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Acknowledgement
I wish to thank Twickenham Cycling Club, Kingston Wheelers, The Dulwich Paragons and
all participants for their support and cooperation throughout this study. I would like to
express my deepest gratitude to my family and Robin for their continued support, help,
encouragement and patience throughout my university studies. I would not have been able to
do it without them. Finally, I would also like to thank Dr Owen Jeffries for his invaluable
knowledge and time; my research would not have been possible without his help.
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Abstract
The purpose of this study was to determine the effect of 470 mg Aloe vera supplementation
over 3 weeks vs. placebo on VO2max on a cycle ergometer, haematocrit, hemoglobin, body
fat percentage, maximum heart rate and RPE.
10 trained subjects (Age: 26 ± 4.4 years; Height: 172 ± 4.3 cm; Weight: 75 ± 10.8 kg)
participated in this study. They were randomly assigned to either Aloe vera or placebo group
for a period of 3 weeks in a double blind design. Prior to and following treatment subjects
performed a VO2max test on Monark 824e Cycle ergometer. Body fat, resting bloods and
finishing blood lactate were taken on both occasions. The pre and post data for both
conditions were analysed using appropriate paired sample t test.
A significant difference was found in the Aloe vera group in VO2max and haematocrit
percentage. No significant treatment effect was observed for hemoglobin, body fat
percentage, RPE, maximum heart rate, resting and finishing blood lactate.
The results of this study support an ergogenic effect on VO2max cycling performance
following 3 week supplementation period of 470 mg Aloe vera in healthy males and females
with moderate to high exercise capacities. These findings highlight the potential for future
studies using Aloe vera supplementation as an ergogenic aid in sport. Additional research is
essential to provide feasible scientific justification why any significant results occurred.
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Introduction
Aloe vera is commonly known as a medicinal plant and has been associated with skin
healing, immune boosting, anti- inflammatory and anti-oxidant properties (Langmead et al.,
2004).
Inflammation is a reaction that occurs in the body due to injury or over-exertion and is
characterised by high levels of pain, swelling, redness, loss of function and heat (Pyne, 1993).
Anshel & Russel (1994), determined that the ability for an athlete to tolerate exercise-induced
pain is a critical factor in a successful performance in endurance sports. Aloe vera contains
natural pain relief properties, salicylic acid and acetylated mannan which have been
demonstrated to promote anti-inflammatory activity which can help with physical
performance and recovery (Hamman, 2008; Reynolds & Dweck, 1999; Vogler & Ernst,
1999).
Clinical studies using Aloe vera have demonstrated a modest, anti-inflammatory therapeutic
effect in diseases such as ulcerative colitis (Langmead et al., 2004). Indeed several studies
have emphasized the anti-inflammatory effect of Aloe vera (Davis, Donato, Hartman & Hass,
1994; Davis, Leitner & Russo, 1987; Vázquez, Avila, Segura, Escalante, 1996; Vogler &
Ernst, 1999). Considering the role of inflammation, research has shown that during
performance, in prolonged exercise such as cycling, inflammatory cytokines such as IL-1
and IL-6 are released (Smith, 2000). These cytokines can cause inflammation and a
reduction in performance (Smith, 2000). The suggested anti-inflammatory effects of Aloe
vera may play a significant role in improving exercise performance (Hammam, 1999; Pyne,
1993; Reynolds & Dweck, 1999).
.
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Supplementation of Aloe vera has been shown to meet the Health Food Manufacture
Association (HFMA) standards in the UK (HFMA 2014). Several performance sports drinks
currently on the market contain Aloe vera and have been shown to demonstrate a significant
effect on endurance performance. They found that it led to an increase in VO2max and an
increase in time to exhaustion in a VO2max treadmill test (Byars, Keith & Snowden, 2009).
However, it is not known whether Aloe vera may have mediated this affect. They argue that
it may have been the high carbohydrate content in the performance sports drink that
facilitated these improvements in performance (Byars, Keith & Snowden, 2009). Therefore, it
is important to understand the role of Aloe vera on performance.
As well as using Aloe vera in sports drinks previous research has shown using Aloe vera in
capsule form can mediate physiological changes inside the body such as fat utilization and
weight loss (Langmead et al., 2004; Choi, 2013; & Huseini, Kianbakht, Hajiaghaee, &
Dabaghian, 2012). Research has established that 700 mg and 300 mg capsules of Aloe vera
daily reduce body fat mass, body weight and fat utilisation over 2 months and were safe for
consumption (Langmead et al., 2004; Choi, 2013; & Huseini, Kianbakht, Hajiaghaee, &
Dabaghian, 2012). Aloe vera capsules sold in high street stores come in a variety of
concentrations, however, typically in a concentration of 470 mg which is in line with effects
noted in the clinical literature.
The aim of this study is to determine the effect Aloe vera has on sporting performance in a
moderately trained population. I hypothesize that Aloe vera may have the potential to
improve cardiovascular endurance performance through its anti-inflammatory effects.
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Methodology
Participants
10
trained participants, from local cycling clubs and St Mary’s University volunteered as
subjects (Table 1). The study was conducted with the approval of St Mary’s University and
participants read and signed a form of written informed consent and a participant activity
readiness questionnaire. Where this questionnaire was not adequately completed and
consumption of Aloe vera was deemed unsafe, the participant was not accepted to join the
study. All males were trained cyclists exercising between 10 – 30 hours a week. Females
were trained, however, in various sports training between 3 – 6 hours a week. The trial was
conducted over 3 weeks and participants were required to attend on two occasions. During
the first testing session, participants were allowed a period of familiarisation in the laboratory
preceding a VO2max test. All exercise tests were conducted on a Watt bike (Monark 824e
Cycle Ergometer). Measurements of individuals seat and handle bar height were noted to
ensure uniformity.
Table 1 Descriptive characteristics of subjects (Mean ± Standard Deviation)
Years (age) Height (cm) Weight (kg)
Male (n = 6) 28 ± 4.5 173 ± 5.2 78 ± 12
Female (n = 4) 23 ± 2.2 170 ± 2.3 69.2 ± 6.5
Total (n = 10) 26 ± 4.4 172 ± 4.3 75 ± 10.8
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Protocol
The initial laboratory session included participant’s body fat and blood sampling from the ear
lobe. Participants then completed a 5 minute warm up followed by an incremental VO2max
test. After this session in a double blind manor subjects were assigned to a test group Aloe
vera (Aloe vera capsule of 470 mg daily for 3 weeks) or placebo group (470 mg placebo
capsule of multidextrose). After 3 weeks of supplementation or placebo participants
completed a second body fat test, blood tests and VO2max, the identical protocol as the first
laboratory session.
Blood
After each participant arrived they were asked to remain seated for 5 minutes before taking
resting blood samples. Resting haemoglobin and haematocrit were tested which involved a
small blood sample taken from the ear lobe. All safety procedures were followed as standard.
Furthermore, at the end of the incremental VO2max test a blood sample was taken from the
ear lobe to determine finishing blood lactate.
Body fat
Body fat measurements were taken from the Biceps, Triceps, Subscapular and Iliac Crest,
using Durin & Womersley (1974) protocol. These measurements were taken using
Harpenden Skinfold Callipers and to the nearest millimetre. The sites were tested twice and if
there is more than a 10% variance a third measurement was taken. The Durin & Womersley,
(1974) equation was used to calculate body fat percentage.
Maximal effort Test
After a warm up of 5 minutes at 80 RPM on the Watt bike (Monark 824e Cycle Ergometer),
the VO2max test began, the starting workload for females was 80 Watts (W) and males 154 W,
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this was determined by previous experience and training level. Intensity gradually increased
at 1 minute intervals by 24 watt increments, until the participant cannot sustain the required
80 RPM and were forced to stop the test. The test was completed on both laboratory sessions,
separated by 3 weeks.
Participants did not have a training program during this study, however, subjects were told to
maintain a similar training volume and intensity throughout the duration of the study.
Gas analysis
Expired air was collected in a series of Douglas bags during each minute of the maximal test.
Expired gas was analysed for oxygen (O2) and carbon dioxide (CO2) using a Servomex 5200
High Flow Gas Analyser, (Servomex Group Ltd. Crowborough East Sussex). VO2max results
were determined using temperature, O2 and CO2 concentration in each bag.
Rated Perceived Exertion
Throughout the VO2max test at minute intervals participants were asked to rate their pain
using the Borg’s RPE scale (Borg, 1998). Throughout both tests the researcher gave verbal
encouragement in both tests equally. Heart rate was taken at the end of each minute
increment.
Statistical testing
Descriptive data are presented as means ± SD. Due to the lack of previous literature
investigating Aloe vera during exercise, a study using a similar method and dependent
variables was selected to provide power calculations (Malik, Mehta & Dahiya, 2013). It was
estimated that a sample size of 13 subjects per group was required to achieve a statistical
power at a beta level of 0.08. Differences in pre and post results for placebo and Aloe vera in
blood lactate, VO2max, HR, RPE, body fat percentage, haemoglobin and haematocrit were
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assessed using appropriate paired sampled t-test. Statistical tests were conducted using SPSS
version 15.0 (Chicago, IL), and significance was accepted when p < 0.05.
Results
No participant reported modifications to their diet or changes in health status throughout the
study. Four out of the six participants who were taking Aloe vera supplementation reported
they felt energised after taking the 470 mg capsule of Aloe vera daily. During the course of
the study one participant withdrew from the trial from the placebo group respectively due to
attribution unrelated to the supplementation.
Body fat
There was no significance in body fat percentage between the two trials. (Placebo: p = 0.149;
Aloe vera: p = 0.916). The placebo group (P) mean difference between pre and post
supplementation was -0.23 % and Aloe vera group (AV) was 0.57 %.
Resting blood lactate
No significant difference was shown between the P and AV trials in resting blood lactate
(mmol/l) (Placebo: p = 0.494; Aloe vera: p = 0.781).
Finishing blood lactate
No significant difference in finishing blood lactate (mmol/l) were found between the P trial (p
= 0.229) and AV trial (p = 0.865).
Hemoglobin
There was no significance shown in hemoglobin (mg/dL) between the P group (p = 0.370)
and AV group (p = 0.149).
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Table 2 mean ± SD for1st trial before supplementation of Aloe vera or placebo and 2nd
trial after 3 weeks.
Haematocrit
A significant difference in haematocrit (%) was found between P (p = 0.391) and AV
supplementation (p = 0.016) after 3 weeks of ingestion shown in Figure 1.
VO2max
There was a significant difference in VO2max (mL/(kg·min) found between P group (p =
0.487) and AV group (p = 0.002) (Figure 2).
Maximum heart rate
No significant differences in maximal HR (beats·min-1
) were found between AV (p = 0.241:
pre 177.6 ± 10.53 vs post 181 ±.01) and P (p = 1.0: pre 183 ± 6.35 vs post 183.5 ± 7.77).
RPE
No significant difference in RPE between the difference conditions P (p = 0.89), AV (p =
0.91).
Aloe vera
1st
trial
(n = 5)
Aloe vera
2nd
trial
(n = 5)
Placebo
1st
trial
(n = 4)
Placebo
2nd
trial
(n = 4)
Body fat (%) 23.34 ± 7.68 22.77 ± 7.61 16.12 ± 3.18 16.35 ± 3.17
Resting blood lactate (mmol/l) 1.08 ± 0.59 0.98 ± 0.50 0.72 ± 0.09 0.76 ± 0.05
Finishing blood lactate (mmol/l) 7.57 ± 2.44 7.71 ± 1.54 9.15 ± 1.65 9.67 ± 1.66
Hemoglobin (mg/dL) 147.6 ± 17.46 153.6 ± 15.66 149 ± 13.83 145.5 ± 9.88
Maximum Heart rate (beats·min-1
) 177.6 ± 10.53 181.8 ± 8.01 183.5 ± 6.35 183.5 ± 7.77
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Figure 1. Haematocrit (%) pre supplemention and post supplementation after 3 weeks of
ingestion of either Aloe Vera or placebo percentage difference. Participants consuming Aloe
Vera had a siginificant increase in haematocrit (%) 3.35% increase over 3 weeks and placebo
-0.53% decrease.
Figure 2. VO2max (mL/(kg·min) pre supplemention and post supplementation after 3 weeks
of ingestion of either Aloe vera or placebo percentage difference. Participants consuming
Aloe vera had a siginificant increase VO2max (mL/(kg·min) over 3 weeks with a percentage
difference of 5.43% increase and placebo -0.57% decrease.
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Discussion
The main findings of this study are that the aerobic performance, specifically VO2max and
haematocrit percentage was significantly improved (p < 0.05) by ingestion of Aloe vera
orally over 3 weeks. Body fat, RPE, resting blood lactate, finishing blood lactate,
hemoglobin, haematocrit, VO2max and heart rate were measured in both trials, before and
after supplementation of either 470 mg of Aloe vera capsule or multidextrose placebo. Body
fat percentage, resting and finishing blood lactate, hemoglobin and heart rate did not differ
between Aloe vera and placebo conditions. Furthermore, Aloe vera did not exhibit a
hypoalgesic effect affecting RPE compared to the placebo. The finding that Aloe vera did not
acutely reduce RPE is consistent with previous literature demonstrating that salicylic acid and
acetylated mannan did not reduced RPE or endurance performance (Hudson, Green, Bishop
& Richardson, 2008; Gilbert, 1996; Wolff, 1971). However, this is contrary to other literature
(Hamman, 2008; Reynolds & Dweck, 1999; Vogler & Ernst, 1999) which has shown that
salicylic acid and acetylated mannan has the potential to improve physiological variables to
increase endurance performance and reduce RPE.
Lee, Chui, Aun, Gin & Lau, (2004) states that Aloe vera can reduce prostaglandin synthesis;
the production of lipid compounds in the cell mediates the biological process of
inflammation. Thus, the properties of Aloe vera can reduce the pain in muscles. However, the
reduction of prostaglandin synthesis has been associated with oxygenation of the blood, the
lipid compounds produced during prostaglandin synthesis stimulate cell signalling, thus,
helping repair muscles through increased red blood cell flow (Lee, Chui, Aun, Gin & Lau,
2004). This research is closely linked with Das et al., (2011) who states that Aloe vera
increases the oxygenation of blood and has a significant impact on reducing strokes and heart
attacks. This research could have a direct effect on increasing red blood cell flow and
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physiological performance variables, providing working muscles with more oxygen,
increasing VO2max and haematocrit percentage.
Aloe vera also has a high concentration of carbohydrate. Previous research has suggested that
performance enhancing drinks with a high volume of carbohydrate produced significant
improvements in time to fatigue and reduction in muscle damage in endurance cycling
athletes (Saunders et al, 2004). Ingesting Aloe vera for 3 weeks could have had a similar
effect to carbohydrate loading which has shown to increase endurance performance (Jardine,
Wiggins, Myburgh & Noakes, 1988; Jentjens, Achten & Jeukendrup, 2004).
Previous research has shown that consuming Aloe vera daily for 2 months can reduce body
fat mass, body weight and fat utilisation (Langmead et al., 2004; Choi, 2013; Huseini,
Kianbakht, Hajiaghaee, & Dabaghian, 2012). The present study showed no significant
difference in body fat percentage over 3 weeks with Aloe vera ingestion. However, previous
research was conducted on diabetic patients, no participants involved in this study were
diabetic. Aloe vera has shown to help balance blood sugar levels, which in turn can provide
diabetics with regulated blood sugar levels which can help improve fat utilisation (Choi,
2013). This study has shown that to reduce body fat mass on healthy individuals using Aloe
vera the supplementation period of 3 weeks is ineffective and does not produce and
significant results.
During aerobic exercise, the combined results of this investigation may provide meaningful
practical applications for coaches and athletes alike regarding potential ergogenic
supplementation using Aloe vera. Further research is warranted investigating the efficiency
of Aloe vera with further emphasis on other variables such as fitness levels, gender
differences and fuel substrate utilisation. Comparisons with other products along with the use
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of Aloe vera under various environmental conditions and competitive conditions would also
be beneficial.
Throughout the study participants were told to continue normal training programmes,
however, no regulation or a specific training plan was put in place, increased training or diet
could have affected results. With research studies suggesting the anti-inflammatory effect of
Aloe vera (Hamman, 2008; Reynolds & Dweck, 1999; Vogler & Ernst, 1999) training could
have been affected during the trial, for example, training volume may have increased and
recovery improved. This is an area of importance which may need further investigation, such
as a study on repeated efforts opposed to VO2max testing. As such, additional research may
be needed in regards to the concentrations and timing of Aloe vera supplementation and their
role in human performance.
Further research is required to provide a feasible scientific justification why any significant
results occurred based on the content of Aloe vera. The current study shows no direct
hypoalgesic effect of Aloe vera on RPE, however, there may have been secondary effects
such as recovery during the trial and increase in oxygenation of the blood. The most likely
explanation for VO2max increase and haematocrit percentage increase is the secondary effect
of prostaglandin synthesis. The lipid compounds produced during prostaglandin synthesis
have shown to stimulate cell signalling and increase red blood cell flow, providing muscles
with the necessary oxygen during endurance performance (Lee, Chui, Aun, Gin & Lau,
2004). Although there is a possibility of experimental error, it is unlikely that this would have
caused such a significant increase. To the author’s knowledge, no previous investigations
have shown similar significant findings utilising Aloe vera supplementation as an ergogenic
aid for sport.
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In conclusion, the current study found that ingestion of 470 mg oral dose of Aloe vera for 3
weeks significantly affected haematocrit percentage and VO2max during maximal cycling.
These findings are potentially significant due to the previous research suggesting Aloe vera
has anti-inflammatory, hypoalgesic and blood cell production properties. In addition, resting
and finishing blood lactate, maximum heart rate, hemoglobin and body fat percentage did not
differ from consuming Aloe vera. These findings highlight the potential for future studies
including, quantity and duration of Aloe vera supplementation with regards to improving
sports performance.
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