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Mark Glaister and Conor Gissane

effects of caffeine supplementation on physiological responses to submaximal exercise. Methods Systematic Review The databases of PubMed, SPORTDiscus, ScienceDirect, and Web of Science were searched for peer-reviewed publications (prior to September 2015) containing “caffeine” in the title and any of the

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Sarah J. Willis, Grégoire P. Millet, and Fabio Borrani

, and so on. During submaximal exercise, a low level of arterial oxygen content may be compensated by an increase in muscle blood flow to maintain oxygen delivery by altering vascular tone. 8 When the muscle mass is small, there is very a high capacity for vasodilation and an increase in blood flow, 9

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Stefano Montanari, Mehmet A. Şahin, Ben J. Lee, Sam D. Blacker, and Mark E.T. Willems

& Howley, 2000 ). Cardiovascular Measurements at Rest and During Submaximal Exercise Cardiovascular parameters were recorded using a beat-to-beat blood pressure monitoring system (Finometer ® PRO). For resting measurements, participants were in a supine position. A finger cuff was placed on the middle or

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Janelle Prince, Eric Schussler, and Ryan McCann

American College of Sports Medicine defines submaximal exercise as aerobic activity occurring at 85% of the age-adjusted maximum heart rate. 18 These terms used by different authors often refer to similar exercise intensities, but they cannot be used interchangeably. Therefore, the purpose of this

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Barbara E. Ainsworth, Robert G. McMurray, and Susan K. Veazey

The purpose of this study was to determine the accuracy of two submaximal exercise tests, the Sitting-Chair Step Test (Smith & Gilligan. 1983) and the Modified Step Test (Amundsen, DeVahl, & Ellingham, 1989) to predict peak oxygen uptake (VO2 peak) in 28 adults ages 60 to 85 years. VO2 peak was measured by indirect calorimetry during a treadmill maximal graded exercise test (VO2 peak, range 11.6–31.1 ml · kg −l · min−1). In each of the submaximal tests, VO2 was predicted by plotting stage-by-stage submaximal heart rate (HR) and perceived exertion (RPE) data against VO2 for each stage and extrapolating the data to respective age-predicted maximal HR or RPE values. In the Sitting-Chair Step Test (n = 23), no significant differences were observed between measured and predicted VO2 peak values (p > .05). However, predicted VO2 peak values from the HR were 4.3 ml · kg−1 · min−1 higher than VO2 peak values predicted from the RPE data (p < .05). In the Modified Step Test (n = 22), no significant differences were observed between measured and predicted VO2 peak values (p > .05). Predictive accuracy was modest, explaining 49–78% of the variance in VO2 peak. These data suggest that the Sitting-Chair Step Test and the Modified Step Test have moderate validity in predicting VO2 peak in older men and women.

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Hun-young Park, Sang-seok Nam, Hirofumi Tanaka, and Dong-jun Lee

Purpose:

The aim of this study was to investigate hemodynamic, hematological, and immunological responses to prolonged submaximal cycle ergometer exercise at a simulated altitude of 3000 m in pubescent girls.

Methods:

Ten girls, 12.8 ± 1.0 years old, exercised on a cycle ergometer for 60 min at a work rate corresponding to 50% maximal oxygen consumption measured at sea level, under two environmental conditions; sea level (normoxia) and a simulated 3000 m altitude (normobaric hypoxia).

Results:

There were no significant differences in tidal volume, ventilation, oxygen consumption, cardiac output, stroke volume, and heart rate between the two exercise conditions. However, reticulocyte, adrenocorticotropic hormone, and cortisol concentrations increased significantly from pre- to postexercise in the hypoxic environment. Leukocyte and T-cell count increased and B-cell count decreased after exercise under both conditions. There were no significant changes in natural killer cell count.

Conclusion:

Our simulated hypoxic environment provided a mild environmental stressor that did not impose a heavy burden on the cardiovascular, hematological, or immunological functions during submaximal exercise in pubescent girls.

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Katia Ferrar, Harrison Evans, Ashleigh Smith, Gaynor Parfitt, and Roger Eston

Many equations to predict maximal oxygen uptake (V̇O2max) from submaximal exercise tests have been proposed for young people, but the composition and accuracy of these equations vary greatly. The purpose of this systematic review was to analyze all submaximal exercise-based equations to predict V̇O2max measured via direct gas analysis for use with young people. Five databases were systematically searched in February 2013. Studies were included if they used a submaximal, exercise-based method to predict V̇O2max; the actual V̇O2max was gas analyzed; participants were younger than 18 years; and equations included at least one submaximal exercise-based variable. A meta-analysis and narrative synthesis were conducted. Sixteen studies were included. The mean equation validity statistic was strong, r = .786 (95% CI 0.747–0.819). Subgroup meta-analysis suggests exercise mode may contribute to the overall model, with running- and walking-based predictive equations reporting the highest mean r values (running r = .880; walking r = .821) and cycling the weakest (r = .743). Selection of the most appropriate equation should be guided by factors such as purpose, logistic limitations, appropriateness of the validation sample, the level of study bias, and the degree of accuracy. Suggestions regarding the most accurate equation for each exercise mode are provided.

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Colin R. Carriker, Christine M. Mermier, Trisha A. VanDusseldorp, Kelly E. Johnson, Nicholas M. Beltz, Roger A. Vaughan, James J. McCormick, Nathan H. Cole, Christopher C. Witt, and Ann L. Gibson

Reduced partial pressure of oxygen impairs exercise performance at altitude. Acute nitrate supplementation, at sea level, may reduce oxygen cost during submaximal exercise in hypobaric hypoxia. Therefore, we investigated the metabolic response during exercise at altitude following acute nitrate consumption. Ten well-trained (61.0 ± 7.4 ml/kg/min) males (age 28 ± 7 yr) completed 3 experimental trials (T1, T2, T3). T1 included baseline demographics, a maximal aerobic capacity test (VO2max) and five submaximal intensity cycling determination bouts at an elevation of 1600 m. A 4-day dietary washout, minimizing consumption of nitrate-rich foods, preceded T2 and T3. In a randomized, double-blind, placebo-controlled, crossover fashion, subjects consumed either a nitrate-depleted beetroot juice (PL) or ~12.8 mmol nitrate rich (NR) beverage 2.5 hr before T2 and T3. Exercise at 3500 m (T2 and T3) via hypobaric hypoxia consisted of a 5-min warm-up (25% of normobaric (VO2max) and four 5-min cycling bouts (40, 50, 60, 70% of normobaric VO2max) each separated by a 4-min rest period. Cycling RPM and watts for each submaximal bout during T2 and T3 were determined during T1. Preexercise plasma nitrite was elevated following NR consumption compared with PL (1.4 ± 1.2 and 0.7 ± 0.3 uM respectively; p < .05). There was no difference in oxygen consumption (−0.5 ± 1.8, 0.1 ± 1.7, 0.7 ± 2.1, and 1.0 ± 3.0 ml/kg/min) at any intensity (40, 50, 60, 70% of VO2max), respectively) between NR and PL. Further, respiratory exchange ratio, oxygen saturation, heart rate and rating of perceived exertion were not different at any submaximal intensity between NR and PL either. Blood lactate, however, was reduced following NR consumption compared with PL at 40 and 60% of VO2max (p < .0.05). Our findings suggest that acute nitrate supplementation before exercise at 3500 m does not reduce oxygen cost but may reduce blood lactate accumulation at lower intensity workloads.

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Scott C. Forbes, Vicki Harber, and Gordon J. Bell

L-arginine may enhance endurance performance mediated by two primary mechanisms including enhanced secretion of endogenous growth hormone (GH) and as a precursor of nitric oxide (NO); however, research in trained participants has been equivocal. The purpose was to investigate the effect of acute L-arginine ingestion on the hormonal and metabolic response during submaximal exercise in trained cyclists. Fifteen aerobically trained men (age: 28 ± 5 y; body mass: 77.4 ± 9.5 kg; height: 180.9 ± 7.9 cm; VO2max: 59.6 ± 5.9 ml·kg-1·min−1) participated in a randomized, double-blind, crossover study. Subjects consumed L-arginine (ARG; 0.075 g·kg-1 body mass) or a placebo (PLA) before performing an acute bout of submaximal exercise (60 min at 80% of power output achieved at ventilatory threshold). The ARG condition significantly increased plasma L-arginine concentrations (~146%), while no change was detected in the PLA condition. There were no differences between conditions for GH, nonesterified fatty acids (NEFA), lactate, glucose, VO2, VCO2, RER, CHO oxidation, and NOx. There was reduced fat oxidation at the start of exercise (ARG: 0.36 ± 0.25 vs. PLA: 0.42 ± 0.23 g·min−1, p < .05) and an elevated plasma glycerol concentrations at the 45-min time point (ARG: 340.3 vs. PLA: 288.5 μmol·L-1, p < .05) after L-arginine consumption. In conclusion, the acute ingestion of L-arginine did not alter any hormonal, metabolic, or cardio-respiratory responses during submaximal exercise except for a small but significant increase in glycerol at the 45-min time point and a reduction in fat oxidation at the start of exercise.

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Mahmoud S. El-Sayed, Angelheart J.M. Rattu, Xia Lin, and Thomas Reilly

We examined the effects of active warm-down (AWD) and carbohydrate ingestion on plasma levels of free fatty acids (FFAs) and glucose changes into recovery following prolonged submaximal exercise. Subjects in Group 1 cycled at 70% of maximal oxygen uptake (VO2max); carbohydrate (CHO) or placebo (PLA) was ingested 15 min before and 45 min during exercise. In the AWD experiment, exercise was followed immediately by an AWD and subjects were given a placebo solution. Group 2 subjects consumed CHO or PLA at 75 min during and after exercise at 70% VO2max. ANOVA revealed a significant decrease in blood glucose levels only in Group 1, with a concomitant increase in FFA concentrations during exercise in both groups. Carbohydrate ingestion in Groups 1 and 2 significantly decreased the normal response of FFAs during exercise and markedly reduced the normal elevation of FFAs in recovery. AWD following submaximal exercise had no effect on plasma FFA elevations in recovery. These results suggest that carbohydrate ingestion, but not active warm-down, attenuates FFA elevations in recovery.