The Effects of Low– and High–Glycemic Index Foods on High-Intensity Intermittent Exercise

2009 ◽  
Vol 4 (3) ◽  
pp. 367-380 ◽  
Author(s):  
Jonathan P. Little ◽  
Philip D. Chilibeck ◽  
Dawn Ciona ◽  
Albert Vandenberg ◽  
Gordon A. Zello
Keyword(s):  
Glycemic Index ◽  
High Intensity ◽  
Intermittent Exercise ◽  
Fat Oxidation ◽  
Mean Difference ◽  
Treadmill Running ◽  
Repeated Sprint ◽  
The Mean ◽  
Improved Performance ◽  
And Performance

The glycemic index (GI) of a pre exercise meal may affect substrate utilization and performance during continuous exercise.Purpose:To examine the effects of low- and high-GI foods on metabolism and performance during high-intensity, intermittent exercise.Methods:Seven male athletes participated in three experimental trials (low-GI, high-GI, and fasted control) separated by ~7 days. Foods were consumed 3 h before (~1.3 g·kg−1 carbohydrate) and halfway through (~0.2 g·kg−1 carbohydrate) 90 min of intermittent treadmill running designed to simulate the activity pattern of soccer. Expired gas was collected during exercise to estimate substrate oxidation. Performance was assessed by the distance covered on fve 1-min sprints during the last 15 min of exercise.Results:Respiratory exchange ratio was higher and fat oxidation lower during exercise in the high-GI condition compared with fasting (P < .05). The mean difference in total distance covered on the repeated sprint test between low GI and fasting (247 m; 90% confidence limits ±352 m) represented an 81% (likely, probable) chance that the low-GI condition improved performance over fasting. The mean difference between high GI and fasted control (223 m; ±385 m) represented a 76% (likely, probable) chance of improved performance. There were no differences between low and high GI.Conclusions:When compared with fasting, both low- and high-GI foods consumed 3 h before and halfway through prolonged, high-intensity intermittent exercise improved repeated sprint performance. High-GI foods impaired fat oxidation during exercise but the GI did not appear to influence high-intensity, intermittent exercise performance.

Effect of Low- and High-Glycemic-Index Meals on Metabolism and Performance During High-Intensity, Intermittent Exercise

2010 ◽  
Vol 20 (6) ◽  
pp. 447-456 ◽  
Author(s):  
Jonathan P. Little ◽  
Philip D. Chilibeck ◽  
Dawn Ciona ◽  
Scott Forbes ◽  
Huw Rees ◽  
...  
Keyword(s):  
Glycemic Index ◽  
Muscle Glycogen ◽  
High Intensity ◽  
Perceived Exertion ◽  
Intermittent Exercise ◽  
Random Order ◽  
Rating Of Perceived Exertion ◽  
Repeated Sprint ◽  
High Glycemic Index ◽  
And Performance

Consuming carbohydrate-rich meals before continuous endurance exercise improves performance, yet few studies have evaluated the ideal preexercise meal for high-intensity intermittent exercise, which is characteristic of many team sports. The authors’ purpose was to investigate the effects of low- and high-glycemic-index (GI) meals on metabolism and performance during high-intensity, intermittent exercise. Sixteen male participants completed three 90-min high-intensity intermittent running trials in a single-blinded random order, separated by ~7 d, while fasted (control) and 2 hr after ingesting an isoenergetic low-GI (lentil), or high-GI (potato and egg white) preexercise meal. Serum free fatty acids were higher and insulin lower throughout exercise in the fasted condition (p < .05), but there were no differences in blood glucose during exercise between conditions. Distance covered on a repeated-sprint test at the end of exercise was significantly greater in the low-GI and high-GI conditions than in the control (p < .05). Rating of perceived exertion was lower in the low-GI condition than in the control (p = .01). In a subsample of 5 participants, muscle glycogen availability was greater in the low- and high-GI conditions versus fasted control before the repeated-sprint test (p < .05), with no differences between low and high GI. When exogenous carbohydrates are not provided during exercise both low- and high-GI preexercise meals improve high-intensity, intermittent exercise performance, probably by increasing the availability of muscle glycogen. However, the GI does not influence markers of substrate oxidation during high-intensity, intermittent exercise.

scholarly journals Metabolism and performance during extended high-intensity intermittent exercise after consumption of low- and high-glycaemic index pre-exercise meals

2012 ◽  
Vol 108 (S1) ◽  
pp. S81-S90 ◽  
Author(s):  
Christine B. Bennett ◽  
Philip D. Chilibeck ◽  
Trevor Barss ◽  
Hassanali Vatanparast ◽  
Albert Vandenberg ◽  
...  
Keyword(s):  
Blood Glucose ◽  
High Intensity ◽  
Intermittent Exercise ◽  
Glycaemic Index ◽  
Treadmill Running ◽  
Postprandial Blood Glucose ◽  
Exercise Session ◽  
Performance Improvements ◽  
And Performance

The metabolic and performance benefits of prior consumption of low-glycaemic index (GI) meals v. high-GI meals were determined in extended high-intensity intermittent exercise. Participants (ten males and four females, aged 25·8 (sd 7·3) years) completed two testing days (each consisting of back-to-back 90-min intermittent high-intensity treadmill running protocols separated by 3 h) spaced by at least 7 d. Using a randomised counterbalanced cross-over design, low-GI, lentil-based meals (GI about 42) or high-GI, potato-based meals (GI about 78) matched for energy value were consumed 2 h before, and within 1 h after, the first exercise session. Performance was measured by the distance covered during five 1-min sprints (separated by 2·5 min walking) at the end of each exercise session. Peak postprandial blood glucose was higher by 30·8 % in the high-GI trial compared with the low-GI trial, as was insulin (P = 0·039 and P = 0·003, respectively). Carbohydrate oxidation was lower by 5·5 % during the low-GI trials compared with the high-GI trials at the start of the first exercise session (P < 0·05). Blood lactate was significantly higher (6·1 v. 2·6 mmol/l; P = 0·019) and blood glucose significantly lower (4·8 v. 5·4 mmol/l; P = 0·039) at the end of the second exercise session during the high-GI trial compared with the low-GI trial. Sprint distance was not significantly different between conditions. A low-GI meal improved the metabolic profile before and during extended high-intensity intermittent exercise, but did not affect performance. Improvements in metabolic responses when consuming low-GI meals before exercise may be beneficial to the long-term health of athletes.

The Effect of 45 Minutes of Soccer-Specific Exercise on the Performance of Soccer Skills

2009 ◽  
Vol 4 (2) ◽  
pp. 163-175 ◽  
Author(s):  
Keeron J. Stone ◽  
Jonathan L. Oliver
Keyword(s):  
High Intensity ◽  
Intermittent Exercise ◽  
Test List ◽  
Soccer Players ◽  
Specific Exercise ◽  
Point Score ◽  
Soccer Match ◽  
The Mean ◽  
Study Participants ◽  
Loughborough Intermittent Shuttle Test

Purpose:The aim of the study was to examine the effect of fatigue, developed during prolonged high-intensity intermittent exercise, on the performance of soccer shooting and dribbling skill.Methods:Nine semiprofessional soccer players with a mean age of 20.7 ± 1.4 years volunteered to participate in the study. Participants completed a slalom dribble test and the Loughborough Soccer Shooting Test (LSST), before and directly following the performance of three 15-min bouts of a modified version of the Loughborough Intermittent Shuttle Test (LIST).Results:Mean heart rates and mean 15-m sprint times remained unchanged across the three bouts of the LIST. Following the LIST slalom dribbling time increased significantly by 4.5 ± 4.0% (P = .009), while the mean total points scored during the LSST was significantly reduced by 7.6 ± 7.0 points (P = .012). When fatigued the frequency of shots in the LSST achieving the highest score of 5 points was reduced by 47% while the frequency of shots achieving the lowest 0 point score increased by 85%.Conclusion:Results show that while 45 min of exercise caused no decrements in sprint performance there were significant reductions in the ability to perform soccer-specific skills. Both the speed (dribbling time) and accuracy (shot performance) with which soccer-specific skills were executed was impaired following exercise replicating one-half of a soccer match.

The W′ Balance Model: Mathematical and Methodological Considerations

2021 ◽  
pp. 1-12
Author(s):  
Philip Friere Skiba ◽  
David C. Clarke
Keyword(s):  
High Intensity ◽  
Intermittent Exercise ◽  
Differential Forms ◽  
Computer Software ◽  
Balance Model ◽  
Calculation Methods ◽  
Desktop Computer ◽  
Intuitive Appeal ◽  
And Performance ◽  
Methodological Considerations

Since its publication in 2012, the W′ balance model has become an important tool in the scientific armamentarium for understanding and predicting human physiology and performance during high-intensity intermittent exercise. Indeed, publications featuring the model are accumulating, and it has been adapted for popular use both in desktop computer software and on wrist-worn devices. Despite the model’s intuitive appeal, it has achieved mixed results thus far, in part due to a lack of clarity in its basis and calculation. Purpose: This review examines the theoretical basis, assumptions, calculation methods, and the strengths and limitations of the integral and differential forms of the W′ balance model. In particular, the authors emphasize that the formulations are based on distinct assumptions about the depletion and reconstitution of W′ during intermittent exercise; understanding the distinctions between the 2 forms will enable practitioners to correctly implement the models and interpret their results. The authors then discuss foundational issues affecting the validity and utility of the model, followed by evaluating potential modifications and suggesting avenues for further research. Conclusions: The W′ balance model has served as a valuable conceptual and computational tool. Improved versions may better predict performance and further advance the physiology of high-intensity intermittent exercise.

scholarly journals Gender Difference in the Relationship between Self-Efficacy and Performance in Science among Secondary School Students in Migori County, Kenya

2020 ◽  
Vol 1 (2) ◽  
pp. p154
Author(s):  
Polycarp O. Gor ◽  
Lucas O. A. Othuon ◽  
Quinter A. Migunde
Keyword(s):  
Gender Difference ◽  
Gender Gap ◽  
Self Efficacy ◽  
Group Discussion ◽  
Mean Difference ◽  
School Students ◽  
Girls In Science ◽  
The Mean ◽  
And Performance ◽  
The Relationship

The purpose of this study was to investigate the gender difference in the relationship between self-efficacy and performance in science. A sample of 327 Form Four students in Migori County was used. Questionnaires, focus group discussion guide and interview schedules were used for data collection. Quantitative data were analyzed using descriptive statistics and correlation. Qualitative data were organized into themes and interpreted. Overall, boys had higher levels of performance in science (Mean=39.21) than girls (Mean=30.80) and the mean difference was statistically significant (t=3.89, p=.00). Boys had higher levels of self-efficacy (Mean=2.89) than girls (Mean=2.81) and the mean difference was not statistically significant (t=1.56, p=.12). Further, the overall correlation between self-efficacy and performance was statistically significant with r=.236 (p=.002, n=327). The correlation between self-efficacy and performance for boys was significant with r=.250 (p=.005, n=200) and non-significant for girls with r=.085 (p=.558, n=127). It is concluded that boys outperform girls in science and record higher scores in self-efficacy than girls. In addition, the variance shared in common between self-efficacy and performance is higher for boys than girls. To improve performance and also reduce the gender gap in science performance, self-efficacy should be enhanced for students but more particularly so for girls.

scholarly journals New Zealand Blackcurrant Extract Improves High-Intensity Intermittent Running

2015 ◽  
Vol 25 (5) ◽  
pp. 487-493 ◽  
Author(s):  
Ian Craig Perkins ◽  
Sarah Anne Vine ◽  
Sam David Blacker ◽  
Mark Elisabeth Theodorus Willems
Keyword(s):  
New Zealand ◽  
Blood Lactate ◽  
High Intensity ◽  
Perceived Exertion ◽  
Intermittent Exercise ◽  
Rating Of Perceived Exertion ◽  
Treadmill Running ◽  
Early Recovery ◽  
Repeated Sprints ◽  
New Zealand Blackcurrant

We examined the effect of New Zealand blackcurrant (NZBC) extract on high-intensity intermittent running and postrunning lactate responses. Thirteen active males (age: 25 ± 4 yrs, height: 1.82 ± 0.07 m, body mass: 81 ± 14 kg, V̇O2max: 56 ± 4 ml∙kg-1∙min-1, v V̇O2max: 17.6 ± 0.8 km∙h-1) performed a treadmill running protocol to exhaustion, which consisted of stages with 6 × 19 s of sprints with 15 s of low-intensity running between sprints. Interstage rest time was 1 min and stages were repeated with increasing sprint speeds. Subjects consumed capsuled NZBC extract (300 mg∙day-1 CurraNZ; containing 105 mg anthocyanin) or placebo for 7 days (double-blind, randomized, crossover design, wash-out at least 14 days). Blood lactate was collected for 30 min postexhaustion. NZBC increased total running distance by 10.6% (NZBC: 4282 ± 833 m, placebo: 3871 ± 622 m, p = .02), with the distance during sprints increased by 10.8% (p = .02). Heart rate, oxygen uptake, lactate and rating of perceived exertion were not different between conditions for the first 4 stages completed by all subjects. At exhaustion, blood lactate tended to be higher for NZBC (NZBC: 6.01 ± 1.07 mmol∙L-1, placebo: 5.22 ± 1.52 mmol∙L-1, p = .07). There was a trend for larger changes in lactate following 15 min (NZBC: -2.89 ± 0.51 mmol∙L-1, placebo: -2.46 ± 0.39 mmol∙L-1, p = .07) of passive recovery. New Zealand blackcurrant extract (CurraNZ) may enhance performance in sports characterized by high-intensity intermittent exercise as greater distances were covered with repeated sprints, there was higher lactate at exhaustion, and larger changes in lactate during early recovery after repeated sprints to exhaustion.

Acute Creatine Supplementation and Performance during a Field Test Simulating Match Play in Elite Female Soccer Players

2002 ◽  
Vol 12 (1) ◽  
pp. 33-46 ◽  
Author(s):  
Greg Cox ◽  
Iñigo Mujika ◽  
Douglas Tumilty ◽  
Louise Burke
Keyword(s):  
Placebo Group ◽  
Creatine Supplementation ◽  
Soccer Players ◽  
Exercise Protocol ◽  
Double Blind ◽  
Match Play ◽  
Repeated Sprint ◽  
Glucose Polymer ◽  
Improved Performance ◽  
And Performance

This study investigated the effects of acute creatine (Cr) supplementation on the performance of elite female soccer players undertaking an exercise protocol simulating match play. On two occasions, 7 days apart, 12 players performed 5 X 11-min exercise testing blocks interspersed with 1 min of rest. Each block consisted of 11 all-out 20-m running sprints, 2 agility runs, and 1 precision ball-kicking drill, separated by recovery 20-m walks, jogs, and runs. After the initial testing session, subjects were assigned to either a CREATINE (5 g of Cr, 4 times per day for 6 days) or a PLACEBO group (same dosage of a glucose polymer) using a double-blind research design. Body mass (BM) increased (61.7 ± 8.9 to 62.5 ± 8.9 kg, p < .01) in the CREATINE group; however, no change was observed in the PLACEBO group (63.4 ± 2.9 kg to 63.7 ± 2.5 kg). No overall change in 20-m sprint times and agility run times were observed, although the CREATINE group achieved faster post-supplementation times in sprints 11, 13, 14, 16, 21, 23, 25, 32, and 39 (p < .05), and agility runs3,5,and8 (p < .05). The accuracy of shooting was unaffected in both groups. In conclusion, acute Cr supplementation improved performance of some repeated sprint and agility tasks simulating soccer match play, despite an increase in BM.

scholarly journals Re-examination of the contribution of substrates to energy expenditure during high-intensity intermittent exercise in endurance athletes

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3769 ◽  
Author(s):  
Zübeyde Aslankeser ◽  
Şükrü Serdar Balcı
Keyword(s):  
Energy Expenditure ◽  
High Intensity ◽  
Oxidation Rate ◽  
Intermittent Exercise ◽  
Lactate Concentration ◽  
Blood Lactate Concentration ◽  
Fat Oxidation ◽  
Substrate Oxidation ◽  
Cycle Ergometer ◽  
Athlete Group

BackgroundIt has been believed that the contribution of fat oxidation to total energy expenditure is becoming negligible at higher exercise intensities (about 85% VO2max). The aim of the present study was to examine the changes in substrate oxidation during high-intensity interval exercise in young adult men.MethodsA total of 18 healthy well-trained (aged 19.60 ± 0.54 years, BMI = 22.19 ± 0.64 kg/m2,n = 10) and untrained (aged 20.25 ± 0.41 years, BMI = 22.78 ± 0.38 kg/m2,n = 8) young men volunteered to participate in this study. After an overnight fast, subjects were tested on a cycle ergometer and completed six 4-min bouts of cycling (at ∼80% VO2max) with 2 min of rests between intervals. Energy expenditure and the substrate oxidation rate were measured during the experiment by using indirect calorimetry. The blood lactate concentration was collected immediately after each interval workout.ResultsThe fat oxidation rate during each workout was significantly different between the untrained and the athlete groups (p < 0.05), and the carbohydrate (CHO) oxidation rate during the experiment was similar between groups (p > 0.05). Moreover, lactate concentration significantly increased in the untrained group (p < 0.05), whereas it did not significantly change in the athlete group during the workouts (p > 0.05). Fat contribution to energy expenditure was significantly higher in the athlete group (∼25%) than in the untrained group (∼2%).ConclusionsThe present study indicates that 17 times more fat oxidation was measured in the athlete group compared to the untrained group. However, the athletes had the same CHO oxidation rate as the recreationally active subjects during high-intensity intermittent exercise. Higher fat oxidation rate despite the same CHO oxidation rate may be related to higher performance in the trained group.

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