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Does dietary nitrate supplementation reduce the O2 cost of walking and running?

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.




Filed under Nutrition, Sport Science Journal Club

Q&As with Antonio Pelliccia, cardiologist for athletes

For 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.

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Functional movement is negatively associated with weight status and positively associated with physical activity in British primary school children

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.


Filed under Physical activity and children

Sudden cardiac death in athletes: Outcomes in athletes with marked ECG repolarization abnormalities

This journal club looked at a paper related to sudden cardiac death in athletes. It’s a very topical subject at the moment, with the press reporting about cardiovascular events in the Boston marathon and the tragic death of a 30 year old lady at the London marathon.

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.

What was the aim of the paper?

It’s known that young athletes may have abnormal ECGs without evidence of cardiac disease. However, the question remains as to whether these abnormal ECG patterns represent the initial stage of cardiovascular disease, or are they just expressions of athletic conditioning? The researchers wanted to look at the long-term outcomes in athletes with ECGs characterised by abnormal repolarization.

What did the study involve?

This was a matched case-control study. The researchers reviewed ECG data from a database of 12,550 athletes evaluated at the Institute of Sports Medicine and Science in Italy. In Italy it is required by law for all athletes to undergo screening to rule out cardiovascular disease that could be associated with an increased risk during training and competition. The researchers identified 81 athletes that had abnormal ECGs (showing marked repolarization abnormalities) and excluded those that had evidence of structural heart disease. They compared this data with a control group of 229 athletes who had normal ECGs and no evidence of cardiovascular disease.

What were the main results?

Five of the 81 athletes with abnormal ECGs had a disease of the heart muscle called cardiomyopathy (one died suddenly at the age of 24 from undetected heart disease, three developed cardiomyopathy after an average of 12 years and one after 9 years of follow-up). None of the 229 control athletes had a cardiac event.

What can we take from it?

The researchers concluded that abnormal ECGs in apparently healthy athletes may show the initial expression of underlying heart disease that may be associated with adverse outcomes.

I really enjoyed reading this research paper and found it very informative. It addressed a very important topic and helped to add to what we already know about sudden cardiac death in athletes. The research question was well-developed, stating the population (young athletes), the parameter (abnormal ECGs) and the outcome (clinical outcomes). The study design was simple, with the researchers analysing data from a large number of athletes who were screened at the Institute of Sports Science and Medicine. We know that randomised controlled trials give the most robust evidence, however this was not ethically appropriate. The researchers didn’t state who analysed the ECGs but it was good to see that the control group were selected from the same database of athletes.

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

  • The article by Pelliccia and colleagues is a well written piece of work and identifies some ECG abnormalities that may contribute to sudden cardiac death in these athletes.
  • Is pre-screening really worth it if athletes continue to play on despite their awareness?!

Overall, this research shows that ECGs showing marked abnormalities can be useful for identifying those athletes who are at risk of subsequent development of heart disease. However, as Carla mentions in her comments, even if athletes knew that they were at risk of heart disease, would they give it all up to prevent such events?

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Filed under Sport Science Journal Club, Sudden cardiac death

The effects of intermittent hypoxic training on aerobic capacity and endurance performance in cyclists

For this journal club we looked at the following journal article:

Czuba M, Waskiewicz Z, Zajac A, et al. The effects of intermittent hypoxic training on aerobic capacity and endurance performance in cyclists. Journal of Sports Science and Medicine 2011; 10: 175-183

What was the aim of the paper?

The aim of the paper was to look at the efficacy of intermittent hypoxic training at 95% of lactate threshold on endurance performance and aerobic capacity in cyclists. The authors did not include a hypothesis. The research was carried out by scientists at the Jerzy Kukuczka Academy of Physical Eduction in Poland.

What did the study involve?

The researchers recruited 20 male elite cyclists and randomly divided them into a hypoxia (H) group (who trained in a normobaric hypoxic environment, O2= 15.2%) and a control group (normoxia environment). The experiment consisted of baseline testing, followed by three weeks of progressive training and one week recovery in which the training load was significantly reduced, and then post-testing. The testing involved taking resting blood samples, body mass and body composition. This was then followed by a progressive cycle ergometer test to determine VO2max and lactate threshold and the researchers measured heart rate, minute ventilation, oxygen uptake and expired carbon dioxide. After 24 hour rest, the participants performed a 30km time trial and heart rate, blood lactate, speed, cadence and power were measured. The training programme was the same for both groups and involved three sessions per week with a 15 minute warm-up, 30-40 minutes of core training (30 min at 95% lactate threshold workload in 1st week, 35 min in second week and 40 min in third week) and a 15 minute cool down. Intensity for the control group was 100% of lactate threshold workload.

What were the main results?

The researchers results showed that after the three week training period, there was a significant increase in VO2max, maximum workload and lactate threshold workload during the incremental test in the hypoxia group compared to the control group. The results also indicated a significant reduction in the time of the trial and a significant increase in average generated power and speed during the time trial in the hypoxia group. However, there was no difference in red blood cell count, haemoglobin concentration and haematocrit value. The authors conclude that intermittent hypoxic training at lactate threshold intensity improves aerobic capacity and endurance performance at sea level.

What can we take from it?

I enjoyed reading this paper and agree with Ben that it had some very interesting points. The research question was focussed and the study design was suitable for the research question, but it was unfortunate that they did not include a hypothesis.

The main point that I want to highlight is that the researchers did not use a repeated measures, crossover design and therefore the participants did not serve as their own control, which means that the groups could have been unbalanced and it may have introduced bias to the results. The training period of three weeks was fairly short, but the training sessions were quite long (around an hour) and at a high intensity, which may not be suitable for the general population. However, as Carla mentions, a three week training programme that improves sea level performance could be appealing to athletes to gain a competitive edge.

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

  • The paper fails to find any changes to haematological parameters, suggesting that this intervention was not harsh enough to bring about significant erythropoiesis.
  • Future research should use the same intervention, but have more follow-up analysis and include muscle biopsies to measure for changes in skeletal muscle.
  • The only problem I can see with the present study is that the training only went for 3 weeks, it does not state what type of program the athletes come off, as a supercompensation effect could have accounted for the increases in power, lactate threshold and such.
  • This paper highlights that hypoxia is a complimentary tool to training and not the primary stimulus.



Filed under Altitude training, Sport Science Journal Club

Low-volume high-intensity interval training induces performance and metabolic adaptations that resemble ‘all-out’ sprint interval training

For journal club we looked at the following paper:

Bayati M, Farzad, B, Gharakhanlou R, et al. A practical model of low-volume high-intensity interval training induces performance and metabolic adaptations that resemble ‘all-out’ sprint interval training. Journal of Sports Science and Medicine, 2011; 10:571-76

What was the aim of the paper?

The researchers wanted to compare a sprint interval training (SIT) protocol (3-4 x 30 seconds ‘all out’ effort with 4 minutes recovery) versus a high intensity interval training (HIT) protocol (6-10 x 30 seconds with 125% Pmax with 2 minutes recovery) . They hypothesised that the training induced changes would be the same between the two protocols. The research was carried out by researchers from the Department of Physical Education and Sports Sciences at Tarbiat Modares University.

What did the study involve?

The researchers recruited 24 male graduate students who were habitually active. After a familiarisation trial, the participants carried out a graded exercise test on a cycle ergometer to measure VO2max and power at VO2 max (Pmax). They also did a test to determine the time to exhaustion at Pmax by cycling to fatigue at a self-selected cadence. Finally they carried out a 30 second Wingate test to analyse peak power output (PPO), mean power output (MPO) and total work (Wtot).

The researchers then assigned the participants to one of three groups; HIT, SIT or a control group. The participants trained 3 times a week for 4 weeks. Following the training intervention, the three tests above were repeated. Blood lactate was measured at rest and three and 20 minutes after the Wingate test only.

What were the main results?

The researchers found that following the four week training programme, Pmax, VO2 max and PPO were significantly increased in both training groups compared to the control group. MPO increased significantly with SIT compared with the control group, but MPO did not change significantly with the HIT group. Blood lactate was significantly different in both training groups compared to the control group.

What can we take from it?

I enjoyed reading this study because I am very interested in the research area, especially after watching it on BBC Horizon. It was an easy paper to read and had some good points to take away from it. The researchers clearly stated a research question and hypothesis, and used a simple study design to test the research question. They used a quick and easy training protocol that would be easy for the general population to carry out and because the researchers used participants that were not athletes, it made the results relevant for the general population. The use of a control group in the study helped to eliminate bias and they used a relatively large number of participants compared to similar research (although they did not state if they had used a power calculation for sample size).

Although the paper had many good points, there were a number of areas that I questioned. The training was only carried out over a period of four weeks and I would have liked to see the long-term effects of the training protocols. The study was not a repeated measures design and the researchers matched the subjects, but they did not state the criteria for this and also did not say how they randomised the participants into the groups. I would have liked to have seen how the diet and physical activity adherence was measured. I also wonder why the researchers only measured blood lactate. They could have measured other markers of fitness, such as heart rate and also perceptual measures, including rating of perceived exertion. Finally, this training protocol would not be suitable for people who had an existing medical condition.

The following points that Dan made about the research are very valid.

  • Are the two adequately distinctive enough to warrant such investigation? 125% Pmax for obese, unfit and/or unaccustomed individuals is still a big ask and questionably unsustainable for long-term exercise prescription. As well as being difficult to quantify this intensity in real life.
  • With regard to adding to current literature, relevant is the finding that lower intensity (125% Pmax vs. ‘all out’) but more repetitions (6-10 vs. 3-5) provide similar metabolic and performance gains.
  • Would be interesting if subjects were to see comparable improvements with the comparison of HIT and SIT protocols used in the current study against the utilisation of those rest periods to conduct low intensity recovery exercise (interval training)

Overall, I enjoyed reading this study but would have liked it to be a bit ‘meatier’ and feel like some important points were missing.

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Filed under High intensity training, Sport Science Journal Club

The role of exercise intensity in the bone metabolic response to an acute bout of weight-bearing exercise

The paper we looked at for journal club was from the Journal of Applied Physiology and entitled ‘The role of exercise intensity in the bone metabolic response to an acute bout of weight-bearing exercise.’

What was the aim of the paper?

The researchers wanted to compare the effects of three different cardiovascular intensities on changes in bone turnover markers during and for 4 days after acute endurance running. They did not state a hypothesis, but previous research has shown that short-duration, high-impact exercise is beneficial for bone mass and endurance running exercise has been linked with detrimental effects on bone. The research was carried out by researchers in the UK.

What did the study involve?

The researchers recruited 10 men who performed at least one bout of endurance running a week. The study consisted of three counterbalanced 8-day experimental conditions, separated by at least a week. You can find out why the researchers carried out this design here. On days 1-3 of the trial, the participants did not carry out physical activity. Day 4 consisted of a single 60 minute bout of running at 55%,65% and 75% of VO2max, followed by 3 hours recovery. The researchers measured 60 seconds of expired air and RPE at 18,38 and 58 minute of exercise. They recorded heart rate continuously. Blood samples were taken at baseline, after 20,40 and 60 min of exercise and 0.5, 1,2 and 3 hours of recovery. The researchers measured the following markers: COOH-terminal telopeptide of procollagen type 1 (β-CTX), NH2-terminal propeptides of procollagen type 1 (P1NP), osteocalin (OC), bone-alkaline phosphatase (ALP), osteoprotegerin (OPG), parathyroid hormone (PTH), albumin-adjusted calcium (ACa), phosphate (PO4) and cortisol. The participants consumed a standardised meal in the lab 3 hours after exercise, and around 4.5 and 7 hours after exercise. On days 5-8 the participants did not carry out physical activity but followed a prescribed diet and went to the lab for analysis.

What were the main results?

The researchers found that β-CTX concentrations were higher in the first hour following exercise at 75% VO2max, compared to 55% and 65%. P1NP increased significantly during exercise only and ALP concentrations increased significantly at 3 and 4 days after exercise, but neither were effected by exercise intensity. PTH and cortisol increased signficiantly with exercise at 75% only. OPG, ACa and PO4 increased signficiantly with exercise but were not effected by exercise intensity.

What can we take from it?

Although I found this paper quite challenging to read, I really enjoyed it and learnt a lot from it. The researchers recruited the participants well because they ensured that they did not have a bone fracture in the previous 12 months, no injury and did not have a condition or take any medication known to affect bone metabolism. They also took into account fasting vitamin D concentration, which is important because low serum vitamin D levels have been associated with low bone density.

I really liked the use of figures and tables in the paper. I think it was good to have a figure outlining the overall study design, which helped with the understanding of the protocol. The table with the subject characteristics was helpful and there was a good use of charts to graphically display the results.

A small point of interest in the study design is that the researchers relied on the participants correctly adhering to the diet that the researchers prescribed. There could have been variation in the timing of the consumption of food, however the researchers ensured that the participants verbally confirmed their adherence.

Overall, I think this was a good study with an appropriate design for the question being asked. Craig Sale, who is one of the authors of the paper, said in conclusion: “There is only a small and transient influence of intensity on the bone metabolic response to one hour of exercise. Most likely, from this and subsequent studies from our group, the effect of exercise duration on bone is more critical.” Further research in this area is being carried out by Craig and his research partners.

Craig has answered some questions about his research that were tweeted by followers on Twitter. It is a great opportunity to find out more about the research and I would highly recommend having a read through his answers.

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Filed under Bone turnover, Sport Science Journal Club