FACULTY OF SCIENCE, ENGINEERING AND COMPUTING

School of Life Sciences

BSc (Hons) DEGREE

IN Sports Science

Hasan MohammedK1153242

Effects of BCAA Supplementation on Exercise Capacity

13th August 2014

Supervisor: Dr. Hannah Moir

WARRANTY STATEMENT

This is a student project. Therefore, neither the student nor Kingston University makes any

warranty, express or implied, as to the accuracy of the data or conclusion of the work

performed in the project and will not be held responsible for any consequences arising out of

any inaccuracies or omissions therein.

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Table of Contents

Acknowledgments.....................................................................................................................3

Abstract.....................................................................................................................................4

1. Introduction..........................................................................................................................5

1.1 BCAA Metabolism...............................................................................................................6

1.2 Central Fatigue.....................................................................................................................8

1.3 Physiological Affects...........................................................................................................9

1.4 Consumption and Dosage...................................................................................................11

1.5 Lactate and Exercise Capacity...........................................................................................12

1.6 Glucose and Exercise Capacity..........................................................................................12

2. Theoretical Framework……………………………………………………………….....14

2.1 Research Question..............................................................................................................14

2.2 Research Aims....................................................................................................................14

2.3 Objectives...........................................................................................................................14

2.4 Operational Definitions......................................................................................................14

3. Methods...............................................................................................................................15

3.1 Literature Review and Study Selection..............................................................................15

3.2 Inclusion/Exclusion Criteria...............................................................................................15

3.3 Data Analysis.....................................................................................................................16

4. Results.................................................................................................................................18

5. Discussion and Conclusions...............................................................................................21

5.1 Limitations.........................................................................................................................22

6. Future Recommendations..................................................................................................23

7. Critical Reflection...............................................................................................................24

References...............................................................................................................................25

Acknowledgements

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May I take this opportunity to show my gratitude to all those who assisted in this work. I am

very grateful for the supervision, guidance and motivation provided throughout this project

by Dr. Hannah Moir. Her invaluable character has provided me with faith in my own

capabilities to carry out such project. She has been approachable and readily available

throughout this project and did not spoon feed all of her knowledge, only to get the best out

of myself and this project for which I thank her for. Her mentoring skills are second to none

and I appreciate all the effort and time she has given.

Abstract

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Branched chain amino acids are becoming more renown in sports drinks as a quick and

efficient supply of energy during exercise. There have been many studies which qualitatively

review this topic but predominantly in relation to central fatigue opposed to peripheral

(metabolic/fatigue) mechanisms. This meta-analysis quantitatively reviews all literature

regarding this topic. Aim: To determine whether BCAA supplementation has an ergogenic

effect on endurance-based exercise capacity. Methods: A search of the literature was carried

out and this that met the inclusion criteria was used for analysis. Six published studies met

the inclusion criteria. The studies included multiple exercise protocols and dosages but either

or both lactate or glucose measures were tested in each study. A total of 9 effect sizes were

established and a total of 67 participants, of which the majority were healthy adult males,

were included in this Meta-analysis. The mean dosage of supplementation across all studies

was 19.45g. Results: This study shows BCAA supplementation improved endurance-based

exercise capacity has; p=0.001 for glucose measures and p=0.000 for lactate measures,

whereby p≤0.05. Conclusion: BCAA supplementation does have an ergogenic effect on

endurance-based exercise capacity thus the null hypothesis can be rejected.

1. Introduction

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Branched-chain-amino-acids (BCAA’s) are known as the umbrella term for three essential

amino acids: leucine, isoleucine and valine. They are known as essential amino acids as they

make up 40% of the daily requirement of all amino acids (Stowers, 2009).BCAA’s cannot be

broken down in the body, rather they are oxidised during exercise (Saris et al., 1989).The

recommended dose for leucine is about 40mg/kg of body weight per day and for isoleucine

and valine approximately 10-30mg/kg per day(Hargreaves, 2006). Although the

recommended daily allowance of BCAA’s were 20% per day, amendments after new

research made the needs of BCAA’s increase to 40% (Stowers, 2009). However this research

was carried out on those who were fasting and living normal lifestyles, not those in need of

more energy or muscle, such as athletes or those carrying out exercise (Zeigler & Filler,

1996). Athletes are now using BCAA’s more commonly as ergogenic aids, thus as RDA

levels have increased, it is likely that BCAA supplementation for athletes should also

increase (Stowers, 2009). During exercise, it has been reported that proteolysis increases and

consequently whole-body-protein and amino acids are used further for energy (De Feo et al.,

2003). As well as the increase in use of BCAA’s during exercise, BCAA plasma

concentrations have shown to be decreased during prolonged exercise, thus supplementation

acts as replenishing this reduction in BCAA availability and consequent energy loss during

prolonged exercise (Bloomstrand et al., 1991). Therefore the protein requirement during

(endurance) exercise is increased and BCAA’s are oxidised further thus need to be

replenished within the diet for increased exercise capacity (Gleeson, 2005).

1.1 BCAA Metabolism

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Once metabolised from protein, most free amino acids are transported to the liver and some

metabolism takes place in the viscera and stomach mucosal areas(Zeigler & Filler, 1996).

However, free BCAA’s are metabolised although metabolised via the liver, they are primarily

oxidised within the muscle and fat (adipose) tissue (Zeigler & Filler, 1996).Some BCAA’s

are exchanged in the intestinal viscera and then travel directly to the bloodstream which

makes them so proficient as an energy source during exercise. Most amino acids can be

broken down in the liver with the exception of BCAA’s. BCAA’s are oxidised from their

converted form called oxo-Keto acids and this essentially means BCAA’s benefits for human

function and exercise capacity is very quick and efficient. They are quick to supply energy

during exercise because they do not have to take time to breakdown in the liver first, opposed

to most other proteins. The enzymes needed to catabolise BCAA’s are known as

mitochondrial dehydrogenase and branched-chain keto acid dehydrogenase (BCKADH).It

has been shown in rats that chronic administration of BCAA’s and a high-protein diet

increases hepatic activity of these enzymes (Shimomura et al., 2000). Keto acids can then be

used by the muscle to resynthesise ATP for energy. However, the product of transiminated

leucine is Alpha-Ketoisocaproic, which can inhibit the breakdown of BCKADH to branched

chain oxo acid (BCOA), an acid that can be used as energy in the liver (Stowers, 2009).Some

supplement companies mistakenly sell the keto acid version of BCAA’s and thus inhibit the

natural breakdown of BCAA’s for energy(Hargreaves, 2006).Once BCAA’s are metabolised

in the liver, the organ muscles or adipose tissue, keto acids can be used to fuel the Krebs

cycle for ATP production and supply energy for all muscles and organs. Furthermore,

BCAA’s can also be converted to glutamine or alinine in the muscle, these amino acids can

then undertake glyconeogenesis within the liver to produce glucose, an essential energy

source during exercise.

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BCAA’s form 35% of muscle tissue and are actively used by the muscle and liver as energy.

Out of all six amino acids, BCAA’s have the most potential as a metabolic energy source for

muscles (Stowers, 2009). Muscle tissue naturally attains 60% of necessary enzymes to

metabolise BCAA’s and it is estimated 3%-18% of energy for all exercise is supplied by

BCAA’s. However, intensity and duration levels can alter this estimate accordingly (Stowers,

2009) and it is often the case that oxidation of BCAA’s succeeds the catabolic capacity

during prolonged endurance exercise (Ohtani et al., 2001).

In essence, leucine is one of the predominant ‘foods’ used as an energy source for muscle

during exercise. The bodies needs for leucine, in the form of BCAA’s, is 25 times greater

than the readily available leucine within the body gained from what is known as the ‘free

amino acid pool’. The body gains this extra need of leucine from supplementation of

BCAA’s, from the free amino pool or breaks down the muscle during workouts for the

luecine necessary for exercise (Zeigler & Filler, 1996).When BCAA’s are taken in the form

of a supplement, the free forms they are taken in surpass the gut and liver and directly enter

the bloodstream. Free forms of BCAA’s are quick to increase blood supply and effect BCAA

circulation for immediate effect on exercise capacity, although this is more prominent when

low levels of glycogen are present (Hargreaves, 2006). Nonetheless, large doses of leucine

are not recommended and Cynober, (2013) states the use of BCAA supplementation should

be in combination with carbohydrates. Two primary ways in which BCAA’s help reduce the

effects of fatigue are its ability to reduce central fatigue via the nervous system and help

produce energy via muscle oxidisation or as a key Krebs cycle component (Cynober, 2013)

and increasing lactate threshold during endurance exercise (Matsumoto et al., 2009).

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1.2Central Fatigue

5-hydroxytryptamine is a serotoninreceptor that is synthesised by the catalyst tryptophan

hydroxylase. As this enzyme is not saturated with substrate, the rate at which 5-HT

synthesises is relevant to the transport of tryptophan across the blood-brain barrier (BBB) as

well as the blood tryptophan concentration within the blood (Young, 1986). The transport of

tryptophan across the BBB is dependent on the amount available for transportation, the

capacity of the BBB transporter, the plasma concentration of tryptophan and the

concentration of other large neutral amino acids (LNAA’s and BCAA’s) which are carried by

the same carrier (Pardridge, 1998). Approximately 10% of total plasma tryptophan is in free

from and the remaining 90% is transported whilst bounded to the protein albumin.

Tryptophan is the only amino acid that binds to albumin. During prolonged endurance

exercise, when free fatty acid levels are elevated in the blood, the level of plasma tryptophan

also increases as free fatty acids and tryptophan compete for the same binding site; albumin

(Curzon et al., 1973). Thus the favourability of the transport of tryptophan into the brain,

when the plasma ratio of tryptophan to free BCAA’s increases, makes the release of 5-HT

from neurons more prominent (Bloomstrand, 2006) and therefore increases central fatigue.

Human studies have shown that during exercise the ratio of plasma tryptophan to BCAA’s

increases and that tryptophan is taken-up by the brain particularly during endurance exercise,

possibly increasing the synthesis of 5-hydroxytryptamine (5-HT), a serotonin receptor.

Once tryptophan enters the brain it causes the brain to release serotonin, an important

hormone that produces fatigue and tiredness (Cynober, 2013). Theory suggests the ingestion

of BCAA’s increases tryptophan/5-HT’s metabolism, which may reduce its uptake within the

brain and thus delay fatigue. A study by Bloomstrand et al., (1997) showed that when

BCAA’s supplied to humans during a standardised cycle ergometer exercise, their ratings of

perceived exertion (RPE) and consequent central fatigue reduced. Cognitive test

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performances also improved after a competitive 30km cross-country race, suggesting

enhanced brain activity which may relate to less fatigue. Furthermore Mittleman et al., (1998)

suggested that central fatigue is increased in heat and thus BCAA’s effectiveness in delaying

fatigue also increases. In this study physical performance measured by, the time to exhaustion

during cycling, improved by approximately 16 minutes for men and women during endurance

exercise at 40% VO2max in the heat. Subjects were given 5ml-kg-1 body weight of a solution

containing either 5.88 g-L-1 of polydextrose as the placebo or 5.88 g-L-1 of BCAA’s every 30

minutes during exercise. However, another similar study by Watson et al., (2004) where male

participants cycled to volitional exhaustion at 50% VO2max in a warm environment consumed

four aliquots of 250ml (3g) of a 12g/L-1 BCAA or placebo solution 30mins prior to exercise

and 150ml every 15min during exercise. The participants had shown no effect in the delay of

fatigue; placebo – 26.9min opposed to BCAA – 29.2min. Thus causing indefinite effects of

BCAA supplementation and exercise capacity.

1.3 Physiological Affects

The effects BCAA’s have on energy is approximately 3-18% of total energy. The amino

acids; isoleucine, leucine and valine can also act as key components of the Krebs cycle to

supply energy, making the three components of BCAA’s a valuable energy source (Cynober,

2013).The uses of BCAA’s have been shown to be effective predominantly with endurance-

based activities and in terms of its physiological effects; one month’s oral supplementation of

9 essential amino acids, including BCAA’s, had increased fasting glucose and decreased

creatine phosphokinase (a key enzyme which breaks down creatine and to resynthesise ATP

and supply energy via the predominantly anaerobic ATP-PC energy system)activity in

middle-long distance runners. Taken before and after workouts, marathoners as well as

cyclists have shown positive effects during and before events where improvements in

cognitive performance and reductions in time have been shown. Reductions in lactate, a key

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component of exercise capacity and muscle mass loss has also shown to be reduced (Ohtani

et al., 2001).

BCAA’s enter the Krebs cycle directly as acetyl-CoA and not via the glycolytic pathway

whereby pyruvate is converted to lactate by lactate dehydrogenase, a wasteful by-product that

may inhibit exercise capacity (Harper et al., 1984). A study by Matsumoto et al., (2009)

shows BCAA metabolism does not produce lactate and is considered to decrease lactate

levels after supplementation. As lactate is a by-product of glycolysis during energy

metabolism, ones lactate threshold and lactate concentration are considered as predictors of

endurance exercise capacity (Yoshida et al., 1987). A study carried out by De Palo et al.,

(2001) reported lactate levels are suppressed within the blood during exercise following the

chronic supplementation of BCAA’s. The study led by De Palo et al., (2001) had given

triathletes 30 days of chronic BCAA supplementation (0.2g/kg-1) and 9.64g of BCAA oral-

supplementation before exercise consisting of 60mins at 70% VO2max.Furthermore,a study

carried out by Matsumoto et al., (2009) proved that 6 day supplementation of a BCAA drink

increased lactate threshold by increasing workload levels at LT as well as VO2maxagainst a

placebo. The study exercise test was an incremental loading exercise until exhaustion using a

cycle ergometer; the test drink amounted to 500ml and was given 15min prior exercise.

Participants took 1500ml/d during the 6 prior days to testing and it was concluded BCAA

ingestion before exercise increases BCAA supply as an energy source to the muscle during

endurance exercise. Thus it was theorised that the increase of acetyl-CoA to the Krebs cycle,

via the BCAA catabolic pathway, inactivates the glycolytic pathway and consequently

suppresses lactate production during the test. This suggests that a reduction in carbohydrate

breakdown and lactate production increases endurance exercise capacity by inactivating the

glycolytic energy system.

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1.4 Consumption and Dosage

On average, BCAA’s make up about 15% of total amino acid content within food protein

(Gleeson, 2005). A Tour De France cyclist averages 25 Mj/d over a 2-3week period (Saris et

al., 1989). Although protein in a tour de Frances’ diet may be relatively less, much energy is

consumed in the form of carbohydrates, the protein is about 12% of total body energy for a

tour de France cyclist. The elite cyclist consumes about 3000 kJ as protein thus about 19g of

this protein are BCAA’s (Saris et al., 1989).

Some studies have compared combined and separated glucose and BCAA supplementation

(Madsen et al., 1996; Calders et al., 1999) and formulas are found to have both ergogenic aids

within. The recommended dosage of BCAA’s is 3-20g a day, before and after workouts. A

study carried out on 23 rugby players, who carried out intensive training, identifying the

effects of a mixture of 9 essential amino acids, including leucine, isoleucine, valine and

carbohydrates, showed significant improvements in vigour and earlier recovery from fatigue

after 90 days of supplementation. They were given 3.6g twice, daily, for 90 days. This

amount has been credited by most studies indicating 7-12g during endurance events, mixed

into carbohydrate solution (Bloomstrand & Newsholme, 1992; Davis et al., 1999; Mero,

1999; Koba et al., 2007). A study by Tipton et al., (2004) showed whey protein ingestion

resulted in a higher amount of blood BCAA concentrations, suggesting an increase in

absorption when taken with whey protein or carbohydrates. Thus this study specifically looks

at post lactate and glucose concentrations after BCAA supplementation as an indicator of

endurance exercise capacity. However, dosage amount may critically vary amongst

individuals which studies did not account for.

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1.5 Lactate and Exercise Capacity

The blood lactate curve and lactate thresholds have recently become an important factor in

the assessment of exercise capacity (Faude et al., 2009). Lactate threshold, inversely related

to blood lactate concentrations (bLa), has been always used as an index of endurance exercise

capacity. In exercise intolerant mice with disrupted branched chain amino acid metabolism,

increased rates of lactate release from skeletal muscle during exercise were described (She et

al., 2010). It is a trend with many studies that graded incremental tests eliciting a rise in blood

lactate concentration have been used to determine lactate thresholds or curves which indicate

exercise capacity (Faude et al., 2009). During the first half of the 20 th century VO2 max levels

were the most common means of evaluating endurance capacity (Faude et al., 2009) and was

developed by Hill et al., (1923). However, in the 1960’s the method by which lactate

concentrations were measured was by capillary blood samples, which led to an increased

popularity of bLa to assess endurance capacity (Hollmann, 2001) and has now become the

most influential factor in the diagnosis of endurance performance/capacity in sport (Jones,

2006).Therefore this study uses bLa as a means of assessing exercise capacity and the

improvements it may have due to BCAA supplementation, as it is generally accepted the

lower the bLa concentration at a given workload the better ones endurance (exercise)

capacity (Yoshida et al., 1990; Bosquet et al., 2002).

1.6Glucose and Exercise Capacity

It has been outlined by Peronnet & Thibault, (1989) that the physiological basis of endurance

capacity, determined by aerobic endurance, is not clearly grasped. It is, however, a

combination of several factors one of which includes the capacity to spare carbohydrates in

the form of glucose. The capacity to save carbohydrate as a reserve fuel by using more fatty

acids as energy substrates increases ones (endurance) exercise capacity (Foster et al.,

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1978).Thus this study uses the means of blood glucose levels (bGl) as a diagnosis of

endurance-based exercise capacity. However, overall bLa are known to be influenced by

depleted glycogen stores (proceeding exhaustive/endurance exercise) (Reilly & Woodbridge,

1999). For example, low bLa at the same work rates have been shown in glycogen-depleted

subjects compared with a subject in normal condition. This may lead to a lower bLa and

should not be interpreted as an increased exercise capacity (Maassen & Busse, 1989).

Although studies suggest BCAA supplementation positively increases endurance exercise

capacity, other studies have shown no effect as mentioned above by Watson et al., (2004) and

as a result, disagreements remain with the effectiveness of BCAA ingestion on endurance

exercise (Matsumoto et al., 2009). However, these studies used different timing and dosages

thus affecting the comparison in relation to the effects of acute BCAA supplementation.

Many studies have identified BCAA’s effects on central fatigue mechanisms opposed to

peripheral fatigue mechanisms such as metabolism or fatigue. As no (Meta) analysis has been

carried out to determine whether BCAA supplementation has an ergogenic effect on exercise

capacity. This study looks at the effects BCAA supplementation has on metabolic (bGl) and

fatigue (bLa) mechanisms in relation to exercise capacity.

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2. Theoretical Framework

2.1 Research Questions

Does BCAA supplementation have an effect on exercise capacity?

2.2 Research Aims

To determine whether BCAA supplementation has an ergogenic effect on endurance-based

exercise capacity.

2.3 Objectives

To quantitatively review the research of BCAA supplementation and its effects on exercise

capacity.

H1- BCAA supplementation will enhance exercise capacity.

H0 - BCAA supplementation will have no ergogenic effect on exercise capacity.

2.4 Operational Definitions

Endurance exercise defined as any exercise mode in excess of 60 minutes work

Work defined as an increase in HR due to physical activity

Exercise capacity is defined as work until exhaustion measured by lactate or glucose

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3. Methods

3.1 Literature Review and Study Selection

The literature used within this meta-analysis was searched using the databases of

GoogleScholar, SPORTDiscuss and PUBMED in July 2014. A variety of key search words

and terms were used, these included but were not limited to: ‘BCAA’, ‘Branched-Chain-

Amino-Acids’, ‘supplementation’, ‘exercise’, ‘capacity’, ‘endurance’, ‘lactate’, ‘glucose’.

Once all potential studies had been identified, studies were included/excluded for analysis in

accordance with the inclusion/exclusion criteria outlined below. Characteristics included

relevant exercise modes such as endurance exercise and lactate/glucose measures.

Homogeneity of participants was considered but inclusion criteria remained as outlined.

3.2 Inclusion/Exclusion Criteria

This meta-analysis was limited to journal articles using human participants in a placebo or

controlled double-blinded condition. These articles were published in English peer-reviewed

journals which had a BCAA supplementation group, possibly including a carbohydrate

solution and a placebo group (PLA). A summary of the processes used to select relevant

articles to be used in the current meta-analysis are outlined in Fig. 1. Studies that were not

included in the bLa analysis had no relevant info (Matsumoto et al., 2009; Greer et al., 2011;

Pasiakos et al., 2011). Other studies that were not included had an inappropriate testing

strategy (MacLean et al., 1996, where an anaerobic-based dynamic knee extensor exercise

was used as a dependant variable), those with inappropriate experimental groups such as

using rats or mice (Shimomura et al., 2000), or no specific numerical data in a table to use for

analysis (Madsen et al., 1996; Coombes et al., 2000; Shimomura et al., 2004; Koba et al.,

2007), or those that only seem to be available as abstracts (Varnier et al., 1994; Gualano et

15

al., 2011) and one that was only available in a Chinese journal hence was not accessible

(Jianhong & Zhihong, 2005).

3.3 Data Analysis

Pre- and Post-supplementation mean and standard-deviations (SD) were obtained from the

original data from the studies used to establish effect size (ES).The effectiveness of the

supplement was quantified by establishing the effects size(Δ) which was calculated by the

difference between the post and pre-supplementation measures divided by the SD of the

control group (Gene Glass’s approach). The control’s group standard deviation is used as it is

not affected by the treatment (Glass et al., 1981).A forest plot as well as 95% confidence

intervals (p≤0.05) displaying the findings of BCAA supplementation to be effective or not

(on exercise capacity) was created by inputting raw data into Comprehensive Meta Analysis

V2 software. Where shown in Fig. 1, n=number of study’s. Two out of six studies did not

provide data indicating clear numerical lactate measurements, these data were instead given

in a figure which was difficult to use for accurate lactate measures to use in this analysis,

hence were excluded. Where information was not available, ‘no relevant data’ was stated, see

Table 1.

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Fig. 1. Flow chart showing the systematic review of studies and selection strategy

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Studies that were excluded due to irrelevant sample, predictors and outcomes (n=16)

Studies used for further evaluation (n=10)

Total studies excluded (n=5)

No relevant available data for lactate (n=2)

Studies included in current meta-analysis (n=5)

Potential relevant studies identified (n=26)

4. Results

Table 1.Effects of BCAA supplementation on glucose (G) and lactate (L) levels on endurance-based exercise capacity.

Study Sample Exercise Protocol Supplementation Protocol

Total Dosage of BCAA (g)

Effect Size

Cheuvront et al., (2004)

Watson et al., (2004)

Matsumoto et al., (2009)

7 Healthy Males

8 Males

21 Trained Males

60min cycling @ 50% VO2 max. Then,30min time-trial

Cycling to volitional exhaustion @ 50% VO2 max.

Incremental loading exercise test with cycle ergometer until exhaustion

60g/l glucose, 10g/l BCAA.

Total of 1.4L; 200ml at 15min intervals

4 250ml aliquots of a 12g/l BCAA solution every 30min prior exercise for a total of 120min

150ml every 15min throughout exercise

6ml BCAA,60ml Carbohydrate solution; 1500ml/d for 6d

500ml 15min prior exercise test

24.4

54

2

(3.23-0.9)/1.27 ES = 1.83 (L)

(6.15-5.02)/1.1 ES = 1

(G)

(1.53-0.59)/0.23

ES = 4.1 (L)

(4.1-4)/1ES = 0.1 (G)

(114-101)/15ES = 0.86(G)

No Relevant info for Lactate

Hsu et al., (2011)

14 Healthy Males

5min warm-up @ 55% VO2 max on a treadmill

Then, ran @ 75% VO2 max for 30min. Thereafter, intensity increased by 1% until

200ml of BCAA drink; valine (0.5g), leucine (1.0g), isoleucine (0.5g) and carbohydrate (12.1g) consumed post-

2 (3.6-1)/0.4ES = 6.5 (L)

(80.3-78.1)/1.5 ES = 1.47 (G)

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exhaustion exercise

19

Study name Statistics for each study Std diff in means and 95% CI

Std diff Standard Lower Upper in means error Variance limit limit Z-Value p-Value

Cheuvront et al., (2004) 0.576 0.545 0.298 -0.493 1.645 1.056 0.291Watson et al., (2004) 0.050 0.500 0.250 -0.930 1.030 0.100 0.920Matsumoto et al., (2009) 1.036 0.329 0.108 0.392 1.680 3.152 0.002Hsu et al., (2011) 0.802 0.393 0.154 0.032 1.572 2.042 0.041Greer et al., (2011) 0.002 0.471 0.222 -0.922 0.926 0.005 0.996Pasiakos et al., (2011) 0.316 0.503 0.253 -0.670 1.302 0.629 0.530

0.576 0.178 0.032 0.227 0.925 3.237 0.001

-1.00 -0.50 0.00 0.50 1.00

Treatment effect p<0.05

Fig 2. Statistical findings of BCAA supplementation on Glucose measures

Study name Statistics for each study Std diff in means and 95% CI

Std diff Standard Lower Upper in means error Variance limit limit Z-Value p-Value

Cheuvront et al., (2004) 1.105 0.574 0.329 -0.020 2.230 1.926 0.054Watson et al., (2004) 0.980 0.529 0.280 -0.057 2.017 1.852 0.064Hsu et al., (2011) 1.554 0.431 0.186 0.709 2.399 3.603 0.000

1.269 0.289 0.083 0.703 1.835 4.394 0.000

-1.00 -0.50 0.00 0.50 1.00

Treatment effect p<0.05

Fig 3. Statistical findings of BCAA supplementation on Lactate measures

Study Sample Exercise Protocol Supplementation Protocol

Total Dosage of BCAA (g)

Effect Size

Greer et al., (2011)

Pasiakos et al., (2011)

9 Untrained

Males

8 Adults

3 90min Cycling bouts @ 55% VO2 max

Cycle ergometer @ 60% VO2 max

BCAA drink; valine (7.3g), leucine (12.2g), isoleucine (4.8g).

Administered 5min prior exercise and at 60min during exercise bout

125ml of 10g BCAA drink (leucine enriched) throughout exercise

24.3

10

(102.36-102.34)/18.84

ES = 0.001 (G)

No relevant info for Lactate

(4.9-4.7)/0.1ES = 2 (G)

No relevant info for Lactate

5. Discussion and Conclusions

This meta-analysis shows the overall effect of BCAA supplementation on endurance-based

exercise capacity has a significant effect where p≤0.05; p=0.001 for glucose measures and

p=0.000 for lactate measures (see fig. 2. and fig.3.). The analysis indicates that a dosage of

19.45g (mean dosage across all studies) of BCAA supplementation will have a positive effect

on lower bLa and higher bGl indicating an enhanced exercise capacity for endurance-based

activities. The results of this study are in agreement with previous studies including (Hsu et

al., 2011; Matsumoto et al., 2011). In accordance to conventional effect size values, (Cohen,

1962) glucose may consider a ‘medium’ effect size for BCAA supplementation to be

applicable and lactate may be considered to have a ‘large’ effect size; (d=0.032, d=0.083

respectively).

The results for this study may be surprising as only two of six studies show significant

differences between treatment and control groups in relation to lactate (Hsu et al., 2011;

Motsumoto et al., 2011). However, the glucose trials identify significant differences which

may be the reason for the significance of this study. It is important that these measurements

are used together to determining the effects of BCAA supplementation as Cynober, (2013)

states the use of BCAA’s should be in combination with carbohydrates. A study by Hsu et

al., (2011) showed a BCAA drink containing 24.2g of carbohydrates may have enhanced the

insulin response during post-exercise period. This suggests when BCAA and carbohydrates

are mixed into a solution; it enhances anabolic responses during recovery (Hsu et al., 2011).

Hsu et al., (2011) also found BCAA drink did not stimulate an increase in bLa, which is

consistent with this study. The reason metabolism (of glucose) may be significant is the fact

that BCAA’s may act as a substrate for muscle metabolism (Hsu et al., 2011).

Amino acids have recently become more prominent in sport beverages due to an apparent

reduction on muscle damage when consumed before or after exercise (Greer et al., 2007).

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However, a concern arises for adding BCAA’s to spots drinks as it may add a potential

carbon drain on the Krebs cycle. In the process of transimination, the first stop of BCAA

catabolism, leucine is accepted and forms glutamate. When pyruvate (which forms lactate) is

not available to supple alinine aminotransferase reaction, it may lead to a depletion of the

Krebs cycle flux to produce ATP, during the oxidation of leucine, an essential amino acid

(Wagenmakers, 1999).

In conclusion the metabolic (bGl) and fatigue (bLa) mechanisms used as diagnosing exercise

capacity has shown to be effective in enhancing exercise capacity by BCAA

supplementation. Therefore the null hypothesis can be rejected in accordance with the above

outlined glucose and lactate significance levels.

5.1 Limitations

The results from this study do go against some previous studies such as (Watson et al., 2004;

Cheuvont et al., 2004) but these studies were done less recently and thus may be irrelevant

when compared with those that have been done more recently. Nonetheless, the studies

included in this meta-analysis may show not significant measures compared with a placebo

due to a better understanding of how to perform trials or a possible ‘placebo effect’ (Laursen

et al., 2003).

This study uses incremental exercise to exhaustion and exercise lasting 60mins or more to

elicit rise in bLa. However, this measure of endurance capacity is hindered by many factors

that may influence overall lactate levels. The magnitude of endurance gains is difficult to

predict by using bLa (Faude et al., 2009) and may lead to this study to lack internal validity.

Nevertheless, studies have shown bLa to be a renowned measurement in the diagnoses of

exercise capacity (Yoshida et al., 1990; Bosquet et al., 2002; Faude et al., 2009).

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6. Future recommendations

In terms of the consumption of BCAA’s, they are safe within recommended dosages and

have shown to improve exercise capacity within this meta-analysis if an average of 19.45g is

taken according to the protocols used in this study. The use of amino acid supplements is not

prohibited by the World-Anti-Doping Agency (WADA) and thus makes it a legal substance

(Williams, 2005). This study proves the increased effects of endurance-based exercise

capacity due to BCAA supplementation and thus may be an effective ergogenic aid for

marathoners, cyclists and those involved in endurance activities. Coaches may use such

supplements to quickly supply energy to athletes for endurance exercise as mentioned,

BCAA’s predominantly metabolise in the muscle and fat tissue (Zeigler & Filler, 1996).

However, the majority of participants in this study were healthy male adults and not elite

athletes. The results in this meta-analysis were also calculated using comparatively few

studies (n=6) which may make this study lack ecological validity. Furthermore, this study

does not consider time-trial based results for measurements and although stated, does not take

dosage effects into calculation. Findings of BCAA supplementation remain equivocal in

particular its physiological effects on exercise capacity. Bloomstrand, (2001) reported

reductions on perceived exertion ratings (RPE) and consequent central fatigue after BCAA

supplementation during prolonged exercise, suggesting improvements in physical

performance but the named study used central fatigue mechanisms to identify exercise

enhancements. This highlights the need for future studies investigating the effects of BCAA

supplementation on exercise capacity, in relation to peripheral fatigue mechanisms, is

necessary with dosage, time-trial (performance), different mode(s) of exercise (muscular

strength/power output) and different types as well as homogeneity amongst subjects as

factors taken into consideration.

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7. Critical reflection

To undertake this research key life skills and technical skills had to be applied in order to

successfully and efficiently carry out work. In doing so, time management skills to stick to

deadlines had to be adhered to as well as excellent communication skills, which included

emails to the supervisor, were made throughout this research project. Discipline to carry out

work out of university hours was implied to keep up-to-date. The organisation of work was

parallel to a successful project; organising relevant and irrelevant research papers into folders

for future reference and usage within this analysis was very important to stay focused and

precise in this project.

Key transferable skills were also learnt and utilised such as the use of meta-analysis software

(Comprehensive Meta Analysis V2), Microsoft Word, Outlook and PowerPoint for a high

level of presentation of data, sending and constantly being aware of emails and presenting

work in a slide show using PowerPoint.

To be able to carry out this research project alongside other commitments such as a job has

increased my ability to juggle many works at a single time and not only plan, but effectively

manage time according to deadlines.

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References

Blomstrand, E. (2001). Amino acids and central fatigue. Amino acids, 20(1), 25-34.

Blomstrand, E. (2006). A role for branched-chain amino acids in reducing central fatigue. The Journal of nutrition, 136(2), 544-547.

Blomstrand, E., Hassmen, P., Ekblom, B. &Newsholme, E. A. (1991).Administration of branched-chain amino acids during sustained exercise—effects on performance and on plasma concentration of some amino acids.European journal of applied physiology and occupational physiology, 63(2), 83-88.

Blomstrand E, Hassmen P, Ekblom B. &Newsholme EA. Influence of ingesting a solution of branched-chain amino acids on perceived exertion during exercise. (1997). ActaPhysiol Scand. (159), 41-9.

Blomstrand, E. &Newsholme, E. A. (1992).Effect of branched chain amino acid ‐supplementation on the exercise induced change in aromatic amino acid concentration in ‐human muscle. Actaphysiologicascandinavica, 146(3), 293-298.

Bosquet, L., Léger, L., &Legros, P. (2002).Methods to determine aerobic endurance. Sports Medicine, 32(11), 675-700.

Calders, P. A. T. R. I. C. K., Matthys, D., Derave, W., & Pannier, J. L. (1999). Effect of branched-chain amino acids (BCAA), glucose, and glucose plus BCAA on endurance performance in rats. Medicine and science in sports and exercise,31(4), 583-587.

Cohen, J. (1962). The statistical power of abnormal-social psychological research: A review. Journal of abnormal and social psychology, 65(3), 145-153.

Coombes, J. S., & McNaughton, L. R. (2000).Effects of branched-chain amino acid supplementation on serum creatine kinase and lactate dehydrogenase after prolonged exercise. The Journal of sports medicine and physical fitness,40(3), 240-246.

Curzon G, Friedel J, Knott PJ. The effect of fatty acids on the binding of tryptophan to plasma protein.Nature. 1973;242:198–200.

Cynober, L. A. (Ed.). (2013). Metabolic & Therapeutic Aspects of Amino Acids in Clinical Nutrition.CRC Press.

Davis, J. M., Welsh, R. S., De Volve, K. L., & Alderson, N. A. (1999). Effects of branched-chain amino acids and carbohydrate on fatigue during intermittent, high-intensity running. International journal of sports medicine, 20(05), 309-314.De Feo, P., Di Loreto, C., Lucidi, P., Murdolo, G., Parlanti, N., De Cicco, A., &Santuesanio, F. P. F. (2003).Metabolic Response to Exercise.Journal of Endocrinological Investigation.26(9), 851-854.

24

De Palo, E. F., Gatti, R., Cappellin, E., Schiraldi, C., De Palo, C. B., &Spinella, P. (2001). Plasma lactate, GH and GH-binding protein levels in exercise following BCAA supplementation in athletes. Amino acids, 20(1), 1-11.

Faude, O., Kindermann, W., & Meyer, T. (2009). Lactate threshold concepts.Sports Medicine, 39(6), 469-490.

Foster, C., Costill, D. L., Daniels, J. T., & Fink, W. J. (1978). Skeletal muscle enzyme activity, fiber composition and\ dot VO2 max in relation to distance running performance. European journal of applied physiology and occupational physiology, 39(2), 73-80.

Glass, G. V., McGraw, B., & Smith, M. L. (1981).Meta-analysis in social research. Beverly Hills: Sage Publications.

Greer, B. K., White, J. P., Arguello, E. M., &Haymes, E. M. (2011). Branched-chain amino acid supplementation lowers perceived exertion but does not affect performance in untrained males. The Journal of Strength & Conditioning Research, 25(2), 539-544.

Greer, B. K., Woodard, J. L., White, J. P., Arguello, E. M., &Haymes, E. M. (2007). Branched-chain amino acid supplementation and indicators of muscle damage after endurance exercise.

Gualano, A. B., Bozza, T., Lopes, D. C. P., Roschel, H., Dos Santos, C. A., Luiz, M. M., ... & Herbert, L. J. A. (2011). Branched-chain amino acids supplementation enhances exercise capacity and lipid oxidation during endurance exercise after muscle glycogen depletion. The Journal of sports medicine and physical fitness, 51(1), 82-88.

Hargreaves, M., Spriet, L. (2006).Exercise Metabolism, Champaign, IL.Human Kinetics.

Harper, A. E., Miller, R. H., & Block, K. P. (1984).Branched-chain amino acid metabolism. Annual review of nutrition, 4(1), 409-454.

Hill, A. V., Long, C. N. H., & Lupton, H. (1924).Muscular exercise, lactic acid, and the supply and utilisation of oxygen. Proceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character, 84-138.

Hollmann, W. (2001).42 Years Ago—Development of the Concepts of Ventilatory and Lactate Threshold. Sports Medicine, 31(5), 315-320.

Jianhong, L., &Zhihong, Z. (2005).Effects of branched-chain amino acid supplementation on blood glucose, alanine and lactate of rowers after different loads of exercise. Chinese Journal of Sports Medicine, 2000.

Jones, A. M. (2006). The physiology of the world record holder for the women's marathon. International Journal of Sports Science and Coaching, 1(2), 101-116.

25

Koba, T., Hamada, K., Sakurai, M., Matsumoto, K., Hayase, H., Imaizumi, K., &Mitsuzono, R. (2007). Branched-chain amino acids supplementation attenuates the accumulation of blood lactate dehydrogenase during distance running. The Journal of sports medicine and physical fitness, 47(3), 316-322.

Laursen, P. B., Shing, C. M., & Jenkins, D. G. (2003).Reproducibility of a laboratory-based 40-km cycle time-trial on a stationary wind-trainer in highly trained cyclists. International journal of sports medicine, 24(07), 481-485.

Maassen, N., &Busse, M. W. (1989). The relationship between lactic acid and work load: a measure for endurance capacity or an indicator of carbohydrate deficiency?. European journal of applied physiology and occupational physiology, 58(7), 728-737.

MacLean, D. A., Graham, T. E., &Saltin, B. (1996).Stimulation of muscle ammonia production during exercise following branched-chain amino acid supplementation in humans. The Journal of physiology, 493(Pt 3), 909-922.

Madsen, K., Maclean, D. A., Kiens, B., & Christensen, D. (1996).Effects of glucose, glucose plus branched-chain amino acids, or placebo on bike performance over 100 km. Journal of Applied Physiology, 81(6), 2644-2650.

Matsumoto, K., Koba, T., Hamada, K., Tsujimoto, H., &Mitsuzono, R. (2009). Branched-chain amino acid supplementation increases the lactate threshold during an incremental exercise test in trained individuals. Journal of nutritional science and vitaminology, 55(1), 52-58.

Mero, A. (1999). Leucine supplementation and intensive training. Sports Medicine, 27(6), 347-358.

Michael Gleeson. (2005). Interrelationship between physical activity and branched-chain amino acids.Journal of Nutrition, 135(6), 15915-15955.

Mittleman KD, Ricci MR, Bailey SP. Branched-chain amino acids prolongexercise during heat stress in men and women. (1998). Med Sci Sports Exerc.(30), 83–91.

Ohtani M, Maruyama K, Sugita M,Kobayashi K. (2001). Amino acid supplementation affects hematological and biochemical parameters in elite rugby players. Bioscience, biotechnology and biochemistry.65(9), 1970.

Ohtani, M., Maruyama, K., Suzuki, S., Sugita, M., & Koboyashi, K. (2001). Changes in hematological parameters of athletes after receiving daily dose of a mixture of 12 amino acids for one month during middle-and long-distance running training.Bioscience, biotechnology and biochemistry.65(2), 348-355.

Pardridge WM. (1998). Blood-brain barrier carrier-mediated transport and brain metabolism of amino acids.Neurochemistry Research.23(635), 44.

26

Pasiakos, S. M., McClung, H. L., McClung, J. P., Margolis, L. M., Andersen, N. E., Cloutier, G. J., & Young, A. J. (2011). Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances postexercise muscle protein synthesis. The American journal of clinical nutrition, 94(3), 809-818.

Pironnet, F., &Thibault, G. (1989).Mathematical analysis of running performance and world running records. J. Appl. Physiol, 67, 453-465.

Reilly, T., & Woodbridge, V. (1999).Effects of moderate dietary manipulations on swim performance and on blood lactate-swimming velocity curves.International journal of sports medicine, 20(02), 93-97.

Saris, W. H. M., van Erp-Baart, M. A., Brouns, F. J. P. H., Westerterp, K. R., & Ten Hoor, F. (1989). Study on food intake and energy expenditure during extreme sustained exercise: the Tour de France. Int J Sports Med, 10(1), 26-31.

She, P., Zhou, Y., Zhang, Z., Griffin, K., Gowda, K., & Lynch, C. J. (2010). Disruption of BCAA metabolism in mice impairs exercise metabolism and endurance. Journal of Applied Physiology, 108(4), 941-949.

Shimomura, Y., Murakami, T., Nakai, N., Nagasaki, M., & Harris, R. A. (2004). Exercise promotes BCAA catabolism: effects of BCAA supplementation on skeletal muscle during exercise. The Journal of nutrition, 134(6), 1583-1587.

Shimomura, Y., Murakami, T., Nakai, N., Nagasaki, M., Obayashi, M., Li, Z., & Sato, M. (2000).Suppression of glycogen consumption during acute exercise by dietary branched-chain amino acids in rats. Journal of nutritional science and vitaminology, 46(2), 71-77.

Stowers, S. (2009). A Primer on Branched Chain Amino Acids. Huntington College of Health Sciences.

Tipton, K. D., Borsheim, E., Wolf, S. E., Sanford, A. P., & Wolfe, R. R. (2003). Acute response of net muscle protein balance reflects 24-h balance after exercise and amino acid ingestion. American Journal of Physiology-Endocrinology And Metabolism, 284(1), 76-89.

Tipton, K. D., Elliott, T. A., Cree, M. G., Wolf, S. E., Sanford, A. P., & Wolfe, R. R. (2004). Ingestion of casein and whey proteins result in muscle anabolism after resistance exercise. Medicine and Science in Sports and Exercise, 36(12), 2073-2081.

Varnier, M., Sarto, P., Martines, D., Lora, L., Carmignoto, F., Leese, G. P., &Naccarato, R. (1994). Effect of infusing branched-chain amino acid during incremental exercise with reduced muscle glycogen content. European journal of applied physiology and occupational physiology, 69(1), 26-31.

Wagenmakers, AJ, (1999). Muscle amino acid metabolism at rest and duringExercise.Diabetes NutrMetab,12, 316–322.

27

Watson, P., Shirreffs, S. M., &Maughan, R. J. (2004).The effect of acute branched-chain amino acid supplementation on prolonged exercise capacity in a warm environment. European journal of applied physiology, 93(3), 306-314.

Williams, M. (2005). Dietary supplements and sports performance: amino acids. J IntSoc Sports Nutr, 2(2), 63-67.

Yoshida, T., Chida, M., Ichioka, M., &Suda, Y. (1987). Blood lactate parameters related to aerobic capacity and endurance performance. European journal of applied physiology and occupational physiology, 56(1), 7-11.

Yoshida, T., Udo, M., Chida, M., Ichioka, M., Makiguchi, K., & Yamaguchi, T. (1990).Specificity of physiological adaptation to endurance training in distance runners and competitive walkers. European journal of applied physiology and occupational physiology, 61(3-4), 197-201.

Young SN. The clinical psychopharmacology of tryptophan. In: WurtmanRJ, Wurtman JJ, editors. Nutrition and the brain, vol 7. New York: Raven Press; 1986. 49–88.

Ziegler, E and Filer, L. (1996) Present Knowledge Nutrition 7th ed. North America Washington D.C. International Life Sciences Institute.

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