Exercise performance and V0₂ kinetics during upright and recumbent high-intensity cycling exercise

This study investigated cycling performance and oxygen uptake (VO₂) kinetics between upright and two commonly used recumbent (R) postures, 65ºR and 30ºR. On three occasions, ten young active males performed three bouts of high-intensity constant-load (85% peak workload achieved during a graded test) cycling in one of the three randomly assigned postures (upright, 65ºR or 30ºR). The first bout was performed to fatigue and second and third bouts were limited to 7 min. A subset of seven subjects performed a final constant-load test to failure in the supine posture. Exercise time to failure was not altered when the body inclination was lowered from the upright (13.1 ± 4.5 min) to 65ºR (10.5 ± 2.7 min) and 30ºR (11.5 ± 4.6 min) postures; but it was significantly shorter in the supine posture (5.8 ± 2.1 min) when compared with the three inclined postures. Resulting kinetic parameters from a tri-exponential analysis of breath-by-breath VO₂ data during the first 7 min of exercise were also not different between the three inclined postures. However, inert gas rebreathing analysis of cardiac output revealed a greater cardiac output and stroke volume in both recumbent postures compared with the upright posture at 30 s into the exercise. These data suggest that increased cardiac function may counteract the reduction of hydrostatic pressure from upright ~25 mmHg; to 65ºR ~22 mmHg; and 30ºR ~18 mmHg such that perfusion of active muscle presumably remains largely unchanged, and also therefore, VO₂ kinetics and performance during high-intensity cycling.

N-Acetylcysteine infusion does not affect glucose disposal during prolonged moderate-intensity exercise in humans

There is evidence that reactive oxygen species (ROS) signalling is required for normal increases in glucose uptake during contraction of isolated mouse skeletal muscle, and that AMP-activated protein kinase (AMPK) is involved. The aim of this study was to determine whether ROS signalling is involved in the regulation of glucose disposal and AMPK activation during moderate-intensity exercise in humans. Nine healthy males completed 80 min of cycle ergometry at 62 ± 1 of peak oxygen consumption ( . A 6,6-2H-glucose tracer was infused at rest and during exercise, and in a double-blind randomised cross-over design, N-acetylcysteine (NAC) or saline (CON) was co-infused. NAC was infused at 125 mg kg?1h?1for 15 min and then at 25 mg kg?1h?1for 20 min before and throughout exercise. NAC infusion elevated plasma NAC and cysteine, and muscle NAC and cysteine concentrations during exercise. Although neither NAC infusion nor exercise significantly affected muscle reduced or oxidised glutathione (GSH or GSSG) concentration (P> 0.05), S-glutathionylation (an indicator of oxidative stress) of a protein band of ?270 kDa was increased ?3-fold with contraction and this increase was prevented by NAC infusion. Despite this, exercised-induced increases in tracer determined glucose disposal, plasma lactate, plasma non-esterified fatty acids (NEFAs), and decreases in plasma insulin were not affected by NAC infusion. In addition, skeletal muscle AMPK? and acetyl-CoA carboxylase-? (ACC?) phosphorylation increased during exercise by ?3- and ?6-fold (P< 0.05), respectively, and this was not affected by NAC infusion. Unlike findings in mouse muscle ex vivo, NAC does not attenuate skeletal muscle glucose disposal or AMPK activation during moderate-intensity exercise in humans.

A low intensity, community based lifestyle programme to prevent weight gain in women with young children : cluster randomised controlled trial

Objective To develop and evaluate the effectiveness of a community behavioural intervention to prevent weight gain and improve health related behaviours in women with young children.
Design Cluster randomised controlled trial.
Setting A community setting in urban Australia. 
Participants 250 adult women with a mean age of 40. 39 years (SD 4.77, range 25-51) and a mean body mass index of 27.82 kg/m2 (SD 5.42, range 18-47) were recruited as clusters through 12 primary (elementary) schools. Intervention Schools were randomly assigned to the intervention or the control. Mothers whose schools fell in the intervention group (n=127) attended four interactive group sessions that involved simple health messages, behaviour change strategies, and group discussion, and received monthly support using mobile telephone text messages for 12 months. The control group (n=123)
attended one non-interactive information session based on population dietary and physical activity guidelines. 
Main outcome measures The main outcome measures were weight change and difference in weight change between the intervention group and the control group at 12 months. Secondary outcomes were changes in serum concentrations of fasting lipids and glucose, and changes in dietary behaviours, physical activity, and self management behaviours.
Results All analyses were adjusted for baseline values and the possible clustering effect. Women in the control group gained weight over the 12 month study period (0.83 kg, 95% confidence interval (CI) 0.12 to 1.54), whereas those in the intervention group lost weight (−0.20 kg, −0.90 to 0.49). The difference in weight change between the intervention group and the control group at 12 months was −1.13 kg (−2.03 to −0.24 kg; P<0.05) on the basis of observed values and −1.11 kg (−2.17 to −0.04) after multiple imputation to account for possible bias created by missing values. Secondary analyses after multiple imputation showed a difference in the intervention group compared with the control group for total cholesterol concentration (−0.35 mmol/l, −0.70 to −0.001), self management behaviours (diet score 0.18, 0.13 to 0.33; physical activity score 0.24, 0.05 to 0.43), and confidence to control weight (0.40, 0.11 to 0.69). Regular self weighing was associated with weight loss in the intervention group only (−1.98 kg, −3.75 to −0.23).
Conclusions Weight gain in women with young children could be prevented using a low intensity self management intervention delivered in a community setting. Self management of health behaviours improved with the intervention. The response rate of 12%, although comparable with that in other community studies, might limit the ability to generalise to other populations.    
Trial registration Australian New Zealand Clinical Trials Registry number ACTRN12608000110381.

Accumulated oxygen deficit measurements during and after high-intensity exercise in trained male and female adolescents

The purpose of this study was to compare accumulated oxygen deficits and markers of anaerobic metabolism [plasma ammonia (NH3) and lactate (La⁻) concentrations] in anaerobically trained male [n = 8, age 14.8 (0.5) years; maximal oxygen consumption V˙O2 max 61.74 (2.23) ml ·  kg⁻¹ · min⁻¹] and female [n = 8, age 14.5 (0.2) years; V˙O2 max 49.62 (3.52) ml · kg⁻¹ · min⁻¹] adolescents. The exercise protocol consisted of runs to exhaustion at speeds predicted to represent 120% and 130% of V˙O2 max. Arterialised blood samples were obtained from a pre-warmed hand via a catheter inserted into a forearm vein. Samples were taken at rest and after 1, 3, 5, 7, 10, 15 and 20 min of recovery. The high-intensity exercise resulted in mean accumulated oxygen deficits that were less (P < 0.05) in females (52.3 ml · kg⁻¹) than in males (68.6 ml · kg⁻¹). Lower (P < 0.05) plasma concentrations of NH3 and La⁻¹, and a higher pH were evident in females compared with males during various stages of the 20-min recovery period. The increase in anaerobic performance in the male adolescent athletes when compared with their female counterparts was associated with an increased plasma concentration of selected plasma and blood metabolites. The observed results may reflect well-established differences between the sexes in the morphology and metabolic power of muscle.

Moderate-intensity resistance exercise training in patients with chronic heart failure improves strength, endurance, heart rate variability, and forearm blood flow

Thirty-nine CHF patients (New York Heart Association Functional Class = 2.3±0.5; left ventricular ejection fraction 28%±7%; age 65±11 years; 33:6 male:female) underwent 2 identical series of tests, 1 week apart, for strength and endurance of the knee and elbow extensors and flexors, VO_2peak, HRV, FBF at rest, and FBF activated by forearm exercise or limb ischemia. Patients were then randomized to 3 months of resistance training (EX, n = 19), consisting of mainly isokinetic (hydraulic) ergometry, interspersed with rest intervals, or continuance with usual care (CON, n = 20), after which they underwent repeat endpoint testing. Combining all 4 movement patterns, strength increased for EX by 21±30% (mean±SD, P<.01) after training, whereas endurance improved 21±21% (P<.01). Corresponding data for CON remained almost unchanged (strength P<.005, endurance P<.003 EX versus CON). VO_2peak improved in EX by 11±15% (P<.01), whereas it decreased by 10±18% (P<.05) in CON (P<.001 EX versus CON). The ratio of low-frequency to high-frequency spectral power fell after resistance training in EX by 44±53% (P<.01), but was unchanged in CON (P<.05 EX versus CON). FBF increased at rest by 20±32% (P<.01), and when stimulated by submaximal exercise (24±32%, P<.01) or limb ischemia (26±45%, P<.01) in EX, but not in CON (P<.01 EX versus CON).

Development and validation of the influenza intensity and impact questionnaire (FluiiQ™)

Clinical trials of new agents to reduce the severity and impact of influenza require accurate assessment of the effect of influenza infection. Because there are limited high-quality adult influenza Patient Reported Outcomes (PRO) measures, the aim was to develop and validate a simple but comprehensive questionnaire for epidemiological research and clinical trials.

Frequency, intensity and duration of physical tasks performed by Australian rural firefighters during bushfire suppression

The current study combined, for the first time, video footage of individual firefighters wearing heart rate monitors and personal GPS units to quantify the frequency, duration and intensity of tasks performed by Australian rural fire crews when. suppressing bushfires. Across the four fireground 'shifts', the firefighters performed 34 distinct fireground tasks. Per shift, the task frequency ranged from once (raking fireline in teams, carrying a quick fill pump) to 103 times {lateral repositioning of a 38-mm charged firehose) .. The tasks lasted between 4 ± 2 s (bowling out 3-8-mm firehose) and 461 ± 387 s (raking fireline in teams). The task intensity~ as measured by average heart rate ranged between 97 ± 16 beats·min-1 (55.7 ± 8.7. %HRmax) and 157 ± 15 beats·min-1 (86.2 ± 10.8 %HRmax)· The tasks were performed a speeds that ranged from 0.12 ± 0.08 m·s-1 (manual hose retraction of 38-mm charged firehose) to 0.79 ± 0.40 m·s-1 (carrying a 38-mm coiled hose). Tasks found to be simultaneously frequent, long and intense (or two of these three) are likely to form the basis for job-specific testing of Australian rural firefighters suppressing bushfires.

The association between perceived sweetness intensity and dietary intake in young adults

Individual differences in taste perception may influence dietary habits, nutritional status, and ultimately nutrition-related chronic disease risk. Individual differences in sweetness intensity perception and the relationship between perceived sweetness intensity, food behaviors, and dietary intake was investigated in 85 adults. Subjects (body mass index [BMI]= 21 ± 3, 21 ± 4 y) completed a food and diet questionnaire, food variety survey, 2 24-h food records, and a perceived sweetness intensity measurement using the general labeled magnitude scale (gLMS). There was interindividual variation in perceived sweetness intensity (0 to 34 gLMS units, mean 10 ± 7). One-way analysis of variance (ANOVA) revealed no difference between perceived sweetness intensity and degree of importance placed on not adding sugar to tea or coffee (P = 0.2) and the degree of importance placed on avoiding sugar-sweetened or fizzy drinks (P = 1.0). Independent t-test analysis revealed no significant association between perceived sweetness intensity and the food variety measure for sugar and confectionary intake (P = 0.6) and selected fruit and vegetable intake (P = 0.1 to 0.9). One-way ANOVA also demonstrated no difference between tertiles of sweetness intensity and BMI (P = 0.1), age (P = 0.3), and food variety score (P = 0.5). No correlation was observed with regards to perceived sweetness intensity and mean total energy (kJ) intake (r = 0.05, P = 0.7), percent energy from total fat, saturated fat, protein, carbohydrate, and grams of fiber (r =–0.1 to 0.1, P = 0.2 to 0.8) and also for intake of the micronutrients: folate, magnesium, calcium, iron, and zinc (r = 0.1 to 0.2, P = 0.1 to 0.4). Only modest correlations were observed between sodium (r = 0.3, P < 0.05), vitamin C (r = 0.3, P < 0.05), and potassium (r = 0.2, P < 0.0) intake and perceived sweetness intensity. Overall, perceived sweetness intensity does not appear to play a role in food behaviors relating to sugar consumption and dietary intake in adults.

Weight status associations with physical activity intensity and physical self-perceptions in 10-to 11-year-old children

The study examined associations between children’s weight status, physical activity intensity, and physical self-perceptions. Data were obtained from 409 children (224 girls) aged 10–11 years categorized as normal-weight or overweight/obese. Physical activity was assessed using accelerometry, and children completed the Physical Self-Perception Profile. After controlling for the effects of age, maturation, and socioeconomic status vigorous physical activity was significantly associated with normal-weight status among boys (OR = 1.13, p = .01) and girls (OR = 1.13, p = .03). Normal-weight status was significantly associated with perceived Physical Condition (Boys: OR = 5.05, p = .008; Girls: OR = 2.50, p = .08), and Body Attractiveness (Boys: OR = 4.44, p = .007; Girls: OR = 2.56, p = .02). Weight status of 10–11 year old children was significantly associated with time spent in vigorous physical activity and self-perceptions of Body Attractiveness and Physical Condition.

Effect of streptozotocin-induced diabetes on glycogen resynthesis in fasted rats post-high-intensity exercise

It has recently been shown that food intake is not essential for the resynthesis of the stores of muscle glycogen in fasted animals recovering from high-intensity exercise. Because the effect of diabetes on this process has never been examined before, we undertook to explore this issue. To this end, groups of rats were treated with streptozotocin (60 mg/kg body mass ip) to induce mild diabetes. After 11 days, each animal was fasted for 24 h before swimming with a lead weight equivalent to 9% body mass attached to the tail. After exercise, the rate and the extent of glycogen repletion in muscles were not affected by diabetes, irrespective of muscle fiber composition. Consistent with these findings, the effect of exercise on the phosphorylation state of glycogen synthase in muscles was only minimally affected by diabetes. In contrast to its effects on nondiabetic animals, exercise in fasted diabetic rats was accompanied by a marked fall in hepatic glycogen levels, which, surprisingly, increased to preexercise levels during recovery despite the absence of food intake.

Fiber-specific responses of muscle glycogen repletion in fasted rats physically active during recovery from high-intensity physical exertion

Mild physical activity performed immediately after a bout of intense exercise in fasting humans results in net glycogen breakdown in their slow oxidative (SO) muscle fibers and glycogen repletion in their fast twitch (FT) fibers. Because several animal species carry a low proportion of SO fibers, it is unclear whether they can also replenish glycogen in their FT fibers under these conditions. Given that most skeletal muscles in rats are poor in SO fibers (<5%), this issue was examined using groups of 24-h fasted Wistar rats (n = 10) that swam for 3 min at high intensity with a 10% weight followed by either a 60-min rest (passive recovery, PR) or a 30-min swim with a 0.5% weight (active recovery, AR) preceding a 30-min rest. The 3-min sprint caused 61–79% glycogen fall across the muscles examined, but not in the soleus (SOL). Glycogen repletion during AR without food was similar to PR in the white gastrocnemius (WG), where glycogen increased by 71%, and less than PR in both the red and mixed gastrocnemius (RG, MG). Glycogen fell by 26% during AR in the SOL. Following AR, glycogen increased by 36%, 87%, and 37% in the SOL, RG, and MG, respectively, and this was accompanied by the sustained activation of glycogen synthase and inhibition of glycogen phosphorylase in the RG and MG. These results suggest that mammals with a low proportion of SO fibers can also replenish the glycogen stores of their FT fibers under extreme conditions combining physical activity and fasting.