Louise A. Turner

Influence of dietary nitrate supplementation on physiological and cognitive responses to incremental cycle exercise

Dietary inorganic nitrate supplementation causes physiological effects which may enhance exercise tolerance. However it is not known whether nitrate might alter cognitive function during exercise. In a double-blind, cross-over study, sixteen subjects ingested either nitrate-rich beetroot juice or a placebo and completed a continuous cycle exercise test involving 20min stages at 50% and 70% V˙O2peak and a final stage at 90% V˙O2peak until volitional exhaustion. Cognitive tasks were completed before, during and after exercise. In the dietary nitrate condition: plasma [nitrite] increased (p<0.01), systolic blood pressure decreased (p<0.05) and there was a trend for a reduced oxygen uptake at 50% V˙O2peak. Tissue oxygenation improved across exercise intensities and exercise tolerance was greater at 90% V˙O2peak (p<0.05). Rating of perceived exertion, energy levels and cognitive performance were similar between conditions with mental fatigue being evident from 70% V˙O2peak onwards (p<0.05). Dietary nitrate supplementation enhanced short-term endurance exercise performance with concomitant mental fatigue but did not improve cognitive performance post-fatigue.

Effect of inspiratory muscle training on exercise tolerance in asthmatic individuals.

PURPOSE The aim of this study was to determine the effects of inspiratory muscle training (IMT) on exercise tolerance, inspiratory muscle fatigue, and the perception of dyspnea in asthmatic individuals. METHODS Using a matched double-blind placebo-controlled design, 15 clinically diagnosed asthmatic individuals underwent either 6 wk of IMT (n = 7) consisting of 30 breaths twice daily at 50% maximum inspiratory pressure (PI max) or sham-IMT (placebo; PLA, n = 8) consisting of 60 breaths daily at 15% PI max. Time to the limit of exercise tolerance (Tlim) was assessed using constant-power output (70% peak power) cycle ergometry. Inspiratory muscle fatigue was determined by comparing the pre- to postexercise reduction in PI max. Dyspnea during the Tlim test was evaluated at 2-min intervals using the Borg CR-10 scale. RESULTS There were no significant changes (P > 0.05) in Tlim, inspiratory muscle fatigue, or perception of dyspnea in the PLA group after the intervention. In contrast, in the IMT group, PI max increased by 28%, and Tlim increased by 16% (P < 0.05). Dyspnea during exercise was also reduced significantly by 16% (P < 0.05). The exercise-induced fall in PI max was reduced from 10% before IMT to 6% after IMT (P < 0.05), despite the longer Tlim. Pulmonary function remained unchanged in both the IMT and PLA groups. CONCLUSIONS These data suggest that IMT attenuates inspiratory muscle fatigue, reduces the perception of dyspnea, and increases exercise tolerance. These findings suggest that IMT may be a helpful adjunct to asthma management that has the potential to improve participation and adherence to exercise training in this group. However, the perception of breathlessness is also an important signal of bronchoconstriction, and thus, caution should be exercised if this symptom is abnormally low.

Inspiratory muscle training lowers the oxygen cost of voluntary hyperpnea

The purpose of this study was to determine if inspiratory muscle training (IMT) alters the oxygen cost of breathing (Vo(2RM)) during voluntary hyperpnea. Sixteen male cyclists completed 6 wk of IMT using an inspiratory load of 50% (IMT) or 15% placebo (CON) of maximal inspiratory pressure (Pi(max)). Prior to training, a maximal incremental cycle ergometer test was performed to determine Vo(2) and ventilation (V(E)) at multiple workloads. Pre- and post-training, subjects performed three separate 4-min bouts of voluntary eucapnic hyperpnea (mimic), matching V(E) that occurred at 50, 75, and 100% of Vo(2 max). Pi(max) was significantly increased (P < 0.05) by 22.5 ± 8.7% from pre- to post-IMT and remained unchanged in the CON group. The Vo(2RM) required during the mimic trial corresponded to 5.1 ± 2.5, 5.7 ± 1.4, and 11.7% ± 2.5% of the total Vo(2) (Vo(2T)) at ventilatory workloads equivalent to 50, 75, and 100% of Vo(2 max), respectively. Following IMT, the Vo(2RM) requirement significantly decreased (P < 0.05) by 1.5% (4.2 ± 1.4% of Vo(2T)) at 75% Vo(2 max) and 3.4% (8.1 ± 3.5% of Vo(2T)) at 100% Vo(2 max). No significant changes were shown in the CON group. IMT significantly reduced the O(2) cost of voluntary hyperpnea, which suggests that a reduction in the O(2) requirement of the respiratory muscles following a period of IMT may facilitate increased O(2) availability to the active muscles during exercise. These data suggest that IMT may reduce the O(2) cost of ventilation during exercise, providing an insight into mechanism(s) underpinning the reported improvements in whole body endurance performance; however, this awaits further investigation.

Randomized Controlled Trial of Fish Oil and Montelukast and Their Combination on Airway Inflammation and Hyperpnea-Induced Bronchoconstriction

Background Both fish oil and montelukast have been shown to reduce the severity of exercise-induced bronchoconstriction (EIB). The purpose of this study was to compare the effects of fish oil and montelukast, alone and in combination, on airway inflammation and bronchoconstriction induced by eucapnic voluntary hyperpnea (EVH) in asthmatics. Methods In this model of EIB, twenty asthmatic subjects with documented hyperpnea-induced bronchoconstriction (HIB) entered a randomized double-blind trial. All subjects entered on their usual diet (pre-treatment, n = 20) and then were randomly assigned to receive either one active 10 mg montelukast tablet and 10 placebo fish oil capsules (n = 10) or one placebo montelukast tablet and 10 active fish oil capsules totaling 3.2 g EPA and 2.0 g DHA (n = 10) taken daily for 3-wk. Thereafter, all subjects (combination treatment; n = 20) underwent another 3-wk treatment period consisting of a 10 mg active montelukast tablet or 10 active fish oil capsules taken daily. Results While HIB was significantly inhibited (p<0.05) by montelukast, fish oil and combination treatment compared to pre-treatment, there was no significant difference (p>0.017) between treatment groups; percent fall in forced expiratory volume in 1-sec was −18.4±2.1%, −9.3±2.8%, −11.6±2.8% and −10.8±1.7% on usual diet (pre-treatment), fish oil, montelukast and combination treatment respectively. All three treatments were associated with a significant reduction (p<0.05) in FENO, exhaled breathe condensate pH and cysteinyl-leukotrienes, while the fish oil and combination treatment significantly reduced (p<0.05) urinary 9α, 11β-prostaglandin F2 after EVH compared to the usual diet; however, there was no significant difference (p>0.017) in these biomarkers between treatments. Conclusion While fish oil and montelukast are both effective in attenuating airway inflammation and HIB, combining fish oil with montelukast did not confer a greater protective effect than either intervention alone. Fish oil supplementation should be considered as an alternative treatment for EIB. Trial Registration ClinicalTrials.gov NCT00676468

Short communication: Patterns of dairy consumption in free-living children and adolescents

According to national survey data, dairy food consumption has fallen in recent years and declines further with age, especially from childhood to adolescence. Dietary surveys typically rely on retrospective dietary assessment methods and use broad age groupings (4-10 yr; 11-18 yr), making it challenging to differentiate between middle-childhood and adolescence. Consequently, there is a need to assess dairy food consumption during middle-childhood and adolescence using more robust dietary assessment tools. Therefore, the present study aimed to describe and compare patterns of dairy consumption throughout middle-childhood and adolescence. Dairy food consumption was assessed during school term-time over 4 consecutive days, including 2 weekdays and 2 weekend days, in a sample of free-living children (9-11 yr, n=40) and adolescents (15-18 yr, n=35). For children, free-living dairy intake was evaluated through parental-weighed food records, and for adolescents, a combined weighed self-reported food record and 24-h dietary recall technique was utilized. Food records were explored to determine types, amounts, and frequency of dairy food consumption, and were analyzed for differences between middle-childhood and adolescence using a between group 2×2 (age×sex) ANOVA. Descriptive data suggested that milk was the most popular dairy product consumed by both children and adolescents. Statistical analysis revealed a main effect for sex on total milk consumption (mL) and number of daily milk portions consumed. No interaction or main effect was present for any other variable. The present study indicates that independent of age, boys consumed greater amounts of milk compared with girls. Contrary to existing literature, findings suggest no difference in milk-based dairy consumption between middle-childhood and adolescence.

Observer Effects on the Rating of Perceived Exertion and Affect during Exercise in Recreationally Active Males

This study examined the effect of introducing either a male or female observer on the ratings of perceived exertion (RPE) and affect of male runners during a moderate intensity running task. 10 moderately active men completed three 20-min. moderate intensity running trials at 60% of their peak treadmill running speed. Each participant completed three trials in random order: control, male-observed, and female-observed, where either the male or female observer joined the trial after 10 min. of the trial had elapsed, during which RPE and affect were monitored. The introduction of a female observer caused a significant decrease in RPE, whereas the introduction of a male observer caused a significant increase in RPE compared to the control trial. Affect was higher in the presence of both a male and female observer compared to control. It was concluded that there is a social, interpersonal, psychological dimension to RPE during exercise.

Calcium Ingestion Suppresses Appetite and Produces Acute Overcompensation of Energy Intake Independent of Protein in Healthy Adults

BACKGROUND Prior evidence suggests that high-calcium intake influences postprandial appetite and insulinemia, possibly due to elevated incretins. In vitro and ex vivo models demonstrate that extracellular calcium and protein synergistically enhance secretion of incretins. This is yet to be shown in humans. OBJECTIVE This study was designed to assess energy intake compensation in response to protein and calcium ingestion. METHODS Twenty healthy adults (13 men; 7 women) completed 4 trials in a randomized, double-blind crossover design separated by ≥48 h. During the trials, each participant consumed a low-calcium and low-protein control preload [(CON); 4 g and 104 mg, respectively], a high-protein preload (PRO; 29 g), a high-calcium preload (CAL; 1170 mg), or a high-protein and high-calcium preload (PROCAL). Blood samples were collected at baseline and 15, 30, 45, and 60 min after preload ingestion to determine insulin and incretin hormone concentrations. Energy intake was assessed by a homogenous test meal 60 min after the preload. Visual analog scales were completed immediately before blood sampling to assess subjective appetite sensations. RESULTS Relative to the CON, the PRO produced 100% (95% CI: 85%, 115%) energy compensation, whereas the CAL produced significant overcompensation [118% (95% CI: 104%, 133%)], which was significantly more positive than with the PRO (P < 0.05). The PROCAL resulted in energy compensation of 109% (95% CI: 95%, 123%), which tended to be greater than with the PRO (P = 0.06). The mean difference in appetite sensations relative to the CON was not significantly different between the PRO (-3 mm; 95% CI: -8, 3 mm), CAL (-5 mm; 95% CI: -9, 0 mm), and PROCAL (-5 mm; 95% CI: -10, -1 mm) (P > 0.05). CONCLUSIONS The addition of protein to a preload results in almost perfect energy compensation, whereas the addition of calcium, with or without protein, suppresses appetite and produces overcompensation of subsequent energy intake. The role of circulating insulin and incretin concentrations in these responses, however, remains unclear. This trial was registered at clinicaltrials.gov as NCT01986036.

Inner Dialogue and its Relationship to Perceived Exertion during Different Running Intensities

This study examined the effect of low- and high-intensity running on cognitive thoughts (an individuals “inner dialogue”) and its relationship to ratings of perceived exertion (RPE). Cognitive thoughts and RPE of eight runners were collected during a 40-min. treadmill run at either a low (50% peak running speed) or a high (70% peak running speed) exercise intensity. Runners were asked to place their thoughts into one of 10 themed categories, which incorporated a broad association/dissociation classification (Schomer, 1986, 1987). At a low intensity and RPE (6–10), runners reported more dissociative thoughts, while at a high intensity and RPE (16–20) they reported more associative thoughts. Further, although the runners may report a particular RPE, the inner dialogue and description of perceived exertion and fatigue may be markedly different. These findings suggest that an athletes “internal dialogue” is intensity dependent, and may relate to the more urgent need to self-monitor physical changes and sensations during high-intensity running.

Increased variability of lap speeds : differentiating medalists and nonmedalists in middle-distance running and swimming events

PURPOSE Previous literature has presented pacing data of groups of competition finalists. The aim of this study was to analyze the pacing patterns displayed by medalists and nonmedalists in international competitive 400-m swimming and 1500-m running finals. METHODS Split times were collected from 48 swimming finalists (four 100-m laps) and 60 running finalists (4 laps) in international competitions from 2004 to 2012. Using a cross-sectional design, lap speeds were normalized to whole-race speed and compared to identify variations of pace between groups of medalists and nonmedalists. Lap-speed variations relative to the gold medalist were compared for the whole field. RESULTS In 400-m swimming the medalist group demonstrated greater variation in speed than the nonmedalist group, being relatively faster in the final lap (P < .001; moderate effect) and slower in laps 1 (P = .03; moderate effect) and 2 (P > .001; moderate effect). There were also greater variations of pace in the 1500-m running medalist group than in the nonmedalist group, with a relatively faster final lap (P = .03; moderate effect) and slower second lap (P = .01; small effect). Swimming gold medalists were relatively faster than all other finalists in lap 4 (P = .04), and running gold medalists were relatively faster than the 5th- to 12th-placed athletes in the final lap (P = .02). CONCLUSIONS Athletes who win medals in 1500-m running and 400-m swimming competitions show different pacing patterns than nonmedalists. End-spurt-speed increases are greater with medalists, who demonstrate a slower relative speed in the early part of races but a faster speed during the final part of races than nonmedalists.

Inspiratory loading and limb locomotor and respiratory muscle deoxygenation during cycling exercise

The aim of this study was to determine the effect of inspiratory loading on limb locomotor (LM) and respiratory muscle (RM) deoxygenation ([deoxy (Hb+Mb)]) using NIRS during constant-power cycling exercise. Sixteen, male cyclists completed three, 6-min trials. The intensity of the first 3-min of each trial was equivalent to ~80% V(O(2max)) (EX(80%)); during the final 3-min, subjects received an intervention consisting of either moderate inspiratory loading (Load(mod)), heavy inspiratory loading (Load(heavy)), or maximal exercise (Load(EX)). Load(heavy) significantly increased LM [deoxy(Hb+Mb)] from 12.2±9.0 μm during EX(80%) to 15.3±11.7 μm, and RM [deoxy(Hb+Mb)] from 5.9±3.6 μm to 9.5±6.6 μm. LM and RM [deoxy(Hb+Mb)] were significantly increased from EX(80%) to Load(EX); 12.8±9.1 μm to 16.4±10.3 μm and 5.9±2.9 μm to 11.0±6.4 μm, respectively. These data suggest an increase in respiratory muscle load increases muscle deoxy(Hb+Mb) and thus may indicate a reduction in oxygen delivery and/or increased oxygen extraction by the active muscles.