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The effects of low and high glycemic index meals on metabolism and performance during soccer-specific intermittent exerciseLittle, Jonathan Peter 24 August 2007
The glycemic index (GI) of a pre-exercise meal has been shown to affect substrate oxidation during exercise and may influence exercise performance. Previous research in this area has focused on continuous, moderate intensity exercise. The purpose of this study was to examine the effects of low and high glycemic index (GI) pre-exercise meals on metabolism and performance during soccer-specific intermittent exercise. Thirteen trained male soccer players (22.3 ± 3.3 yrs) participated in four experimental trials in a repeated crossover design. Isocaloric low GI-high protein (lentils), high GI-high protein (potato + egg whites), or high GI-low protein (potato) meals were consumed two hours before a 90-minute treadmill soccer match simulation. A fasted control condition was also employed. Blood and expired gas samples were collected before and during exercise to assess markers of carbohydrate and fat metabolism. The distance covered on five 1-minute sprints (separated by 2.5 minutes of recovery) performed during the last 15 minutes of the match was used to assess performance. Serum insulin concentration at the start of exercise was higher in the high GI-low protein condition compared to all other conditions (p<0.001). During exercise, the rate of carbohydrate oxidation was significantly higher and the rate of fat oxidation was significantly lower in the high GI-low protein condition compared to control (p<0.05). The distance covered on sprints 1 and 2 was significantly greater in the low GI-high protein condition compared to control (p<0.05). The distance covered on sprint 2 was significantly greater in the high GI-high protein condition compared to control (p<0.05). There were no significant differences between conditions for sprints 3-5. Ratings of perceived exertion (RPE) throughout exercise were significantly lower in the low GI-high protein condition compared to both control and high GI-low protein conditions (p<0.05). It is concluded that low GI-high protein and high GI-high protein pre-exercise meals result in small improvements in initial repeated sprint performance compared to fasted control. Performance was not improved following a high GI-low protein pre-exercise meal compared to control, indicating that the increased carbohydrate oxidation and decreased fat oxidation in this condition may have negated any potential performance advantage of carbohydrate consumption. The lower RPE throughout exercise in low GI-high protein compared to control and high GI-low protein indicates a possible beneficial effect of consuming a low GI meal prior to soccer-specific intermittent exercise.
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The effects of low and high glycemic index meals on metabolism and performance during soccer-specific intermittent exerciseLittle, Jonathan Peter 24 August 2007 (has links)
The glycemic index (GI) of a pre-exercise meal has been shown to affect substrate oxidation during exercise and may influence exercise performance. Previous research in this area has focused on continuous, moderate intensity exercise. The purpose of this study was to examine the effects of low and high glycemic index (GI) pre-exercise meals on metabolism and performance during soccer-specific intermittent exercise. Thirteen trained male soccer players (22.3 ± 3.3 yrs) participated in four experimental trials in a repeated crossover design. Isocaloric low GI-high protein (lentils), high GI-high protein (potato + egg whites), or high GI-low protein (potato) meals were consumed two hours before a 90-minute treadmill soccer match simulation. A fasted control condition was also employed. Blood and expired gas samples were collected before and during exercise to assess markers of carbohydrate and fat metabolism. The distance covered on five 1-minute sprints (separated by 2.5 minutes of recovery) performed during the last 15 minutes of the match was used to assess performance. Serum insulin concentration at the start of exercise was higher in the high GI-low protein condition compared to all other conditions (p<0.001). During exercise, the rate of carbohydrate oxidation was significantly higher and the rate of fat oxidation was significantly lower in the high GI-low protein condition compared to control (p<0.05). The distance covered on sprints 1 and 2 was significantly greater in the low GI-high protein condition compared to control (p<0.05). The distance covered on sprint 2 was significantly greater in the high GI-high protein condition compared to control (p<0.05). There were no significant differences between conditions for sprints 3-5. Ratings of perceived exertion (RPE) throughout exercise were significantly lower in the low GI-high protein condition compared to both control and high GI-low protein conditions (p<0.05). It is concluded that low GI-high protein and high GI-high protein pre-exercise meals result in small improvements in initial repeated sprint performance compared to fasted control. Performance was not improved following a high GI-low protein pre-exercise meal compared to control, indicating that the increased carbohydrate oxidation and decreased fat oxidation in this condition may have negated any potential performance advantage of carbohydrate consumption. The lower RPE throughout exercise in low GI-high protein compared to control and high GI-low protein indicates a possible beneficial effect of consuming a low GI meal prior to soccer-specific intermittent exercise.
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Pre-exercise carbohydrate supplementation effects on intermittent critical velocity, anaerobic running capacity, and critical rest intervalsBialecki, Adam 29 August 2017 (has links)
No description available.
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Förändringar av hjärtfrekvens och systoliskt blodtryck under ett symtombegränsat cykeltest efter hjärthändelse : En kvantitativ tvärsnittsstudie från pre-exercise screeningSandberg, Ebba, Olofsson, Elsa January 2021 (has links)
Bakgrund: Hjärt- och kärlsjukdom är idag den vanligaste dödsorsaken nationellt och internationellt. Hälso- och sjukvården bör erbjuda individanpassad fysisk träning efter inträffad hjärthändelse. För att möjliggöra individanpassad fysisk träning bör patienten genomgå pre-exercise screening. Kunskapen om förändringar av hjärtfrekvens (HF) och systoliskt blodtryck (SBT) under symtombegränsat cykeltest vid pre-exercise screening av personer efter hjärthändelse är idag begränsad. Syfte: Huvudsyftet i denna studie var att i) undersöka förändring av HF och SBT hos personer som genomgått hjärthändelse under ett symtombegränsat cykeltest. Vidare var delsyftet att ii) undersöka eventuell korrelation mellan aerob prestationsförmåga och greppstyrka respektive muskulär uthållighet samt att iii) jämföra deltagarnas greppstyrka med referensvärden. Metod: Data som analyserats är insamlat från pre-exercise screening efter hjärthändelse och 68 deltagare inkluderades (median [25e percentilen; 75e percentilen] ålder, 66,4 [59,6; 71,7]; 89,7% män). Vid pre-exercise screening utfördes ett symtombegränsat cykeltest, där HF och SBT mättes med tidsintervall enligt standardiserat protokoll. Deltagarna fick även genomgå tester för muskulär uthållighet samt greppstyrka. Resultat: 68 deltagare genomförde symtombegränsat cykeltest, 59 genomförde test av greppstyrka, 60 axelflexionstester samt 59 tåhävningstester. HF och SBT ökade 14,5 (10; 18,5) slag/minut respektive 15 (10; 25) mmHg per belastningsnivå. HF sjönk i median 21,5 (15; 30,25) slag/minut 1 minut efter avslutat test. En stark korrelation sågs mellan maximal greppstyrka och peak prestationsförmåga (W) vid cykeltest (Rho=0,600, p<0,001). Slutsats: Vårt resultat visar på en linjär ökning av HF och SBT samt en tydlig Heart Rate Recovery efter avslutat test, vilket överensstämmer med en frisk befolkning. Då greppstyrka har ett prognostiskt värde och att vi här visar att greppstyrka har en stark korrelation med peak prestationsförmåga rekommenderar vi att inkludera greppstyrka vid pre-exercise screening.
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Effect of Pre-Exercise Drinks on Anaerobic Endurance PerformanceStayton, Ben January 2008 (has links)
No description available.
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Analyzing The Effectiveness of Electrical Stimulation (E-Stim) On Knee Injuries: Exploring The Optimal Timing of UseLarenas, Briana M 01 January 2024 (has links) (PDF)
This paper investigates the importance of electrical stimulation (E-Stim) treatment pre- exercise, during exercise, and post-exercise on knee pain management and exercise performance on individuals with knee injuries. Common problems from which individuals experience pain and injuries are arthritis, ACL tears, and osteoarthritis. One therapeutic approach to address the pain has been electrical stimulation. This is a non-invasive treatment that introduces electrical currents into the injured tissue or muscle. However, there are several modalities of electrical stimulation treatment that include Transcutaneous Electrical Nerve Stimulation (TENS), Neuromuscular Electrical Stimulation (NMES), and Patterned Electrical Neuromuscular Stimulation (PENS). These treatments have the same goal: to provide a non-invasive method to stimulate the muscles and nerves to aid the healing process.
Throughout this research, the populations targeted were females and males with age ranging from adolescents to older adults. The subjects were 15 – 75 years of age and had experienced knee injuries. They included athletes, older adults with osteoarthritis, and those who required arthroplasty. Between January 2023 and April 2024, the review of literature was conducted using UCF Libraries, PubMed, (MedLine), and SPORTDiscus (EBSCOhost). Keywords used included “TENS (Transcutaneous Electrical Nerve Stimulation) *”, “NMES (Neuromuscular Electrical Stimulation) *”, “osteoarthritis (OA)*”, Electrical Stimulation (E- Stim) *”, “knee injuries*”, “pain management*”, “before exercise*”, “after exercise*” and “during exercise*”. The results from these studies suggested that the application of e-stim was favored either during or after exercise.
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The Effects of Pre-Exercise Carbohydrate Supplementation on Resistance Training Performance During an Acute Resistance Training SessionRaposo, Kelly 01 January 2011 (has links)
Abstract
It appears that "carbohydrate loading" may enhance the performance of resistance training, but studies on CHO supplementation prior to a resistance-training bout are limited and have resulted in conflicting findings. PURPOSE: To investigate the effects of pre-exercise CHO supplementation on high-intensity (>75% 1RM) resistance training performance for resistance-trained women during an acute bout of resistance exercise. METHODS: Thirteen resistance trained female participants (21.9 ± 4.8 yrs; 64.5 ± 3.0 in; 137.0 ± 14.8 lbs) came to the Exercise and Performance Nutrition Laboratory on three separate occasions; the day of the Familiarization Trial (FT) and the two Exercise Testing sessions (ET1 and ET2, respectively) all separated by seven days. Familiarization testing determined each participant's 1RM of the bench press and leg press and then 75% of the bench press 1RM and 85% of the leg press 1RM was determined. The participants were then randomly assigned to either the CHO or P treatment session using a double blind, counterbalanced technique in a cross-over design with each participant consuming 1.0 g CHO/kg body weight or a non-caloric P beverage 60 minutes before beginning the exercise bout for each ET. The total volume of weight lifted during five sets of the bench press, the total volume of the weight lifted during five sets of the leg press, and whole body total lifting volume was analyzed by a two-way repeated measures within subjects ANOVA with significance set at P <.05. RESULTS: There was no statistically significant difference between the CHO and P treatments in the three variables analyzed. Specifically total volume of weight lifted in pounds during five sets of the bench press was 3,200 (± 912) and 3,152 (± 852) (p = 0.655), total volume of weight lifted during five sets of the leg press was 44,004 (± 29,711) and 37,705 (± 19,681) (p = 0.136), and total lifting volume was 47,204 (± 30,399) and 40,857 (± 20,434) for the CHO and P treatment, respectively (p = 0.138). CONCLUSIONS: Pre-exercise CHO supplementation does not improve high-intensity resistance training performance for resistance-trained women during an acute resistance training session. PRACTICAL APPLICATIONS: It is evident that consuming CHO 60 minutes prior to performing resistance training exercises will not increase the number of sets, repetitions, or total work volume completed during acute high-intensity (>75% 1RM) resistance training sessions for women. During lower-intensity resistance training sessions, however, pre-exercise CHO supplementation may provide ergogenic effects and enhance resistance-training performance.
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Meta-analysis and systematic review of the benefits expected when the glycaemic index is used in planning diets / Anna Margaretha OppermanOpperman, Anna Margaretha January 2004 (has links)
Motivation: The prevalence of non-communicable diseases such as diabetes mellitus (DM)
and cardiovascular disease (CVD) is rapidly increasing in industrialized societies. Experts
believe that lifestyle, and in particular its nutritional aspects, plays a decisive role in
increasing the burden of these chronic conditions. Dietary habits would, therefore, be
modified to exert a positive impact on the prevention and treatment of chronic diseases of
lifestyle. It is believed that the state of hyperglycaemia that is observed following food intake
under certain dietary regimes contributes to the development of various metabolic conditions.
This is not only true for individuals with poor glycaemic control such as some diabetics, but
could also be true for healthy individuals. It would, therefore, be helpful to be able to reduce
the amplitude and duration of postprandial hyperglycaemia. Selecting the correct type of
carbohydrate (CHO) foods may produce less postprandial hyperglycaemia, representing a
possible strategy in the prevention and treatment of chronic metabolic diseases. At the same
time, a key focus of sport nutrition is the optimal amount of CHO that an athlete should
consume and the optimal timing of consumption. The most important nutritional goals of the
athlete are to prepare body CHO stores pre-exercise, provide energy during prolonged
exercise and restore glycogen stores during the recovery period. The ultimate aim of these
strategies is to maintain CHO availability to the muscle and central nervous system during
prolonged moderate to high intensity exercise, since these are important factors in exercise
capacity and performance. However, the type of CHO has been studied less often and with
less attention to practical concerns than the amount of CHO.
The glycaemic index (GI) refers to the blood glucose raising potential of CHO foods and,
therefore, influences secretion of insulin. In several metabolic disorders, secretion of insulin
is inadequate or impossible, leading to poor glycaemic control. It has been suggested that
low GI diets could potentially contribute to a significant improvement of the conditions
associated with poor glycaemic control. Insulin secretion is also important to athletes since
the rate of glycogen synthesis depends on insulin due to it stimulatory effect on the activity of
glycogen synthase.
Objectives: Three main objectives were identified for this study. The first was to conduct a
meta-analysis of the effects of the GI on markers for CHO and lipid metabolism with the
emphasis on randomised controlled trials (RCT's). Secondly, a systematic review was
performed to determine the strength of the body of scientific evidence from epidemiological
studies combined with RCT's to encourage dieticians to incorporate the GI concept in meal
planning. Finally, a systematic review of the effect of the GI in sport performance was
conducted on all available literature up to date to investigate whether the application of the
GI in an athlete's diet can enhance physical performance.
Methodology: For the meta-analysis, the search was for randomised controlled trials with a
cross-over or parallel design published in English between 1981 and 2003, investigating the
effect of low GI vs high GI diets on markers of carbohydrate and lipid metabolism. The main
outcomes were serum fructosamine, glycosylated haemoglobin (HbA1c), high-density
lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c), total cholesterol
(TC) and triacylglycerols (TG). For the systematic review, epidemiological studies as well as
RCT's investigating the effect of LGI vs HGI diets on markers for carbohydrate and lipid
metabolism were used. For the systematic review on the effect of the GI on sport
performance, RCT's with either a cross-over or parallel design that were published in English
between January 1981 and September 2004 were used. All relevant manuscripts for the
systematic reviews as well as meta-analysis were obtained through a literature search on
relevant databases such as the Cochrane Central Register of Controlled Trials, MEDLINE
(1981 to present), EMBASE, LILACS, SPORTDiscus, ScienceDirect and PubMed. This
thesis is presented in the article format.
Results and conclusions of the individual manuscripts:
For the meta-analysis, literature searches identified 16 studies that met the strict
inclusion criteria. Low GI diets significantly reduced fructosamine (p<0.05), HbA1c,
(p<0.03), TC(p<0.0001) and tended to reduce LDL-c (p=0.06) compared to high GI diets.
No changes were observed in HDL-c and TG concentrations. Results from this meta analysis,
therefore, support the use of the GI concept in choosing CHO-containing foods
to reduce TC and improve blood glucose control in diabetics.
The systematic review combined the results of the preceding meta-analysis and results
from epidemiological studies. Prospective epidemiological studies showed improvements
in HDL-c concentrations over longer time periods with low GI diets vs. high GI diets, while
the RCT's failed to show an improvement in HDL-c over the short-term. This could be
attributed to the short intervention period during which the RCT's were conducted.
Furthermore, epidemiological studies failed to show positive relationships between LDL-c
and TC and low GI diets, while RCT's reported positive results on both these lipids with
low GI diets. However, the epidemiological studies, as well as the RCT's showed positive
results with low GI diets on markers of CHO metabolism. Taken together, convincing
evidence from RCT's as well as epidemiological studies exists to recommend the use of
low GI diets to improve markers of CHO as well as of lipid metabolism.
3 From the systematic review regarding the GI and sport performance it does not seem that
low GI pre-exercise meals provide any advantages over high GI pre-exercise meals.
Although low GI pre-exercise meals may better maintain CHO availability during exercise,
low GI pre-exercise meals offer no added advantage over high GI meals regarding
performance. Furthermore, the exaggerated metabolic responses from high GI compared
to low GI CHO seems not be detrimental to exercise performance. However, athletes
who experience hypoglycaemia when consuming CHO-rich feedings in the hour prior to
exercise are advised to rather consume low GI pre-exercise meals. No studies have
been reported on the GI during exercise. Current evidence suggests a combination of
CHO with differing Gl's such as glucose (high GI), sucrose (moderate GI) and fructose
(low GI) will deliver the best results in terms of exogenous CHO oxidation due to different
transport mechanisms. Although no studies are conducted on the effect of the GI on
short-term recovery it is speculated that high GI CHO is most effective when the recovery
period is between 0-8 hours, however, evidence suggests that when the recovery period
is longer (20-24 hours), the total amount of CHO is more important than the type of CHO.
Conclusion: There is an important body of evidence in support of a therapeutic and
preventative potential of low GI diets to improve markers for CHO and lipid metabolism. By
substituting high GI CHO-rich with low GI CHO-rich foods improved overall metabolic control.
In addition, these diets reduced TC, tended to improve LDL-c and might have a positive
effect over the long term on HDL-c. This confirms the place for low GI diets in disease
prevention and management, particularly in populations characterised by already high
incidences of insulin resistance, glucose intolerance and abnormal lipid levels. For athletes it
seems that low GI pre-exercise meals do not provide any advantage regarding performance
over high GI pre-exercise meals. However, low GI meals can be recommended to athletes
who are prone to develop hypoglycaemia after a CHO-rich meal in the hour prior to exercise.
No studies have been reported on the effect of the GI during exercise. However, it has been
speculated that a combination of CHO with varying Gl's deliver the best results in terms of
exogenous CHO oxidation. No studies exist investigating the effect of the GI on short-term
recovery, however, it is speculated that high GI CHO-rich foods are suitable when the
recovery period is short (0-8 h), while the total amount rather than the type of CHO is
important when the recovery period is longer (20-24 h). Therefore, the GI is a scientifically
based tool to enable the selection of CHO-containing foods to improve markers for CHO and
lipid metabolism as well as to help athletes to prepare optimally for competitions.
Recommendations: Although a step nearer has been taken to confirm a place for the GI in
human health, additional randomised, controlled, medium and long-term studies as well as
more epidemiological studies are needed to investigate further the effect of low GI diets on
LDL-c. HDL-c and TG. These studies are essential to investigate the effect of low GI diets
on endpoints such as CVD and DM. This will also show whether low GI diets can reduce the
risk of diabetic complications such as neuropathy and nephropathy. Furthermore, the public
at large must be educated about the usefulness and application of the GI in meal planning.
For sport nutrition, randomised controlled trials should be performed to investigate the role of
the GI during exercise as well as in sports of longer duration such as cricket and tennis.
More studies are needed to elucidate the short-term effect of the GI post-exercise as well as
to determine the mechanism of lower glycogen storage with LGI meals post-exercise. / Thesis (Ph.D. (Dietetics))--North-West University, Potchefstroom Campus, 2005.
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Meta-analysis and systematic review of the benefits expected when the glycaemic index is used in planning diets / Anna Margaretha OppermanOpperman, Anna Margaretha January 2004 (has links)
Motivation: The prevalence of non-communicable diseases such as diabetes mellitus (DM)
and cardiovascular disease (CVD) is rapidly increasing in industrialized societies. Experts
believe that lifestyle, and in particular its nutritional aspects, plays a decisive role in
increasing the burden of these chronic conditions. Dietary habits would, therefore, be
modified to exert a positive impact on the prevention and treatment of chronic diseases of
lifestyle. It is believed that the state of hyperglycaemia that is observed following food intake
under certain dietary regimes contributes to the development of various metabolic conditions.
This is not only true for individuals with poor glycaemic control such as some diabetics, but
could also be true for healthy individuals. It would, therefore, be helpful to be able to reduce
the amplitude and duration of postprandial hyperglycaemia. Selecting the correct type of
carbohydrate (CHO) foods may produce less postprandial hyperglycaemia, representing a
possible strategy in the prevention and treatment of chronic metabolic diseases. At the same
time, a key focus of sport nutrition is the optimal amount of CHO that an athlete should
consume and the optimal timing of consumption. The most important nutritional goals of the
athlete are to prepare body CHO stores pre-exercise, provide energy during prolonged
exercise and restore glycogen stores during the recovery period. The ultimate aim of these
strategies is to maintain CHO availability to the muscle and central nervous system during
prolonged moderate to high intensity exercise, since these are important factors in exercise
capacity and performance. However, the type of CHO has been studied less often and with
less attention to practical concerns than the amount of CHO.
The glycaemic index (GI) refers to the blood glucose raising potential of CHO foods and,
therefore, influences secretion of insulin. In several metabolic disorders, secretion of insulin
is inadequate or impossible, leading to poor glycaemic control. It has been suggested that
low GI diets could potentially contribute to a significant improvement of the conditions
associated with poor glycaemic control. Insulin secretion is also important to athletes since
the rate of glycogen synthesis depends on insulin due to it stimulatory effect on the activity of
glycogen synthase.
Objectives: Three main objectives were identified for this study. The first was to conduct a
meta-analysis of the effects of the GI on markers for CHO and lipid metabolism with the
emphasis on randomised controlled trials (RCT's). Secondly, a systematic review was
performed to determine the strength of the body of scientific evidence from epidemiological
studies combined with RCT's to encourage dieticians to incorporate the GI concept in meal
planning. Finally, a systematic review of the effect of the GI in sport performance was
conducted on all available literature up to date to investigate whether the application of the
GI in an athlete's diet can enhance physical performance.
Methodology: For the meta-analysis, the search was for randomised controlled trials with a
cross-over or parallel design published in English between 1981 and 2003, investigating the
effect of low GI vs high GI diets on markers of carbohydrate and lipid metabolism. The main
outcomes were serum fructosamine, glycosylated haemoglobin (HbA1c), high-density
lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c), total cholesterol
(TC) and triacylglycerols (TG). For the systematic review, epidemiological studies as well as
RCT's investigating the effect of LGI vs HGI diets on markers for carbohydrate and lipid
metabolism were used. For the systematic review on the effect of the GI on sport
performance, RCT's with either a cross-over or parallel design that were published in English
between January 1981 and September 2004 were used. All relevant manuscripts for the
systematic reviews as well as meta-analysis were obtained through a literature search on
relevant databases such as the Cochrane Central Register of Controlled Trials, MEDLINE
(1981 to present), EMBASE, LILACS, SPORTDiscus, ScienceDirect and PubMed. This
thesis is presented in the article format.
Results and conclusions of the individual manuscripts:
For the meta-analysis, literature searches identified 16 studies that met the strict
inclusion criteria. Low GI diets significantly reduced fructosamine (p<0.05), HbA1c,
(p<0.03), TC(p<0.0001) and tended to reduce LDL-c (p=0.06) compared to high GI diets.
No changes were observed in HDL-c and TG concentrations. Results from this meta analysis,
therefore, support the use of the GI concept in choosing CHO-containing foods
to reduce TC and improve blood glucose control in diabetics.
The systematic review combined the results of the preceding meta-analysis and results
from epidemiological studies. Prospective epidemiological studies showed improvements
in HDL-c concentrations over longer time periods with low GI diets vs. high GI diets, while
the RCT's failed to show an improvement in HDL-c over the short-term. This could be
attributed to the short intervention period during which the RCT's were conducted.
Furthermore, epidemiological studies failed to show positive relationships between LDL-c
and TC and low GI diets, while RCT's reported positive results on both these lipids with
low GI diets. However, the epidemiological studies, as well as the RCT's showed positive
results with low GI diets on markers of CHO metabolism. Taken together, convincing
evidence from RCT's as well as epidemiological studies exists to recommend the use of
low GI diets to improve markers of CHO as well as of lipid metabolism.
3 From the systematic review regarding the GI and sport performance it does not seem that
low GI pre-exercise meals provide any advantages over high GI pre-exercise meals.
Although low GI pre-exercise meals may better maintain CHO availability during exercise,
low GI pre-exercise meals offer no added advantage over high GI meals regarding
performance. Furthermore, the exaggerated metabolic responses from high GI compared
to low GI CHO seems not be detrimental to exercise performance. However, athletes
who experience hypoglycaemia when consuming CHO-rich feedings in the hour prior to
exercise are advised to rather consume low GI pre-exercise meals. No studies have
been reported on the GI during exercise. Current evidence suggests a combination of
CHO with differing Gl's such as glucose (high GI), sucrose (moderate GI) and fructose
(low GI) will deliver the best results in terms of exogenous CHO oxidation due to different
transport mechanisms. Although no studies are conducted on the effect of the GI on
short-term recovery it is speculated that high GI CHO is most effective when the recovery
period is between 0-8 hours, however, evidence suggests that when the recovery period
is longer (20-24 hours), the total amount of CHO is more important than the type of CHO.
Conclusion: There is an important body of evidence in support of a therapeutic and
preventative potential of low GI diets to improve markers for CHO and lipid metabolism. By
substituting high GI CHO-rich with low GI CHO-rich foods improved overall metabolic control.
In addition, these diets reduced TC, tended to improve LDL-c and might have a positive
effect over the long term on HDL-c. This confirms the place for low GI diets in disease
prevention and management, particularly in populations characterised by already high
incidences of insulin resistance, glucose intolerance and abnormal lipid levels. For athletes it
seems that low GI pre-exercise meals do not provide any advantage regarding performance
over high GI pre-exercise meals. However, low GI meals can be recommended to athletes
who are prone to develop hypoglycaemia after a CHO-rich meal in the hour prior to exercise.
No studies have been reported on the effect of the GI during exercise. However, it has been
speculated that a combination of CHO with varying Gl's deliver the best results in terms of
exogenous CHO oxidation. No studies exist investigating the effect of the GI on short-term
recovery, however, it is speculated that high GI CHO-rich foods are suitable when the
recovery period is short (0-8 h), while the total amount rather than the type of CHO is
important when the recovery period is longer (20-24 h). Therefore, the GI is a scientifically
based tool to enable the selection of CHO-containing foods to improve markers for CHO and
lipid metabolism as well as to help athletes to prepare optimally for competitions.
Recommendations: Although a step nearer has been taken to confirm a place for the GI in
human health, additional randomised, controlled, medium and long-term studies as well as
more epidemiological studies are needed to investigate further the effect of low GI diets on
LDL-c. HDL-c and TG. These studies are essential to investigate the effect of low GI diets
on endpoints such as CVD and DM. This will also show whether low GI diets can reduce the
risk of diabetic complications such as neuropathy and nephropathy. Furthermore, the public
at large must be educated about the usefulness and application of the GI in meal planning.
For sport nutrition, randomised controlled trials should be performed to investigate the role of
the GI during exercise as well as in sports of longer duration such as cricket and tennis.
More studies are needed to elucidate the short-term effect of the GI post-exercise as well as
to determine the mechanism of lower glycogen storage with LGI meals post-exercise. / Thesis (Ph.D. (Dietetics))--North-West University, Potchefstroom Campus, 2005.
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