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Effect of combining pre-exercise carbohydrate intake and repeated short sprints on the blood glucose response to moderate-intensity exercise in young individuals with Type 1 diabetes.
Soon, WHK, Guelfi, KJ, Davis, EA, Smith, GJ, Jones, TW, Fournier, PA
Diabetic medicine : a journal of the British Diabetic Association. 2019;(5):612-619
Abstract
AIMS: To determine whether pre-exercise ingestion of carbohydrates to maintain stable glycaemia during moderate-intensity exercise results in excessive hyperglycaemia if combined with repeated sprints in individuals with Type 1 diabetes. METHODS Eight overnight-fasted people with Type 1 diabetes completed the following four 40-min exercise sessions on separate days in a randomized counterbalanced order under basal insulinaemic conditions: continuous moderate-intensity exercise at 50% V˙O2 peak; intermittent high-intensity exercise (moderate-intensity exercise interspersed with 4-s sprints every 2 min and a final 10-s sprint); continuous moderate-intensity exercise with prior carbohydrate intake (~10 g per person); and intermittent high-intensity exercise with prior carbohydrate intake. Venous blood was sampled during and 2 h after exercise to measure glucose and lactate levels. RESULTS The difference in marginal mean time-averaged area under the blood glucose curve between continuous moderate-intensity exercise + prior carbohydrate and intermittent high-intensity exercise + prior carbohydrate during exercise and recovery was not significant [0.2 mmol/l (95% CI -0.7, 1.1); P = 0.635], nor was the difference in peak blood glucose level after adjusting for baseline level [0.2 mmol/l (95% CI -0.7, 1.1); P = 0.695]. The difference in marginal mean time-averaged area under the blood glucose curve between continuous moderate-intensity and intermittent high-intensity exercise during exercise and recovery was also not significant [-0.2 mmol/l (95% CI -1.2, 0.8); P = 0.651]. CONCLUSIONS When carbohydrates are ingested prior to moderate-intensity exercise, adding repeated sprints is not significantly detrimental to glycaemic management in overnight fasted people with Type 1 diabetes under basal insulin conditions.
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Repeated-sprint training in the fasted state during Ramadan: morning or evening training?
Aloui, A, Driss, T, Baklouti, H, Jaafar, H, Hammouda, O, Chamari, K, Souissi, N
The Journal of sports medicine and physical fitness. 2018;(7-8):990-997
Abstract
BACKGROUND The present study assessed the optimal moment of the day for repeated-sprint training in the fasted state during Ramadan. METHODS Thirty amateur soccer players were randomly assigned to a morning training group (MTG, training at ~08:00 a.m., N.=10), an evening training group (ETG, training around 06:00 p.m., N.=10), and a control group (N.=10). Training sessions, conducted on alternate days, consisted of 3 sets of 6×40-m shuttle sprints (2×20 m with 180° direction changes). A 20-second passive recovery and a 4-minute passive recovery were allowed between repetitions and sets, respectively. Before and after Ramadan, performance was assessed at both 08:00 a.m. and 06:00 p.m. by Countermovement Jump (CMJ), Repeated-Sprint Test (RST), and Yo-Yo Intermittent Recovery Test Level 1 (YYIRT1). RESULTS After Ramadan, YYIRT1 performances were enhanced for both groups in the morning (7.82% and 6.29% for MTG and ETG, respectively, P<0.05), and in the evening (6.61% and 11.20%, respectively, P<0.05). Relative changes in YYIRT1 (P=0.33) and RST (-2.13% and -3.44% for MTG and ETG, respectively, P=0.49) at the specific time of training were similar for both groups. No differences were observed in CMJ performances before and after Ramadan for any group (P>0.05). CONCLUSIONS Morning or evening repeated-sprint training conducted in the fasted state during Ramadan enhanced soccer-specific endurance similarly.
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Three Days of Intermittent Fasting: Repeated-Sprint Performance Decreased by Vertical-Stiffness Impairment.
Cherif, A, Meeusen, R, Farooq, A, Ryu, J, Fenneni, MA, Nikolovski, Z, Elshafie, S, Chamari, K, Roelands, B
International journal of sports physiology and performance. 2017;(3):287-294
Abstract
PURPOSE To examine the effects of 3 d of intermittent fasting (3d-IF: abstaining from eating/drinking from dawn to sunset) on physical performance and metabolic responses to repeated sprints (RSs). METHODS Twenty-one active males performed an RS test (2 sets: 5 × 5-s maximal sprints with 25 s of recovery between and 3 min of recovery between sets on an instrumented treadmill) in 2 conditions: counterbalanced fed/control session (CS) and fasting session (FS). Biomechanical and biochemical markers were assessed preexercise and postexercise. RESULTS Significant main effects of IF were observed for sprints: maximal speed (P = .016), mean speed (P = .015), maximal power (P = .035), mean power (P = .049), vertical stiffness (P = .032), and vertical center-of-mass displacement (P = .047). Sprint speed and vertical stiffness decreased during the 1st (P = .003 and P = .005) and 2nd sprints (P = .046 and P = .048) of set 2, respectively. Postexercise insulin decreased in CS (P = .023) but not in FS (P = .230). Free-fatty-acid levels were higher in FS than in CS at preexercise (P < .001) and at postexercise (P = .009). High-density lipoprotein cholesterol (HDL-C) was higher at postexercise in FS (1.32 ± 0.22 mmol/L) than in CS (1.26 ± 0.21 mmol/L, P = .039). The triglyceride (TG) concentration was decreased in FS (P < .05) compared with CS. CONCLUSIONS 3d-IF impaired speed and power through a decrease in vertical stiffness during the initial runs of the 2nd set of RS. The findings of the current study confirmed the benefits of 3d-IF: improved HDL-C and TG profiles while maintaining total cholesterol and low-density lipoprotein cholesterol levels. Moreover, improving muscle power might be a key factor to retain a higher vertical stiffness and to partly counteract the negative effects of intermittent fasting.
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Effects of Ramadan intermittent fasting on middle-distance running performance in well-trained runners.
Brisswalter, J, Bouhlel, E, Falola, JM, Abbiss, CR, Vallier, JM, Hausswirth, C
Clinical journal of sport medicine : official journal of the Canadian Academy of Sport Medicine. 2011;(5):422-7
Abstract
OBJECTIVE To assess whether Ramadan intermittent fasting (RIF) affects 5000-m running performance and physiological parameters classically associated with middle-distance performance. DESIGN Two experimental groups (Ramadan fasting, n = 9, vs control, n = 9) participated in 2 experimental sessions, one before RIF and the other at the last week of fasting. SETTING For each session, subjects completed 4 tests in the same order: a maximal running test, a maximal voluntary contraction (MVC) of knee extensor, 2 rectangular submaximal exercises on treadmill for 6 minutes at an intensity corresponding to the first ventilatory threshold (VT1), and a running performance test (5000 m). PARTICIPANTS Eighteen, well-trained, middle-distance runners. MAIN OUTCOME MEASURES Maximal oxygen consumption, MVC, running performance, running efficiency, submaximal VO(2) kinetics parameters (VO(2), VO(2)b, time constant τ, and amplitude A1) and anthropometric parameters were recorded or calculated. RESULTS At the end of Ramadan fasting, a decrease in MVC was observed (-3.2%; P < 0.00001; η, 0.80), associated with an increase in the time constant of oxygen kinetics (+51%; P < 0.00007; η, 0.72) and a decrease in performance (-5%; P < 0.0007; η, 0.51). No effect was observed on running efficiency or maximal aerobic power. CONCLUSIONS These results suggest that Ramadan changes in muscular performance and oxygen kinetics could affect performance during middle-distance events and need to be considered to choose training protocols during RIF.
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The effects of low- and high-glycemic index foods on high-intensity intermittent exercise.
Little, JP, Chilibeck, PD, Ciona, D, Vandenberg, A, Zello, GA
International journal of sports physiology and performance. 2009;(3):367-80
Abstract
UNLABELLED The glycemic index (GI) of a preexercise 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 approximately 7 days. Foods were consumed 3 h before (approximately 1.3 g x kg(-1) carbohydrate) and halfway through (approximately 0.2 g x 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 five 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.
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Graduated compression stockings: physiological and perceptual responses during and after exercise.
Ali, A, Caine, MP, Snow, BG
Journal of sports sciences. 2007;(4):413-9
Abstract
The aim of this study was to examine the effect of wearing graduated compression stockings on physiological and perceptual variables during and after intermittent (Experiment 1) and continuous (Experiment 2) running exercise. Fourteen recreational runners performed two multi-stage intermittent shuttle running tests with 1 h recovery between tests (Experiment 1). A further 14 participants performed a fast-paced continuous 10-km road run (Experiment 2). Participants wore commercially available knee-length graduated compression stockings (pressure at ankle 18 - 22 mmHg) beneath ankle-length sports socks (experimental trials) or just the latter (control trials) in a randomized counterbalanced design (for both experiments). No performance or physiological differences were observed between conditions during intermittent shuttle running. During the 10-km trials, there was a reduction in delayed-onset muscle soreness 24 h after exercise when wearing graduated compression stockings (P < 0.05). There was a marked difference in the frequency and location of soreness: two participants in the stockings trial but 13 participants in the control trial indicated soreness in the lower legs. Wearing graduated compression stockings during a 10-km road run appears to reduce delayed-onset muscle soreness after exercise in recreationally active men.