Browsing by Author "Ganio, Matthew S."
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Item Cardiovascular Drift is Related to Reduced Maximal Oxygen Uptake During Heat StressWingo, Jonathan E.; Lafrenz, Andrew J.; Ganio, Matthew S.; Edwards, Gaylen L.; Cureton, Kirk J.; University of Alabama TuscaloosaIntroduction/Purpose: This study investigated whether the progressive rise in heart rate (HR) and fall in stroke volume (SV) during prolonged, constant-rate, moderate-intensity exercise (cardiovascular drift, CVdrift) in a hot environment is associated with a reduction in VO2max. Methods: CVdrift was measured in nine male cyclists between 15 and 45 min of cycling at 60% VO2max in 35degreesC that was immediately followed by measurement of VO2max. VO2max also was measured after 15 min of cycling on a separate day, so that any change in VO2max between 15 and 45 min could be associated with the CVdrift that occurred during that time interval. This protocol was performed under one condition in which fluid was ingested and there was no significant body weight change (0.3 +/- 0.4%), and under another in which no fluid was ingested and dehydration occurred (2.5 +/- 1%, P < 0.05). Results: Fluid ingestion did not affect CVdrift or change in VO2max. A 12% increase in HR (151 +/- 9 vs 169 +/- 10 bpm, P < 0.05) and 16% decrease in SV (120 +/- 12 vs 101 +/- 10 mL(.)beat(-1), P < 0.05) between 15 and 45 min was accompanied by a 19% decrease in VO2max (4.4 +/- 0.6 vs 3.6 +/- 0.4 L(.)min(-1), P < 0.05) despite attainment of a higher maximal HR (P < 0.05) at 45 min (194 +/- 5 bpm) vs 15 min (191 +/- 5 bpm). Submaximal VO2 increased only slightly over time, but %VO2max increased from 63 +/- 5% at 15 min to 78 +/- 8% at 45 min (P < 0.05). Conclusion: We conclude CVdrift during 45 min of exercise in the heat is associated with decreased VO2max and increased relative metabolic intensity. The results support the validity of using changes in HR to reflect changes in relative metabolic intensity during prolonged exercise in a hot environment in which CVdrift occurs.Item Fluid Ingestion Attenuates the Decline in VO2peak Associated with Cardiovascular DriftGanio, Matthew S.; Wingo, Jonathan E.; Carroll, Candace E.; Thomas, Mia K.; Cureton, Kirk J.; University of Alabama TuscaloosaThis study investigated whether manipulation of cardiovascular drift (CV drift) by changing exercise duration or by fluid ingestion is associated with altered peak oxygen uptake VO(2peak). METHODS: VO(2peak) was measured in 11 trained men immediately after they cycled at 60% control VO(2max) in 30 degrees C, 40% relative humidity for 15, 60, and 120 min with no fluid (15 NF, 60 NF, 120 NF) or 120 min with fluid (120 F). Stroke volume (SV), heart rate (HR), and related measures were measured in 120 NF and 120 F at 15, 60, and 120 min. RESULTS: Body mass decreased 0.7, 2.3, and 3.7% in 120 F, 60 NF, and 120 NF. SV at the end of submaximal exercise and VO(2peak) measured immediately thereafter were reduced significantly (P < 0.05) from 15-min values in 120 NF (13.8 and 8.7%) but not in 60 NF (4.6 and 1.2%) or 120 F (2.1 and 1.9%). CONCLUSIONS: The progressive decline in SV during prolonged, constant-rate submaximal exercise in a warm environment, reflective of increased cardiovascular strain associated with hyperthermia, dehydration, and other changes that occur over time, reduces VO(2peak). Fluid ingestion improves performance in prolonged exercise, in part, by mitigating the decline in SV and its determinants, and preserving VO(2peak).Item Nutritional, Physiological and Perceptual Responses During a Summer Ultra-Endurance Cycling EventArmstrong, Lawrence E.; Casa, Douglas J.; Emmanuel, Holly; Ganio, Matthew S.; Klau, Jennifer F.; Lee, Elaine C.; Maresh, Carl M.; McDermott, Brendon P.; Stearns, Rebecca L.; Vingren, Jakob L.; Wingo, Jonathan E.; Williamson, Keith H.; Yamamoto, Linda M.; University of Alabama TuscaloosaDespite the rapid growth of mass-participation road cycling, little is known about the dietary, metabolic and behavioral responses of ultra-endurance cyclists. This investigation describes physiological responses, perceptual ratings, energy balance, and macronutrient intake of 42 men (mean ± SD; age, 38±6 y; height, 179.7±7.1 cm; body mass, 85.85±14.79 kg) and 6 women (age, 41±4 y; height, 168.0±2.9 cm; body mass, 67.32±7.21 kg) during a summer 164-km road cycling event. Measurements were recorded one day before, and on Event Day (10.5 h) at the start (0 km), at two aid stations (52 km and 97 km), and at the finish line (164 km). Ambient temperature was >39.0°C during the final 2 h of exercise. Mean finish times for men (9.1±1.2 h) and women (9.0±0.2 h) were similar, as were mean gastrointestinal temperature [TGI], four hydration biomarkers, and five perceptual (e.g., thermal, thirst, pain) ratings. Male cyclists consumed enough fluids on Event Day (5.91±2.38 L; 49% water) to maintain body mass within 0.76 kg, start to finish, despite a sweat loss of 1.13±0.54 L·h-1 and calculated energy expenditure of 3,115 Kcal·10.5h-1 . However, men voluntarily underconsumed food energy (deficit of 2,594 Kcal, 10.9 MJ), and specific macronutrients (carbohydrates, 106±48 g; protein, 8 ± 7 g; and sodium, 852 ± 531 mg) between 0530 and 1400 h. Also, a few men exhibited extreme final values (i.e., urine specific gravity of 1.035 to 1.038, n=5; body mass loss >4 kg, n=2; TGI, 39.4 and 40.2). We concluded that these findings provide information regarding energy consumption, macronutrient intake, hydration status and the physiological stresses that are unique to ultra-endurance exercise in a hot environment.