Article

Metabolic and performance effects of raisins versus sports gel as pre-exercise feedings in cyclists.

Department of Exercise and Nutritional Sciences, San Diego State University, San Diego, California 92182, USA.
The Journal of Strength and Conditioning Research (Impact Factor: 1.8). 12/2007; 21(4):1204-7. DOI: 10.1519/R-21226.1
Source: PubMed

ABSTRACT Research suggests that pre-exercise sources of dietary carbohydrate with varying glycemic indexes may differentially affect metabolism and endurance. This study was designed to examine potential differences in metabolism and cycling performance after consumption of moderate glycemic raisins vs. a high glycemic commercial sports gel. Eight endurance-trained male (n = 4) and female (n = 4) cyclists 30 +/- 5 years of age completed 2 trials in random order. Subjects were fed 1 g carbohydrate per kilogram body weight from either raisins or sports gel 45 minutes prior to exercise on a cycle ergometer at 70% V(.-)O2max. After 45 minutes of submaximal exercise, subjects completed a 15-minute performance trial. Blood was collected prior to the exercise bout, as well as after the 45th minute of exercise, to determine serum concentrations of glucose, insulin, lactate, free fatty acids (FFAs), triglycerides, and beta-hydroxybutyrate. Performance was not different (p > 0.05) between the raisin (189.5 +/- 69.9 kJ) and gel (188.0 +/- 64.8 kJ) trials. Prior to exercise, serum concentrations of glucose and other fuel substrates did not differ between trials; however, insulin was higher (p < 0.05) for the gel (110.0 +/- 70.4 microU x ml(-1)) vs. raisin trial (61.4 +/- 37.4 microU x ml(-1)). After 45 minutes of exercise, insulin decreased to 14.2 +/- 6.2 microU x ml(-1) and 13.3 +/- 18.9 microU x ml(-1) for gel and raisin trials, respectively. The FFA concentration increased (+0.2 +/- 0.1 mmol x L(-1)) significantly (p < 0.05) during the raisin trial. Overall, minor differences in metabolism and no difference in performance were detected between the trials. Raisins appear to be a cost-effective source of carbohydrate for pre-exercise feeding in comparison to sports gel for short-term exercise bouts.

1 Bookmark
 · 
309 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to examine the effects of a natural carbohydrate (CHO) source in the form of sun-dried raisins (SDRs) vs. Sports Jelly Beans™ (SJBs) on endurance performance in trained cyclists and triathletes. Ten healthy men (18-33 years) completed 1 water-only acclimatization exercise trial and 2 randomized exercise trials administered in a crossover fashion. Each trial consisted of a 120-minute constant-intensity glycogen depletion period followed by a 10-km time trial (TT). During each experimental trial, participants consumed isocaloric amounts of SDRs or SJBs in 20-minute intervals. Measurements included time to complete 10-km TT, power output during 10-km TT, blood glucose levels and respiratory exchange ratio during glycogen depletion period, rate of perceived exertion (RPE), 'flow' questionnaire responses, and a hedonic (i.e., pleasantness) sensory acceptance test. There were no significant differences in endurance performance for TT time (SDRs vs. SJBs, 17.3 ± 0.4 vs. 17.3 ± 0.4 seconds) or power (229.3 ± 13.0 vs. 232.0 ± 13.6 W), resting blood glucose levels (5.8 ± 04 mmol·L(-1) for SDRs and 5.4 ± 0.2 mmol·L(-1) for SJBs), RPE, or flow experiences between SDR and SJB trials. However, the mean sensory acceptance scores were significantly higher for the SDRs compared to the SJBs (50.7 ± 1.7 vs. 44.3 ± 2.7). Consuming SDRs or SJBs during 120 minutes of intense cycling results in similar subsequent TT performances and are equally effective in maintaining blood glucose levels during exercise. Therefore, SDRs are a natural, pleasant, cost-effective CHO alternative to commercial SJBs that can be used during moderate- to high-intensity endurance exercise.
    The Journal of Strength and Conditioning Research 08/2011; 25(11):3150-6. · 1.80 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We examined the metabolic, performance and gastrointestinal (GI) effects of supplementation with a natural food product (raisins) compared to a commercial product (sport chews). Eleven male (29.3 ± 7.9 yrs; mean and SD) runners completed three randomized trials (raisins, chews and water only) separated by seven days. Each trial consisted of 80-min (75%VO2max) treadmill running followed by a 5-km time trial (TT). Heart rate (HR), respiratory exchange ratio (RER), blood lactate, serum free fatty acids (FFA), glycerol and insulin, plasma glucose and creatine kinase, GI symptoms and rating of perceived exertion (RPE) were recorded every 20-min. We employed a within-subject two-way analysis of variance (ANOVA) for repeated measures with a Fisher's post hoc analysis to determine significant differences. VO2, HR, lactate, glycerol and RPE did not differ due to treatment. Average plasma glucose was maintained at resting levels (5.3 ± 0.4 mmol·L-1) during the sub-maximal exercise bout (5.9 ± 0.6, 5.7 ± 0.6 and 5.5 ± 0.5 mmol·L-1 for chews, raisins and water respectively), and was significantly higher with chews than water only. RER and % of non-protein macronutrient oxidation derived from carbohydrate was highest with chews, followed by raisins and water was the lowest (74.4 ± 6.4, 70.0 ± 7.0 and 65.1 ± 8.7% for chews, raisins and water respectively) during the sub-maximal exercise period. Serum FFA was higher in the water treatment versus both raisins and chews at 80 min of sub-maximal exercise. Serum insulin was higher with the chews than both raisins and water (5.1 ± 2.0, 3.1 ± 0.8, 1.9 ± 0.6 uU·ml-1 for chews, raisins and water respectively). Plasma creatine kinase, corrected for baseline values, for the last 40 min of the sub-maximal exercise bout, was higher with raisins compared to other treatments. The TT was faster for both carbohydrate supplements (20.6 ± 2.6, 20.7 ± 2.5, 21.6 ± 2.7 min for raisin, chews and water respectively). GI disturbance was mild for all treatments. Raisins and chews promoted higher carbohydrate oxidation and improved running performance compared to water only. Running performance was similar between the raisins and chews, with no significant GI differences.
    Journal of the International Society of Sports Nutrition 06/2012; 9(1):27. · 1.83 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Endurance athletes rarely compete in the fasted state, as this may compromise fuel stores. Thus, the timing and composition of the pre-exercise meal is a significant consideration for optimizing metabolism and subsequent endurance performance. Carbohydrate feedings prior to endurance exercise are common and have generally been shown to enhance performance, despite increasing insulin levels and reducing fat oxidation. These metabolic effects may be attenuated by consuming low glycemic index carbohydrates and/or modified starches before exercise. High fat meals seem to have beneficial metabolic effects (e.g., increasing fat oxidation and possibly sparing muscle glycogen). However, these effects do not necessarily translate into enhanced performance. Relatively little research has examined the effects of a pre-exercise high protein meal on subsequent performance, but there is some evidence to suggest enhanced pre-exercise glycogen synthesis and benefits to metabolism during exercise. Finally, various supplements (i.e., caffeine and beetroot juice) also warrant possible inclusion into pre-race nutrition for endurance athletes. Ultimately, further research is needed to optimize pre-exercise nutritional strategies for endurance performance.
    Nutrients 01/2014; 6(5):1782-1808. · 3.15 Impact Factor

Full-text

View
18 Downloads