Phosphocreatine is a high-energy storage molecule found within skeletal muscle. During intense exercise, phosphocreatine provides immediate replenishment of ATP (Adenosine-5′-triphosphate), which transports chemical energy from within cells for metabolic processes.

Traditional endurance training induces physiological adaptations such as improved aerobic capacity, along with a reduction in glycogen utilization and lactate accumulation. HITT has been shown to be an efficient way to produce similar effects.

Multiple HIIT bouts are designed to deplete phosphocreatine stores in the working skeletal muscle, and so reducing power output.

It takes more than six minutes to fully recover phospho-creatine stores after exercise-induced depletion. Therefore, if recovery intervals during HIIT bouts are less than six minutes, phosphocreatine may not be fully replenished, leading to a reduced performance.

Supplementing with creatine has been demonstrated to effectively increase muscle phosphocreatine stores. Specifically, one study showed a 20% increase in muscle creatine with ingestion of 20 g of creatine per day for just 5 days.

The purpose of the study published in the Journal of the International Society of Sports Nutrition was to determine the effects of high-intensity interval training and creatine supplementation on cardiorespiratory fitness and endurance performance.

The subjects were 43 college-aged men who typically performed 1-5 hours of exercise per week. None had taken sports supplements, including any form of creatine, in the three months prior to the beginning of the study.

Participants were randomly assigned to a creatine or a placebo group and supplemented for 30 days at a dose of 10 g per training day, taken in two doses – one dose 30 minutes prior to and one dose immediately following training.

• Creatine group consumed 5 g of creatine citrate mixed with 15 g dextrose
• Placebo group consumed 20 g of dextrose

A control group, consumed no supplements nor completed the high-intensity interval training, and instead only completed the testing measurements.

Participants performed HIIT five days per week, for six weeks at progressively increasing workloads, determined as a percentage of the participant’s baseline VO_2PEAK max workload. Training increased in intensity each session beginning at 90% of their VO_2PEAK max workload and progressing up to 120% of their VO_2PEAK max workload.

Each training session began with a five-minute warm up, followed by a protocol of five sets of two-minute exercise bouts, with one minute of passive rest in between exercise bouts.

A maximal graded exercise test on a cycle ergometer was used to determine:

• maximal oxygen consumption (VO_2PEAK)
• maximum heart rate (HRmax).
• total work done (TWD)
• time to exhaustion (VO_2PEAKTTE)
• ventilatory threshold (VT), this is the point during graded exercise in which venitilation increases disproportionately to oxygen uptake.

Endurance performance is commonly assessed using a measure of aerobic capacity. While the HIIT program was effective in improving maximal oxygen consumption by 9%, creatine supplementation had no further influence on aerobic capacity. Ventilatory Threshold (VT) is another useful predictor of endurance performance as an indicator of the ability of the cardiovascular system to adequately supply oxygen to the working muscles. Performing exercise at intensities greater than VT often result in an inadequate supply of oxygen to the working muscles, quickly leading to fatigue.

If VT can be improved it could increase the time to exhaustion, reduce fatigue, and may enhance the efficiency of the body to supply oxygen to the working muscles.

However, when measuring VT in this study, significant improvements were only observed in the creatine group (16%), although the placebo group demonstrated a trend for improved VT (10%).

The researchers from University of Oklahoma found that HITT is an effective way to improve maximal endurance performance. The study also demonstrated an improvement to time to exhaustion with HIIT. However, whilst adding the use of creatine did improved ventilatory threshold, it did not increase total work done.

Previous studies have shown improvements in TWD after creatine supplementation which included a loading phase (20 g/d for 5-7 days). A loading phase was not used in the current study, so it may be possible that muscle phosphocreatine levels were not increased enough to aid in improving TWD.

The researchers did suggest that it is possibile that any benefits of low-dose creatine supplementation were masked by the effectiveness of HIIT alone.

ASA claim this advert was misleading

Today’s upholding of a complaint by the Advertising Standards Authority (ASA) supports my view that you should investigate claims of health benefits of products you supplement your diet with, to ensure you don’t waste your time, money or even damage your health.

The TV advert in question is for Actimel, a pro-biotic drinking yoghurt intended to be consumed by every one of all ages. One viewer had challenged whether the claim by the ad voice-over that “Actimel was scientifically proven to help support your kids’ defences” could be substantiated.

In their defence to the ASA, Danone claimed that the health benefits of Actimel had been demonstrated in 23 human studies conducted on over 6000 people across different age ranges, with eight studies carried out on children up to 16 years of age.

Danone claimed that the health benefit of Actimel is through the support of the human body’s natural defence system, helping to protect against pathogens and harmful environmental factors, as some of the most important defence systems are located within the gastrointestinal tract. Danone said they had referred to Actimel as being “scientifically proven” in their ads based on a significant body of published scientific evidence that showed that Actimel supported the natural defences of different age groups, including children.

The ASA thought that the ad suggested through the image of an Actimel bottle jumping over a skipping rope and the sound of children laughing and playing implies that the product is intended for normal, healthy children of school age (five to sixteen years old). The ASA also considered that most consumers would understand the claim that Actimel “was scientifically proven to support your kids’ defences” to mean that the product would help defend those children against common, every-day childhood infections. Whilst Danone submitted scientific studies in support of the claims, they were not involving subjects who could be considered ‘normal, healthy children of school age’.

• One study examined the effect of Actimel on hospitalised children in India suffering from acute diarrhoea another involved those receiving medication for chronic Helicobacter pylori. Both trials were considered to be unsuitable for use in support of a claim that was likely to be seen as referring to normal, healthy children.
• Children in another study assessed the effect of Actimel on the occurrence and duration of a range of symptoms, including asthma, rhinitis, diarrhoea, nausea and vomiting, abdominal pains and fever, in children aged two to five years who suffered from allergic conditions. Again meaning the results of the study could not necessarily be applied to normal, healthy children.
• Three other trials were on children between the ages of 6 and 33 months, much lower than the target group of school-age children suggested by the ad. The ASA understood that the developing immune systems of children under two differed from those of older children, and so did not think that it could be safely assumed that the results reported for the young children in these studies would be the same for school-aged children.
• A further area of concern was the portion sizes used in the studies. The children in some studies were supplemented with portion sizes that were larger than the recommended serving size of one 100 g pot of Actimel per day. The observed benefit for Actimel in the clinical trials might not therefore, be representative of the effect of the product when consumed on an ‘everyday’ basis.

The ASA considered that the ad was making an absolute claim that Actimel would support the defences of children, and that the reference to “your kids” was implying to consumers that Actimel would benefit their child.

The ASA understood that some children would not see a benefit from consuming Actimel, and because were concerned that any observed effects for Actimel in the trials might not be representative of the efficacy of the product when consumed in line with the recommended daily serving. It was concluded that a serving of Actimel was not scientifically proven to support the defences of normal, healthy school-aged children against common, every-day childhood infections and that the ad was misleading.

The ASA have ruled that the ad must not be broadcast again in its current form. Whilst there is no suggestion that this product could damage anyone’s health, the findings of the ASA support my previous articles on supplement efficacy and safety: Even with claims of supporting scientific evidence, many products may only benefit specific groups of people. Before you waste your money on ‘healthy’ products, consider if you are actually deficient in the nutrients they are supplying?  If they can cure illnesses, is it something you are suffering from? Do you fit the target group scientific studies have shown benefit in? If in any doubt consult a healthcare professional.

Athletes are such a group of people who you would think would pay more attention to their body. In 1996 spending on supplements in US was $6.5 billion and in 2002 was $18 billion with sports nutritional products making up one third of sales, so sports supplements are a huge market.

It was interesting to read a recent study in the Singapore Medical Journal, which examined the use of nutritional supplements by university athletes in Singapore. As most studies have focused on Caucasian populations, this study looked at university students in Asia, who would be highly educated with access to scientific literature, yet also exposed to traditional herbal products since birth. Over 75% of the 82 athletes questioned used supplements, consuming on average up to 3 products a day. The most popular products included sports drinks (90%), vitamin C (49%) multivitamins (30%) and glucosamine (20%). Over 90% of the athletes were Chinese which could explain why other popular products were traditional/herbal preparations such as essence of chicken (11%), edible birds nest (11%), and ginseng. Interestingly only one athlete took creatine. Similar to studies of their peers in the West, the most popular products were sports drinks and vitamin/mineral supplements. However, whilst the majority of Western university females reportedly consume supplements for general health benefits and male athletes aim to enhance sporting performance, all but one of the Singapore students consumed supplements for health benefits. This could be because elite sports aren’t as prestigious as in the West. You could speculate that some of those taking supplements for sports may be ignorant or blasé to the risks if they are intent on enhancing sporting performance. But surprisingly in this study, it is the university educated people taking supplements to improve their health, who don’t investigate the health risks of what they are consuming.

The study found that:

• 93% didn’t know where to obtain reliable information
• 86.4% unaware supplementation can have adverse health effects.
• More than 1/3 had no or minimal knowledge about the product they consumed
• Males were more likely than females (81% vs 52%) to research a product and those with more knowledge were more likely to use supplements.
• Before using 65.9% sought info from the media, internet, coaches and fellow athletes.
• The most frequent explaination (38.5%) for not seeking further information was that ‘the product must be safe since it is commonly available’

Whilst this study may have limitations, it is concerning that people are unaware of the health effects of their supplements, nor do they know where to get reliable information from. I agree with the conclusions of the authors, which should be taken on board by those taking supplements for either health benefits or sporting performance.

• Supplements with scientific evidence may only benefit specific athletes.
• Athletes must be aware of the additive or synergistic effects of the supplements.
• Endorsements by well known personalities fail to mention the long hours of training and sound nutrition which were responsible for their success.
• Whilst some products have sound scientific backing, many traditional/herbal preparations have not been validated by rigorous scientific investigation.
• Use supplements with caution and examine the product for safety, efficacy, potency and legality with a healthcare professional prior to use.

Now a study from Victoria University, Australia has set out to examine the effects of creatine supplementation on the recovery of muscle proteins and force after eccentrically induced muscle damage.

Eccentric contractions are used to decelerate a body part or object, such as when you lower an object gently rather than just letting it drop. Damage caused by eccentric exercise is known to lead to a reduction in muscle force, increased muscle soreness and impaired muscle function.

During the study 14 untrained male subjects consumed either creatine and carbohydrate (Cr-CHO) or only carbohydrate (CHO) for five days before a resistance exercise session. The Cr-CHO group consumed a daily supplement of creatine (0.3 g per kg of body weight) and glucose (1.2 g per kg of body weight); The CHO group took glucose only.

The workout consisted of three exercises: 1) leg press; 2) leg extension and 3) leg curl. For each exercise their concentric 1-RM (repetition maximum) was determined. This is the maximum weight that a single repetition could be performed of a muscle shortening exercise, such as a curl. The resistance exercise session involved 4 sets of 10 eccentric only repetitions at 120% of their maximum concentric 1-RM, lowering the weight by themselves through the entire range of motion over 4 seconds.

Every day for 14 days whilst recovering from the exercises the Cr-CHO group took 0.1 g per kg of body weight of creatine and 0.4 g per kg of body weight of glucose, again the CHO group took glucose only.

The study found isokinetic strength, (where the muscle contracts and shortens at a constant speed), was 10% greater during recovery in the Cr-CHO group compared to the placebo group of CHO alone.

During isometric knee extension (where the muscle length stays the same even though it contracts), it was also found that the creatine supplemented groups had significantly greater strength (21%) during recovery from exercise induced muscle damage.

The paper’s author Matthew Cooke concluded that there is a significant improvement in the rate of recovery of knee extensor muscle function after creatine supplementation following injury. Blood creatine kinase (CK) activity was significantly lower by an average of 84% after 48hrs recovery in the creatine supplement group and peaked at 96hrs. Levels had returned to baseline by 7 days in both groups.

Blood CK levels can be raised from damage of the muscle tissue as a result of intense training, but also due to a number of other factors:

• Age – levels decline slightly with age
• Gender – at rest CK levels are lower in females than males.
• Race – black men usually have higher values than Caucasians.
• Climate – standard exercise in cold weather induces higher blood CK levels than the same exercise in warm weather.
• Muscle mass and physical activity – at rest CK levels in athletes are higher than in sedentary subjects, this may be due to persistent training which keeps the CK levels elevated.

However, if trained and untrained subjects do the same exercise the CK levels will still be lower in athletes than the untrained. This study published in the Journal of International Society Sports Nutrition did involve untrained subjects which may have resulted in the very high CK levels initially following the exercise.

The major finding of this study was the significantly higher muscle strength after creatine supplementation during recovery from a muscle damaging exercise session; this may be due in part to a faster muscle growth during the recovery period. The study did not report if the subjects gained weight before or after the exercise session as is often reported with taking creatine supplements.

It is not known how creatine may act to increase recovery although it may be that the reduced leakage of creatine kinase from the muscle is an indication of less initial damage to the muscle.  There appears to be a large number of studies supporting the use of creatine supplements whether to increase muscle mass or aiding recovery to allow further training. Maybe now scientists need to discover just how creatine supplements work so they can advise athletes on the ideal duration and concentration to use to aid recovery, optimise weight gain and avoid side effects.

Creatine is a natural occurring substance that helps supply energy to muscles. Half of stored creatine comes from food, mainly fresh meat, so as a vegetarian I am likely to have lower levels of muscle creatine.  The enzyme creatine kinase (CK) is responsible for the reversible reaction whereby creatine is converted along with ATP to create phosphocreatine and ADP to generate energy.

Whilst creatine has been shown to be beneficial for short high intensity exercises such as weight lifting, it has not shown to have any benefit to endurance activity performance. In fact as creatine is also responsible for weight gain of around 1kg when taking the ‘loading dose’ of 20g a day it may even slow an endurance athlete down without providing any benefit to performance. A study has however, looked at the benefits of creatine on muscle recovery following endurance running

In the study published in Life Sciences journal, subjects were given 4 doses a day of 5g of creatine and 15g of maltodextrine, while the control group received just maltodextrine for 5 days, before a 30km race. The runners were experienced marathon runners with personal best (PB) times of 2.5 -3 hours.

Blood CK levels can be raised from damage of the muscle tissue as a result of intense training and it is often used as a marker of muscle injury. In this study by the University of São Paulo, it was found that athletes from the control group had increased CK levels suggesting a high level of cell injury and inflammation while Creatine supplementation reduced these increases.

In short term studies of less than two weeks there have not been reported side effects of taking creatine supplements. Dr Santos, the papers author reported that ‘the runners finished in times equivalent to their PB, without any side effects such as cramping, dehydration or diarrhoea whilst taking the supplements or during the race.’ However athletes who have taken it long term have reported muscle cramping and kidney damage.

In 2007 International Society of Sports Nutrition published its position on the use of creatine supplementation and exercise. Amongst some of their statements they concluded that ‘there is no scientific evidence that the short- or long-term use of creatine monohydrate has any detrimental effects on otherwise healthy individuals. Creatine monohydrate supplementation is not only safe, but possibly beneficial in regard to preventing injury and/or management of select medical conditions when taken within recommended guidelines.’

Recovering from endurance exercise is important for the long distance runner, but is it worth taking creatine supplements in the days leading up to a marathon to prevent damage and aid recovery. Is it worth possible muscle cramps and other side effects during the race after all you don’t know how your individual body will react?

What’s your view? Are you an endurance athlete who has tried creatine supplements, or do you think we shouldn’t use any type of ergogenic aids? Let us know you experiences or opinions.

Also read related post Can creatine supplements enhance muscle recovery?

Sporting Benefits of Caffeine

Consuming moderate amounts of caffeine (3-6mg/kg Body Mass), 60 minutes prior to exercise has been shown to enhance performance during prolonged, sub maximal exercise, and during short bursts of high intensity exercise. It has been consistently shown to reduce an athlete’s rating of perceived exertion and the reporting that exercise feels easier.

Caffeine can stimulate the Central Nervous System and reduce the perception of effort so you feel better and can increase push yourself harder or for longer. In both time trials, and exercise to exhaustion tests, caffeine has been shown to improve performance and delay the onset of fatigue, but benefits varies between individuals, another reason you should try before using caffeine in a competition.

Caffeine has also been shown to improve an athlete’s ability to maintain performance during repeated bouts of high intensity activity, by improving mental processing important to sport alertness, concentration, reaction time, focus. Improvements have been seen with concentrations of just 1-2 mg/kg Body Mass.

Caffeine Side Effects

Caffeine has been reported to produce minimal adverse effects, but include insomnia, headaches, dizziness, flushing, tachycardia (rapid heart rate), trembling and gastrointestinal distress. Whilst these symptoms are caused by the effect of caffeine on the Central Nervous System, they are individual in nature which is why trying caffeine should be trialed in training prior to use in competition especially if you aren’t used to consuming caffeine on a regular basis.

When ingested in high doses (greater than 500 mg per day) for use in sport, caffeine can have side effects. Consuming too much caffeine may reduce the performance benefit due to reducing your sensitivity to caffeine. As a result, caffeine is best used as a performance aid in competition, and not regularly in training except in the right circumstances such as a tough training session.

Whilst caffeine is a known diuretic, (generally at doses exceeding 9mg/kg Body Mass), if it is consumed just before or during exercise it doesn’t affect known markers of hydration. In moderation caffeine also has no effect on thermoregulation during exercise.

How Much Caffeine Should You Consume?

3-13mg/kg Body Mass caffeine is suggested to improve endurance performance. For someone weighing 60kg this is around 180-780mg, although unless you normally consume a lot in your diet, there isn’t much benefit reported with more than 3mg/kg.

Caffeine is found already in many foods and drinks so you may not need to supplement your diet that much, although here are some common caffeine sources:

• 40-100mg in cup of instant coffee
• 60-150mg in brewed coffee
• 40-50 mg in 12oz cola drink
• 100mg in 2 tablets of caffeine tablets such as Pro Plus
• 80mg in 250ml can of Red Bull
• 80mg in 500ml of Lucozade Sport with caffeine

It is recommended to consume caffeine 1 hour prior to exercise to allow the caffeine to peak in the blood stream. However, caffeine is likely to start to exert an effect within 15 minutes and therefore consuming a caffeine drink or supplement at the start of exercise could still have a beneficial effect as long as the duration of exercise is longer than 45 minutes.