Browsing by Author "Seifert, John"

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Blood glucose/lactate responses from ingesting high fructose corn syrup and sucrose beverages
(2013-03) Bloemendal, Amy; Seifert, John
Fructose has been the focus of many researchers. High fructose corn syrup has replaced sucrose in food products and has gained notoriety concerning possible negative effects on metabolism. Purpose: To examine whether a HFCS beverage alters glucose and lactate responses compared to a sucrose beverage. METHODS: Seven (3 male, 4 female: Mean±SD; 23.7±2.4yrs, 71.5±16.2kg, 173.9±9.6cm) adults volunteered. Subjects participated in two experimental trials after a 12 hour fast. A 10% beverage sweetened with HFCS or sucrose (30 g/300mL) was ingested. Blood samples were taken at -5, 30, 60, 90 and 120 minutes, coagulated for 20 minutes and centrifuged for 10 minutes. An ANOVA with repeated measures was used for statistical analysis. T-tests were used to differentiate means with Bonferroni adjustment (alpha level < 0.05). RESULTS: No interaction effect was observed between time and treatments. No treatment main effect was found for glucose (Means±SD: sucrose 4.0±0.92 mM/L; HFCS 4.28±1.06mM/L) or lactate (Mean±SD: sucrose 2.10±0.67mM/L; HFCS 2.15±0.68mMol/L). There was a significant time effect within blood glucose levels. Mean glucose concentration at 30 minutes was increased over baseline (Mean±SD: 5.6±0.98mM/L), and 60, 90, and 120 minutes. CONCLUSIONS: Glucose and lactate responses were not different from one another after ingestion of HFCS and sucrose.
Heel riser height influence on kinematics and muscle activity of ski mountaineering – A field based study
(University of Bern, 2024-05) Turczyn, Daniel; Graham, David; Lasshofer, Michael; Seifert, John
Hydration Perceptions, Hydration Practices and Reaction Times of Fighter and Helicopter Pilots
(2013-03) Strubeck, Eric; Seifert, John
Military operations can be conducted over extended periods of time in varying environments. Pilots also have to overcome vibration, noise, and accelerations. PURPOSE: The purpose of this study is to describe hydration perceptions and practices, perceived stresses, and reaction times of pilots before and after a training flight. METHODS: 14 male pilots (Mean ±SD: 40 ± 6 y, 93 ± 10 Kg) provided subjective and objective data regarding their hydration perceptions and practices. Urine specific gravity (Usg) was used to quantify hydration status. Auditory reaction times were used as a measure of performance RESULTS: There was no change in mean Usg, (Pre 1.014 ±0.009, Post 1.014 ±0.007). Subjective thirst increased among the pilots (Pre 2.45 ±1.33, Post 3.41 ±0.82). Mean reaction time slowed (Pre 0.190 ±0.027 s, Post 0.198 ±0.031 s). The relationship between Usg and reaction time was poor (post R = 0.07). CONCLUSIONS: Differences in reaction time could be explained by flight length and aircraft. Helicopter pilots reported a greater pre to post flight change in mental fatigue which could explain their slowed reaction time. Pilots could be better hydrated at the start of missions.
The Influence of Pre-Exercise Solid and Liquid Caloric Ingestion on Blood Glucose and Lactate
(2013-03) Connor, David; Seifert, John
Energy supplements for endurance training and racing are often used as an effective way of improving performance. Pre-exercise feedings may increase glycogen synthesis and provide additional substrate for exercise, yet most athletes prefer not to eat solid food right before an endurance activity due to potential gastrointestinal issues and possible side effects in regard to blood glucose response to the feeding. Caloric feedings may be desirable before certain sub-maximal training events. However, it is not known whether a cereal feeding would be tolerated, compared to liquid feeding, when ingested prior to exercise. PURPOSE. The purpose of this study was to investigate blood glucose levels (BG), lactate, rating of perceived exertion (RPE), and respiratory exchange ratio (RER) when iso-caloric liquid or solid food was consumed 10 min prior to moderate intensity exercise. METHODS. Nine low-risk subjects, six males and three females, participated in the study. Each subject completed a maximal heart rate test prior to the two exercise trials to determine target heart rate throughout the study. For one trial, subjects consumed a sports drink containing 40g carbohydrate and 10g protein 10 min prior to exercise. For the second trial, subjects consumed cereal with skim milk consisting of 44g of carbohydrate and 6g protein 10 min prior to exercise. Each exercise trial consisted of riding a cycle ergometer at 65% of maximal heart rate for 50 min. Blood glucose lactate, and RPE were recorded at 25 and 50-minute time points. RER was collected between 20-25 minutes and 45-50 minutes. An ANOVA with repeated measures was performed on the dependent variables. Alpha level of significance was set at p < 0.05. RESULTS. Average BG and lactate were significantly greater for the Liquid trial (4.93 ±0.94 mM/L and 3.7 2.2 mM/L) compared to Solid trial (4.52 ±0.5 mM/L and 2.3 1.2 mM/L). There were no significant differences between trials for RPE and RER. CONCLUSIONS. The blood glucose findings support the idea that gastric emptying is slower with solid feeding than with fluid feeding. Although the effect was small, the increased blood glucose concentration secondary to liquid feeding represents increased energy available to muscle cells. Interestingly, the women in the study seemed to have overall lower BG and lactate levels compared to the men. One limitation of the study is that only one dosage and one timing of pre-exercise ingestion was investigated. By varying dosage and timing, the exact differences on gastric emptying and subsequent physiological variables could be quantified.
Physiological Responses and Predictors of Performance in a Simulated Competitive Ski Mountaineering Race
(Journal of Sports Science and Medicine, 2021-03) Lasshofer, Michael; Seifert, John; Wörndle, Anna-Maria; Stöggl, Thomas
Competitive ski mountaineering (SKIMO) has achieved great popularity within the past years. However, knowledge about the predictors of performance and physiological response to SKIMO racing is limited. Therefore, 21 male SKIMO athletes split into two performance groups (elite: VO2max 71.2 ± 6.8 ml· min-1· kg-1 vs. sub-elite: 62.5 ± 4.7 ml· min-1· kg-1) were tested and analysed during a vertical SKIMO race simulation (523 m elevation gain) and in a laboratory SKIMO specific ramp test. In both cases, oxygen consumption (VO2), heart rate (HR), blood lactate and cycle characteristics were measured. During the race simulation, the elite athletes were approximately 5 min faster compared with the sub-elite (27:15 ± 1:16 min; 32:31 ± 2:13 min; p < 0.001). VO2 was higher for elite athletes during the race simulation (p = 0.046) and in the laboratory test at ventilatory threshold 2 (p = 0.005) and at maximum VO2 (p = 0.003). Laboratory maximum power output is displayed as treadmill speed and was higher for elite than sub-elite athletes (7.4 ± 0.3 km h-1; 6.6 ± 0.3 km h-1; p < 0.001). Lactate values were higher in the laboratory maximum ramp test than in the race simulation (p < 0.001). Pearson’s correlation coefficient between race time and performance parameters was highest for velocity and VO2 related parameters during the laboratory test (r > 0.6). Elite athletes showed their superiority in the race simulation as well as during the maximum ramp test. While HR analysis revealed a similar strain to both cohorts in both tests, the superiority can be explainable by higher VO2 and power output. To further push the performance of SKIMO athletes, the development of named factors like power output at maximum and ventilatory threshold 2 seems crucial.