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Mark D. Haub, Jeffrey A. Potteiger, Dennis J. Jacobsen, Karen L. Nau, Lawrence A. Magee and Matthew J. Comeau

We investigated the effects of carbohydrate ingestion on glycogen replenishment and subsequent short duration, high intensity exercise performance. During Session 1, aerobic power was determined and each subject (N = 6) was familiarized with the 100-kJ cycling test (lOOKJ-Test). During the treatment sessions, the subjects performed a lOOKJ-Test (Ride-1), then consumed 0.7 g ⋅ kg body mass-1 of maltodextrin (CHO) or placebo (PLC), rested 60 min, and then performed a second lOOKJ-Test (Ride-2). Muscle tissue was collected before (Pre-1) and after Ride-1 (Post-1), and before (Pre-2) and after Ride-2 (Post-2), and analyzed for glycogen concentration. Both treatments yielded a significant increase in glycogen levels following the 60-min recovery, but there was no difference between treatments. Time to complete the lOOKJ-Test increased significantly for PLC, but not for CHO. These data indicate that the decrease in performance during Ride-2 in PLC was not the result of a difference in glycogen concentration.

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Stephen R. Stannard, Martin W. Thompson and Janette C. Brand Miller

Consumption of low glycemic index (GI) foods before submaximal endurance exercise may be beneficial to performance. To test whether this may also be true for high intensity exercise. 10 trained cyclists began an incremental exercise test to exhaustion 65 min after consuming equal carbohydrate portions of glucose (HGI), pasta (LGI), and a noncarbohydrate control (PL). Time to fatigue did not differ significantly (p = 0.05) between treatments. Plasma glucose concentration was significantly lower after LGI vs. HGI from 15 to 45 min of rest postprandial. During exercise, plasma glucose concentration was significantly lower after HGI vs. LGI from 200 W until exhaustion. Plasma lactate concentration following HGI was significantly higher than PL from 30 min of rest postprandial through to the end of the 200-W workload. Plasma lactate concentration following LGI was significantly lower than after HGI from 45 min of rest postprandial through to the end of the 100-W workload. At higher exercise intensities, there was no significant difference in plasma lactate levels between treatments. These findings suggest that a high GI carbohydrate meal (1 g/kg body wt) 65 min prior to exercise decreases plasma glucose and increases plasma lactate levels compared to a low GI meal, but not enough to be detrimental to incremental exercise performance.

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Darryn S. Willoughby, Mark Roozen and Randall Barnes

This study attempted to determine the effects of 12-week low- and high-intensity aerobic exercise programs on functional capacity and cardiovascular efficiency of elderly post-coronary artery bypass graft (CABG) patients. Time (Timemax). estimated maximum VO2 (VO2max), heart rate (HRmax), systolic blood pressure(SBPmax), estimated mean arterial blood pressure (MABPmax), and rate × pressure product (RPPmax) were assessed during graded exercise tests before and after 12 weeks of low-intensity (65% HRmax) and high-intensity (85% HRmax) exercise. Subjects (n = 92) were placed in either a low-intensity (LIEX), high-intensity (HIEX), or nonexercising control group (CON). LIEX and HIEX showed increases from pre- to postprogram for Timemax and VO2max. LIEX and HIEX showed decreases for SBPmax, MABPmax, and RPPmax. HIEX and LIEX produced greater improvements than CON for these four variables, while HIEX was superior to LIEX. It was concluded that 12 weeks of low- and high-intensity aerobic exercise can increase functional capacity and cardiovascular efficiency in elderly post-CABG patients; however, high-intensity exercise may produce greater improvements than low-intensity exercise.

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Kent W. Goben, Gary A. Sforzo and Patricia A. Frye

This study investigated the effect of varying exercise intensity on the thermic effect of food (TEF). Sixteen lean male subjects were matched for VO2max and randomly assigned to either a high or low intensity group for 30 min of treadmill exercise. Caloric expenditure was measured using indirect calorimetry at rest and at 30-min intervals OYer 3 hrs following each of three conditions: a 750-kcal liquid meal, high or low intensity exercise, and a 750-kcal liquid meal followed by high or low intensity exercise. Low intensity exercise enhanced the TEF during recovery at 60 and 90 min while high intensity enhanced it only at 180 min but depressed it at 30 min. Total metabolic expense for a 3-hr postmeal period was not differently affected by the two exercise intensities. Exercise following a meal had a synergistic effect on metabolism; however, this effect was delayed until 180 min postmeal when exercise intensity was high. The circulatory demands of high intensity exercise may have initially blunted the TEF, but ultimately the TEF measured over the 3-hr period was at least equal to that experienced following low intensity exercise.

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Roy C.M. Mulder, Dionne A. Noordhof, Katherine R. Malterer, Carl Foster and Jos J. de Koning

Previous research showed that gross efficiency (GE) declines during exercise and therefore influences the expenditure of anaerobic and aerobic resources.

Purpose:

To calculate the anaerobic work produced during cycling time trials of different length, with and without a GE correction.

Methods:

Anaerobic work was calculated in 18 trained competitive cyclists during 4 time trials (500, 1000, 2000, and 4000-m). Two additional time trials (1000 and 4000 m) that were stopped at 50% of the corresponding “full” time trial were performed to study the rate of the decline in GE.

Results:

Correcting for a declining GE during time-trial exercise resulted in a significant (P < .001) increase in anaerobically attributable work of 30%, with a 95% confidence interval of [25%, 36%]. A significant interaction effect between calculation method (constant GE, declining GE) and distance (500, 1000, 2000, 4000 m) was found (P < .001). Further analysis revealed that the constant-GE calculation method was different from the declining method for all distances and that anaerobic work calculated assuming a constant GE did not result in equal values for anaerobic work calculated over different time-trial distances (P < .001). However, correcting for a declining GE resulted in a constant value for anaerobically attributable work (P = .18).

Conclusions:

Anaerobic work calculated during short time trials (<4000 m) with a correction for a declining GE is increased by 30% [25%, 36%] and may represent anaerobic energy contributions during high-intensity exercise better than calculating anaerobic work assuming a constant GE.

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David Paul, Kevin A. Jacobs, Raymond J. Geor and Kenneth W. Hinchcliff

To determine the effect of macronutrient composition of pre-exercise meals on exercise metabolism and performance, 8 trained men exercised for 30 min above lactate threshold (30LT), followed by a 20-km time trial (TT). Approximately 3.5 h before exercise, subjects consumed a carbohydrate meal (C; 3 g carbohydrate/kg), an isoenergetic fat meal (F; 1.3 g fat/kg), or a placebo meal (P; no energy content) on 3 separate occasions in randomized order. Treatments had no effect on carbohydrate oxidation during exercise, but C decreased whole-body fat oxidation during the last 5 min of 30LT and TT, respectively (3.2 ± 1.6 and 4.8 ± 2.1 mmol · kg−1 · min−1, p < .05) when compared to F (13.3 ± 1.6 and 16.5 ± 2.7 mmol · kg−1 · min−1) and P (15.9 ± 2.7 and 17.0 ± 3.2 mmol · kg−1 · min−1). Glucose rate of appearance (Ra) and disappearance (Rd), and muscle glycogen utilization were not significantly different among treatments during exercise. TT performances were similar for C, F, and P (32.7 ± 0.5 vs. 33.1 ± 1.1 and 33.0 ± 0.8 min, p > .05). We conclude that the consumption of a pre-exercise meal has minor effects on fat oxidation during high-intensity exercise, and no effect on carbohydrate oxidation or TT performance.

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Rachael C. Gliottoni and Robert W. Motl

This experiment examined the effect of a moderate dose of caffeine on perceptions of leg-muscle pain during a bout of high-intensity cycling exercise and the role of anxiety sensitivity in the hypoalgesic effect of caffeine on muscle pain during exercise. Sixteen college-age women ingested caffeine (5 mg/kg body weight) or a placebo and 1 hr later completed 30 min of cycling on an ergometer at 80% of peak aerobic capacity. The conditions were completed in a counterbalanced order, and perceptions of leg-muscle pain were recorded during the bouts of exercise. Caffeine resulted in a large reduction in leg-muscle pain-intensity ratings compared with placebo (d = −0.95), and the reduction in leg-muscle pain-intensity ratings was larger in those with lower anxiety-sensitivity scores than those with higher anxiety-sensitivity scores (d = −1.28 based on a difference in difference scores). The results support that caffeine ingestion has a large effect on reducing leg-muscle pain during high-intensity exercise, and the effect is moderated by anxiety sensitivity.

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Yoonyoung Hwang, Jonghoon Park and Kiwon Lim

We examined the effects of a Pilates exercise program on the mucosal immune function in older women. The study population comprised 12 older women who were divided into a Pilates group (PG, n = 6) and a control group (CG, n = 6). Saliva samples were obtained from both groups before and after the experimental period for salivary secretory immunoglobulin A level measurement. In addition, acute high-intensity exercises were performed before and after the three-month Pilates exercise program. After three months, salivary flow was significantly higher in the PG than in the CG. After the acute high-intensity exercises were performed following the three-month Pilates exercise program, the salivary flow rate was significantly higher at all time points. The S-IgA secretion rate significantly increased 30 min after acute high-intensity exercise performed following the three-month Pilates exercise program. This study suggests that regular participation in a moderate-intensity Pilates exercise program can increase salivary flow rate and S-IgA secretion in older women.

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Stephanie Whisnant Cash, Shirley A.A. Beresford, Thomas L. Vaughan, Patrick J. Heagerty, Leslie Bernstein, Emily White and Marian L. Neuhouser

Background:

Limited evidence suggests that very high-intensity exercise is positively associated with DNA damage but moderate exercise may be associated with DNA repair.

Methods:

Participants were 220 healthy, Washington State 50- to 76-year-olds in the validity/biomarker substudy of the VITamins And Lifestyle (VITAL) cohort, who provided blood samples and completed questionnaires assessing recent physical activity and demographic and health factors. Measures included nested activity subsets: total activity, moderate- plus high-intensity activity, and high-intensity activity. DNA damage (n = 122) and repair (n = 99) were measured using the comet assay. Multivariate linear regression was used to estimate regression coefficients and associated 95% confidence intervals (CIs) for relationships between MET-hours per week of activity and each DNA outcome (damage, and 15- and 60-minute repair capacities).

Results:

DNA damage was not associated with any measure of activity. However, 60-minute DNA repair was positively associated with both total activity (β = 0.21, 95% CI: 0.0057–0.412; P = .044) and high-intensity activity (β = 0.31, 95% CI: 0.20–0.60; P = .036), adjusting for age, sex, BMI, and current multivitamin use.

Conclusions:

This study is the first to assess broad ranges of activity intensity levels related to DNA damage and repair. Physical activity was unrelated to DNA damage but was associated with increased repair.

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Mitch D. VanBruggen, Anthony C. Hackney, Robert G. McMurray and Kristin S. Ondrak

Purpose:

The effect of exercise intensity on the tracking of serum and salivary cortisol responses was examined in 12 endurance-trained males (maximal oxygen uptake [VO2max] = 58.2 ± 6.4 mL/kg/min).

Methods:

Subjects rested for 30 min (control) and exercised on a cycle ergometer for 30 min at 40% (low), 60% (moderate), and 80% (high intensity) of VO2max on separate days. Serum and saliva samples were collected pretrial, immediately posttrial, and 30 min into the recovery period from each trial.

Results:

Cortisol responses increased significantly for both serum (40.4%; P = .001) and saliva (170.6%; P = .007) only in response to high-intensity exercise. Peak saliva cortisol occurred at 30 min of recovery, whereas peak serum was at the immediate posttrial sampling time point. The association between serum and saliva cortisol across all trials was examined using concordance correlation (Rc) analysis, which accounts for repeated measures. The overall correlation between serum and saliva cortisol levels in all matched samples was significant (Rc = 0.728; P = .001). The scatter plot revealed that salivary cortisol responses tracked closely to those of serum at lower concentrations, but not as well at higher concentrations.

Conclusions:

Findings suggest salivary measurements of cortisol closely mirror those in the serum and that peak salivary concentrations do not occur until at least 30 min into the recovery from intense exercise.