Sunday, April 7, 2013

Top 10 of 2012

It’s been way too long since I posted on this blog. Unfortunately due to a variety of personal and professional reasons I simply haven’t had time over the last nine months or so to sit down and write the next one, as most posts take several hours of work to create. But recently I’ve finally had a chance to do something about it.

So to follow up from my post on New Year’s Eve in 2011, I decided to put together a summary of 2012, as far as sports nutrition research, insights or other news is concerned. 2012 did not see quite the quantity and depth in sports nutrition research publications as we had in 2011, but there’s still plenty to talk about. Rather than choose 12 for 2012 (as I chose 11 for 2011), instead I’ve capped it at 10, and will endeavour to continue with the top 10 each year moving forward.



10 - Protein and weight training – confirmation of what we already knew (but still important)

For those of you not from a scientific background, a meta-analysis is a review of previously published studies on a particular topic, grouped together and statistically analysed. In essence it’s a study of the studies on a topic, and can be very useful to draw a single conclusions from a number of studies that may provide conflicting results.

In November 2012 a meta-analysis was published in the American Journal of Clinical Nutrition on the topic of consuming protein together with (weight) training. This analysis looked specifically at studies that investigated the effect of protein supplementation (or higher protein diet) with weight training over a number of weeks (minimum of six), where body composition and strength outcomes were measured.

There were 22 studies that were of sufficient quality (and where all data was available for the analysis), all published between 1995-2010. The studies included a mixture of males (15), females (4) or a combination (3), older people (6) and younger people (16), and among the younger people those who were already doing weight training (5) or previously untrained participants (11).

The types of protein supplements used are shown in the table below. 15 of the 22 studies involved supplementing with protein (average 42g) immediately before, during or immediately and/or after weight training.




Type of protein consumed

Number of studies

Combination of whey, casein or whole milk proteins

12

Whey

6

Casein

1

Essential Amino Acids only

2

Egg protein added to boost total protein consumed

1

The results of the meta-analysis were probably not surprising to many people. Protein supplementation improved the gains in fat free mass (primarily muscle) compared to either a placebo or no supplementation by an average of 0.69kg over an average of 12 weeks, but increased to 0.81kg for the younger participants and 0.98kg in the younger participants who already did weight training prior to the study. The 1-RM strength on leg press was also significantly improved with protein compared to placebo or no change in protein, by an average of 14.4kg in the younger participants.


Forest plot of the results of a random-effects meta-analysis shown as pooled mean differences with 95% CIs on fat-free mass in younger untrained and younger trained subjects.
 
Source: Cermark NM et al. Am J Clin Nutr 2012;96:1454–64.



9. Sweat rate decreases as distance increases

I described in a previous post in 2012 about Prof. Tim Noakes’ presentation at the ESSA (Exercise & Sports Science Australia) conference on the Gold Coast back in May. One of the more interesting points that I picked up from Tim’s presentation and which I’d never seen data on before is the relationship between endurance race distance and hourly sweat rates. That is, as the duration of exercise increases, the pace that the athlete works at is obviously lower (you can’t run a 100km ultra marathon at 10km speed). This means that less body heat is generated and therefore the amount of sweat lost per hour of exercise is less. Quite intuitive really, but it is an important reminder that you can’t generalise your sweat losses in a one or two hour run to what you do in an ultra, unless of course you complete the shorter run at the pace that you would realistically run the longer distance.

Interestingly, Noakes also described how the overall sweat lost (ie. from start to finish of the event) was not very different between the a half-marathon and a 100km ultra, due to the greater sweat rates at shorter distances, but the shorter duration. It further highlights the importance in preventing over-hydration in ultra-endurance sports – you have more opportunity to drink, and the amount you’re losing each hour is less.


Analysis from separate studies of % body weight loss (presented here as % dehydration) in running races of 21, 42, 56 and 89km. Note that the % weight loss is not significantly different, which means that as the races get progressively longer the sweat rate (mL/hr) is progressively lower. This results in the total volume of sweat lost being similar by the end of each of the races. Image photographed from Waterlogged, by Prof. T Noakes.

Source: Noakes T. Waterlogged, Human Kinetics, 2012.


8. Protein timing matters, not just the quantity

In recent years sports scientists have been able to quantify the actual amount of protein being built in the muscles after training (muscle protein synthesis), which is a marker of the adaptation the body makes in response to the training session. This has led to an explosion in studies that explore the effects of different types, quantities and timings of protein consumption around exercise, in order to try and find the optimal strategy for athletes.

Part of that puzzle that had not been explored much prior to 2012 was the frequency of multiple doses of protein taken after training. In the first of a series of papers on the topic published in Nutrition & Metabolism, participants undertook 4 sets of 10 repetitions of a leg extension exercise. Following the exercise they consumed 80g of whey protein over 12 hours, but in very different patterns. One group consumed 8 doses of 10g of protein, one consumed 4 doses of 20g, and one consumed 2 doses of 40g. The differences were small, but overall there appeared to be a benefit from the 4 X 20g pattern over the other two.

The effect of different patterns of protein consumption on whole body protein balance (muscle protein synthesis minus breakdown) expressed per kg body weight over a 12 hour post-exercise period. Bolus = 2 X 40g, Int = 4 X 20g, Pulse = 8 X 10g. Likely moderate increases for Pulse and Int compared to Bolus, and possible small increase for Int compared to Pulse. Source: Moore DR et al. Nutr Metab (Lond). 2012 Oct 16;9(1):91.

Although not conclusive, this study did confirm the long held belief that the pattern of protein intake and not just the total daily amount is important to optimise the body’s response to training. Over the next year or two we should start to gain a much better understanding of what this ideal pattern looks like, with one of the study’s authors, Jose Areta, completing his PhD at RMIT University in this area.


7. ISENC – Focus on road cycling:

I didn’t attend the International Sports & Exercise Nutrition Conference in Newcastle upon Tyne in December 2012, but I wish I did. From what I’ve read about and spoken to others about it there was a great session on sports nutrition in road cycling generally and the Tour de France specifically. Here are some of the great take-away messages I had fed back:

Prof. Louise Burke, Australian Institute of Sport

On the importance of muscle mass and power-to-weight ratios in cycling:

Losing a kg of lean body mass in the thighs of cyclists will decrease power at the anaerobic threshold by around 12W. To counteract this and produce the same power-to-weight ratio you’d have to lose 3kg body fat, but absolute power on the flat would still be compromised. Cycling is not all about reducing weight, it’s about minimising body fat whilst also maintaining leg muscle size and power.

On weight loss strategies employed by professional cyclists:

Some riders are advised by their sporting directors to stay fasted with no carbohydrate after a long ride, using sleeping pills to sleep through the period of hunger.


Nigel Mitchell, Nutritionist for Team Sky on the daily diet of his riders at the Tour de France:

Riders typically ate 7-8g/kg Carbohydrate, and around 200g (almost 3g/kg) of fat per day. They also ate  up to 250g of protein (around 2.7-3.5g/kg) a day. That’s significantly less carbohydrate and significantly more fat and protein than most sports dietitians would recommend.

Looking at some of the photos being tweeted by from Team Sky’s chef Soren Kristiansen throughout the Tour that isn’t a big surprise. I corresponded with Kristiansen in the closing days of the Tour and he highlighted the psychological aspect to providing food to a team of tired, hungry riders throughout an exhausting and stressful three week race. He mentioned that they deliberately try to lower the amount of gluten in the diet to avoid any possible gut problems, but don’t avoid it completely (eg. they eat normal pasta).

Given that Sky finished 1st and 2nd in the Tour last year with Bradley Wiggins and Chris Froome who’s to argue the success of their strategy?


6.  Low glycogen does not reduce the response in the muscle after weight training

One of the arguments that many sports dietitians have put forward to athletes in strength and power sports is that they still need to fuel up on carbohydrate prior to a weight training session to maximise their performance in the session. Studies of muscle glycogen (ie. stored carbohydrate) use during weight training sessions suggest that as little as three sets of exercises in the same muscle group can deplete glycogen stores by at least a third.

The effect of weights on muscle glycogen. This led to the assumption that performance in weight training may be compromised if athletes start a session with low glycogen stores.

But in recent years sports scientists have been able to quantify the actual amount of protein being built in the muscles after training (muscle protein synthesis), which is a marker of the adaptation the body makes in response to the training session. This has led to the finding that training does not always have to be performed at the maximum intensity or quality in order to maximise the body’s adaptive response. And in May 2012 a study was published in the Journal of Applied Physiology that measured the muscle protein synthesis following a standardised weight training session in either a high glycogen or low glycogen state.

In the study, a collaboration between RMIT and Deakin Universities in Melbourne and McMaster University in Canada, participants performed 8 sets of 5 rep’s of a one-sided leg press, at 80% of 1RM, with either normal or low glycogen stores. The muscle protein synthesis (Fractional Synthesis Rate, FSR) was then measured over the four hours following the exercise, and subjects also consumed either a protein drink or a placebo (no protein) after the exercise.

The results showed that the starting level of muscle glycogen made no difference to the muscle protein synthesis that followed the session, suggesting that fuelling up for a weights session may not be quite as important as some people thought. However there still may be a difference in a weights session where multiple exercises are performed using the same or similar muscle groups, and the total number of sets (across all exercises) is much greater than 8.

Source: Camera D et al. J Appl Physiol 113:206-214, 2012.



5. Dose-response study of carbohydrate on endurance performance

Another first in 2012 was a study that looked the effectiveness of different levels of carbohydrate consumption during endurance exercise, with intakes ranging from 0 to 140 grams of carbs per hour. No previous study has compared endurance performance over such a large range of intakes, and certainly never greater than 60g/hr. There are previous studies showing benefits of 90g/hr or even 120g/hr coming from glucose and fructose versus glucose alone, but whilst these findings implied a probable benefit of higher carb intakes (because glucose alone is not absorbed from the gut at much more than 60g/hr), they never actually compared different levels directly.

This study was performed as a collaboration between several US laboratories in order to test enough participants to make it work, but was headed by John-Eric Smith from the Gatorade Sports Science Institute, and was published online in Medicine & Science in Sports & Exercise in August 2012.
Endurance performance was tested with a 2 hour ride at 95% of the participant’s lactate threshold, followed by a 20km time trial. The results showed that as the amount of carbohydrate consumed increased, performance improved up to 80g/hr, after which performance actually started to drop slightly again. Interestingly though the test was performed after fasting for 10 hours overnight, which is not very representative of how athletes would prepare for a race.

For me there are two unanswered questions here – would the result have been the same if the athletes had not fasted prior to the performance trial? And if the performance was longer than this trial (~2.5 hours), and more representative of ultraendurance events such as an Ironman or ultramarathon, would higher levels of carbohydrate consumption above 80g/hr have been of any extra benefit?

 

Source: Med Sci Sports Exerc. 2013 Feb;45(2):336-41.



4. Amino acid appearance in the blood from real foods when combined with weights

Another interesting study published in 2012 looked at the response of protein consumption on blood levels of amino acids. It’s these levels, particularly of the essential amino acids and probably Leucine in particular, that drive the adaptations that occur in the muscles after a training session.

In the past studies have looked at the effect on different types of protein powders on the appearance of amino acids in the blood, but very little research has looked at the effects of whole foods. In this study, which appeared in the International Journal of Sports Nutrition & Exercise Metabolism in December, the effect of consuming a standardised 20 gram protein serving from skim milk, soy milk, steak, eggs and a liquid meal supplement (Powerbar Protein Plus with water) on the blood levels of total amino acids, essential amino acids, branched chain amino acids, and Leucine.



The results showed significant differences in the way protein enters the blood as amino acids, in a similar way to the rate of entry of carbohydrate is measured as Glycaemic Index.

What do these differences mean? We actually don’t know for sure yet, as there aren’t studies that measure the effect of digestion and absorption rate of real foods on actual protein synthesis. But expect to see this work done in the near future. Is a steak with dinner just as effective as a protein shake after a training session? Time will tell.

Reference: Burke LM et al. Int J Sport Nutr Exerc Metab. 2012 Dec;22(6):452-62.


3. Large dehydration does not cause cramping – at least when cramping is caused by electrical stimulation

Studying cramping doesn’t occur very often, mainly because it’s so difficult to predictably make someone cramp when you want to. But a research team in the US has been working on the issue by using electrodes to stimulate muscle cramps. They can then study various factors that increase or reduce the risk of cramping by measuring how much they need to stimulate the muscle before it cramps.

In their latest study, published in the British Journal of Sports Medicine in December, participants exercised until either they lost 5% of their body weight (regarded as a large level of sweat loss) or until they could no longer exercise. This level of dehydration did not alter the level of stimulation required to induce cramping, or the intensity of the cramps.

This paper adds to observational studies from ultra marathon and Ironman triathlon events that suggest that dehydration does not increase the risk of cramping. We’re not likely to see a well controlled randomised control trial of hydration and cramping during exercise any time soon, as it’s all but impossible to achieve. So for now we’re relying on studies like these to guide our understanding of exercise associated muscle cramps.


Reference: Braulick KW et al. Br J Sports Med 2012 Dec 6 (published ahead of print).



2. Carbohydrate mouth rinse – bigger gains when fasted, but overall better performance when fed

There’s been quite a few studies over the last couple of years that have looked at the benefits of rinsing your mouth out with carbohydrate (but not actually swallowing it) before exercise efforts of around an hour. To date the studies have generally found that mouth rinsing improves performance when the athlete begins the exercise having fasted, but minimal effect if a carbohydrate meal has been consumed in the hour leading up. The effect seems to be due to the brain’s ability to sense carbohydrate in the mouth, allowing a greater intensity of exercise as a consequence.
In November a team from RMIT investigated the effect of mouth rinsing before and during a time trial of approximately 1 hour, both in a fed (high carbohydrate meal 2 hours before) and a fasted (overnight) state. They found that mouth rinsing improved performance in both the fed and fasted state, but the amount of improvement was greater when fasted (3.4%) compared to fasted (1.8%). However the overall best performance was achieved when both fed and mouth rinsing, showing the advantages of both.

It’s important to remember though that the concept of mouth rinsing has only been used to effect in shorter endurance efforts, generally of an hour or less, and that actually swallowing the drink rather than rinsing and spitting it out is just as effective. But in very high intensity efforts such as cycling time trials where there may be a chance of reflux or even vomiting up sports drink, there may be a distinct benefit of the rinse and spit method.


Reference: Lane SC et al. Appl Physiol Nutr Metab. 2013 Feb;38(2):134-9. (Epub 2012 Nov 26).



1.   The Sensewear armband – a new and convenient way of measuring energy expenditure

The final of my top ten bits of new sports nutrition knowledge I picked up in 2012 came back in April at the Exercise & Sports Science Australia/Sports Dietitians Australia national conference. There, a team from the Australian Institute of Sport presented research on the Sensewear armband, a device designed to measure the energy (kilojoule or calorie) expenditure over the day. The athlete (or anyone else) wears the Sensewear band on their upper arm, and a series of sensors measure movement, body heat production and other variables. Together these sensors estimate the energy expended by the wearer.

The study found that the armbands were adequate in estimating energy expenditure, and also useful to pick up patterns of activity of the course of the day. It’ll be interesting to see whether or not Sensewear armbands become a common item in the toolkit of those wanting to lose weight, or simply as a research tool to assist in studies where measuring energy expenditure or activity patterns over the day is important. 
Reference:  Moran ST et al. Proceedings from the ESSA/SDA Conference, 2012: 164.


So there’s my top 10 for 2012, quite a bit later than I’d hoped but better late than never.

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