<![CDATA[Nathan Jeffs - Blog]]>Tue, 20 Aug 2019 21:59:48 -0700Weebly<![CDATA[#NoMore - blaming poor core stability for low back pain]]>Mon, 07 Jan 2019 17:04:58 GMThttp://nathanjeffs.ca/blog/nomore-blaming-poor-core-stability-for-low-back-pain
This is the first post in my #NoMore series. It has to do with movement beliefs and manual handling theories which need updating based on the most up to date evidence. The main purpose of this series is to encourage a shift from the traditional kinesiopathological model of movement to a movement optimist approach. Another purpose is to educate people in the current evidence in a short and concise(ish) manor. I hope that you learn something and enjoy the read. 

First, I would like to acknowledge three blogs which were extremely influential in the creation of this post:

1. Ben Cormack - Core Stability - Does it matter? A Look at the evidence 

2. Brendan Moutt - Why we need to stop blaming the Transversus Abdominis for back pain​​

3. Greg Lehman - Core stability and pain: is it time to stop using the word stability to explain pain?

Next, I should start with a brief overview on some statistics for back pain. Throughout their lifetime, 60-80% of people experience low back pain at least once (Gordan & Bloxham, 2016). The majority of this pain can be labeled as non-specific in nature, meaning not caused from a insidious pathology. Finding a solution to this problem is an extremely difficult and complicated task; one of the proposed ways to do this is through core stabilization exercises to help stabilize the spine. 

Brief History of the Core Stability Theory for LBP

First we must start with a bit of history to understand why lack of core stability has earned blame as the cause of low back pain. 

The setting is Queensland University in Australia in the 1990's. Two researchers, Dr. Paul Hodges and Dr. Carolyn Richardson, published a series of papers which looked at transverse abdominis (TVA) and multifidus timing while performing various tasks in people with and without low back pain. 

The first study, published in November 1996, looked at the difference in TVA timing in subjects (n=15) with low back pain (LBP) and subjects (n=15) in a control group without LBP. The researchers instructed both groups to move their shoulders in various planes of motion and they measured the timing of TVA and multifidus via EMG. They identified that these two core muscles turned on before or within 70-113 msec of the deltoid activation. Therefore the conclusion from their research was that in those with LBP the TVA and multifidus was delayed in activating (by 70-113 msec). 

The second study, published in February of 1998, investigated the association between lower limb movement in people with LBP (n=15) and a control group without LBP (n=15). While performing these movements they had an EMG recording timing for TVA, rectus abdominis, abdominis obliquus externus, abdominis obliquus internus, and the erector spinae. With this study they found that the TVA was delayed 57-86 msec in those who were experiencing LBP. 

One of the main conclusions from these two studies from Hodges and Richardson was " The mechanism of delay in abdominal muscle activity is also uncertain. Furthermore, it is not known whether the delay in abdominal muscle contraction associated with limb movement proceeds the onset of LBP or is a result of the pain." They hypothesized that a diminishment of stabilization of the lumbar spine is one of the contributors for those experiencing LBP. 

Now, we should be asking ourselves (like Hodges & Richardson did) why was there this delay. Was this caused by the LBP or was it in response to the LBP. Whichever it is we must also question the relevance of a ~50 ms delay. 

This research lead to the idea of the feed-forward criteria as speculated by Hodges & Richardson (1998) for the core stabilizer muscle timing. The idea is that the brain prepares/plans for the movement prior to and not in response to the movement; this was proposed as a result of their findings that prior to the movement of the deltoid, the TVA and multifidus activated.

And BOOM, this research was extrapolated by chiros, physios, and other manual therapists as  we need to focus on spinal stability for rehab because the TVA and other spinal stabilizers are weak and the spine is unstable. This is however not what this study found; all it found was that there was a delay.

Current Research on Core Stability and LBP

When we move to focus on more recent research, which looks at the utilization of core stabilization exercises and outcomes of reduction in LBP, we find the following: 

1. Research conducted by Vassejen et al. (2012) looked at the effect of core stabilization exercise on the feed forward mechanism of activation with a similar deltoid movement that Hodges used. They also compared this core stabilization group to a high load sling exercise group, and to a general exercise group. After an intervention period of 8 weeks in all groups they looked to see if there was a difference in onset of the abdominal muscles. 

After 8 weeks they found that there was no difference in pain between the three groups. They did find that their was a change from 19 msec delay to 15 msec in the high load sling exercise group, but no changes in the two other groups. From these findings they concluding that the "abdominal muscle onset was largely unaffected by 8 weeks of exercise in chronic LBP patients. There was no association between changes in onset and LBP". Therefore, from this study we find that 8 weeks of stabilization exercise training didn't have an effect on the timing via the feed forward mechanism. This means that if this delay is the cause of pain we may not be able to affect it through stabilization specific exercises. 

2. Another RCT published by Carnes, Foster, & Wright (2006) looked at spinal stabilization exercise against "conventional physiotherapy" exercises (general activity exercises) in patients who experienced recurring LBP with a follow up at 6 and 12 months. Using metrics to analyze physical functioning, pain, psychological distress, and quality of life to determine if there was a difference between the two groups and also when compared to a control group. 

Their conclusion from this research was that "specific spinal stabilization exercises provide no additional benefit in terms of physical functioning, pain, psychological distress, and quality of life over a package of care consisting of advice and conventional physiotherapy (mainly exercise and manual therapy). Both groups had a clinically meaningful improvement in function and reduction in pain over time, but no statistical difference between groups was shown." Therefore, both groups were able to experience decrease in their scores, showing that general exercise is equally as effective in providing clincially meaningful improvements as spinal stabilization exercises.

3. Next we must look to see if a change in abdominal muscle contraction is associated with improved clincial outcomes, luckily we have Marrion et al. (2012) who carried out exactly this research. They looked at spine stabilization exercises in the treatment of chronic LBP to see if it had a better clinical outcome. They also tried to identify if there was a change in the feed forward activation of TVA, obliquus internus, and obliquus externus during rapid arm movement pre and post stabilization exercise program. They also measured to see if there was a decrease in pain (0-10 scale) and disability (Roland - Morris Questionnaire). 

They found that post intervention there was a significant difference in the ability for the subjects to voluntarily activate their TVA (4.5%, P=0.045), however based on their data they concluded that clinical outcomes based on the utilization of spine stabilization exercises didn't depend on the patients ability to recruit TVA during the task.  Another way they phrased that was that the TVA muscle function before or after intervention wasn't a statistical predictor of a good clinical outcome. This is a significant result because if the voluntary activation of TVA isn't related to beneficial clinical outcomes, then we have to identify some other cause for the decrease in pain and disability.

4. One last study which I will look at is Marshal et al. (2013), Pilates or cycling for chronic LBP.  The participants (n=64) were randomized into two groups; one which completed specific trunk exercise (the Pilates group) and one which cycled on a stationary bike. Both groups went through 8 weeks of intervention. At the start of the study, at 8 weeks, and at a 6 month follow up, they had the participants rate their pain, disability, and catastrophizing.

They found that after 8 weeks of intervention disability was significantly lower in the Pilates group. They also found that pain and catastrophizing were reduced from baseline in both groups. When they moved to the follow up at 6 months they determined that there was no long-term difference between groups on clinically meaningful improvements. It is important to note whether or not having a decrease in pain at 8 weeks was relevant. Since these patients were chronic in nature, the difference in the groups could have been a result of their beliefs on pain and not due to the stabilization exercises. Either way this study is important because it is more evidence to show that general exercise is equally as effective of a treatment for LBP as spinal stabilization exercise in the long term. 

When we summarize the studies looked at in this post, there is a clear direction in which the evidence appears to point. However, how can we be sure that this is indeed the way the evidence actually looks and not just the result of my selection bias (and me not wanting to summarize study after study)? Well, we can look at systematic reviews and meta analysis and find out what additional information they have to offer. 

Literature Reviews

There have been numerous systematic reviews and meta-analyses (Saragiotto, et al, 2016; Rackwitz, et al., 2006: Macedo et al., 2009; May & Johnson, 2008; Ferreira et al., 2006; Smith, Littlewood, & May, 2014) published regarding stabilization exercises and their influence on outcomes for LBP. The conclusion of most include a statement which reads similar to this: there is no additional benefit of prescribing motor control or TVA activation exercises over other forms of exercise for long term outcomes. 
However, we do find one outlier to this general theme by Bystrom, Rasmussen-Barr, & Grooten, (2013). Their review did find that motor control exercises had better outcomes, however the researchers stated "It is to date not known if the effect of MCE (motor control exercises) on pain and physical impairment in LBP is due to the isolated activation of the local musculature or subsequent stages of the intervention involving loaded postures engaging all trunk muscles." They were not able to identify if the intervention was successful due to its specificity or due to the engagement in activity. 

Another review I want to highlight, which had a very strong conclusion, was by Smith, Littlewood, & May (2014). They found "there is strong evidence stabilization exercises are not more effective than any other form of active exercise in the long term. The low levels of heterogeneity and large number of high methodological quality of available studies, at long term follow-up, strengthen our current findings, and further research is unlikely to considerably alter this conclusion." 

Fairly conclusively, the evidence points (and not just due to my selection bias) that the theory of the spine being unstable and needing stability does not stand up to the academic process. However, as we know about many other theories out there, it takes a lot of time to reverse false narratives which have been widely regarded for some time. Hopefully this post is a drop in the bucket which moves us closer to better understanding. 

5 Key Take Aways

1. LBP is a multifactorial issue and many aspects of the biopsychosocial framework have relevant influence upon pain and disability. Many times a single intervention as a blanket treatment is not the best option. 

​2. Yes, core stabilization exercises help to reduce LBP. However, it doesn't seem like it is because there is a change in TVA timing or spinal stability, and it doesn't appear to reduce pain any more than other active exercise in the long term (Smith, Littlewood, & May, 2014).

3. A great take away is that we don't have to prescribe these over-complicated stabilization exercises if that isn't what the person in pain wants. We can get people back to doing what they want to do through general graded activity. 

4. Focus on individuality, educate patients about pain, treat the whole person in front of you and not only the condition. 

5. Empowering someone in pain to be able to choose the activity can have a positive influence on their adherence to the exercise (Middleton, Anton, & Perri, 2013). If they are more active they will also get all of the other secondary benefits that exercise gives. 

All the information in this post gives us all the more reason to be/become Movement Optimists

Thank you for reading,
<![CDATA[Winter Reading List]]>Thu, 06 Dec 2018 18:07:21 GMThttp://nathanjeffs.ca/blog/winter-reading-listNot much beats curling up with a book by the fire during the winter months
Well, I saw TSN post the first updates about this years World Juniors tournament so I guess that means its officially the holiday season. With that comes shorter days and longer nights; what better way to spend them than learning valuable skills and/or becoming inspired for future adventures. I have compiled a list of books which I have read this year which I highly recommend you take a look at:

Endure - Alex Hutchinson

The body vs the mind; what is the body's rate limiter? Hutchinson sets out to provide insight on the topic in his most recent novel. He identifies two different views of endurance which range from A. V. Hill's view of "The Body is a Machine" to Tim Noakes view of "it's all in your head". Individual topic's in the book range from analyzing free divers and their need for oxygen to antarctic expeditions where food is scarce. 

When you finish this book you will gain an appreciation for how it isn't just the mind which limits human performance; and it also isn't just the body. It's a network which interacts concisely and unconsciously to propel us to reach the limits of our potential and performance.  

Runners of the Nish - Alex Cyr

I am a little bit biased on this pick because it was written by good friend and team mate, Alex Cyr. Throughout this book, Cyr outlines the 2016 Cross Country season for the StFX X-Men. He highlights the ups and downs that were experienced throughout the season through his own unique perspective. He describes the high hopes that our team had that year and how the season played out heading towards the U Sport Championships which were held in 2016 on the Plains of Abraham. If you want to know the day to day journey of a Canadian University XC Athlete look no further. Throughout this book you will find humorous stories such as accidentally leaving teammates in trunks to more trying events such as not performing to the teams potential on the national stage. It truly is a one of a kind book in which you won't want to put down.  

Motivational Interviewing  - William R. Miller & Stephen Rollnick

This book arrived on my radar through a recommendation from a practicing Physical Therapist. Interviewing skills are a fundamental skill a health care practitioner needs to master in order to gain sufficient insight into the history of each patient's injury and also in order to provide the best care possible.

​This book enables you to be confident in your ability to help people help themselves. Through teaching you about instilling confidence in your patients to helping facilitate change in themselves. This book is a must read for anyone who interacts with people as part of their profession.  

Astrophysics for People in a Hurry - Neil Degrasse Tyson

I often find myself staring up at the stars in amazement at how "humongous big" the universe is (insert Ilya Bryzgalov video). I decided I wanted to learn more about the solar system and space so I picked up this book.
As someone who is relatively unfamiliar with astrophysics and its concepts, I figured this would be a perfect place to start. Never before has so much complex information been so accessible to the average individual. Tyson explains concepts such as the Big Bang, dark matter, what is located between galaxies, and so much more. 

This book truly is for people in a hurry. At around 200 pages it is a quick and thought provoking read which you can be sure to use to impress relatives this holiday season.

12 Rules for Life - Jordan B. Peterson

12 Rules for Life  is not your ordinary self-help book; backed by many years as a clinical psychologist, Jordan Peterson uses all his experience to give tips on how to take responsibility in your own life. He explains why you should clean up your room in order to get your life in order, why you should always stop to pet a cat you find on the street, and also why you should stand up straight like a lobster. He also identifies the wisdom which is found in old texts that can be used to help us understand ourselves and  Western culture.

This book will provide motivation for those who need to adopt responsibility in their life, develop more discipline, and encourage you to find adventure in your life.

My World - Peter Sagan

This book just arrived at my door the other day after having pre-ordered in the Spring. I am just starting to dive into it so I cannot give as much as a in depth review, however I can describe what this book is about. Sagan who is arguably one of the worlds best all round cyclists outlines the three seasons he spent wearing the Rainbow jersey as the Road Cycling World Champion.  He talks about his time on Team Tinkov and the transition to BORA-Hansgrohe. He provides insights from a behind the scenes standpoint that few get to experience. 

Towards the back of the book he has also included some beautiful pictures which commemorate the last three seasons as the world champion. I look forward to reading this book over the Christmas holidays and will update this review once completed.

<![CDATA[Beetroot Supplementation: A possible ergogenic aid?]]>Mon, 12 Nov 2018 08:00:00 GMThttp://nathanjeffs.ca/blog/beetroot-supplementation-a-possible-ergogenic-aidIntroduction

Citius, Altius, Fortius; the Olympic motto meaning Faster, Higher, Stronger. That is in essence the goal of athletic performance; however it is to not only to go faster, higher, and/or stronger than your competition but also from your previous self. With this in mind, athletes are always trying to get a leg up on their competition. They look for specific training programs, substances, recovery techniques, etc so they can perform better than the rest. This is where the interest of beetroot supplementation as an ergogenic aid arises.

Beetroot (BR) supplementation has had lots of interest from a performance enhancement standpoint due to its high concentrations of dietary nitrate (NO3-); which is reduced within the body to nitrate (NO2-) and nitric oxide (NO) (Larsen, Weitzberg, Lundberg & Ekblom, 2010). Once NO is in the body it produces multiple physiological effects which include, but are not limited to vasodilation of blood vessels, mitochondrial biogenesis, and increased glucose uptake (Zaferiridis, 2014). These effects work to reduce exercise-related fatigue, increase exercise efficiency, and to increase exercise performance (Jones, 2014). Throughout the literature BR supplementation has been shown at times to be an ergogenic air for endurance exercise. Throughout this post I will try to identify the dosage, timing, and population that supplementation seems to be most effective so that you can tailor it to your own training regime and reap the benefits. 

Physiologic Effects of BR Supplementation

The bioavailability of nitrate in the upper gastrointestinal tract is 100%, which enables all nitrate which is ingested to be taken up in the blood stream without undergoing “first-pass” hepatic metabolism (van Velzen, Sips, Schothorst, Lambers & Meulenbeltg, 2008). When the saliva enters the mouth the initial breakdown of NO3to NO2occurs (Figure 1) through nitrate-reducing commensal bacteria, which are contained on the tongue (Larsen, et al, 2010). The nitrite is then further reduced to NO after entering the acidic environment of the stomach (Bryan & Ivy, 2015). NO3which is not reduced by oral bacteria is absorbed in the small intestine, enters the blood stream, and is then reduced to NO2then NO (Larsen, et al, 2010). NO is then circulated through the blood steam where its effects are elicited. This breakdown reaction is an irreversible reaction, meaning that NO cannot be converted back into NO2- (Campbell, 1999). The physiological function of NO within the body is through the regulation of blood flow, neurotransmission, muscle contractility, and mitochondrial biogenesis (Wylie, et al., 2013).

Nitrate supplementation has exhibited an increase in endurance exercise economy by allowing one to use less O2 while maintaining the same work rate (Vanhatalo et, al., 2010; Cermak et, al., 2012; Christensen et, al., 2013). Nitrate supplementation has also been shown to enhance exercise tolerance by 3%-25% in both cycling and running during time-to-exhaustion trials and reduces steady-state VO2 by 3-14% in endurance trials (Boorsma, Whitfield & Spriet, 2014). Beetroot also been shown to decrease systolic and diastolic blood pressure by ~4%, and in combination these changes may lead to less physiological stress prior to exercise and a prolonged exercise duration (Jones, 2014). Common interventions include administration of nitrate as beetroot juice or sodium nitrate capsules, and both have demonstrated a decrease in oxygen consumption and reduced rating of perceived exertion.
Figure 1: Nitrate reduction to nitric oxide within the body. Beginning with reduction by anaerobic bacteria in oral cavity, then further reduction in the stomach. Nitrate which has not been reduced is absorbed by the small intestine then enters the blood stream (Domínguez et al., 2017)
Dosage of Supplementation 

With BR supplementation there seems to be an amount where taking more does not provide additional benefits. This is helpful information for the average individual because BR juice is expensive and by knowing the ideal dosage it is easier to purchase the amount needed and therefore not needlessly wasting money. The recommended dosage appears to be ~6-8mM nitrate/day and taken 120 minutes prior to exercise (Dominguez et al., 2017). Since it appears to have the most effect around 2-3 hours after ingestion this should provide the maximal ergogenic effect (Jones, 2014).

Length of Supplementation

Long term supplementation appears to be the most effective means of evoking performance benefits from BR supplementation. This may be due to in order to see physiologic changes such as mitochondrial biogenesis, a longer supplementation is required (Dominguez et al., 2017). The recommended amount of time for long-term supplementation is 4-7 days in length and to be ingested 2-3 hours before exercise (like stated above) because this is when nitrate concentrations peak (Figure 2) within the blood plasma (Jones, 2014). 
Figure 2: Steady state VO2 at 40, 60, and 80% of VO2MAX following 5 days of supplementation with placebo (PL) or beetroot (BR)
Target Population
Throughout the literature it seems as though there is a ceiling as to when a person is too fit to experience an increase in performance due to supplementation. BR supplementation does not appear to be effective with a population of a VO2max above 70 mL/kg/min (Boorsma et al., 2014; Hoon et al., 2013; Peacock et al., 2012). BR supplementation  was most effective when looking at a population with a VO2max with less than 60 mL/kg/min (Bailey, et al., 2009; Cermak et al., 2012; Larsen et al., 2007; Carriker et al., 2016). These studies found that the main ergogenic effect is the reduction of O2 consumption (~5%) at sub maximal efforts (40, 60, 80% of VO2max). There, however is some gaps in these research and when looking at some studies which focus on elite athletes, such as the Boorsma et al. (2014), it appears their can be outliers who respond positively to BR supplementation and exhibit performance benefits.  

Overall, nitrate supplementation is typically shown to be an effective means to reduce O2 consumption during endurance activity for recreational athletes with a VO2max below 60 mL/kg/min.  ​Dietary nitrate research suggests that the most notable effect of nitrate is a decrease in the oxygen cost of exercise and an increased tolerance for submaximal work rates. (Zafeiridis, 2014). Christensen et al. (2013) and Boorsma et al. (2014) have hypothesized that approximately 25% of elite athletes may benefit from nitrate supplementation. As far as dosage it appears that a quantity of 6-8 mM nitrate/day to be most effective when combined with a 5-7 day supplementation.


Bailey, S. J., Winyard, P., Vanhatalo, A., Blackwell, J. R., Dimenna, F. J., Wilkerson, D. P., Jones, A. M. (2009). Dietary nitrate supplementation reduces the O2 cost of low-intensity exercise and enhances tolerance to high-intensity exercise in humans. Journal of Applied Physiology, 107(4), 1144-1155.

Boorsma, R. K., Whitfield, J., & Spriet, L. L. (2014). Beetroot juice supplementation does not improve performance of elite 1500-m runners. Medicine and Science in Sports and Exercise46(12), 2326–34. https://doi.org/10.1249/MSS.0000000000000364

Bryan, N. S., & Ivy, J. L. (2015). Inorganic nitrite and nitrate: evidence to support consideration as dietary nutrients. Nutrition Research35(8), 643–654. https://doi.org/10.1016/j.nutres.2015.06.001
Campbell, W. H. (1999). Nitrate Reductase Structure, Function And Regulation: Bridging the Gap between Biochemistry and Physiology. Annu. Rev. Plant Physiol. Plant Mol. Biol50, 277–303.
Carriker, C. R., Vaughan, R. A., VanDusseldorp, T. A., Johnson, K. E., Beltz, N. M., McCormick, J. J., Cole, N. H., Gibson, A. L. (2016). Nitrate-Containing Beetroot Juice Reduces Oxygen Consumption During Submaximal Exercise in Low but Not High Aerobically Fit Male Runners. Journal of Exercise Nutrition & Biochemistry20(4), 27–34. https://doi.org/10.20463/jenb.2016.0029

​Cermak, N. M., Gibala, M. J., & van Loon, L. J. C. (2012). Nitrate supplementation’s improvement of 10-km time-trial performance in trained cyclists. International Journal of Sport Nutrition and Exercise Metabolism
22(1), 64–71. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/22248502

Christensen, P. M., Nyberg, M., & Bangsbo, J. (2013). Influence of nitrate supplementation on VOkinetics and endurance of elite cyclists. Scandinavian Journal of Medicine & Science in Sports23(1), e21-31. https://doi.org/10.1111/sms.12005
Domínguez, R., Cuenca, E., Maté-Muñoz, J., García-Fernández, P., Serra-Paya, N., Estevan, M., Garnacho-Castaño, M. (2017). Effects of Beetroot Juice Supplementation on Cardiorespiratory Endurance in Athletes. A Systematic Review. Nutrients9(1), 43. https://doi.org/10.3390/nu9010043

Hoon, M. W., Hopkins, W. G., Jones, A. M., Martin, D. T., Halson, S. L., West, N. P., Burke, L. M. (2014). Nitrate supplementation and high-intensity performance in competitive cyclists.Applied Physiology, Nutrition, and Metabolism39(9), 1043–1049. https://doi.org/10.1139/apnm-2013-0574

Jones, A. M. (2014). Dietary nitrate supplementation and exercise performance. Sports Medicine (Auckland, N.Z.)
44 Suppl 1, S35-45. https://doi.org/10.1007/s40279-014-0149-y
Larsen, F. J., Weitzberg, E., Lundberg, J. O., & Ekblom, B. (2010). Dietary nitrate reduces maximal oxygen consumption while maintaining work performance in maximal exercise.Free Radical Biology and Medicine, 48(2), 342–347. https://doi.org/10.1016/j.freeradbiomed.2009.11.006

Larsen, F. J., Weitzberg, E., Lundberg, J. O., & Ekblom, B. (2010). Dietary nitrate reduces maximal oxygen consumption while maintaining work performance in maximal exercise.Free Radical Biology and Medicine48(2), 342–347. https://doi.org/10.1016/j.freeradbiomed.2009.11.006
Peacock, O., Tjønna, A. E., James, P., Wisløff, U., Welde, B., Böhlke, N., Sandbakk, Ø. (2012). Dietary Nitrate Does Not Enhance Running Performance in Elite Cross-Country Skiers.Medicine & Science in Sports & Exercise44(11), 2213–2219. https://doi.org/10.1249/MSS.0b013e3182640f48

van Velzen, A. G., Sips, A. J. A. M., Schothorst, R. C., Lambers, A. C., & Meulenbelt, J. (2008). The oral bioavailability of nitrate from nitrate-rich vegetables in humans. Toxicology Letters181(3), 177–81. https://doi.org/10.1016/j.toxlet.2008.07.019
Vanhatalo, A., Bailey, S. J., Blackwell, J. R., DiMenna, F. J., Pavey, T. G., Wilkerson, D. P., Jones, A. M. (2010). Acute and chronic effects of dietary nitrate supplementation on blood pressure and the physiological responses to moderate-intensity and incremental exercise.American Journal of Physiology. Regulatory, Integrative and Comparative Physiology,299(4), R1121-31. https://doi.org/10.1152/ajpregu.00206.2010

Wylie, L. J., Kelly, J., Bailey, S. J., Blackwell, J. R., Skiba, P. F., Winyard, P. G., Jones, A. M. (2013). Beetroot juice and exercise: pharmacodynamic and dose-response relationships.Journal of Applied Physiology (Bethesda, Md. : 1985)
115(3), 325–36. https://doi.org/10.1152/japplphysiol.00372.2013
Zafeiridis, A. (2014). The effects of dietary nitrate (beetroot juice) supplementation on exercise performance: A review. American Journal of Sports Science, 2(4), 97–110. https://doi.org/10.11648/j.ajss.20140204.15