. Today, a major component of exercise physiology research examines the effects of anaerobic training with a great number of studies today sharing information regarding the benefits of various forms of resistance training.

Passwater: Some people confuse “sports medicine” with “sports nutrition” and “exercise physiology.” All are trying to help athletes achieve their best performance. Is it accurate to say that exercise physiologists specialize in optimizing an athlete’s training to produce his/her best performance, whereas in sports medicine, the goal is to optimize an athlete’s recovery from an injury?

Jacobs: I would agree that sport performance specialists do utilize the concepts and strategies of “exercise physiology” and “sports nutrition” as means to enhance physiological functioning and thereby boost performance. The field of “sports medicine” is generally considered to prevent and treat sports or exercise injuries, particularly injuries of the muscular and skeletal systems. However, it is my opinion that the “exercise physiologist” has much to offer in clinical settings as the progression of many diseases is linked with physical inactivity and poor nutritional habits.

Passwater: What led your interests to especially helping those with spinal cord injuries?

Jacobs: It has been my privilege to work with many outstanding athletes. As part of sports, we decide to participate knowing the risks associated with them. The vast majority of traumatic injuries are not sports related and often the injured persons did not contribute to the injury. Unfortunately, one of the outstanding athletes for whom I served as coach and agent, Dave Pasanella, did not survive a cervical spinal cord injury during an automobile accident with a drunk driver. At the time of the injury, Dave was the director of player development at Georgia Tech. He held many world powerlifting records and was poised to set records that were previously inconceivable. It was a shock to me when several persons voiced the opinion that it was better that he had not survived rather than to have had to face a life possibly defined by spinal paralysis. This perspective was strange to me and it angered me.

Several months later, I had the opportunity to join the efforts of the Miami Project to Cure Paralysis at the University of Miami Medical School. That organization is the largest group dedicated to researching the effects and treatments of spinal cord injuries. It was my privilege to coordinate research studies with persons that had spinal injuries utilizing strategies generally used in the sports performance arena and not applied commonly within the clinical setting.

Passwater: These efforts are outstanding human service; I hope you find it rewarding. You also invented several exercise devices. What types of exercise devices have you created?

Jacobs: It is obvious that the wheelchair user, including most persons with significant spinal injuries, have limited exercise options. Much of my work involves the redesign of basic exercise machines to allow safe and effective training from the wheelchair. This is important, as transferring from wheelchair to another position often involves awkward and dangerous movements, if such movement is possible at all. Our efforts of redesigning basic weight-training stations to allow wheelchair access demonstrated both safety and efficacy, which prompted several large equipment companies to now offer their own wheelchair access lines.

Upper body endurance training is generally limited to the arm cranking-type devices, which are really little more than half of a stationary cycle bolted atop a table. These cranking devices are often quite useful in upper body cardiovascular testing. However, the repetitive pressing actions have been reported to increase shoulder and elbow pain over time. I am proud to have been involved in the design of a wheelchair-accessible, upper-body exercise device, the VitaGlide, which incorporates alternating arm pressing and pulling motions. The hand movements are coordinated to allow a stronger limb to assist a challenged limb and the movement pattern involves intersecting line of action thereby introducing a degree of rotation. It is always gratifying when some aspect of your research leaves the laboratory and in this case, the VitaGlide is a successful commercial product, marketed by S. R. Smith, a major recreation product manufacturer.

Passwater: How did nutrition enter into your research?

Jacobs: It is now pretty well agreed upon that your chances of excelling in sports are greatly improved with scientifically proven nutritional habits. Certain specific dietary compounds are known to provide physiological benefits and thereby enhance physical performance. Based on a sports performance background, it seemed logical to me that similar strategies might be effective in certain clinical populations.

For example, in an early study, we examined the effects of creatine monohydrate on upper body work capacity in people with cervical-level spinal cord injuries. Persons with motor complete tetraplegia are paralyzed from the neck down. They have no control of their legs and some control of the upper body. The triceps muscle receives much less neural input, thereby limiting the strength and endurance, while there is little, if any, appreciable pectoral strength. So, when people with tetraplegia perform upper bodywork, they are unable to stabilize their body position with leg tensing and they have much less intact functional upper body muscle available to help with the work. Low levels of work capacity can dramatically limit the degree of independence and life opportunities.

In this study, we looked at how much work could be done exercising on a hand crank exerciser as the workload was increased every three minutes. After only one week of supplementing the normal diet with 20 grams per day of creatine, the research participants with tetraplegia exhibited an increase of 18.6% in arm work capacity as determined by measurements of peak oxygen consumption (VO2peak). The increased work output was similar (on average) to that of persons with spinal injuries at two or three segments lower. Thus, in a manner similar to that used by professional athletes to gain a safe and ethical benefit, the physical limitations associated chronic physical disability may be reduced in some cases.

Passwater: We have discussed NO several times in this column in terms of heart and artery health as well as sports performance. Athletes are reading more and more about products that mention NO, NOX or NOS. What is the importance of NO to athletes?

Jacobs: NO carries out several very important functions. First, NO serves a primary role in the dilation of arterioles, the small-diameter blood vessels that branch out from arteries and lead to the capillaries, in order to increase blood flow into skeletal muscle. The quest for increased muscle blood flow so as to increase performance or training effects has produced a striking market of dietary supplements that claim to increase NO levels. The common active ingredient in most of these products is some form of arginine, which is the “precursor” or “building block” to form NO in the body. Unfortunately, in this case, there is no scientific evidence for increased NO with increased dietary intake of arginine in the product dosages. There is also absolutely no published evidence that any arginine-based commercial product produces significantly elevated blood flow during or following exercise.

Your chances of excelling in sports are greatly improved with scientifically proven nutritional habits.

In addition to vasodilation, NO carries out other vascular functions. These functions include anti-thrombotic and anti-inflammatory actions, which reduce endothelial adhesions of blood platelets and white blood cells, respectively. The vasodilatory effects of NO are produced by the relaxation of smooth muscle that spirals around the arterials. NO also blunts the hypertrophy that can occur in smooth muscles over time if exposed to extended periods of arterial constriction and elevated blood pressures.

Passwater: Since NO is a gas and you can’t eat it or take it as a pill, how can athletes best optimize the NO in their cardiovascular system?

Jacobs: We can attempt to increase NO with specific training strategies and with dietary supplementation. In general, the level of blood flow is directly related to NO levels. The kind of exercise that produces acute muscle swelling, or pump, is the kind of exercise that elevates NO levels. Today, the best elite coaches utilize high-intensity repeated bouts not only for performance benefits, but also for general conditioning and weight-loss programs.

Passwater: So, what type of exercise is this?

Jacobs: Repeated 30-second to two-minute sprints on the treadmill or bike with recovery periods in between that may be progressively reduced in length over several weeks. NO is known to be increased with repeated sets of weight-training exercise. Advanced strategies of the elite bodybuilder (e.g., supersets, forced reps) are to some degree utilizing biochemical and mechanical mechanisms that signal increased synthesis of NO.
Although you cannot take NO in pill format, you can take an oral nutritional supplement that has been shown to increase NO. Glycine propionyl l-carnitine (GPLC) has been shown in a clinical study to produce increased NO levels. That study, performed by Richard Bloomer, Ph.D. and associates, reported elevated NO levels at rest and in response to simulated high-intensity exercise.

Passwater: Yes, last month, we chatted with Dr. Bloomer about that research with GPLC (GlycoCarn) and he mentioned your research shows that GPLC allows a significant improvement in high-intensity exercise performance, as well as a significant reduction in blood lactate. What does this mean to an athlete?

Jacobs: Laboratory testing with repeated bouts of high-intensity interval exercise can provide measurements of peak and average work per bout and the rate of work decline as you get tired. Peak work output indicates the ability to produce work for a short period and the rate of work decline can show resistance to ongoing muscle fatigue with continued bouts. Improvement in peak work might be beneficial in sports tasks that involve high effort for a limited length of time. Sports that emphasize performing repeated bursts of physical work with limited recovery periods (stamina) might be related to the rate of work output decline. Improvements in high-intensity work capacity would presumably benefit athletes competing in the traditional team sports (e.g., football, basketball).

Repeated peak efforts of high-intensity exercise are generally associated with increased blood lactate levels. As exercise continues at high-intensity, anaerobic metabolism functions at a rate greater than the aerobic energy pathway is capable. At critical levels of work, there is a substantial accumulation of blood lactate and muscle fatigue. Lower levels of blood lactate at the same or greater work level indicate an enhanced metabolic efficiency.

Passwater: You mentioned football and basketball. Spring is here. Do these results apply to baseball and track as well?

Jacobs: First, it is important to point out that research studies will need to specifically examine the effects of GPLC in each of these sports. However, based on our laboratory testing we can predict benefits in these sports. Performance in sports like baseball and track are related to a high degree to the conditioning training leading up to game day, and they commonly involve repeated sprints as a means of conditioning. So, we might reason that this supplement may allow more intense training thereby producing greater training effects and superior performances. It has also been reported that GPLC may assist in better recovery between training sessions so there may be a benefit in baseball for which it is not uncommon to play games on successive days or to play double-headers. But again, future studies will need to be performed specifically addressing these situations.

Passwater: Please give us some specifics about your findings.

Jacobs: In this study, we looked at how GPLC affected the ability to perform five sprints on a stationary cycle in weight-trained, college-age men. Each sprint was performed for 10 seconds against a high-effort resistance based on bodyweight. A one-minute active recovery (slow pedaling to prevent muscle cramping) was allowed between each sprint. We measured the peak and average work performed during each sprint and the rate of work decline in addition to heart rate and lactate levels. Each subject completed the testing twice with one week between tests, once with GPLC and once with a placebo. The results of the testing indicated that with GPLC, these resistance-trained men were able to achieve significantly more work on the third (4.1%), fourth (15.7%) and fifth (4.4%) of the five sprints. That is, with GPLC there was a significantly reduced rate of work decline indicating a dramatic resistance to ongoing muscle fatigue. Lactate levels were significantly lower four minutes (15.6%) and 14 minutes (16.2%) after the last sprint. With GPLC, there was a 22.8% lower accumulation of lactate for given work output indicating a dramatic enhancement of metabolic efficiency.

Passwater: That’s a significant improvement that translates from the laboratory to the game or meet. Do you consider GPLC a safe and ethical dietary supplement that can help an athlete optimize his/her performance?

Jacobs: As Dr. Bloomer mentioned last month, GPLC is a USP-approved nutraceutical dietary ingredient used in numerous products marketed by different distributors. My confidence in GPLC is substantially supported by certification approved by Informed Choice. The tests by Informed Choice ensure that supplements and their ingredients are not contaminated and do not contain substances prohibited in different sports.

It is my belief that the use of nutritional strategies by sports participants for improved performance is completely ethical. Yes, there will be an advantage for persons who chose to apply such strategies just as there are performance benefits for persons who train intensely for their sport. The concept of an “even playing field” is not realistic. We all strive to gain some sort of performance edge over our competitors. This is not only true in sports, but also in all aspects of life. Compared with the questionable ethical actions of businessmen and politicians reported regularly, there really isn’t much of a question regarding the use of safe and legal nutritional supplements by athletes.

Passwater: What are your recommendations for using GPLC as a dietary supplement in terms of when to use it and how much to take?

Jacobs: Our initial study showed significant acute improvements in peak sprint work, reduced decline in work rate, with reduced lactate accumulated. In that study, the participants took 4.5 grams of GPLC in capsule with eight ounces of water 90 minutes prior to the exercise testing.

However, the next study indicated that 4.5 grams may not be the best dosage for chronic supplementation depending on the persons and goals. The results of this study have been presented at the annual meetings of the International Society of Sports Nutrition, and examined how one month of GPLC supplementation at one of three dosages 1.5, 3.0 or 4.5 grams per day would influence the sprint testing. The results showed significant performance benefits (increased work output and decreased lactate accumulation) with the 1.5 grams per day dosage. The 3.0 and 4.5 grams per day dosages did produce some degree of lower lactate levels. However, the higher dosages not only neglected to improve the sprint performance, but also resulted in lower work output in many cases than that produced the first day with placebo. The participants who took the 3.0 and 4.5 grams per day dosage during the one month of supplementation reported a very, very high level of muscle swelling (or pumping), which resulted in muscle stiffness and difficulty in sprint performance.

At this point, we have very few published scientific studies of GPLC and exercise, particularly in active healthy persons. Essentially, we have Dr. Bloomer’s study that suggested increased production of NO with exercise-like physical stress and the two-cycle sprint studies I have just described. Based on this limited amount of information, one might draw early speculations such as the daily dosage might be based on the sport goal. That is, it is not unreasonable to postulate that higher dosages, up to 4.5 grams in 90-kilo (198-pound) men, provide vasodilatory effects that may be beneficial in bodybuilding settings. One might also propose that in high-speed, high-intensity sports such as football or basketball, such a dosage would be detrimental but that a lower dosage such as 1.5 grams in 90-kilo (198-pound) men may provide performance benefits.

Please note that I am using words such as “speculate,” “propose” and “postulate” as the existing scientific data are currently insufficient to draw firm conclusions. Again, we are early in the scientific examination of GPLC. I feel that our position with GPLC is similar to the situation with creatine 15 years ago. We have a pivotal study showing changes in blood markers with oral ingestion and an initial performance study series that documents an increase in work output. While it is appealing to speculate regarding the “best” method to use GPLC, it is much too early in the research process.

Passwater: Where are your research interests taking you now? What are you working on?

Jacobs: I am currently continuing with studies on GPLC, but in the real world setting. These studies are conducted in the real life exercise laboratory, training gyms and community parks. These settings allow field testing of the outcomes that are truly  important to the consumer of nutritional supplements including strength, stamina, endurance and body composition.

Another important area of my research is looking at the use of whole body vibration (WBV) devices as a very interesting and exciting means of physical conditioning. My first studies used vibrating platforms with current and future studies expanded to include a number of different strategies to provide vibratory influences during exercise. The results of completed studies have shown impressive effects of these WBV devices in athletes and in persons with spinal cord injury. The preliminary findings suggest the application of this technology in both sports performance and in clinical settings.

Passwater: WBV is interesting to me and I have been waiting for more research and lower equipment prices. Thank you, Dr. Jacobs, for sharing your knowledge with our readers and for helping so many people, especially spinal cord injury victims. Your research lifts the spirit as well as the body. WF

Dr. Richard Passwater is the author of more than 40 books and 500 articles on nutrition. He is the vice president of research and development for Solgar, Inc. Dr. Passwater has been WholeFoods Magazine’s science editor and author of this column since 1984. More information is available on his Web site,


Published in WholeFoods Magazine, April 2010