Thermoregulation and fluid balance during a 30-km march in 60-versus 80-year-old subjects

The presence of impaired thermoregulatory and fluid balance responses to exercise in older individuals is well established. To improve our understanding on thermoregulation and fluid balance during exercise in older individuals, we compared thermoregulatory and fluid balance responses between sexagenarians and octogenarians during prolonged exercise. Forty sexagenarians (60 ± 1 year) and 36 octogenarians (81 ± 2 year) volunteered to participate in a 30-km march at a self-selected pace. Intestinal temperature (T in) and heart rate were recorded every 5 km. Subjects reported fluid intake, while urine output was measured and sweat rate was calculated. Octogenarians demonstrated a lower baseline T in and a larger exercise-induced increase in T in compared to sexagenarians (1.2 ± 0.5 °C versus 0.7 ± 0.4 °C, p  0.05). These results suggest that thermoregulatory responses deteriorate with advancing age, while fluid balance is regulated appropriately during a 30-km walking march under moderate ambient conditions

Impact of flavonoid-rich black tea and beetroot juice on postprandial peripheral vascular resistance and glucose homeostasis in obese, insulin-resistant men: a randomized controlled trial.

BACKGROUND: Insulin-stimulated muscle blood flow facilitates plasma glucose disposal after a meal, a mechanism that is impaired in obese, insulin-resistant volunteers. Nitrate- or flavonoid-rich products, through their proposed effects on nitric oxide, may improve postprandial blood flow and, subsequently, glucose disposal. To investigate whether a single dose of nitrate-rich beetroot juice or flavonoid-rich black tea lowers postprandial muscle vascular resistance in obese volunteers and alters postprandial glucose or insulin concentrations. METHOD: In a randomised, controlled, cross-over study, 16 obese, insulin-resistant males consumed 75 g glucose, which was combined with 100 ml black tea, beetroot juice or control (water). Peripheral vascular resistance (VR), calculated as mean arterial pressure divided by blood flow, was assessed in the arm and leg conduit arteries, resistance arteries and muscle microcirculation across 3 h (every 30-min) after the oral glucose load. RESULTS: During control, we found no postprandial response in VR in conduit, resistance and microvessels (all P > 0.05). Black tea decreased VR compared to control in conduit, resistance and microvessels (all P < 0.05). Beetroot juice decreased postprandial VR in resistance vessels, but not in conduit artery and microvessels. Although postprandial glucose response was similar after all interventions, postprandial insulin response was attenuated by ~29 % after tea (P < 0.0005), but not beetroot juice. CONCLUSIONS: A single dose of black tea decreased peripheral VR across upper and lower limbs after a glucose load which was accompanied by a lower insulin response. Future studies in insulin-resistant subjects are warranted to confirm the observed effects and to explore whether long-term regular tea consumption affects glucose homeostasis. TRIAL REGISTRATION: The study was registered at clinicaltrials.gov on 30(th) November 2012 (NCT01746329)

Glycemic control during consecutive days with prolonged walking exercise in individuals with type 1 diabetes mellitus

Aims: Despite its general benefits for health, exercise complicates the maintenance of stable blood glucose concentrations in individuals with type 1 diabetes. The aim of the current study was to examine changes in food intake, insulin administration, and 24-h glycemic control in response to consecutive days with prolonged walking exercise (~8 h daily) in individuals with type 1 diabetes. Methods: Ten individuals with type 1 diabetes participating in the worlds' largest walking event were recruited for this observational study. Simultaneous measurements of 24-h glycemic control (continuous glucose monitoring), insulin administration and food intake were performed during a non-walking day (control) and during three subsequent days with prolonged walking exercise (daily distance 40 or 50 km). Results: Despite an increase in daily energy (31 ± 18%; p 10 mmol/L) and hypoglycemia (blood glucose 0.05 for all variables). The prolonged walking exercise was associated with a modest increase in glycemic variability compared with the control day (p < 0.05). Conclusion: Prolonged walking exercise allows for profound reductions in daily insulin administration in persons with type 1 diabetes, despite large increments in energy and carbohydrate intake. When taking such adjustments into account, prolonged moderate-intensity exercise does not necessarily impair 24-h glycemic control. © 2016 Elsevier Ireland Ltd

Ergogenic effects of dietary nitrate

Intake of dietary nitrate, such as beetroot juice, has received a lot of attention the past few years because of possible performance-enhancing effects for athletes. This thesis describes various factors important to gain this effect. It shows nitrate-rich vegetables (such as beetroot and spinach) are the most effective sources of nitrate. Research among athletes also shows that high intensity athletes such as football players could benefit from dietary nitrate intake, whereas endurance athletes such as cyclists would not. The thesis concludes that nitrate stored in muscle tissue and could play an important part in providing beneficial effects in sports performance

Could intramuscular storage of dietary nitrate contribute to its ergogenic effect? A mini -review

Extensive research performed over the past 10 years has resulted in dietary nitrate being considered a nutritional supplement that can improve exercise performance. However, there is still limited insight in the metabolic fate of dietary nitrate following the appearance of nitrate and nitrite in the circulation. Recent observations in humans suggest the storage of nitrate in skeletal muscle tissue. This short review discusses the possibility of nitrate being stored and utilized in human skeletal muscle tissue, and why confirming this may increase our understanding of how the nitrate-nitrite-NO pathway improves exercise performance. Further insight in skeletal muscle nitrate storage and metabolism may provide answers to current gaps in knowledge, such as the ergogenic benefit of acute vs multiday dietary nitrate supplementation, as well as the suggested muscle fiber-type specific effects on exercise performance. In this mini-review, specific questions that need further exploration are also discussed

No Effect of Acute and 6-Day Nitrate Supplementation on VO2 and Time-Trial Performance in Highly Trained Cyclists

While the majority of studies reporting ergogenic effects of dietary nitrate have used a multiday supplemen-tation protocol, some studies suggest that a single dose of dietary nitrate before exercise can also improve subsequent performance. We aimed to compare the impact of acute and 6-day sodium nitrate supplementation on oxygen uptake (V˙ O2) and time-trial performance in trained cyclists. Using a randomized, double-blind, cross-over design, 17 male cyclists (25 ± 4 y, V˙ O2peak 65 ± 4 ml·kg-1·min-1, Wmax 411 ± 35 W) were subjected to 3 different trials; 5 days placebo and 1 day sodium nitrate supplementation (1-DAY); 6 days sodium nitrate supplementation (6-DAY); 6 days placebo supplementation (PLA). Nitrate was administered as 1097 mg sodium nitrate providing 800 mg (~12.9 mmol) nitrate per day. Three hours after ingestion of the last supplemental bolus, indirect calorimetry was performed while subjects performed 30 min of exercise at 45% Wmax and 30 min at 65% Wmax on a cycle ergometer, followed by a 10 km time-trial. Immediately before exercise, plasma [nitrate] and [nitrite] increased to a similar extent during the 6-DAY and 1-DAY trial, but not with PLA (plasma nitrite: 501 ± 205, 553 ± 278, and 239 ± 74 nM, respectively; p < .001). No differences were observed between interventions in V˙ O2 during submaximal exercise, or in time to complete the time-trial (6-DAY: 1004 ± 61, 1-DAY: 1022 ± 72, PLA: 1017 ± 71 s; p = .28). We conclude that both acute and 6-days of sodium nitrate supplementation do not alter V˙ O2 during submaximal exercise or improve time-trial performance in highly trained cyclists, despite increasing plasma [nitrate] and [nitrite]

Team Rwanda:will Africans dominate professional road cycling in the future?

Kenya-born cyclist Chris Froome has once again won the Tour de France. Although the current title-holder is not a native Kenyan, some believe that the multiday stage race will one day be won by a cyclist with East-African roots. In 2015, the world got a glimpse of what might become a common sight in future editions of the Tour. The latest edition of the event introduced MTN-Qhubeka ( currently known as Team Dimension Data for Qhubeka ) as its first professional African cycling team ever to participate. The team's Eritrean cyclist Daniel Teklehaimanot exceeded all expectations by becoming the first native African to win the King of the Mountains classification of Critérium du Dauphiné, as well as by claiming the polka dot jersey in the early stages of the tour a few weeks later. But are riders such as Daniel Teklehaimanot and his Rwandan team-mate Adrien Niyonshuti the first of many native Africans who will soon be dominating professional road cycling? Besides the fact that most African countries lack a well-embedded cycling culture, with the exception of Daniel Teklehaimanot's Eritrea, do native African cyclists have what it takes to become elite cyclists? To the best of our knowledge, no data have yet been published on the performance capacity of African cyclists. This report presents unique performance data collected from four cyclists from the National Road Cycling Team of Rwanda