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Dennis van Erck, Eric J. Wenker, Koen Levels, Carl Foster, Jos J. de Koning and Dionne A. Noordhof

. Furthermore, multiple studies have shown a decrease in GE during a high-intensity exercise bout performed at sea level. 14 – 17 Thus far, it is unknown if the decrease in GE, observed during a high-intensity exercise bout, 14 is the same at acute altitude compared with sea level. Therefore, the second

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Sjors Groot, Lars H.J. van de Westelaken, Dionne A. Noordhof, Koen Levels and Jos J. de Koning

model, 8 it has been shown that a decrease in GE of 0.9% results in a 25.6-second slower finish time during a 20,000-m cycling time trial. 9 Multiple studies found a decreased GE after high-intensity exercise. 10 – 13 Noordhof et al 11 showed that GE was lower after time-trial exercise than before

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Anna E. Voskamp, Senna van den Bos, Carl Foster, Jos J. de Koning and Dionne A. Noordhof

larger decrement in GE after the shorter time trials. The lower running economy found by Hoff et al 10 when blood lactate concentration ([La − ]) increased from 3 to 5 mmol/L supports this notion. During high-intensity exercise there is a significant energy contribution from anaerobic glycolysis. 11

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Al Haddad Hani, Paul B. Laursen, Ahmaidi Said and Buchheit Martin

Purpose:

To assess the effect of supramaximal intermittent exercise on long-term cardiac autonomic activity, inferred from heart rate variability (HRV).

Methods:

Eleven healthy males performed a series of two consecutive intermittent 15-s runs at 95% VIFT (i.e., speed reached at the end of the 30-15 Intermittent Fitness Test) interspersed with 15 s of active recovery at 45% VIFT until exhaustion. Beat-to-beat intervals were recorded during two consecutive nights (habituation night and 1st night) before, 10 min before and immediately after exercise, as well as 12 h (2nd night) and 36 h (3rd night) after supramaximal intermittent exercise. The HRV indices were calculated from the last 5 min of resting and recovery periods, and the first 10 min of the first estimated slow wave sleep period.

Results:

Immediate post-supramaximal exercise vagal-related HRV indices were significantly lower than immediate pre-supramaximal exercise values (P < .001). Most vagal-related indices were lower during the 2nd night compared with the 1st night (eg, mean RR intervals, P = .03). Compared with the 2nd night, vagal-related HRV indices were significantly higher during the 3rd night. Variables were not different between the 1st and 3rd nights; however, we noted a tendency (adjusted effect size, aES) for an increased normalized high-frequency component (P = .06 and aES = 0.70) and a tendency toward a decreased low-frequency component (P = .06 and aES = 0.74).

Conclusion:

Results confirm the strong influence of exercise intensity on short- and long-term post exercise heart rate variability recovery and might help explain the high efficiency of supramaximal training for enhancing indices of cardiorespiratory fitness.

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Bryan Saunders, Craig Sale, Roger C. Harris and Caroline Sunderland

Purpose:

To determine whether gastrointestinal (GI) distress affects the ergogenicity of sodium bicarbonate and whether the degree of alkalemia or other metabolic responses is different between individuals who improve exercise capacity and those who do not.

Methods:

Twenty-one men completed 2 cycling-capacity tests at 110% of maximum power output. Participants were supplemented with 0.3 g/kg body mass of either placebo (maltodextrin) or sodium bicarbonate (SB). Blood pH, bicarbonate, base excess, and lactate were determined at baseline, preexercise, immediately postexercise, and 5 min postexercise.

Results:

SB supplementation did not significantly increase total work done (TWD; P = .16, 46.8 · 9.1 vs 45.6 · 8.4 kJ, d = 0.14), although magnitude-based inferences suggested a 63% likelihood of a positive effect. When data were analyzed without 4 participants who experienced GI discomfort, TWD (P = .01) was significantly improved with SB. Immediately postexercise blood lactate was higher in SB for the individuals who improved but not for those who did not. There were also differences in the preexercise-to-postexercise change in blood pH, bicarbonate, and base excess between individuals who improved and those who did not.

Conclusions:

SB improved high-intensity-cycling capacity but only with the exclusion of participants experiencing GI discomfort. Differences in blood responses suggest that SB may not be beneficial to all individuals. Magnitude-based inferences suggested that the exercise effects are unlikely to be negative; therefore, individuals should determine whether they respond well to SB supplementation before competition.

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Suzanna Russell, Angus G. Evans, David G. Jenkins and Vincent G. Kelly

adult preexercise screening tool, aged 18–45 years, and capable of completing both a 1.2 SRT and high-intensity exercise. Participants completed an average of 7:15 hours, across 4 to 5 sessions, per week of training and competition across sports including Australian football, field hockey, soccer

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Takeshi Kokubo, Yuta Komano, Ryohei Tsuji, Daisuke Fujiwara, Toshio Fujii and Osamu Kanauchi

diseases ( Kanauchi et al., 2018 ). In a clinical trial, LC-Plasma relieved morbidity and symptoms of URTI via activation of pDC and decreased fatigue accumulation during consecutive high-intensity exercise in athletes; the detailed mechanism was not investigated ( Komano et al., 2018 ). To investigate the

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Guy El Hajj Boutros, José A. Morais and Antony D. Karelis

). Interestingly, a large population study with a 16-year follow-up showed that a single weekly session of high-intensity exercise (∼90% of maximal heart rate) for at least 30 min was sufficient in reducing the risk of cardiovascular death (ischemic heart disease and stroke) by 36% in the age group of 60–69 years

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Franck Brocherie, Grégoire P. Millet and Olivier Girard

Purpose:

To compare psychophysiological responses to 6 repeated-sprint sessions in normobaric hypoxia (RSH) and normoxia (RSN) in team-sport athletes during a 2-wk “live high–train low” training camp.

Methods:

While residing under normobaric hypoxia (≥14 h/d, FiO2 14.5–14.2%), 23 lowland elite field hockey players performed, in addition to their usual training, 6 sessions (4 × 5 × 5-s maximal sprints, 25-s passive recovery, 5 min rest) under either RSH (FiO2 ~14.5%) or RSN (FiO2 21%). Sprint 1 and 5 times, physiological strain (heart rate [HR], arterial oxyhemoglobin saturation [SpO2]), and perceptual responses (overall peripheral discomfort, difficulty breathing, and lower-limb discomfort) were monitored.

Results:

During the 1st session, HR increased across sets (P < .001) independently of the conditions, while SpO2 was globally lower (P < .001) for RSH (averaged value: 91.9% ± 1.2%) vs RSN (96.9% ± 0.6%). Thereafter, SpO2 and HR remained similar across sessions for each condition. While 1st-sprint time remained similar, last-sprint time and fatigue index significantly decreased across sets (P < .01) and sessions (P < .05) but not between conditions. Ratings of overall perceived discomfort, difficulty breathing, and lower-limb discomfort were higher (P < .05) in RSH vs RSN at the 1st session. During subsequent sessions, values for overall perceived discomfort (time [P < .001] and condition [P < .05] effects), difficulty breathing (time effect; P < .001), and lower-limb discomfort (condition [P < .001] and interaction [P < .05] effects) decreased to a larger extent in RSH vs RSN.

Conclusion:

Despite higher hypoxia-induced physiological and perceptual strain during the 1st session, perceptual responses improved thereafter in RSH so as not to differ from RSN. This indicates an effective acclimation and tolerance to this innovative training.

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Richard Ebreo, Louis Passfield and James Hopker

can be accounted for via expired gases measured at the mouth. However, during high-intensity exercise (HIE) with a significant anaerobic energy contribution, V ˙ O 2 measured at the mouth cannot be used to estimate the total energy expenditure. Therefore, conventional measurement of GE during