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Neither Beetroot Juice Supplementation nor Increased Carbohydrate Oxidation Enhance Economy of Prolonged Exercise in Elite Race Walkers.
Burke, LM, Hall, R, Heikura, IA, Ross, ML, Tee, N, Kent, GL, Whitfield, J, Forbes, SF, Sharma, AP, Jones, AM, et al
Nutrients. 2021;(8)
Abstract
Given the importance of exercise economy to endurance performance, we implemented two strategies purported to reduce the oxygen cost of exercise within a 4 week training camp in 21 elite male race walkers. Fourteen athletes undertook a crossover investigation with beetroot juice (BRJ) or placebo (PLA) [2 d preload, 2 h pre-exercise + 35 min during exercise] during a 26 km race walking at speeds simulating competitive events. Separately, 19 athletes undertook a parallel group investigation of a multi-pronged strategy (MAX; n = 9) involving chronic (2 w high carbohydrate [CHO] diet + gut training) and acute (CHO loading + 90 g/h CHO during exercise) strategies to promote endogenous and exogenous CHO availability, compared with strategies reflecting lower ranges of current guidelines (CON; n = 10). There were no differences between BRJ and PLA trials for rates of CHO (p = 0.203) or fat (p = 0.818) oxidation or oxygen consumption (p = 0.090). Compared with CON, MAX was associated with higher rates of CHO oxidation during exercise, with increased exogenous CHO use (CON; peak = ~0.45 g/min; MAX: peak = ~1.45 g/min, p < 0.001). High rates of exogenous CHO use were achieved prior to gut training, without further improvement, suggesting that elite athletes already optimise intestinal CHO absorption via habitual practices. No differences in exercise economy were detected despite small differences in substrate use. Future studies should investigate the impact of these strategies on sub-elite athletes' economy as well as the performance effects in elite groups.
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Anabolic Bone Stimulus Requires a Pre-Exercise Meal and 45-Minute Walking Impulse of Suprathreshold Speed-Enhanced Momentum to Prevent or Mitigate Postmenopausal Osteoporosis within Circadian Constraints.
Zheng, Q, Kernozek, T, Daoud-Gray, A, Borer, KT
Nutrients. 2021;(11)
Abstract
Osteoporosis currently afflicts 8 million postmenopausal women in the US, increasing the risk of bone fractures and morbidity, and reducing overall quality of life. We sought to define moderate exercise protocols that can prevent postmenopausal osteoporosis. Our previous findings singled out higher walking speed and pre-exercise meals as necessary for suppression of bone resorption and increasing of markers of bone formation. Since both studies were amenable to alternate biomechanical, nutritional, and circadian interpretations, we sought to determine the relative importance of higher speed, momentum, speed-enhanced load, duration of impulse, and meal timing on osteogenic response. We hypothesized that: (1) 20 min of exercise one hour after eating is sufficient to suppress bone resorption as much as a 40-min impulse and that two 20 min exercise bouts separated by 7 h would double the anabolic effect; (2) early morning exercise performed after eating will be as effective as mid-day exercise for anabolic outcome; and (3) the 08:00 h 40-min. exercise uphill would be as osteogenic as the 40-min exercise downhill. Healthy postmenopausal women, 8 each, were assigned to a no-exercise condition (SED) or to 40- or 20-min exercise bouts, spaced 7 h apart, for walking uphill (40 Up and 20 Up) or downhill (40 Down and 20 Down) to produce differences in biomechanical variables. Exercise was initiated at 08:00 h one hour after eating in 40-min groups, and also 7 h later, two hours after the midday meal, in 20-min groups. Measurements were made of CICP (c-terminal peptide of type I collagen), osteocalcin (OC), and bone-specific alkaline phosphatase (BALP), markers of bone formation, and of the bone resorptive marker CTX (c-terminal telopeptide of type 1 collagen). The osteogenic ratios CICP/CTX, OC/CTX, and BALP/CTX were calculated. Only the 40-min downhill exercise of suprathreshold speed-enhanced momentum, increased the three osteogenic ratios, demonstrating the necessity of a 40-min, and inadequacy of a 20-min, exercise impulse. The failure of anabolic outcome in 40-min uphill exercise was attributed to a sustained elevation of PTH concentration, as its high morning elevation enhances the CTX circadian rhythm. We conclude that postmenopausal osteoporosis can be prevented or mitigated in sedentary women by 45 min of morning exercise of suprathreshold speed-enhanced increased momentum performed shortly after a meal while walking on level ground, or by 40-min downhill, but not 40-min uphill, exercise to avoid circadian PTH oversecretion. The principal stimulus for the anabolic effect is exercise, but the prerequisite for a pre-exercise meal demonstrates the requirement for nutrient facilitation.
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MAMBO: Measuring ambulation, motor, and behavioral outcomes with post-stroke fluoxetine in Tanzania: Protocol of a phase II clinical trial.
Vogel, AC, Okeng'o, K, Chiwanga, F, Ismail, SS, Buma, D, Pothier, L, Mateen, FJ
Journal of the neurological sciences. 2020;:116563
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Abstract
BACKGROUND SSA has a high stroke incidence and post-stroke morbidity. An inexpensive pharmacological treatment for stroke recovery would be beneficial to patients in the region. Fluoxetine, currently on the World Health Organization Essential Medicines List, holds promise as a treatment for motor recovery after ischemic stroke, but its effectiveness is controversial and untested in this context in SSA. AIM: To determine if fluoxetine 20 mg by mouth daily, given within 14 days of acute ischemic stroke, and taken for 90 days, is well-tolerated and safe with adequate adherence to justify a future randomized, controlled trial of fluoxetine in the United Republic of Tanzania. METHODS Open-label, phase II clinical trial enrolling up to 120 patients. Participants will be recruited from the Muhimbili National Hospital in Dar es Salaam, Tanzania, and followed for 90 days. The primary outcomes are: 1) safety, including serum sodium and hepatic enzyme levels; and 2) tolerability, as measured through study case report forms. The secondary outcomes are: 1) change in motor strength, as measured through the Fugl-Meyer Motor Scale; 2) adherence, as measured with electronic pill bottles; and 3) participant depressive symptom burden measured via standard questionnaires. CONCLUSIONS Expanding the evidence base for fluoxetine for Sub-Saharan African stroke survivors requires testing of its safety, tolerability, and adherence. Compared to prior studies in France and the United Kingdom, the patient characteristics, health infrastructure, and usual care for stroke recovery differ substantially in Tanzania. If fluoxetine reveals favorable endpoints, scale up of its use post-stroke is possible.
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The Effects of Dietary Pattern during Intensified Training on Stool Microbiota of Elite Race Walkers.
Murtaza, N, Burke, LM, Vlahovich, N, Charlesson, B, O' Neill, H, Ross, ML, Campbell, KL, Krause, L, Morrison, M
Nutrients. 2019;(2)
Abstract
We investigated extreme changes in diet patterns on the gut microbiota of elite race walkers undertaking intensified training and its possible links with athlete performance. Numerous studies with sedentary subjects have shown that diet and/or exercise can exert strong selective pressures on the gut microbiota. Similar studies with elite athletes are relatively scant, despite the recognition that diet is an important contributor to sports performance. In this study, stool samples were collected from the cohort at the beginning (baseline; BL) and end (post-treatment; PT) of a three-week intensified training program during which athletes were assigned to a High Carbohydrate (HCHO), Periodised Carbohydrate (PCHO) or ketogenic Low Carbohydrate High Fat (LCHF) diet (post treatment). Microbial community profiles were determined by 16S rRNA gene amplicon sequencing. The microbiota profiles at BL could be separated into distinct "enterotypes," with either a Prevotella or Bacteroides dominated enterotype. While enterotypes were relatively stable and remained evident post treatment, the LCHF diet resulted in a greater relative abundance of Bacteroides and Dorea and a reduction of Faecalibacterium. Significant negative correlations were observed between Bacteroides and fat oxidation and between Dorea and economy test following LCHF intervention.
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High-intensity interval walking in combination with acute green tea extract supplementation reduces postprandial blood glucose concentrations in physically inactive participants.
Bulmer, JM, McBain, TR, Peart, DJ
Nutrition and health. 2018;(3):193-198
Abstract
BACKGROUND Exercise and green tea supplementation have been shown to have the potential to improve postprandial blood glucose concentrations, but past interventions have not often investigated attainable and time effective exercise protocols. AIM:: The purpose of this study was to investigate the effects of interval walking exercise and acute green tea extract supplementation on the glycaemic response to an oral glucose tolerance test (OGTT). METHOD Twelve physically inactive participants (nine male, three female, age: 22 ± 1 years; body mass: 81.2 ± 16.3 kg; stature: 175.7 ± 9.6 cm; body mass index (in kg/m2): 26.2 ± 4.3) underwent a 2-h OGTT immediately following i) no intervention (REST), ii) placebo and exercise (EX-PLAC), iii) green tea extract supplementation and exercise (EX-GTE), in a random order. The walking exercise consisted of 6 × 1 min of brisk walking (7.92 ± 0.56 km/h) separated by 1 min of slower walking (4.8 km/h). Differences between groups were identified using magnitude-based inferences. RESULTS The EX-GTE intervention resulted in a ∼9% most likely beneficial effect on blood glucose area under the curve response to the OGTT (702.18 ± 76.90 mmol/L-1·120 min-1) compared with REST (775.30 ± 86.76 mmol/L-1·120 min-1), and a very likely beneficial effect compared with the EX-PLAC (772.04 ± 81.53 mmol/L-1·120 min-1). CONCLUSION These data suggest that an EX-GTE intervention can reduce postprandial glucose concentrations in physically inactive individuals.
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Maximum Tolerated Dose of Walking for Community-Dwelling People Recovering From Hip Fracture: A Dose-Response Trial.
Peiris, C, Shields, N, Kingsley, M, Yeung, J, Hau, R, Taylor, N
Archives of physical medicine and rehabilitation. 2017;(12):2533-2539
Abstract
OBJECTIVE To determine how much moderate-intensity physical activity, in the form of walking, could be prescribed for people living in the community after hip fracture in terms of safety, tolerability, and feasibility. DESIGN Phase I dose-response design. SETTING Public community rehabilitation centers. PARTICIPANTS Community-dwelling adults (N=21; 16 women; mean age, 75±9y) who were cognitively alert, attending community rehabilitation after hip fracture (mean days postfracture, 110±47d), able to walk with or without a gait aid, and for whom it was safe to participate in physical activity. INTERVENTIONS Individually supervised doses of moderate-intensity walking completed in 1 week in addition to their usual levels of physical activity. Three participants were required to complete a dose of walking before dose escalation for the next cohort of 3 participants. Dose escalation ceased when >1 participant in a cohort had an adverse event or was unable to tolerate the dose or if the maximum dose of 150min/wk was achieved. MAIN OUTCOME MEASURES Maximum tolerated dose of walking per week (in minutes), adverse events, mobility, and walking confidence. RESULTS The maximum tolerated dose of walking for adults after hip fracture before significant discomfort was experienced (eg, breathlessness, pain, and fatigue) by any participant was 100min/wk. No adverse events occurred, but participants began to be unable to tolerate higher doses beyond 100min/wk. CONCLUSIONS This provides preliminary evidence that community-dwelling older adults recovering from hip fracture can complete a sufficient amount of moderate-intensity physical activity to maintain and improve their health.
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Energy expenditure and physiological responses during walking on a treadmill and moving on the Torqway vehicle.
Maciejczyk, M, Wiecek, M, Szymura, J, Szygula, Z
Acta of bioengineering and biomechanics. 2016;(2):137-43
Abstract
PURPOSE One of the new products which can be used to increase physical activity and energy expenditure is the Torqway vehicle, powered by the upper limbs. The aim of this study was to (1) assess the usefulness and repeatability of the Torqway vehicle for physical exercise, (2) compare energy expenditure and physiological responses during walking on a treadmill and during physical effort while moving on the Torqway at a constant speed. METHODS The participants (11 men, aged 20.2 ± 1.3) performed the incremental test and submaximal exercises (walking on the treadmill and moving on the Torqway vehicle at the same speed). RESULTS Energy expenditure during the exercise on the Torqway was significantly higher (p = 0.001) than during the walking performed at the same speed. The intensity of the exercise performed on the Torqway expressed as %VO2max and %HRmax was significantly ( p < 0.001) higher than during walking (respectively: 35.0 ± 6.0 vs. 29.4 ± 7.4 %VO2max and 65.1 ± 7.3 vs. 47.2 ± 7.4 %HRmax). CONCLUSIONS Exercise on the Torqway vehicle allows for the intensification of the exercise at a low movement speed, comparable to walking. Moving on the Torqway vehicle could be an effective alternative activity for physical fitness and exercise rehabilitation programs.
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The Acute Effects of Interval-Type Exercise on Glycemic Control in Type 2 Diabetes Subjects: Importance of Interval Length. A Controlled, Counterbalanced, Crossover Study.
Jakobsen, I, Solomon, TP, Karstoft, K
PloS one. 2016;(10):e0163562
Abstract
UNLABELLED Interval-type exercise is effective for improving glycemic control, but the optimal approach is unknown. The purpose of this study was to determine the importance of the interval length on changes in postprandial glycemic control following a single exercise bout. Twelve subjects with type 2 diabetes completed a cross-over study with three 1-hour interventions performed in a non-randomized but counter-balanced order: 1) Interval walking consisting of repeated cycles of 3 min slow (aiming for 54% of Peak oxygen consumption rate [VO2peak]) and 3 min fast (aiming for 89% of VO2peak) walking (IW3); 2) Interval walking consisting of repeated cycles of 1 min slow and 1 min fast walking (IW1) and 3) No walking (CON). The exercise interventions were matched with regards to walking speed, and VO2 and heart rate was assessed throughout all interventions. A 4-hour liquid mixed meal tolerance test commenced 30 min after each intervention, with blood samples taken regularly. IW3 and IW1 resulted in comparable mean VO2 and heart rates. Overall mean postprandial blood glucose levels were lower after IW3 compared to CON (10.3±3.0 vs. 11.1±3.3 mmol/L; P < 0.05), with no significant differences between IW1 (10.5±2.8 mmol/L) and CON or IW3 and IW1 (P > 0.05 for both). Conversely blood glucose levels at specific time points during the MMTT differed significantly following both IW3 and IW1 as compared to CON. Our findings support the previously found blood glucose lowering effect of IW3 and suggest that reducing the interval length, while keeping the walking speed and time spend on fast and slow walking constant, does not result in additional improvements. TRIAL REGISTRATION ClinicalTrials.gov NCT02257190.
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Bed rest promotes reductions in walking speed, functional parameters, and aerobic fitness in older, healthy adults.
Coker, RH, Hays, NP, Williams, RH, Wolfe, RR, Evans, WJ
The journals of gerontology. Series A, Biological sciences and medical sciences. 2015;(1):91-6
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Abstract
CONTEXT The exact relationship between the bed rest-induced loss of skeletal muscle and reductions in muscle strength and physical performance in the older individuals is still unclear. OBJECTIVE We examined the effect of 10 days of bed rest on changes in regional body composition, muscle strength, and functional status, and the relationship between these variables in older individuals. DESIGN, PARTICIPANTS, AND INTERVENTION Regional body composition was measured using dual energy x-ray absorptiometry. We also determined changes in leg strength and several indices of functional status, including walking speed. RESULTS Body weight, body mass index, and total and lower extremity lean mass decreased with bed rest. There were also significant reductions in knee extension one repetition maximum, isometric knee extension, knee extension 60° concentric, stair ascent time, stair ascent power, stair descent time, VO2 max, floor transfer test, 5-minute walk time, and chair stand. The overall change in total and lower extremity lean mass was also directly related to bed rest-induced reductions in one repetition maximum knee extension. CONCLUSIONS Bed rest promoted overall declines in muscle mass, muscle strength, and physical function in older individuals. The changes in lean tissue were closely correlated with the bed rest-induced decline of muscle strength.
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Effect of Nordic Walking training on iron metabolism in elderly women.
Kortas, J, Prusik, K, Flis, D, Prusik, K, Ziemann, E, Leaver, N, Antosiewicz, J
Clinical interventions in aging. 2015;:1889-96
Abstract
BACKGROUND Despite several, well-documented pro-healthy effects of regular physical training, its influence on body iron stores in elderly people remains unknown. At the same time, body iron accumulation is associated with high risk of different morbidities. PURPOSE We hypothesized that Nordic Walking training would result in pro-healthy changes in an elderly group of subjects by reducing body iron stores via shifts in iron metabolism-regulating proteins. METHODS Thirty-seven women aged 67.7±5.3 years participated in this study. They underwent 32 weeks of training, 1-hour sessions three times a week, between October 2012 and May 2013. Fitness level, blood morphology, CRP, vitamin D, ferritin, hepcidin, and soluble Hjv were assessed before and after the training. RESULTS The training program caused a significant decrease in ferritin, which serves as a good marker of body iron stores. Simultaneously, the physical cardiorespiratory fitness had improved. Furthermore, blood hepcidin was positively correlated with the ferritin concentration after the training. The concentration of blood CRP dropped, but the change was nonsignificant. The applied training resulted in a blood Hjv increase, which was inversely correlated with the vitamin D concentration. CONCLUSION Overall the Nordic Walking training applied in elderly people significantly reduced blood ferritin concentration, which explains the observed decrease in body iron stores.