Effects of stair stepping on late day postprandial glycemia

Increased postprandial glycemia is problematic as chronic increases make one more susceptible to diabetes, cardiovascular disease and mortality. It is important to explore exercise interventions that are convenient and effective in reducing postprandial glycemia. PURPOSE: The purpose of the current study was to investigate whether the benefits of very short, single bout stair stepping established for early day food consumption extend to late day food consumption. METHODS: Seven participants without glycemic control abnormalities performed two standard oral glucose tolerance tests (OGTT), consuming 75g of glucose dissolved in 350mL of water followed by assessment of blood glucose response for 2 hours.Participants performed the OGTTs in the evening on two separate days. One day was the control condition, where participants remained seated throughout the entire duration of the OGTT. The other day (in randomized order) participants performed 1 min of stair stepping at a self-selected, comfortable pace 58 min after the consumption of the glucose solution. Blood glucose measurement via standard finger sticks were performed at 0, 30, 60, 70, 80, 90 and 120 min of the OGTT. Rating of perceived exertion (RPE) was assessed immediately following the stair stepping. Participants were instructed to not vary their diet or exercise during the two testing days. Diet and activity logs were collected to verify compliance.RESULTS:Blood glucose was not different at baseline and 30min. At the 60, 70, and 80min time points blood glucose was lower in the stair stepping compared to control conditions with narrowing margins as time progressed. At 90 and 120 min values were again not different between conditions. The change in blood glucose from baseline to peak values (60min) was statistically significantly lower in the stair-stepping (mean = 26, SD = 45 mg/dL) compared to control (mean = 63, SD = 41 mg/dL) condition (p = .032). All participants reported an RPE of 1 showing an overall low perception of intensity. CONCLUSION: A single 1-minute bout of low-intensity stair-stepping showed a marked reduction in peak postprandial blood glucose in the evening

Evaluation and Validity of a Predictive Equation for Measuring Core Temperature during Exercise in Heat Stress

Exercising in the heat is very common yet can pose significant health risks such as heat exhaustion and heat stroke when core temperature exceeds 38°C and 40°C, respectively. However, current methods of core temperature measurement are invasive and impractical. Recent research indicates that core temperature can be predicted with two non-invasive inputs, heart rate (HR) and skin temperature. PURPOSE: The objective of this study was to assess the validity and reliability of this predictive equation against the direct measurement of core temperature. METHODS: Participants (n = 11) cycled in an environmental chamber (40°C, 40% humidity) at 75% of maximal HR for 45 minutes. Measurements included HR, scapular skin and core temperature, blood pressure, and rating of perceived exertion. Exercise stopped if core temperature exceeded 38.5°C for two consecutive measurements or volitional fatigue. Agreement between predicted and actual core temperature was assessed with Bland–Altman analysis. RESULTS: There was a low correlation (r2 = 0.2) between the direct measure and predicted core temperatures. The Bland–Altman analysis for core minus predicted temperatures showed a bias of 0.14°C and limits of agreement ranging from 0.72°C to −0.45°C. In addition, a large proportion of measurements (40.5%) of the total scores had a difference in temperature greater than ±0.3°C. The predictive equation overpredicted as mean temperature increased from the average core temperature (37°C). CONCLUSION: Based on the narrow temperature range the human body must stay within to prevent heat-related issues, we’ve concluded that the predictive equation lacks sufficient validity and reliability

Mechanochemical Removal of Ribosome Biogenesis Factors from Nascent 60S Ribosomal Subunits

SummaryThe dynein-related AAA ATPase Rea1 is a preribosomal factor that triggers an unknown maturation step in 60S subunit biogenesis. Using electron microscopy, we show that Rea1's motor domain is docked to the pre-60S particle and its tail-like structure, harboring a metal ion-dependent adhesion site (MIDAS), protrudes from the preribosome. Typically, integrins utilize a MIDAS to bind extracellular ligands, an interaction that is strengthened under applied tensile force. Likewise, the Rea1 MIDAS binds the preribosomal factor Rsa4, which is located on the pre-60S subunit at a site that is contacted by the flexible Rea1 tail. The MIDAS-Rsa4 interaction is essential for ATP-dependent dissociation of a group of non-ribosomal factors from the pre-60S particle. Thus, Rea1 aligns with its interacting partners on the preribosome to effect a necessary step on the path to the export-competent 60S subunit

A network of assembly factors is involved in remodeling rRNA elements during preribosome maturation

Eukaryotic ribosome biogenesis involves ∼200 assembly factors, but how these contribute to ribosome maturation is poorly understood. Here, we identify a network of factors on the nascent 60S subunit that actively remodels preribosome structure. At its hub is Rsa4, a direct substrate of the force-generating ATPase Rea1. We show that Rsa4 is connected to the central protuberance by binding to Rpl5 and to ribosomal RNA (rRNA) helix 89 of the nascent peptidyl transferase center (PTC) through Nsa2. Importantly, Nsa2 binds to helix 89 before relocation of helix 89 to the PTC. Structure-based mutations of these factors reveal the functional importance of their interactions for ribosome assembly. Thus, Rsa4 is held tightly in the preribosome and can serve as a “distribution box,” transmitting remodeling energy from Rea1 into the developing ribosome. We suggest that a relay-like factor network coupled to a mechano-enzyme is strategically positioned to relocate rRNA elements during ribosome maturation

Driving ribosome assembly

Ribosome biogenesis is a fundamental process that provides cells with the molecular factories for cellular protein production. Accordingly, its misregulation lies at the heart of several hereditary diseases (e.g., Diamond-Blackfan anemia). The process of ribosome assembly comprises the processing and folding of the pre-rRNA and its concomitant assembly with the ribosomal proteins. Eukaryotic ribosome biogenesis relies on a large number (> 200) of non-ribosomal factors, which confer directionality and accuracy to this process. Many of these non-ribosomal factors fall into different families of energy-consuming enzymes, notably including ATP-dependent RNA helicases, AAA-ATPases, GTPases, and kinases. Ribosome biogenesis is highly conserved within eukaryotic organisms; however, due to the combination of powerful genetic and biochemical methods, it is best studied in the yeast Saccharomyces cerevisiae. This review summarizes our current knowledge on eukaryotic ribosome assembly, with particular focus on the molecular role of the involved energy-consuming enzymes

Sildenafil Does Not Improve Cardiovascular Hemodynamics, Peak Power, or 15-km Time Trial Performance at Simulated Moderate or High Altitudes in Men or Women

Sildenafil increases oxygen delivery and maximal exercise capacity at very high altitudes (greater than or equal to 4300 m) and has been shown to improve short-duration exercise performance in some individuals at simulated high altitude (3900 m). It is unknown whether sildenafil improves maximal exercise capacity and longer duration exercise performance at moderate and high altitudes where competitions are more common. Additionally, the effects of sildenafil on women exercising at altitude have not been examined. The purpose of this study was to determine the effects of sildenafil on cardiovascular hemodynamics, arterial oxygen saturation (SaO2), peak exercise capacity (Wpeak), and 15-km time trial performance, in endurance-trained men and women at simulated moderate (MA; 2100 m, 16.2 % FIO2) and high (HA; 3900 m, 12.8% FIO2) altitudes. Eleven male and 10 female subjects completed two HA Wpeak trials following the ingestion of placebo or 50 mg sildenafil in randomized, counterbalanced, and double blind fashion. Subjects then completed four exercise trials (30 min at 55% of Wpeak + 15-km time trial) at MA and HA following the ingestion of placebo or 50 mg sildenafil in randomized, counterbalanced, and double blind fashion. Sildenafil had little influence on cardiovascular hemodynamics for either gender at MA or HA, but did result in higher SaO2 values compared to placebo during steady state and time trial exercise in men at HA only. Sildenafil did not affect Wpeak or 15-km time trial performance in either gender at MA or HA. We conclude that sildenafil is unlikely to exert beneficial effects at altitudes \u3c 4000 m for a majority of the population

Model Programs to Address Obesity and Cardiometabolic Disease: Interventions for Suboptimal Nutrition and Sedentary Lifestyles

Problems posed by obesity-related endocrine diseases embody a national health crisis. Caloric excess and sedentary lifestyle from which they develop also pose significant challenges for rehabilitation providers. Almost two thirds of the U.S. population are currently overweight or obese, a number that has increased by >10% within the last decade and is expected to grow. An overweight body habitus is strongly associated with clinical hazards, including cardiometabolic syndrome, diabetes hypertension, and coronary artery disease. The component health risks of the cardiometabolic syndrome include coalescing of risk factors that predict a health calamity unless effective interventions can be developed and widely adopted. Obesity by itself is now considered an American Diabetes Association–qualified disability, but it is also disturbingly prevalent in other physical disability groupings of adults and children. This monograph describes successes of the Diabetes Prevention Program (DPP), a National Institutes of Health multisite randomized controlled trial that reported significant weight reduction and a 58% decreased incidence of type-2 diabetes accompanying 1 year of structured lifestyle intervention. This treatment benefit (1) exceeded that of metformin pharmacotherapy, (2) was so powerful that the trial was closed before reaching endpoints, and (3) was judged cost-effective for the patient and society. The DPP roadmap incorporating physical activity, diet, and behavioral approaches has been widely adapted to specific community, faith, racial, ethnic, school, and national populations with excellent outcomes success. The lockstep physical activity approach, activity prescription, and long-term success of the program are described and compared with other programs to illustrate effective countermeasures for the pandemics of obesity and obesity-related cardioendocrine disease. We will illustrate adaptation of the DPP for a cohort of persons with disability from spinal cord injury and the benefits observed

Use of Functional Electrical Stimulation Cycle Ergometers by Individuals With Spinal Cord Injury

PURPOSE: To assess the use of network-connected home-based functional electrical stimulation (FES) cycle ergometers. METHOD: De-identified data on >20,000 FES sessions for 314 users with spinal cord injury were analyzed for usage patterns and energy expenditure. These were compared with authoritative exercise guidelines of 150 minutes of moderate-intensity aerobic activity per week over at least 2 days per week for a total of 1,000 kcals. RESULTS: Seven percent of participants were classified as high- (≥5 days/week), 11% as medium- (2-5 days/week), and 82% as low-frequency users (<2 days/week). CONCLUSION: None of the users satisfied authoritative energy expenditure recommendations for disease prevention with FES cycling alone

Physiological Responses to Exergaming After Spinal Cord Injury

PURPOSE: To investigate whether exergaming satisfies guideline-based intensity standards for exercise conditioning (40%/50% oxygen uptake reserve [VO(2)R] or heart rate reserve (HRR), or 64%/70% of peak heart rate [HR(peak)]) in persons with paraplegia. METHODS: Nine men and women (18-65 years old) with chronic paraplegia (T1-L1, AIS A-C) underwent intensity-graded arm cycle exercise (AE) to evaluate VO2(peak) and HR(peak). On 2 randomized nonconsecutive days, participants underwent graded exercise using a custom arm cycle ergometer that controls the video display of a Nintendo Gamecube (GameCycle; Three Rivers Holdings LLC, Mesa, AZ) or 15 minutes of incrementally wrist-weighted tennis gameplay against a televised opponent (XaviX Tennis System; SSD Co Ltd, Kusatsu, Japan). RESULTS: GameCycle exergaming (GCE) resistance settings ≥0.88 Nm evoked on average ≥50% VO(2)R. During XaviX Tennis System exergaming (XTSE) with wrist weights ≥2 lbs, average VO(2) reached a plateau of ~40% VO(2)R. Measurements of HR were highly variable and reached average values ≥50% HRR during GCE at resistance settings ≥0.88 Nm. During XTSE, average HR did not reach threshold levels based on HRR for any wrist weight (20%-35% HRR). CONCLUSIONS: On average, intensity responses to GCE at resistance setting ≥0.88 Nm were sufficient to elicit exercise intensities needed to promote cardiorespiratory fitness in individuals with SCI. The ability of XTSE to elicit cardiorespiratory fitness benefits is most likely limited to individuals with very low fitness levels and may become subminimal with time if used as a conditioning stimulus