Respective effects of malnutrition and phosphate depletion on endurance swimming and muscle metabolism in rats

8 weeks of 2S-hesperidin prevents a decrease in pO2 at submaximal intensity in amateur cyclists in off-season: randomized controlled trial

Although chronic supplementation with 2S-hesperidin has been shown to improve performance, to date, the possible mechanisms underlying this effect have not been explored. Therefore, the aim of this study was to assess whether changes in gasometry may be associated with improved performance after the intake of 2S-hesperidin (500 mg d^-1, 8 weeks). Forty amateur cyclists (n = 20 2S-hesperidin, n = 20 placebo) performed a rectangular test, during which capillary blood samples were taken at the baseline, FatMax1, ventilatory threshold 1 and 2 (VT1 and VT2), power maximum (P_MAX), FatMax2 and excess post-exercise O₂ consumption (EPOC) to measure gasometry parameters. Significantly increased CO₂ and tCO₂ was found at FatMax1, VT1, FatMax2 and EPOC (p = <0.05) after 8 weeks of 2S-hesperidin ingestion. Conversely, the placebo group had a significant decrease in pO₂ at VT2 (p = 0.04) during the rectangular test, with no changes in the 2S-hesperidin group. Therefore, chronic supplementation with 2S-hesperidin prevents decreases in pO₂ at submaximal intensities in amateur cyclists in an off-season period.

Default network connectivity decodes brain states with simulated microgravity

With great progress of space navigation technology, it becomes possible to travel beyond Earth's gravity. So far, it remains unclear whether the human brain can function normally within an environment of microgravity and confinement. Particularly, it is a challenge to figure out some neuroimaging-based markers for rapid screening diagnosis of disrupted brain function in microgravity environment. In this study, a 7-day -6° head down tilt bed rest experiment was used to simulate the microgravity, and twenty healthy male participants underwent resting-state functional magnetic resonance imaging scans at baseline and after the simulated microgravity experiment. We used a multivariate pattern analysis approach to distinguish the brain states with simulated microgravity from normal gravity based on the functional connectivity within the default network, resulting in an accuracy of no less than 85 % via cross-validation. Moreover, most discriminative functional connections were mainly located between the limbic system and cortical areas and were enhanced after simulated microgravity, implying a self-adaption or compensatory enhancement to fulfill the need of complex demand in spatial navigation and motor control functions in microgravity environment. Overall, the findings suggest that the brain states in microgravity are likely different from those in normal gravity and that brain connectome could act as a biomarker to indicate the brain state in microgravity.

Recovery after aerobic exercise is manipulated by tempo change in a rhythmic sound pattern, as indicated by autonomic reaction on heart functioning

Physical prowess is associated with rapid recovery from exhaustion. Here we examined whether recovery from aerobic exercise could be manipulated with a rhythmic sound pattern that either decreased or increased in tempo. Six men and six women exercised repeatedly for six minutes on a cycle ergometer at 60 percent of their individual maximal oxygen consumption, and then relaxed for six minutes while listening to one of two sound pattern conditions, which seemed to infinitely either decrease or increase in tempo, during which heart and breathing activity was measured. Participants exhibited more high-frequent heart rate variability when listening to decreasing tempo than when listening to increasing tempo, accompanied by a non-significant trend towards lower heart rate. The results show that neuropsychological entrainment to a sound pattern may directly affect the autonomic nervous system, which in turn may facilitate physiological recovery after exercise. Applications using rhythmic entrainment to aid physical recovery are discussed.

Energy expenditure characteristics of weight lifting: 2 sets to fatigue

We investigated the work performed and energy expenditure characteristics within and among 2 sets of the bench press at 70%, 80%, and 90% of 1 repetition maximum (1RM). For both sets fatigue was the end point. We asked: do multiple sets affect subsequent work output along with aerobic, anaerobic, and excess postexercise oxygen consumption (EPOC) contributions? Ten males participated. Work was significantly less for the 2nd set within the 70% and 80% protocols, but not the 90% protocol. Anaerobic (glycolytic) energy expenditure was less for the 2nd set within all protocols. However, within all protocols, the work / energy expenditure ratio was not different between sets. Overall work was significantly different among protocols, becoming less as the weight lifted was increased: 70%, 637.1 ± 122.4 J; 80%, 512.4 ± 93.4 J; 90%, 324.7 ± 92.6 J (p < 0.001). EPOC was not different among protocols after the 1st set, 2nd set, or combined overall. Moreover, the overall EPOC did not correlate with overall work performed (r = 0.31, p = 0.11). EPOC overall did correlate with aerobic (r = 0.68, p < 0.001) and anaerobic (r = 0.65, p < 0.001) energy expenditures. In terms of a work / energy expenditure ratio, the least amount of completed work at 90% 1RM required greater energy expenditure as compared with 70% and 80% because of an EPOC that is similar for all. As more work is completed (i.e., lower weight, more repetitions), aerobic and anaerobic exercise energy expenditures appear to increase accordingly, yet absolute EPOC remains essentially unchanged, contributing less to the overall energy expenditure.

Fat-free mass and excess post-exercise oxygen consumption in the 40 minutes after short-duration exhaustive exercise in young male Japanese athletes

The relationship between fat-free mass (FFM) and excess post-exercise oxygen consumption (EPOC) has not been well researched because of the relatively small number of subjects studied. This study investigated the effects of FFM on EPOC and EPOC/maximum oxygen consumption. 250 Japanese male athletes between 16 and 21 years old from Nagasaki prefecture had their EPOC measured up to 40 minutes after short-duration exhaustive exercise. The value was named as EPOC40 min. The proportions of EPOC up to 1, 3, 6, 10, and 25 minutes to EPOC40 min were calculated and named as P1, P3, P6, P10, and P25, respectively. Body size and composition, VO2max and resting metabolic rate (RMR) were also measured. Mean EPOC40 min was 9.04 L or 158 ml/kg FFM. EPOC40 min was related to FFM (r=0.55, p<0.001) and VO2max (r=0.37, p<0.001). The ratio of EPOC40 min to VO2max was related to FFM (r=0.28, p<0.001). P1, P3, P6, P10, and P25 were negatively related to EPOC40 min/FFM, EPOC40 min/VO2max, and FFM. Athletes who had larger FFM had larger EPOC40 40 min and EPOC40 40 min/VO2max, and smaller P1, P3, P10, and P25.

Effects of exercise intensity and duration on the excess post-exercise oxygen consumption

Recovery from a bout of exercise is associated with an elevation in metabolism referred to as the excess post-exercise oxygen consumption (EPOC). A number of investigators in the first half of the last century reported prolonged EPOC durations and that the EPOC was a major component of the thermic effect of activity. It was therefore thought that the EPOC was a major contributor to total daily energy expenditure and hence the maintenance of body mass. Investigations conducted over the last two or three decades have improved the experimental protocols used in the pioneering studies and therefore have more accurately characterized the EPOC. Evidence has accumulated to suggest an exponential relationship between exercise intensity and the magnitude of the EPOC for specific exercise durations. Furthermore, work at exercise intensities >or=50-60% VO2max stimulate a linear increase in EPOC as exercise duration increases. The existence of these relationships with resistance exercise at this stage remains unclear because of the limited number of studies and problems with quantification of work intensity for this type of exercise. Although the more recent studies do not support the extended EPOC durations reported by some of the pioneering investigators, it is now apparent that a prolonged EPOC (3-24 h) may result from an appropriate exercise stimulus (submaximal: >or=50 min at >or=70% VO2max; supramaximal: >or=6 min at >or=105% VO2max). However, even those studies incorporating exercise stimuli resulting in prolonged EPOC durations have identified that the EPOC comprises only 6-15% of the net total oxygen cost of the exercise. But this figure may need to be increased when studies utilizing intermittent work bouts are designed to allow the determination of rest interval EPOCs, which should logically contribute to the EPOC determined following the cessation of the last work bout. Notwithstanding the aforementioned, the earlier research optimism regarding an important role for the EPOC in weight loss is generally unfounded. This is further reinforced by acknowledging that the exercise stimuli required to promote a prolonged EPOC are unlikely to be tolerated by non-athletic individuals. The role of exercise in the maintenance of body mass is therefore predominantly mediated via the cumulative effect of the energy expenditure during the actual exercise.

Excess post-exercise oxygen consumption in untrained males: effects of intermittent durations of arm ergometry

The purpose of this study was to investigate excess post-exercise oxygen consumption (EPOC) following a continuous 30 min bout of upper-body exercise (UBE) compared with 3 consecutive 10 min bouts of UBE. Ten male subjects (age (mean +/- standard deviation), 25.7 +/- 5.83 years; arm VO(2) (peak), 2.2 +/- 0.25 L x min(-1), on separate days (48 h between trials) and in counterbalanced order, performed a continuous 30 min bout of arm exercise at 60% of arm VO2 peak and 3 separate 10 min bouts of arm exercise at 60% of arm VO(2) (peak). Subjects reported to the laboratory rested and after a 12 h fast. Each test was preceded by a 30 min baseline test to determine resting metabolic rate. Post-exercise VO2 was continuously monitored until baseline was re-established. Results showed that the combined magnitude of the EPOCs from the intermittent exercise sessions was significantly (p > .05) greater (4.47 +/- 1.58 L O2) than that elicited from the continuous exercise session (1.54 +/- 1.25 L O2). These data indicate that separating a continuous 30 min arm exercise into 3 equal 10 min arm exercises will elicit a small but significantly higher EPOC, and thus result in greater post-exercise energy expenditure. This could be beneficial for those unable to perform lower-body exercise (LBE), or for those with limited exercise capacities.

Effects of resistance exercise bouts of different intensities but equal work on EPOC

PURPOSE

To compare the effect of low- and high-intensity resistance exercise of equal work output, on exercise and excess postexercise oxygen consumption (EPOC).

METHODS

Fourteen female subjects performed a no-exercise baseline control (CN), and nine exercises for two sets of 15 repetitions at 45% of their 8-RM during one session (LO) and two sets of 8 repetitions at 85% of their 8-RM during another session (HI). Measures for all three sessions included: heart rate (HR) and blood lactate (La) preexercise, immediately postexercise and 20 min, 60 min, and 120 min postexercise; and ventilation volume (VE), oxygen consumption (VO(2)), and respiratory exchange ratio (RER) during exercise and at intervals 0-20 min, 45-60 min, and 105-120 min postexercise.

RESULTS

Exercise .VO(2) was not significantly different between HI and LO, but VE, [La], and HR were significantly greater for HI compared with LO. Exercise RER for HI (1.07 +/- 0.03 and LO (1.05 +/- 0.02) were significantly higher than CN (0.86 +/- 0.02), but there were no differences among conditions postexercise. EPOC was greater for HI compared with low at 0-20 min (HI,1.72 +/- 0.70 LO(2); LO, 0.9 +/- 0.65, LO(2)), 45-60 min (HI, 0.35 +/- 0.25 LO(2); LO, 0.14 +/- 0.19 LO2), and 105-120 min (HI, 0.22 +/- 0.22 LO(2); LO, 0.05 +/- 0.11, LO(2)).

CONCLUSION

These data indicate that for resistance exercise bouts with an equated work volume, high-intensity exercise (85% 8-RM) will produce similar exercise oxygen consumption, with a greater EPOC magnitude and volume than low-intensity exercise (45% 8-RM).

Hypophosphataemia: cause of the disturbed metabolism in the metabolic syndrome

The clustering of risk factors for cardiovascular disease (CVD) and non-insulin-dependent diabetes mellitus (NIDDM) in obese patients may be attributable to a disturbed metabolism caused by hypophosphataemia. A low serum phosphate (S-P) level may be a limiting factor for glucose metabolism and may account for hyperglycaemia, with an increased risk of NIDDM and hypertension and consequent increased risk of stroke. Low S-HDL levels, known to exist in the metabolic syndrome, as well as high serum triglycerides may also have been the results of phosphate depletion. The hypothesis presents a new serious disturbance which accounts for the dyslipidaemia, hyperglycaemia and the hypertension in metabolic syndrome. The proposed causal relationship between low S-P and the clustering of risk factors is based on results from a cross-sectional study of obese patients, where low S-P was associated with high body mass index (BMI), high blood glucose (B-glu), high systolic blood pressure (SBP), high diastolic blood pressure (DBP), but low serum high density lipoprotein (S-HDL) and serum magnesium (S-Mg) levels. Knowledge from experimental and clinical studies on hypophosphataemia and/or phosphate depletion are referred to when discussing the hypothesis.

Sympathetic discharge and vascular resistance after bed rest

The effect of -6 degrees head-down-tilt bed rest (HDBR) for 14 days on supine sympathetic discharge and cardiovascular hemodynamics at rest was assessed. Mean arterial pressure, heart rate (n = 25), muscle sympathetic nerve activity (MSNA; n = 16) burst frequency, and forearm blood flow (n = 14) were measured, and forearm vascular resistance (FVR) was calculated. Stroke distance, our index of stroke volume, was derived from measurements of aortic mean blood velocity (Doppler) and R-R interval (n = 7). With these data, an index of total peripheral resistance was determined. Heart rate at rest was greater in the post (71 +/- 2 beats/min)- compared with the pre-HDBR test (66 +/- 2 beats/min; P < 0.003), but mean arterial pressure was unchanged. Aortic stroke distance during post-HDBR (15.5 +/- 1.1 cm/beat) was reduced from pre-HDBR levels (20.0 +/- 1.5 cm/beat) (P < 0.03). Also, MSNA burst frequency was reduced in the post (16.7 +/- 2.8 beats/min)- compared with the pre (25.2 +/- 2.6 beats/min)-HDBR condition (P < 0.01). Bed rest did not alter forearm blood flow, FVR, or total peripheral resistance. Thus reductions in MSNA with HDBR were not associated with a decrease in FVR.

Beta 1-adrenoreceptors regulate resting metabolic rate

This was a randomized, cross-over experiment designed to determine which beta-adrenergic receptors, beta 1, beta 2, or both, regulate metabolic rate in humans. All subjects (3 women, 4 men) were administered a 7-d therapeutic dose of a selective beta 1-antagonist (atenolol 50 mg BID), a combined beta 1, beta 2-antagonist (propranolol 80 mg BID), and a placebo control (BID). Indirect calorimetry was determined before and after 1 h of submaximal exercise. Exercise was performed at 50% of the trial specific VO2peak because maximal exercise was significantly decreased in the presence of the nonselective beta 1, beta 2-antagonist (VO2peak placebo: 44.90 +/- 4.40 mL.kg-1.min-1 vs beta 1, beta 2-antagonism: 39.20 +/- 3.00 mL.kg-1.min-1; P < 0.05). Both the beta 1 and the combined beta 1, beta 2-adrenoreceptor antagonists reduced resting oxygen consumption to a similar extent (0.247 +/- 0.007 L.min-1 placebo, vs 0.218 +/- 0.007 L.min-1 beta 1-antagonism, vs 0.226 +/- 0.007 L.min-1 beta 1, beta 2-antagonism; P < 0.05). However, the 30-min and 60-min excess post-exercise oxygen consumption (mean EPOC) remained unchanged. It is concluded that the beta 1-receptors are regulating the effects of the sympathetic nervous system on resting but not exercise recovery metabolic rate. These metabolic side effects may suggest that changes need to be made in the nutritional requirements of patients using beta-adrenergic antagonists.

Recovery of muscular energy status in chronic alcoholics after 2 weeks of abstinence

Repeated and excessive consumption of alcohol leads to pathophysiological disorders in skeletal muscles. A successful management of this syndrome requires a strict abstinence and a nutritionally adequate diet. We propose here a simple and noninvasive investigation using 31P magnetic resonance spectroscopy (MRS) to monitor the recovery of the basal energy status of eminence thenar muscles from documented chronic alcoholic patients during a controlled 15-day period of abstinence. Cessation of alcohol abuse induced a significant recovery of the PCr/(PCr+P(i)) ratio otherwise depressed before the abstinence. On the contrary, the relative level of free inorganic phosphate decreased, whereas intracellular pH was not affected. These results demonstrate (a) the rapid improvement of basal muscular energy metabolism during abstinence for patients with a chronic and heavy alcohol consumption, and (b) the feasibility of a follow-up of this recovery by serial examinations using 31P MRS.