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Fueling the young athlete
Asker JEUKENDRUP
Thursday, Sept. 21, 2017 · 3:36 p.m. · 24m 09s
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yes thank you thank you very much thank you very much to the organise us uh
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a market for the uh for the introduction and it's a great pleasure to uh to be here it's uh
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doesn't take long uh to make a decision when you get an invitation to come to a place like this and actually i
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said earlier to um uh boards that this is the place
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um whatever they give jeannie that is the place where
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um i spend time writing uh my textbook of sports impression that's the place that i uh chose so
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glad glad to be back here here i'm i'm
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talking about sports impression for a young athletes
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all i think the title in the program is fuelling uh the young athlete um
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but i haven't actually done much work with uh with with young athletes all not an expert maybe an
00:00:53
hour little bit about school situation and we've done the research in the area of exercise metabolism but
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as far as uh children goes at the moment i work with a few um academies um
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but uh that's my daughter in the uh in the picture so um i well
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try and put all this information that we have on sports addition put children together
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a challenging in the time that we have but hopefully um
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i can send you home with some food for thought
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so i'm gonna talk about is this question our children small adults
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and i think to answer that question we need to know a little bit
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about exercise metabolism how that is different from children compared to adults
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i'll talk about energy expenditure protein metabolism fruit balance carbohydrate and fat metabolism
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and then once we have that picture clear we can talk about how does
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that influence the nutrition requirements in terms of energy protein through its
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carbohydrate intake maybe supplements and and can we actually come up with a recommendation
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the problem um that we have sorry let me let me um give you the conclusion first
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and then uh just just in case i miss you at the end um
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and this conclusion may be fairly controversial but hopefully i can explain what what i mean by this
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the conclusion is most guidelines for adult after it can also be applied to children
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and that's sounds maybe a little bit strange uh maybe that goes
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a little bit against our comic emotions around this topic
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um we bought the may also be some exceptions but
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hopefully i can convince you that a lot
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of the guidelines actually do a white who got at the cost of my presentation yeah but
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so most yeah most of the um i go back to
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this so most of the um the guidelines i think can be applied um partly because i think
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usually the the way that we into but the guidelines for adult
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athletes that's way the problem is it's not so much
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in the uh the kite on some cells will get that in them and
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first i wanna uh i want to identify two issues one is that
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uh this is just if you if you them in that line at the uh the words
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x. item metabolism as the search terms um you
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get a number of uh publications um
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and of course it's it's very obvious that if you add the word
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children that number of publications is uh is very very limited
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if you had the word sports um then the number of publications become even smaller
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so what i'm gonna try and do is really on the basis of this data
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i'm gonna come up with some uh recommendations so very
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challenging and all that you keep that in mind
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that really we have very very little data on a on children
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the other problem is how we interpret the studies that we do have available
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and how we scale and most people here in the audience all very aware of this a problem
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um if we talk about performance how do we scale performance how do how do we compare
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handles with children um or do we yeah that's running for example
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do we have to take like planks stride length into account um i
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do we uh scale to body mass or do we
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scale too fat free mass do we compare at
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absolute axes i wasn't hands these all relative exercise and and see some some of these issues will
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well come up as i go through the uh through talk the example that idea um i use at the bottom
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there is the effect of a sports wrinkle on metabolism
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and performance if you're interested in that a topic
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um then all of these factors are actually important because depending on how you measure performance
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uh how you express your measures of carbohydrate all fat
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metabolism you'll get completely different conclusions of course
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oh
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so let's start with uh with energy and that can be really
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brief on on this topic because we have recommendations for
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uh uh for for children for energy intake but as
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soon as you are talking about a young athletes
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and those recommendations of fairly meaningless because the the very large component
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uh all the energy expenditure for very active uh athletes
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is of course uh the uh the exercise uh itself so it's
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impossible i think to give general recommendations on on energy intake
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um and that's also the the exercise component is also
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the uh the highly variable component in the
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died not finding the um one thing that i uh i want to say up front is
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my told is really about athletes and it is not about the general healthy diet and they
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they are two very different discussions i think uh of course obesity is a problem
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um and of course there for we have to make sure that we
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eat healthy up with that energy intake is not too high
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but here my talk is focused on athletes where all these the
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really isn't the main issue the main issue is performance
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and and very often especially in the media dues to uh get confused
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one of the arguments has been that it's um children use more energy because that that's sufficient
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and this is partly based on the old studies by yeah they're all of a asked round
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and we showed up running had a fixed intensity or a fixed a speed
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and you can actually measure that that uh younger
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children uh less efficient all less economical
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uh other studies have shown that children maybe thirty percent less
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economical than or less efficient than uh than adults
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um but that's also difficult then sobered because if
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you correct that force try playing all
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uh treadmills be then uh that difference goes away so the that
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may not be intrinsically it different in the in the muscle
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it just may be a result of that you're comparing them at the same speed
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that discussion i think is also fairly meaningless because even if there is a difference
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the main variation and energy expenditure and everyone energy
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intake is gonna come from the exercise so
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of course we also have the issue of increased protein requirements and
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this is just a table of the r. d. a. recommendations
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for the general population of for uh for children of different ages
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and you can see in that table that the requirements
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are higher for younger athletes if you express protein intake per kilogram a body weight
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that's probably as a as expected uh it's very important to sport growth
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with a with protein now they are the aces some then that is sort of a minimum requirement
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when we work with athletes that may not actually be that relevant we are looking for
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what is the optimal amount of protein to support what this young athlete is uh doing
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so the question is are these are the a.'s the meaningful
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and very little literature and this is one study in fourteen year old
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uh soccer players to train ten to twelve hours a week
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so quite a quite a lot they use the technique called nitrogen balance
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and to see how much protein is uh is really required
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from that they actually come up with a higher number forty audi
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a of one point four grams per kilogram that day
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um so that would suggest that athletes who are uh training
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a sample hours per week have higher a protein requirements
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now i don't think that is a real issue because the vast majority almost all of the athlete
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that i know at that age would eat more anyway then the one point four
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grams per kilogram today so it's probably in practical terms unknown a she
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yeah
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now we move to thermal regulation because there there are
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some differences there between um adults and children
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it's on the left you see the uh the child on the right the uh the adult
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and uh because of differences in the
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uh surface area to mass ratio
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uh which is a much higher in the in the children um
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conduction convection and radiation are really good ways to get rid of heat
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and actually that's seems to work better in children then in adults
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simply because of this uh service area to weight ratio
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where there is a another difference is in the ability to cool down through sweating
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um that is lower in children
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there are a number of reasons for that this last swept us what land or less a sweat glands
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so uh children can not get rid of heat as easily through a sweating as adults
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now what's what implications does that have um it probably has no
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implications in when you're exercising enough um a neutral environment
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so fairly normal uh temperatures because uh children can get rid of
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heat through other mechanisms but when you get to you
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and temperatures where they yeah all the other ways to
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get rid of heat are um on not affective
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so very hot and humid um fireman's and you have to rely on sweating
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that is where it becomes a little bit more problematic for children
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i usually that that is in in the guidelines for events that is taken into account
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um there are usually more breaks in those uh the games to make
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sure that uh that those um a fax negative effect or minimise
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hydration may also play a a a roll 'em hash as you sweat
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you become a de hydrated hand that may affect
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the rate of change and rectal temperature
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now for a given a percentage or for a high
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she lose body weight through uh through sweating
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the increase in rectal temperature core temperature is a greater in
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children than it is in the apples that means that
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children are a little bit more at risk for
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these higher temperatures when they become a dehydrated
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um why is this a problem well it depends probably on the uh on the conditions
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um but it also has to be taken accounted all of
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that is is expressed the kilogram body a body mass
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and therefore the volumes that children would have to drink a much
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smaller than the volumes that and i don't have to drink
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but at some point so here's some of the conclusions of this uh first parts
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of the small the person the launch of the surface to weight ratio
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he'd conduction complexion radiation should be more and effective in children
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as a result of that's what grade per unit service opus wetlands lower in children
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children therefore sweat last there's actually two reasons uh because generally
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he'd production of course is also last thing in children
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good kilogram body mass sweat breaks are similar
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and in what conditions core temperature may rise faster
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in children with increasing levels of dehydration
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as i said children generally have lower level so he production because the power outputs or lower
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oh
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the reviews studies but this is this is one of those uh studies here they
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looked at fifty nine young lead male athletes in a variety of sports
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and they measured how much these athletes de hydrated uh during yeah
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and activities so they mentioned to change in a body mass
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a percentage of the body of the body mass um one
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of the fifty nine fifty four stay within within
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two percent and i think most people in the world would be great at staying within two percent is
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no problem whatsoever so fifty four out of the fifty nine
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there is no no problem in terms of uh
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dehydration we have one um actually to actually gains weight
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um that is totally unnecessary to the advice would there
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be my you can drink a little bit less
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there are a couple of uh the people uh uh that's what between two and three percent
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um whether that is an issue is probably depending on who
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you talk to um i don't think that uh
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anything on the three percent a body muscles is is an
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issue unless you go to really extreme uh situations
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um and then there are maybe a couple of people that
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actually slept more than three percent dose would potentially the
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the ones that uh that are at risk and those
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are the ones that um would be worthwhile identify
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now this is one study so ninety two percent of all the
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athletes stay within that a safe uh save range no problems
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um this is another study that uh that was conducted in
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mostly in florida but different places in the world generally
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in very hot climates i would say that eighty percent of this data was collected in
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in hot climates eh these are all a
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very good athletes mostly team sport athletes
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um the data that you see here unfortunately is a mix
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of a young and uh adult uh i think it's
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um but i know that when you actually look at the break down of that data it there was
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hardly any difference between young and older athletes in this in this particular population
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so it here in the us what rates are a little bit higher than in the a previous study and i think
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that is mostly due to a two factors one is that the body weight
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in these athletes american sports was um was a little bit higher um
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and also the studies were all done in very hot conditions so i would almost say that this is
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the extreme of the uh of the picture so even notice whether it's now a little bit higher
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they still still not ridiculously high body and uh maybe if you exceptions
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when it comes to the uh risk heat illness then of
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course the weather conditions are very important a fact so
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the physiology sweat glands and this is um very important for uh
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for children because that's where they potentially function a little bit
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less than a idols level of acclamation is important
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the size intends these important and hypo hydration uh may also
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the important i think if all of those factors
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um but i at the same time that's in the in the central
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that that's where you really aren't at risk for heat illness um
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and then the best way to deal with that of course is to uh take away the or uh
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d. yeah in terms the have more breaks uh don't have the uh
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uh the training at that time of the a day i'm making sure that there's water available
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so the conclusions from the the from this part reduce but raising children does not
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seem to impair he'd lost during exercise in most conditions but in what conditions
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um you have to be a little bit more careful typically you would see in most
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activities for children one to two percent body weight loss not not an issue
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um if those the body weight losses are greater
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greater than three percent then i think we should follow the same guidelines as we use for at all that it's
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oh
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now i'm gonna talk about metabolism a little bit then the uh the
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first there's a time line of the uh of the studies
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um the uh the first study was in the nineteen thirties where they basically showed
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the difference in the r. e. r. so carbohydrate and fat oxidation in uh
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that in in children uh_huh uh children generally a better doctor dowsing trend
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um if we go a little bit further to the nineteen seventies
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i'll show you some data from that that was a um
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still a lot of the shorts that we have around and nutrition for children based on that study
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and it was studies where muscle biopsies were taken and since that time
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and for some reason those studies have and then repeat it
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um and then in the nineteen nineties some studies with exogenous carbohydrate oxidation
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and so i'll i'll go and talk about somebody says studies the first couple i'll go really
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quickly because i think it was also covered in the uh in in the last all
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um children are a better anaerobic activities
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they produce more uh um
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uh so you the the children are not as good in the anaerobic activities they produce last uh lactate
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um but they are a little bit more like and you're exactly
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to where the aerobic capacity is very well the thought
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we see this also in language and uh um glycogen stores in the uh in the muscle
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oh
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and when we measure fat oxidation and this is a a study
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from mike yeah rebel and he measured a different stages
00:20:51
of acuity measured fat observation over a range of uh intense
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these and eh em and found that uh um
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that observation uh is best at the uh the uh at the early stages
00:21:11
when we ingest carbohydrate really reduce the um the uh fat observation uh um
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but one of the striking findings is i think that children
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when you express this per kilogram fat free mass
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are more reliant on the ingested carbohydrates than adults and
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some of this has to do i think with
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the uh with the scaling and the fact that energy expenditure just channel i guess it's lower
00:21:41
so the conclusions from this part of children have less developed anaerobic energy systems
00:21:45
but well developed aerobic capacity let but usually say she is generally higher
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um children use more exogenous carbide as if you will
00:21:58
and therefore when i combine all of this into some guidelines um
00:22:03
i didn't talk about this extreme carbohydrate loading not recommended
00:22:07
energy balance of course is important for growth the maturation didn't talk about that
00:22:13
carbohydrate intake during exercise well that really depends on
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the goals the intensity and the duration
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a fluid intake to limit fluid losses to about three percent
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um what should you drink well water is probably sufficient in most cases
00:22:32
unless you have identified that the exercise intense these high enough
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and iteration is long enough to warrant we use of carbohydrate
00:22:43
didn't talk about supplements but put solutions uh should always be preferred yeah instead of
00:22:48
supplements and no need to supplement it it's not a necessary of course
00:22:54
and the general recommendation is no supplements but the reality is of course
00:22:59
that eighty percent of of young athletes uh are using supplements
00:23:08
so the guidelines for adults really are very simple and depend
00:23:13
very much on the goals of that they the
00:23:16
intensity and the duration of the exercise and it is not different in that should say young athletes
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so if we talk about supplements concentration the balance tired i think we should start at the bottom
00:23:31
make sure that there's enough attention for the uh for the diet if there is a need we
00:23:37
useful situation and uh and at the very last resort we yeah we talk about supplements so
00:23:44
it's one that leave you with that uh that last slide that uh i
00:23:47
think the futures will situation it's not this debate we have about high
00:23:51
fat or high cock diets it is really about personalising it to the individual
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