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Effects of Medium-Chain Triacylglycerol Ingested With Carbohydrate on Metabolism and Exercise Performance

Julia H. Goedecke, Richard Elmer, Steven C. Dennis, Ingrid Schloss, Timothy D. Noakes, and Estelle V. Lambert

The effects of ingesting different amounts of medium-chain triacylglycerol (MCT) and carbohydrate (CHO) on gastric symptoms, fuel metabolism, and exercise performance were measured in 9 endurance-trained cyclists. Participants, 2 hr after a standardized lunch, cycled for 2 hr at 63% of peak oxygen consumption and then performed a simulated 40-km time trial (T trial). During the rides, participants ingested either 10% 14C-glucose (GLU), 10% 14C-GLU + 1.72%MCT(LO-MCT), or 10% l4C-GLU + 3.44%MCT(HI-MCT) solutions: 400 ml at the start of exercise and then 100 ml every lOmin.MCTingestiondid not affect gastrointestinal symptoms. It only raised serum free fatty acid (FFA) and ß-hydroxybutyrate concentrations. Higher FFA and ß-hydroxybutyrate concentrations with MCT ingestion did not affect fuel oxidation or T-trial performance. The high CHO content of the pretrial lunch increased starting plasma insulin levels, which may have promoted CHO oxidation despite elevated circulating FFA concentrations with MCT ingestion.

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Sequential Pulse Compression’s Effect on Blood Flow in the Lower-Extremity

Kelly A. Brock, Lindsey E. Eberman, Richard H. Laird IV, David J. Elmer, and Kenneth E. Games

Context: Several interventions are available to reduce the intensity and duration of the unwanted effects (eg, muscle soreness) associated with physical activity, such as massage, compression garments, and sequential pulse compression (SPC). Such interventions aim to increase blood flow to alleviate symptoms. However, there is a lack of evidence to support the use of SPC to alter total hemoglobin concentration (THb) in active individuals. Objective: To examine the acute effects of a single session of SPC on hemoglobin concentration compared with a control condition. Design: Single cohort, crossover design. Participants: Thirty-four physically active and healthy participants (females = 12 and males = 22) completed the study. Interventions: The authors randomly assigned participants to first receive the experimental (SPC) or control condition. Measures were recorded precondition and postcondition. Participants returned to the laboratory to complete the second condition ≥24 hours after the first condition. Main Outcome Measures: Relative changes in THb, deoxygenated hemoglobin, and oxygenated hemoglobin measures were recorded using near-infrared spectroscopy placed on the muscle belly of the medial gastrocnemius of the dominant limb. Results: SPC significantly increased THb (P < .001, d = 0.505) and oxygenated hemoglobin (P < .001, d = 0.745) change scores compared with the control condition. No statistical difference in deoxygenated hemoglobin change scores was found between the SPC and control conditions, but a medium effect size suggests potential biological significance (P = .06, d = 0.339). Conclusions: Overall, SPC increases THb to the lower-extremity and may be a viable option in the management of muscle soreness related to physical activity.

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Hypoxia Does Not Change Performance and Psychophysiological Responses During Repeated Cycling Sprints to Exhaustion With Short Exercise-to-Rest Ratio

Antoine Raberin, Sarah J. Willis, Thomas Richard, Joakim Elmer, Gianluca Vernillo, F. Marcello Iaia, Olivier Girard, Davide Malatesta, and Grégoire P. Millet

Purpose: To compare the acute performance and psychophysiological responses of repeated cycling sprints to exhaustion with a short exercise-to-rest ratio (1:6), between different effort durations and inspired oxygen fractions. Methods: On separate visits, 10 active participants completed 6 repeated cycling sprint exercises to exhaustion with 3 different effort durations (5, 10, and 20 s) and 2 conditions of inspired oxygen (20.9% and 13.6%). Exercise-to-rest ratio was 1:6 for all trials (ie, 5:30, 10:60, and 20:120). Vastus lateralis muscle oxygenation (near-infrared spectroscopy), blood lactate concentration, and lower-limb and breathing discomfort, using ratings of perceived exertion, were measured. Results: Number of sprints and peak power output decreased while blood lactate increased (all P < .001) during 5:30 compared with 10:60 or 20:120. No condition or interaction effects were reported for blood lactate and exercise-related sensation. Muscle deoxyhemoglobin increased (P < .001) and total hemoglobin decreased (P = .002) during sprint with increasing sprint duration (no condition or interaction). Conclusion: During repeated-sprint exercise to exhaustion with a short exercise-to-rest ratio, the psychophysiological responses did not differ between normoxia and moderate hypoxia, probably due to an extended recovery period. It means that hypoxia did not modify repeated-sprint exercise performance with a short exercise-to-rest ratio. The sprint duration was the primary underlying factor of the observed differences in performance and muscle oxygenation reported between the repeated-sprint exercise sessions.