Week 10 journal club

For this journal club we will be looking at the following article in the Journal of Sport Sciences.

Carling C, Le Gall F, Dupont G. Analysis of repeated high-intensity running performance in professional soccer. Journal of Sports Sciences 2012, 30:4, 325-336

The article was chosen by Steven Curnyn, a fitness instructor who is studying an MSc in Sport Performance Enhancement. There were two main aims to the research, firstly to characterise repeated high intensity movement profiles of a football team and secondly to verify the validity of tests that are often used to look at repeated sprint ability in football.

Have a read of the research, review and then add your comments about the research below. Do you like the study? Do you think it used the best design to answer the research question? You may find these tools useful when critically appraising the article. I will summarise the comments on the weekend of 23rd June.

Week 9 journal club summary

We looked at the paper below for this sport science journal club. It focused on the effects of beetroot (BR) juice on running and walking.

Lansley KE, Winyard JF, Fulford J, et al. Dietary nitrate supplementation reduces the O2 cost of walking and running: a placebo-controlled study. J Appl Physiol 2011; 110: 591-600.

What was the aim of the paper?

Beetroot juice has previously been shown to reduce resting blood pressure, and the oxygen cost of submaximal exercise. Research has also shown that it can increase tolerance to high intensity cycling. The researchers had three main aims for this study:

1. Were the physiological effects of BR due to the high nitrate content?
2. How much of the increase of nitrate bioavailability with BR may increase mitochondrial biogenesis (process by which new mitochondria are formed in the cells)?
3. Extend the previous findings to walking and running.

The researchers hypothesised that BR supplementation would increase plasma nitrate and reduce blood pressure, reduce oxygen cost of walking and running and increase exercise tolerance and increase muscle oxidative capacity. The researchers were from the University of Exeter.

What did the study involve?

Nine men were recruited for the study and after the researchers determined their VO2 max and the participants completed ‘step’ running tests, they were assigned to either consume 0.5 l/day of nitrate rich BR (containing around 6.2 mmol of nitrate) or nitrate depleted BR for 6 days. During days 4 and 5, participants repeated the step running tests and on day 6 they performed knee-extension exercise tests. The participants were told to drink the BR slowly, 3 hours before exercise.

What were the main results?

The researchers found that mitochondrial oxidative capacity was not different between placebo and beetroot but the oxygen cost of walking, moderate intensity running and severe intensity running was reduced by BR. They also found that time to exhaustion during severe intensity running was increased.

What can we take from it?

This was a really interesting and very in-depth study that adds to what we already know about BR juice and exercise. The findings suggest that short-term dietary supplementation with nitrate rich BR juice reduced the oxygen cost of walking and moderate and severe running, and increased time to exhaustion. An important point in this study was that the researchers were able to use nitrate depleted placebo juice, which made sure that the protocol was double-blind and the participants did not know which juice they were drinking.  The researchers believe that the results may be important for people with cardiovascular problems as the BR was shown to reduce the oxygen cost of walking, which may significantly improve their quality of life.

I really enjoyed reading this study and thought it was well written and included lots of detail, such as the subjects abstaining from using chewing gum throughout the study. The use of the randomised, crossover design ensured that the participants acted as their own controls which helped to reduce bias. I liked the use of illustrations to show the exercise test protocol and the tables and figures. I’m looking forward to reading more research in this area. The author from this paper has answered a number of questions about his research for sport science journal club, which you can read here.

Week 9 journal club – Q&As with the author

For week 9 journal club we looked at the following beetroot juice research paper:

Lansley KE, Winyard JF, Fulford J, et al. Dietary nitrate supplementation reduces the O2 cost of walking and running: a placebo-controlled study. J Appl Physiol 2011; 110: 591-600.

I received lots of questions for the researcher, Dr Stephen Bailey, about his research. Stephen is a lecturer in exercise physiology at Exeter University. He has very kindly answered all of our questions and you can read the responses below.

Q. Your study only used 9 participants. Did you carry out a power calculation to calculate the minimum sample size for your study? Sarah Rossiter (Sport and Exercise Physiologist)

A. Yes, we calculated the number of participants required to detect significant differences by using the effect size reported in the initial study by Larsen et al. (2007).  We and others have since published a number of papers confirming these effects using 8-10 subjects.  This indicates that the sample size provided an appropriate level of statistical power to detect the physiological and performance changes after beetroot juice supplementation.

Q. Is there potential for beetroot juice to positively impact intermittent exercise? Kevin L Merry (lecturer in Sports and Exercise Science at Loughborough College)

A. We have previously shown that beetroot juice supplementation can reduce the ATP cost of muscle force production during high-intensity exercise (Bailey et al., 2010, Journal of Applied Physiology, 109, 135-148).  We showed that this reduced muscle phosphocreatine (PCr) utilisation and it might also have reduced muscle glycogen utilisation.  Since PCr and glycogen are important substrates for anaerobic metabolism within the muscle, then a reduced utilisation of these substrates during exercise may increase the number of high-intensity bouts an individual can complete before these reserves attain low levels and performance is compromised.  In addition we also showed in this study that the accumulation of inorganic phosphate (Pi) and adenosine diphosphate (ADP), metabolites that are associated with the development of muscle fatigue, was lower.  Therefore the potential for sparing the limited anaerobic energy reserves and for lowering the accumulation of metabolites linked to the process of muscle fatigue after beetroot juice supplementation would be hypothesised to improve intermittent exercise performance.  While this hypothesis has yet to be empirically tested, we have anecdotal evidence from team sports players who are very positive that beetroot juice supplementation is capable of enhancing intermittent exercise performance.

Q. Would you expect to see significant improvements in performance the more endurance trained the athlete? James Bray (part-time exercise physiology PhD student)

A. There is some evidence showing that the plasma nitrite and nitrate concentrations might be higher in training compared to untrained humans.  Since beetroot juice supplementation is effective because of its ability to increase the plasma nitrite concentration, the scope for beetroot juice to be effective in trained athletes might be lower compared to untrained or lesser trained individuals.  Alternatively, a larger dose may be needed to provoke the physiological and performance benefits observed in less training individuals in trained athletes.  Moreover, trained athletes have better muscle oxygenation and since the conversion of nitrite to nitric oxide is enhanced when oxygen levels are lowered, it is possible that nitric oxide production from nitrite might be lower in this population.  At the moment the literature is equivocal with regards to the ergogenic effects of beetroot juice supplementation in trained endurance athletes.  It is possible that the extent to which beetroot juice supplementation is ergogenic in athletes might be dependent on the interaction between the nitrate dose, the event duration and intensity, and the training status of the athletes.  Therefore, further research is required before beetroot juice supplementation can or cannot be recommended as an ergogenic aid for athletes.

Q. Should one drink beetroot juice if they experience GI issues? Perhaps the night before? Aaron Paige (Aspiring exercise physiologist and athletic trainer)

A. The subjects who have participated in our studies to date have not reported any significant GI troubles so this is likely to be uncommon following the ingestion of the volumes of beetroot juice consumed in our studies.  For individuals who do experience GI issues, you could have them use the new concentrated beetroot juice shots which provide the same nitrate dose for a lower volume (70 ml rather than 500 ml).  We know that plasma nitrite attains peak values 2.5 hours after beetroot juice ingestion and declines thereafter.  Therefore, is someone was going to drink beetroot juice the night before, they would still need to top up, perhaps with a couple of shots, 2.5 hours before competition.  

Q. When supplementing beetroot, is there a minimum time delay from seeing the effects of beetroot on performance? In your study the supplement was taken on 6 days, where others studies, I believe, have seen the effects of beetroot after 2 hours. Tom Watkiss (Sport and Exercise Physiology MSc student)

A. The plasma nitrite concentration peaks approximately 2.5 hours after consuming beetroot juice so we would not expected to see any changes less than 2 hours after drinking beetroot juice.  We have shown that supplementation with beetroot juice for 15 days appears to be more effective than 6 days and a single dose ingested 2.5 hours prior to exercise, so longer supplementation may be more beneficial.

Q. In terms of practicality for athletes, is there a limit to its effects? I.e. distance of race or total of race. Tom Watkiss (Sport and Exercise Physiology MSc student)

A. We have shown that beetroot juice supplementation is effective during event durations of ~6-20 minutes, but it is not known whether this applies to longer duration athletic events.  There is some evidence to show that the plasma nitrite levels decline during exercise so, while beetroot juice supplementation can elevate plasma nitrite levels, this will eventually be used up during exercise.  Therefore, it might be useful during long-distance endurance events to top up with beetroot juice shots during the race.

Q. From previous experience of research with BR (Beet it), some of my participants / athletes have anecdotally stated that they struggled with the palatability of BR & saw that as a potential limiter to usage. As you conclude that the positive physiological effects are due to high content levels of nitrate & you now have a mechanism of extracting nitrate, are there any plans to examine the potential for making a more palatable, high nitrate drink to compare against the effects of BR? Dylan Merkett (Health Editor at Bupa)

A. For individuals who struggle with the palatability of beetroot juice, you could have them use the new concentrated beetroot juice shots which provide the same nitrate dose for a lower volume (70 ml rather than 500 ml).  It is also important to note that it is the nitrate in the beetroot juice, not beetroot juice per se, that is responsible for the effects.  Therefore, the consumption of other foods rich in nitrates such as lettuce (particularly rocket), spinach, radishes etc., could be an alternative method to provoke these responses.  However, one thing that individuals should avoid is the uncontrolled consumption of nitrite and nitrate salts since this is dangerous and potential fatal (http://jap.physiology.org/content/111/2/616.long).  Accordingly, dietary interventions should be used to obtain these effects.

Many thanks to everyone who asked a question and to Stephen for responding to the questions and giving us a better insight into beetroot juice and exercise.

Week 9 journal club

The paper for this journal club is on the benefits of beetroot juice and exercise.

Lansley KE, Winyard JF, Fulford J, et al. Dietary nitrate supplementation reduces the O2 cost of walking and running: a placebo-controlled study. J Appl Physiol 2011; 110: 591-600.

Beetroot juice has received a large amount of press coverage recently, and one of the authors of this paper, Andy Jones, was recently on the BBC One Bang Goes the Theory TV programme.

We are lucky enough to have the opportunity to ask the author, Stephen Bailey, questions about his research. If you have a question, do send a Tweet or write it in the comments below.

Once you have read the paper, all you need to do is add your comments below so we can learn from each other and share our thoughts. I will summarise the paper and your comments on the 23rd May. When you read the research paper, have a think about the questions below.

• Why was this study done?
• Was it the best type of research design for the question?
• Was the process of treatment allocation truly random?
• Would participants have been able to know or guess their treatment allocation?
• Were participants and researchers ‘blinded’ to participants’ treatment group?
• Were outcomes assessed objectively?
• Were all participants who were randomly allocated a treatment accounted for in the final analysis?
• Were all participants’ data analyzed in the group to which they were randomly allocated?

 

 

Week 8 journal club summary

The paper for this journal club was related to functional movement, physical activity and weight in children.

Duncan M, Stanley M. Functional movement is negatively associated with weight status and positively associated with physical activity in
British primary school children. Journal of Obesity 2012.

What was the aim of the paper?

The researchers were aware that there was a lack of research on the structural and functional limitations of excess weight in children. The aim of their research was to look at the relationship between physical activity, functional movement and weight in children. The authors were from the Department of Biomolecular and Sport Science in Coventry University in the UK.

What did the study involve?

58 British school children (mean age of 10.7 years, over 80% Caucasian) were recruited for the study. The researchers measured body mass and height and calculated BMI. The children were classed as overweight or obese according to the International Obesity Taskforce (IOTF) criteria. Physical activity was measured using pedometers which the children used over four days (2 week days and 2 weekend days). Functional movement was assessed using the Functional Movement Screen (FMS). This included seven tests (deep squat, hurdle step, in-line lunge, shoulder mobility, active straight leg raise, truck stability push-up and rotary stability) and the children were given three trials of each test. The researchers took the highest score from the three trials for each test and used this to create a FMS score.

What were the main results?

The researchers found that FMS was negatively associated with BMI and positively related to physical activity. Normal weight children score significantly better for FMS score compared to overweight or obese children. BMI and physical activity were also significant predictors of FMS score, with BMI being a stronger predictor.

What can we take from it?

This was an enjoyable study to read with a simple research design. It would have been good to see a larger sample size with children of different ages and from different parts of the UK, not just Coventry. I would have also liked to have seen a power calculation for the sample size needed for this study.

The research design was explained clearly, but I feel like specific details about times of measurement of BMI, FMS and physical activity levels would have been helpful to give a better insight into the research. As Jon mentions, it’s well-known that BMI may not be completely accurate for body fat measurement, but the author Mike said that they used it because it’s used as part of the national child measurement programme. Mike also believes that he probably wouldn’t have reached a different conclusion if they had measured adiposity directly.

I’ve picked out the following comments about the research.

• Although the sample size was small, it gives a positive indication that this topic requires further research, with larger sample sizes.
• It may also be relevant to extend the objectives of this study to a wider age range, such as 8 to 16 year olds, to compare any differences between FMS score and physical activity across an age range.
• My concern is how can a test (FMS) be utilized for two different populations and come to useful and reliable conclusions?
• Can the level of obesity be more categorically reported than BMI?
• I think it would be interesting to see whether an intervention of exercise, diet, or exercise + diet significantly improves FMS score, to see what extent functional skill or functional limitation effect movement.
• we should consider the implications of reduced functional movement, altered gait, and lower body loads on the design of exercise prescriptions in overweight children.

Overall, this was a simple study that adds to the little research that has been carried out on physical activity, functional movement and obesity in children. Mike now wants to see what impact a physical activity intervention might have on children’s obesity and functional movement.

You can see more comments, questions and answers from fellow Sport Scientists and the author Mike here.

Week 7 journal club – Q&As from the author

For week 7 journal club we looked at the paper below. You can read a summary of this paper here.

Pelliccia A, Di Paolo FM, Quattrini FM, et al. Outcomes in athletes with marked ECG repolarization abnormalities. N Engl J Med 2008. 10: 152-61.

I was given the unique opportunity to ask the lead author, Antonio Pelliccia, some questions about his research. You can find out more about Antonio and his resarch here. I hope you find this Q&A session interesting and it gives you a better insight into his research and sudden cardiac death in athletes.

Q. Why did you decide to carry out this research?

A. The reason we carried out this work derived from our clinical practice. Not infrequently we observed, in our Olympic program, abnormal ECG patterns in the absence of any evidence for structural cardiac abnormality, symptoms or family evidence of cardiomyopathies. We were extremely curious to understand if these abnormal patterns, i.e., markedly and diffusely  inverted T-waves, were related to training or were the first and unique expression of unexpressed cardiac disease (i.e., cardiomyopathies).

Q. Why did you carry out a case-control design study and not a cohort?

A. The study started simply as an observational, prospective study on a cohort of athletes with abnormal repolarization pattern. Subsequently, the Editor of the NEJM asked for a control group and, therefore, we adapted our study population consistently. This has made our results more reliable and strengthen our observations.

Q. As a result of your research and other research in this area, do you think the regulations need changing for screening athletes?

A. Our result support the utility of ECG in screening athlete population during childhood and youth. Our results suggest that individuals showing abnormal repolarization patterns need to undergo serial (annual) evaluation, because they have the risk to develop a clinically patent disease.

Q. If athletes and the general public are worried about the increased media coverage of sudden cardiac death in athletes, what advice would you give to them?

A. Apparently, this is a period the media pay particular attention to the sudden deaths in elite and competitive athletes. Information should possibly include the effective value of the pre-participation screening, capable to pick most (although not all) subjects with cardiomyopathies. However, the screening does not guarantee the zero risk, due to lack of reliable strategies to identify in life other conditions, such as congenital coronary artery anomalies. Therefore, we should also support the implementation of the AEDs on the athletic fields as largely as possible.

Q. I recently attended the Marathon Medicine 2012 conference in London where we were informed about the differences in risk between men and women for sudden cardiac death. Were the athletes with cardiovascular conditions in your study male or female and do you think this affected your results?

A. In our study population, majority were males (63, or 78%) at the study entry. This disproportion between sexes reflects the larger proportion of male vs. female competitive athletes, as well as the larger incidence of abnormal repolarization patterns in males vs. females. Finally, all the events we reported in this study occurred in males. Our observations are in agreement with previous reports describing larger proportion of either abnormal ECGs and incidence of cardiac events, including sudden deaths, in males vs. females.

Q. Are you carrying out any further research in this field to see if the abnormal ECGs are initial expressions of heart disease or innocent expressions of cardiac remodelling that is associated with an athlete’s heart?

A. We are still working on this field. In particular, we were wondering why the largest  proportion of athletes we observed after a long-term did not develop symptoms or morphologic evidence for a disease. We want to be sure that this proportion does not reflect uniquely the limitations of the imaging testing or their still relative young age, and we want to asses which is the impact of their participation to competitive events for a long time period. So far, we had the chance to observe a few of these athletes reaching senior age without experiencing symptoms, or any structural cardiac disease.

Q. And finally, do you think pre-screening is really worth it if athletes continue to play on despite their awareness of an underlying heart condition?

A. The pre-participation screening is really worthy to identify individuals with silent cardiomyopathies that may be at risk. Then, appropriate evaluation and risk stratification should follow, including appropriate management and treatment (that occasionally includes drugs, or ICD, and/or withdrawn from competitive sport). Playing sport despite contrary advice is senseless and, as physician’s opinion requires condemnation  on behalf of the family, sport bodies  and scientific association. In Italy there is a federal law supporting the final physician decision and, therefore, playing against proper physical advice is illegal.

Thank you to Antonio for giving us a great insight into his research and for taking the time out to answer the questions.

Week 8 journal club

The paper for this journal club is related to functional movement, physical activity and weight in children.

Duncan M, Stanley M. Functional movement is negatively associated with weight status and positively associated with physical activity in
British primary school children. Journal of Obesity 2012.

The paper was recommended by the lead researcher, Mike Duncan who is a BASES Accredited Exercise Physiologist, Sports Scientist, Researcher and Senior Lecturer at Coventry University. We know that overweight and obesity in childhood are a major health concern worldwide but there is limited research on the structural and functional limitations of excess weight in children. This research helps to add to the research in this area. Mike is happy to answer any questions that we have, so send sport science journal club a Tweet with your question.

Have a read of the paper and then comment below. Here are some questions to help when you read the paper.

1. Did the study address a clearly focused issue?

2. Is the study design appropriate to the stated aims?

3. Are the measurements likely to be valid and reliable?

4. Were the basic data adequately described?

5. Are the statistical methods described?

6. Do the numbers add up?

7. How large was the effect size?

8. How precise was the estimate of the effect (look for the confidence intervals!)

9. Did untoward events occur during the study?

10. Could there be confounding?

11. What do the findings mean?

12. What implications does the study have?

I will summarise the research and everyone’s comments on the weekend of the 5th May.