ResearchPad - physiology-biochemistry https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[Impact of Ice Slurry Ingestion During Break-Times on Repeated-Sprint Exercise in the Heat]]> https://www.researchpad.co/article/N4803c751-34ee-4b32-b63e-5a1f5e8c6b04 The study aimed to investigate the effects of ice slurry ingestion during break times and half-time (HT) on repeated-sprint performance and core temperature in the heat. Seven males performed two different trials as follows: ice slurry (−1°C) or room temperature water ingestion at each break and HT break at 36.5°C, 50% relative humidity. Participants performed 30 sets of 1-min periods of repeated- sprint exercises protocol using a cycling ergometer. Each period consisted of 5 sec of maximal pedaling, 25 sec of pedaling with no workload, and 30 sec of rest; two sets of exercise periods were separated by 10 min of rest. Each break was implemented for 1 min after every 5 sets. The rectal temperature in ice slurry ingestion was significantly lower than that of the room temperature water at 45 set (p=0.04). Total and mean work done was greater in ice slurry ingestion compared to room temperature water ingestion (p < 0.05). These results suggested that ice slurry ingestion during break times and HT break may be an effective cooling strategy to attenuate the rise of core temperature in the second half of exercise and improve the repeated-sprint exercise capacity in the heat.

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<![CDATA[Sex Differences in Cardiac AMP-Activated Protein Kinase Following Exhaustive Exercise]]> https://www.researchpad.co/article/N94a014b3-0744-4835-847c-906c3132f682

Ischemic heart disease presents with significant differences between sexes. Endurance exercise protects the heart against ischemic disease and also distinctly impacts male and female patients through unidentified mechanisms, though some evidence implicates 5′-AMP-activated protein kinase (AMPK). The purpose of this investigation was to assess the impact of training and sex on cardiac AMPK activation following exhaustive exercise. AMPK activation was measured in trained and sedentary mice of both sexes. Trained mice ran on a treadmill at progressively increasing speeds and duration for 12 weeks. Trained and sedentary mice of both sexes were euthanized immediately following exhaustive exercise and compared to sedentary controls. Endurance training elicited adaptations indicative of aerobic adaptation including higher max running velocities and cardiac hypertrophy with no differences between males and females. AMPK activity was higher in male compared to females, and trained exhibited higher AMPK activity compared to sedentary mice. In response to training, male mice activated AMPK more robustly than female mice. Chronic exercise training increases the ability to activate cardiac AMPK in response to exhaustive exercise in a sex-specific manner. Understanding the interaction between exercise and sex is vital for use of exercise as medicine for heart disease in both men and women.

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<![CDATA[Effect of Crop Volume on Contraction Rate in Adult House Fly]]> https://www.researchpad.co/article/N338ab037-04b4-4636-abfe-cf4da4af0e94

Abstract

The functional aspects of the adult house fly crop have not been studied even though various human and domestic animal pathogens have been discovered within the crop lumen. The average volume consumed (midgut and crop) by flies starved for 24 h was 3.88 μl by feeding both sexes on a sucrose phosphate glutamate buffer. In addition, various volumes of a solution (0.125 M sucrose plus Amaranth dye) were fed to 3-d-old adult female house flies to quantify the crop contraction rate as affected by crop volume. As crop volume increased, the contraction rate increased until it reached a peak at 2 μl, after which it declined. It is hypothesized that the high contraction rate of the crop, which in house fly is almost twice the rate of three other fly species, is one of the factors that makes house fly an excellent vector. The mechanism for such a high contraction rate needs to be investigated.

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<![CDATA[The Influence of Oxygen Saturation on the Relationship Between Hemoglobin Mass and VO2max]]> https://www.researchpad.co/article/5c19af80d5eed0c484c46ad3

Hemoglobin mass (tHb) is a key determinant of maximal oxygen uptake (VO 2 max). We examined whether oxyhemoglobin desaturation (ΔS a O 2 ) at VO 2 max modifies the relationship between tHb and VO 2 max at moderate altitude (1,625 m). Seventeen female and 16 male competitive, endurance-trained moderate-altitude residents performed two tHb assessments and two graded exercise tests on a cycle ergometer to determine VO 2 max and ΔS a O 2 . In males and females respectively, VO 2 max (ml·kg −1 ·min −1 ) ranged from 62.5–83.0 and 44.5–67.3; tHb (g·kg −1 ) ranged from 12.1–17.5 and 9.1–13.0; and S a O 2 at VO 2 max (%) ranged from 81.7–94.0 and 85.7–95.0. tHb was related to VO 2 max when expressed in absolute terms and after correcting for body mass (r=0.94 and 0.86, respectively); correcting by ΔS a O 2 did not improve these relationships (r=0.93 and 0.83). Additionally, there was a negative relationship between tHb and S a O 2 at VO 2 max (r=–0.57). In conclusion, across a range of endurance athletes at moderate altitude, the relationship between tHb and VO 2 max was found to be similar to that observed at sea level. However, correcting tHb by ΔS a O 2 did not explain additional variability in VO 2 max despite significant variability in ΔS a O 2 ; this raises the possibility that tHb and exercise-induced ΔS a O 2 are not independent in endurance athletes.

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<![CDATA[Does Metabolic Rate Increase Linearly with Running Speed in all Distance Runners?]]> https://www.researchpad.co/article/5c19af6dd5eed0c484c4674c

Running economy (oxygen uptake or metabolic rate for running at a submaximal speed) is one of the key determinants of distance running performance. Previous studies reported linear relationships between oxygen uptake or metabolic rate and speed, and an invariant cost of transport across speed. We quantified oxygen uptake, metabolic rate, and cost of transport in 10 average and 10 sub-elite runners. We increased treadmill speed by 0.45 m · s −1 from 1.78 m · s −1 (day 1) and 2.01 m · s −1 (day 2) during each subsequent 4-min stage until reaching a speed that elicited a rating of perceived exertion of 15. Average runners’ oxygen uptake and metabolic rate vs. speed relationships were best described by linear fits. In contrast, the sub-elite runners’ relationships were best described by increasing curvilinear fits. For the sub-elites, oxygen cost of transport and energy cost of transport increased by 12.8% and 9.6%, respectively, from 3.58 to 5.14 m · s −1 . Our results indicate that it is not possible to accurately predict metabolic rates at race pace for sub-elite competitive runners from data collected at moderate submaximal running speeds (2.68–3.58 m · s −1 ). To do so, metabolic rate should be measured at speeds that approach competitive race pace and curvilinear fits should be used for extrapolation to race pace.

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<![CDATA[Effects of Backpack Load and Trekking Poles on Energy Expenditure During Field Track Walking]]> https://www.researchpad.co/article/5c19b354d5eed0c484c5336f

This study evaluates the effects of the use of backpack load and trekking poles on field track walking energy expenditure. Twenty male volunteer pole walkers (age: 22.70±2.89 years; body mass: 77.90±11.19 kg; height: 1.77±0.06 m; percentage of body fat: 14.6±6.0%) walked at a self-selected pace on a pedestrian field track over a period of more than six months. Each subject was examined at random based on four walking conditions: non-poles and non-load, with poles and non-load, non-poles and with load, with poles and with load. Heart rate, oxygen uptake and energy expenditure were continuously recorded by a portable telemetric system. Non-load walking speed was lower during walking with poles when compared with no poles ( p ≤0.05). Oxygen uptake, energy expenditure and heart rate varied significantly across different conditions. Our results suggest that the use of trekking poles does not influence energy expenditure when walking without an additional load, but it can have an effect during backpack load walking. Moreover, our results indicate that the use of trekking poles may not be helpful to lower the exertion perceived by the subjects when walking with an additional load.

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